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Sample records for acquired resistance mechanisms

  1. Intrinsic and acquired resistance mechanisms in enterococcus

    PubMed Central

    Hollenbeck, Brian L.; Rice, Louis B.

    2012-01-01

    Enterococci have the potential for resistance to virtually all clinically useful antibiotics. Their emergence as important nosocomial pathogens has coincided with increased expression of antimicrobial resistance by members of the genus. The mechanisms underlying antibiotic resistance in enterococci may be intrinsic to the species or acquired through mutation of intrinsic genes or horizontal exchange of genetic material encoding resistance determinants. This paper reviews the antibiotic resistance mechanisms in Enterococcus faecium and Enterococcus faecalis and discusses treatment options. PMID:23076243

  2. Genomic Insights into Intrinsic and Acquired Drug Resistance Mechanisms in Achromobacter xylosoxidans

    PubMed Central

    Hu, Yongfei; Zhu, Yuying; Ma, Yanan; Liu, Fei; Lu, Na; Yang, Xi; Luan, Chunguang; Yi, Yong

    2014-01-01

    Achromobacter xylosoxidans is an opportunistic pathogen known to be resistant to a wide range of antibiotics; however, the knowledge about the drug resistance mechanisms is limited. We used a high-throughput sequencing approach to sequence the genomes of the A. xylosoxidans type strain ATCC 27061 and a clinical isolate, A. xylosoxidans X02736, and then we used different bioinformatics tools to analyze the drug resistance genes in these bacteria. We obtained the complete genome sequence for A. xylosoxidans ATCC 27061 and the draft sequence for X02736. We predicted a total of 50 drug resistance-associated genes in the type strain, including 5 genes for β-lactamases and 17 genes for efflux pump systems; these genes are also conserved among other A. xylosoxidans genomes. In the clinical isolate, except for the conserved resistance genes, we also identified several acquired resistance genes carried by a new transposon embedded in a novel integrative and conjugative element. Our study provides new insights into the intrinsic and acquired drug resistance mechanisms in A. xylosoxidans, which will be helpful for better understanding the physiology of A. xylosoxidans and the evolution of antibiotic resistance in this bacterium. PMID:25487802

  3. Mutational and acquired carbapenem resistance mechanisms in multidrug resistant Pseudomonas aeruginosa clinical isolates from Recife, Brazil

    PubMed Central

    Cavalcanti, Felipe Lira de Sá; Mirones, Cristina Rodríguez; Paucar, Elena Román; Montes, Laura Álvarez; Leal-Balbino, Tereza Cristina; de Morais, Marcia Maria Camargo; Martínez-Martínez, Luis; Ocampo-Sosa, Alain Antonio

    2015-01-01

    An investigation was carried out into the genetic mechanisms responsible for multidrug resistance in nine carbapenem-resistant Pseudomonas aeruginosaisolates from different hospitals in Recife, Brazil. Susceptibility to antimicrobial agents was determined by broth microdilution. Polymerase chain reaction (PCR) was employed to detect the presence of genes encoding β-lactamases, aminoglycoside-modifying enzymes (AMEs), 16S rRNA methylases, integron-related genes and OprD. Expression of genes coding for efflux pumps and AmpC cephalosporinase were assessed by quantitative PCR. The outer membrane proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The blaSPM-1, blaKPC-2 and blaGES-1 genes were detected in P. aeruginosaisolates in addition to different AME genes. The loss of OprD in nine isolates was mainly due to frameshift mutations, premature stop codons and point mutations. An association of loss of OprD with the overexpression of MexAB-OprM and MexXY-OprM was observed in most isolates. Hyper-production of AmpC was also observed in three isolates. Clonal relationship of the isolates was determined by repetitive element palindromic-PCR and multilocus sequence typing. Our results show that the loss of OprD along with overexpression of efflux pumps and β-lactamase production were responsible for the multidrug resistance in the isolates analysed. PMID:26676375

  4. Systemic Acquired Resistance in Moss: Further Evidence for Conserved Defense Mechanisms in Plants

    PubMed Central

    Winter, Peter S.; Bowman, Collin E.; Villani, Philip J.; Dolan, Thomas E.; Hauck, Nathanael R.

    2014-01-01

    Vascular plants possess multiple mechanisms for defending themselves against pathogens. One well-characterized defense mechanism is systemic acquired resistance (SAR). In SAR, a plant detects the presence of a pathogen and transmits a signal throughout the plant, inducing changes in the expression of various pathogenesis-related (PR) genes. Once SAR is established, the plant is capable of mounting rapid responses to subsequent pathogen attacks. SAR has been characterized in numerous angiosperm and gymnosperm species; however, despite several pieces of evidence suggesting SAR may also exist in non-vascular plants6–8, its presence in non-vascular plants has not been conclusively demonstrated, in part due to the lack of an appropriate culture system. Here, we describe and use a novel culture system to demonstrate that the moss species Amblystegium serpens does initiate a SAR-like reaction upon inoculation with Pythium irregulare, a common soil-borne oomycete. Infection of A. serpens gametophores by P. irregulare is characterized by localized cytoplasmic shrinkage within 34 h and chlorosis and necrosis within 7 d of inoculation. Within 24 h of a primary inoculation (induction), moss gametophores grown in culture became highly resistant to infection following subsequent inoculation (challenge) by the same pathogen. This increased resistance was a response to the pathogen itself and not to physical wounding. Treatment with β-1,3 glucan, a structural component of oomycete cell walls, was equally effective at triggering SAR. Our results demonstrate, for the first time, that this important defense mechanism exists in a non-vascular plant, and, together with previous studies, suggest that SAR arose prior to the divergence of vascular and non-vascular plants. In addition, this novel moss – pathogen culture system will be valuable for future characterization of the mechanism of SAR in moss, which is necessary for a better understanding of the evolutionary history of SAR

  5. ESR1 mutations as a mechanism for acquired endocrine resistance in breast cancer

    PubMed Central

    Jeselsohn, Rinath; Buchwalter, Gilles; De Angelis, Carmine; Brown, Myles; Schiff, Rachel

    2016-01-01

    Most breast cancers are estrogen receptor α (ER)-positive (+) and are treated with endocrine therapies targeting ER activity. Despite efforts, the mechanisms of the frequent clinical resistance to these therapies remain largely unknown. Several recent parallel studies unveiled gain-of-function recurrent ESR1 mutations in up to 20% of patients with metastatic ER+ disease who all received endocrine therapies, which for more cases included an aromatase inhibitor. These mutations, clustered in a hotspot within the ligand-binding domain (LBD), lead to ligand independent ER activity and tumor growth, partial resistance to tamoxifen and fulvestrant, and potentially increased metastatic capacity. Together, these findings suggest that the ESR1 LBD mutations account for acquired endocrine resistance in a substantial fraction of patients with metastatic disease. The absence of detectable ESR1 mutations in treatment-naïve disease and the correlation with the number of endocrine treatments indicate a clonal expansion of rare mutant clones, selected under the pressure of treatment. New technologies to detect low/ultra rare ESR1 mutations together with tissue and liquid biopsies are required to fully expose their clinical relevance in prognosis and treatment. Pre-clinical and clinical development of rationale-based novel therapeutic strategies to inhibit these mutants has the potential to substantially improve treatment outcomes. PMID:26122181

  6. Mechanisms of resistance to etoposide and teniposide in acquired resistant human colon and lung carcinoma cell lines.

    PubMed

    Long, B H; Wang, L; Lorico, A; Wang, R C; Brattain, M G; Casazza, A M

    1991-10-01

    Stable acquired resistance to etoposide (VP-16) or teniposide (VM-26) in HCT116 human colon carcinoma cells and A549 human lung adenocarcinoma cells, was previously obtained by weekly 1-h exposures to either drug (B. H. Long, Natl. Cancer Inst. Monogr., 4: 123-127, 1987). The purpose of this study was to identify possible mechanisms of resistance present in these cells by using human mdr1 and topoisomerase II DNA probes, antibodies to these gene products, and P4 phage unknotting assay for topoisomerase II activities. HCT116(VP)35 cells were 9-, 7-, and 6-fold resistant to VP-16, VM-26, and Adriamycin, respectively, and showed no cross-resistance to colchicine and actinomycin D. These cells had no differences in mdr1 gene, mdr1 mRNA, or P-glycoprotein levels but displayed decreased levels of topoisomerase II mRNA and enzyme activity without any alteration of drug sensitivity displayed by the enzyme. HCT116(VM)34 cells were 5-, 7-, and 21-fold resistant to VP-16, VM-26, and Adriamycin; were cross-resistant to colchicine (7-fold) and actinomycin D (18-fold); and possessed a 9-fold increase in mdr1 mRNA and increased P-glycoprotein without evidence of mdr1 gene amplification. No alterations in topoisomerase II gene or mRNA levels, enzyme activity, or drug sensitivity were observed. A549(VP)28 and A549(VM)28 cells were 8-fold resistant to VP-16 and VM-26 and 3-fold resistant to Adriamycin. Both lines were not cross-resistant to colchicine or actinomycin D but were hypersensitive to cis-platinum. No alterations in mdr1 gene, mdr1 mRNA, or P-glycoprotein levels, but lower topoisomerase II mRNA levels and decreased enzyme activities, were observed. Of the four acquired resistant cell lines, resistance is likely related to elevated mdr1 expression in one line and to decreased topoisomerase II expression in the other three lines. PMID:1717144

  7. The mechanism of acquired resistance to irreversible EGFR tyrosine kinase inhibitor-afatinib in lung adenocarcinoma patients

    PubMed Central

    Wu, Shang-Gin; Liu, Yi-Nan; Tsai, Meng-Feng; Chang, Yih-Leong; Yu, Chong-Jen; Yang, Pan-Chyr; Yang, James Chih-Hsin; Wen, Yueh-Feng; Shih, Jin-Yuan

    2016-01-01

    Introduction Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are associated with favorable response in EGFR mutant lung cancer. Acquired resistance to reversible EGFR TKIs remains a significant barrier, and acquired EGFR T790M-mutation is the major mechanism. Second-generation irreversible EGFR TKI, afatinib, had also been approved for treating EGFR mutant lung cancer patients, but the mechanism of acquired resistance to afatinib has not been well studied. Results Forty-two patients had tissue specimens taken after acquiring resistance to afatinib. The sensitizing EGFR mutation were all consistent between pre- and post-afatinib tissues. Twenty patients (47.6%) had acquired T790M mutation. T790M rate was not different between first-generation EGFR TKI-naïve patients (50%) and first-generation EGFR TKI-treated patients (46.4%) (p = 0.827). No clinical characteristics or EGFR mutation types were associated with the development of acquired T790M. No other second-site EGFR mutations were detected. There were no small cell or squamous cell lung cancer transformation. Other genetic mutations were not identified in PIK3CA, BRAF, HER2, KRAS, NRAS, MEK1, AKT2, LKB1 and JAK2. Methods Afatinib-prescription record of our department of pharmacy from January 2007 and December 2014 was retrieved. We investigated patients with tissue specimens available after acquiring resistance to afatinib. Enrolled patients should have partial response or durable stable disease of treatment response to afatinib. Various mechanisms of acquired resistance to first-generation EGFR TKIs were evaluated. Histology and cytology were reviewed. EGFR, PIK3CA, BRAF, HER2, KRAS, NRAS, MEK1, AKT2, LKB1 and JAK2 genetic alterations were evaluated by sequencing. Statistical analysis was performed using Chi-square test and Kaplan-Meier method. Conclusions T790M was detected in half of the lung adenocarcinoma after acquiring resistance to afatinib. T790M is still the major acquired

  8. Mechanisms of Acquired Resistance to ALK Inhibitors and the Rationale for Treating ALK-positive Lung Cancer.

    PubMed

    Isozaki, Hideko; Takigawa, Nagio; Kiura, Katsuyuki

    2015-01-01

    The discovery of an echinoderm microtubule-associated protein-like 4 (EML4)-anaplastic lymphoma kinase (ALK) fusion gene led to improved clinical outcomes in patients with lung cancer after the development of the first ALK-targeting agent, crizotinib. Some second-generation ALK tyrosine kinase inhibitors (TKIs), which might be more potent than crizotinib or effective on crizotinib-resistant patients, have been developed. Although these ALK-TKIs show an excellent response initially, most patients eventually acquire resistance. Therefore, careful consideration of the resistance mechanisms might lead to superior therapeutic strategies. Here, we summarize the history of ALK-TKIs and their underlying resistance mechanisms in both the preclinical and clinical settings. In addition, we discuss potential future treatment strategies in ALK-TKI-naïve and -resistant patients with lung cancer harboring the EML4-ALK fusion gene. PMID:25941796

  9. Mechanisms of Acquired Resistance to ALK Inhibitors and the Rationale for Treating ALK-positive Lung Cancer

    PubMed Central

    Isozaki, Hideko; Takigawa, Nagio; Kiura, Katsuyuki

    2015-01-01

    The discovery of an echinoderm microtubule-associated protein-like 4 (EML4)-anaplastic lymphoma kinase (ALK) fusion gene led to improved clinical outcomes in patients with lung cancer after the development of the first ALK-targeting agent, crizotinib. Some second-generation ALK tyrosine kinase inhibitors (TKIs), which might be more potent than crizotinib or effective on crizotinib-resistant patients, have been developed. Although these ALK-TKIs show an excellent response initially, most patients eventually acquire resistance. Therefore, careful consideration of the resistance mechanisms might lead to superior therapeutic strategies. Here, we summarize the history of ALK-TKIs and their underlying resistance mechanisms in both the preclinical and clinical settings. In addition, we discuss potential future treatment strategies in ALK-TKI-naïve and -resistant patients with lung cancer harboring the EML4-ALK fusion gene. PMID:25941796

  10. In Vitro Activity of ASP2397 against Aspergillus Isolates with or without Acquired Azole Resistance Mechanisms.

    PubMed

    Arendrup, Maiken Cavling; Jensen, Rasmus Hare; Cuenca-Estrella, Manuel

    2016-01-01

    ASP2397 is a new compound with a novel and as-yet-unknown target different from that of licensed antifungal agents. It has activity against Aspergillus and Candida glabrata. We compared its in vitro activity against wild-type and azole-resistant A. fumigatus and A. terreus isolates with that of amphotericin B, itraconazole, posaconazole, and voriconazole. Thirty-four isolates, including 4 wild-type A. fumigatus isolates, 24 A. fumigatus isolates with alterations in CYP51A TR/L98H (5 isolates), M220 (9 isolates), G54 (9 isolates), and HapE (1 isolate), and A. terreus isolates (2 wild-type isolates and 1 isolate with an M217I CYP51A alteration), were analyzed. EUCAST E.Def 9.2 and CLSI M38-A2 MIC susceptibility testing was performed. ASP2397 MIC50 values (in milligrams per liter, with MIC ranges in parentheses) determined by EUCAST and CLSI were 0.5 (0.25 to 1) and 0.25 (0.06 to 0.25) against A. fumigatus CYP51A wild-type isolates and were similarly 0.5 (0.125 to >4) and 0.125 (0.06 to >4) against azole-resistant A. fumigatus isolates, respectively. These values were comparable to those for amphotericin B, which were 0.25 (0.125 to 0.5) and 0.25 (0.125 to 0.25) against wild-type isolates and 0.25 (0.125 to 1) and 0.25 (0.125 to 1) against isolates with azole resistance mechanisms, respectively. In contrast, MICs for the azole compounds were elevated and highest for itraconazole: >4 (1 to >4) and 4 (0.5 to >4) against isolates with azole resistance mechanisms compared to 0.125 (0.125 to 0.25) and 0.125 (0.06 to 0.25) against wild-type isolates, respectively. ASP2397 was active against A. terreus CYP51A wild-type isolates (MIC 0.5 to 1), whereas MICs of both azole and ASP2397 were elevated for the mutant isolate. ASP2397 displayed in vitro activity against A. fumigatus and A. terreus isolates which was independent of the presence or absence of azole target gene resistance mutations in A. fumigatus. The findings are promising at a time when azole-resistant A. fumigatus

  11. A molecular model for the mechanism of acquired tamoxifen resistance in breast cancer

    PubMed Central

    Fan, Ping; Agboke, Fadeke A.; Cunliffe, Heather E.; Ramos, Pilar; Jordan, V. Craig

    2014-01-01

    Purpose: Estrogen (E2)-stimulated growth re-emerges after a c-Src inhibitor blocking E2-induced apoptosis. A resulting cell line, MCF-7:PF, is selected with features of functional estrogen receptor (ER) and over-expression of insulin-like growth factor-1 receptor beta (IGF-1Rβ). We addressed the question of whether the selective ER modulator (SERM), 4-hydroxytamoxifen (4-OHT) or other SERMs could target ER to prevent E2-stimulated growth in MCF-7:PF cells. Methods: Protein levels of receptors and signaling pathways were examined by immunoblotting. Expression of mRNA was measured through real-time RT-PCR. Recruitment of ER or nuclear receptor coactivator 3 (SRC3) to the promoter of ER-target gene was detected by chromatin-immunoprecipitation (ChIP). Results: 4-OHT and other SERMs stimulated cell growth in an ER-dependent manner. However, unlike E2, 4-OHT suppressed classical ER-target genes as does the pure antiestrogen ICI 182,780 (ICI). ChIP assay indicated that 4-OHT did not recruit ER or SRC3 to the promoter of ER-target gene, pS2. Paradoxically, 4-OHT reduced total IGF-1Rβ but increased phosphorylation of IGF-1Rβ. Mechanistic studies revealed that 4-OHT functioned as an agonist to enhance the non-genomic activity of ER and activate focal adhesion molecules to further increase phosphorylation of IGF-1Rβ. Disruption of membrane-associated signaling, IGF-1R and focal adhesion kinase (FAK), completely abolished 4-OHT-stimulated cell growth. Conclusions: This study is the first to recapitulate a cellular model in vitro of acquired tamoxifen resistance developed in athymic mice in vivo. Importantly, it provides a rationale that membrane-associated pathways may be valuable therapeutic targets for tamoxifen resistant patients in clinic. PMID:25204804

  12. Acquired resistance mechanisms to tyrosine kinase inhibitors in lung cancer with activating epidermal growth factor receptor mutation--diversity, ductility, and destiny.

    PubMed

    Suda, Kenichi; Mizuuchi, Hiroshi; Maehara, Yoshihiko; Mitsudomi, Tetsuya

    2012-12-01

    Lung cancers that harbor somatic activating mutations in the gene for the epidermal growth factor receptor (EGFR) depend on mutant EGFR for their proliferation and survival; therefore, lung cancer patients with EGFR mutations often dramatically respond to orally available EGFR tyrosine kinase inhibitors (TKIs). However, emergence of acquired resistance is virtually inevitable, thus limiting improvement in patient outcomes. To elucidate and overcome this acquired resistance, multidisciplinary basic and clinical investigational approaches have been applied, using in vitro cell line models or samples obtained from lung cancer patients treated with EGFR-TKIs. These efforts have revealed several acquired resistance mechanisms and candidates, including EGFR secondary mutations (T790M and other rare mutations), MET amplification, PTEN downregulation, CRKL amplification, high-level HGF expression, FAS-NFκB pathway activation, epithelial-mesenchymal transition, and conversion to small cell lung cancer. Interestingly, cancer cells harbor potential destiny and ductility together in acquiring resistance to EGFR-TKIs, as shown in in vitro acquired resistance models. Molecular mechanisms of "reversible EGFR-TKI tolerance" that occur in early phase EGFR-TKI exposure have been identified in cell line models. Furthermore, others have reported molecular markers that can predict response to EGFR-TKIs in clinical settings. Deeper understanding of acquired resistance mechanisms to EGFR-TKIs, followed by the development of molecular target drugs that can overcome the resistance, might turn this fatal disease into a chronic disorder. PMID:22736441

  13. Acquired Antibiotic Resistance Genes: An Overview

    PubMed Central

    van Hoek, Angela H. A. M.; Mevius, Dik; Guerra, Beatriz; Mullany, Peter; Roberts, Adam Paul; Aarts, Henk J. M.

    2011-01-01

    In this review an overview is given on antibiotic resistance (AR) mechanisms with special attentions to the AR genes described so far preceded by a short introduction on the discovery and mode of action of the different classes of antibiotics. As this review is only dealing with acquired resistance, attention is also paid to mobile genetic elements such as plasmids, transposons, and integrons, which are associated with AR genes, and involved in the dispersal of antimicrobial determinants between different bacteria. PMID:22046172

  14. Oncogene swap as a novel mechanism of acquired resistance to epidermal growth factor receptor-tyrosine kinase inhibitor in lung cancer.

    PubMed

    Mizuuchi, Hiroshi; Suda, Kenichi; Murakami, Isao; Sakai, Kazuko; Sato, Katsuaki; Kobayashi, Yoshihisa; Shimoji, Masaki; Chiba, Masato; Sesumi, Yuichi; Tomizawa, Kenji; Takemoto, Toshiki; Sekido, Yoshitaka; Nishio, Kazuto; Mitsudomi, Tetsuya

    2016-04-01

    Mutant selective epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs), such as rociletinib and AZD9291, are effective for tumors with T790M secondary mutation that become refractory to first-generation EGFR-TKI. However, acquired resistance to these prospective drugs is anticipated considering the high adaptability of cancer cells and the mechanisms remain largely obscure. Here, CNX-2006 (tool compound of rociletinib) resistant sublines were established by chronic exposure of HCC827EPR cells harboring exon 19 deletion and T790M to CNX-2006. Through the analyses of these resistant subclones, we identified two resistant mechanisms accompanied by MET amplification. One was bypass signaling by MET amplification in addition to T790M, which was inhibited by the combination of CNX-2006 and MET-TKI. Another was loss of amplified EGFR mutant allele including T790M while acquiring MET amplification. Interestingly, MET-TKI alone was able to overcome this resistance, suggesting that oncogenic dependence completely shifted from EGFR to MET. We propose describing this phenomenon as an "oncogene swap." Furthermore, we analyzed multiple lesions from a patient who died of acquired resistance to gefitinib, then found a clinical example of an oncogene swap in which the EGFR mutation was lost and a MET gene copy was gained. In conclusion, an "oncogene swap" from EGFR to MET is a novel resistant mechanism to the EGFR-TKI. This novel mechanism should be considered in order to avoid futile inhibition of the original oncogene. PMID:26845230

  15. Acquired Resistance in Barley (The Resistance Mechanism Induced by 2,6-Dichloroisonicotinic Acid Is a Phenocopy of a Genetically Based Mechanism Governing Race-Specific Powdery Mildew Resistance).

    PubMed Central

    Kogel, K. H.; Beckhove, U.; Dreschers, J.; Munch, S.; Romme, Y.

    1994-01-01

    Treatment of susceptible barley (Hordeum vulgare) seedlings with 2,6-dichloroisonicotinic acid (DCINA) induces disease resistance against the powdery mildew fungus (Erysiphe graminis f. sp. hordei). A cytological analysis of the interaction reveals the hypersensitive cell collapse in attacked, short epidermal cells, along with the accumulation of fluorescent material in papillae, that appear at the time of fungal arrest. The cell-type-specific hypersensitive reaction occurs prior to formation of haustoria, reminiscent of the mechanism identified in genetically resistant barley plants containing the functionally active Mlg gene (R. Gorg, K. Hollricher, P. Schulze-Lefert [1993] Plant J 3: 857-866). This observation indicates that the mechanism of DCINA-induced resistance is a phenocopy of the mechanism governed by the Mlg locus. The onset of acquired resistance correlates with high-level transcript accumulation of barley defense-related genes encoding pathogenesis-related protein-1, peroxidase, and chitinase but not [beta]-1,3-glucanase. Subcellular localization of peroxidase activity shows an increase in enzyme activity in the epidermal cell layer and in the intercellular fluids of barley leaves. Four out of more than 10 identified extracellular isozymes are induced by DCINA. The epidermal cell layer contains a major constitutively formed isozyme, together with two isozymes specifically induced by DCINA. The data support the hypothesis that host cell death and high-level accumulation of defense-related gene transcripts are not only commonly controlled in certain types of race-specific resistance (A. Freialdenhoven, B. Scherag, K. Hollricher, D.B. Collinge, H. Thordal-Christensen, P. Schulze-Lefert [1994] Plant Cell 6: 983-994) but also in acquired resistance, which confers protection to a broad spectrum of different pathogens. PMID:12232407

  16. Natural and acquired macrolide resistance in mycobacteria.

    PubMed

    Doucet-Populaire, F; Buriánková, K; Weiser, J; Pernodet, J-L

    2002-12-01

    The genus Mycobacterium contains two of the most important human pathogens, Mycobacterium tuberculosis and Mycobacterium leprae, the etiologic agents of tuberculosis and leprosy, respectively. Other mycobacteria are mostly saprophytic organisms, living in soil and water, but some of them can cause opportunistic infections. The increasing incidence of tuberculosis as well as infections with non-tuberculous mycobacteria (NTM) in AIDS patients has renewed interest in molecular mechanisms of drug resistance in these pathogens. Mycobacteria show a high degree of intrinsic resistance to most common antibiotics. For instance, species from the M. tuberculosis complex (MTC) are intrinsically resistant to macrolides. Nevertheless, some semi-synthetic macrolides as the erythromycin derivatives clarithromycin, azithromycin and most recently the ketolides, are active against NTM, particularly Mycobacterium avium, and some of them are widely used for infection treatment. However, shortly after the introduction of these new drugs, resistant strains appeared due to mutations in the macrolide target, the ribosome. The mycobacterial cell wall with its specific composition and structure is considered to be a major factor in promoting the natural resistance of mycobacteria to various antibiotics. However, to explain the difference in macrolide sensitivity between the MTC and NTM, the synergistic contribution of a specific resistance mechanism might be required, in addition to possible differences in cell wall permeability. This mini-review summarizes the current knowledge on the natural and acquired macrolide resistance in mycobacteria, gives an overview of potential mechanisms implicated in the intrinsic resistance and brings recent data concerning a macrolide resistance determinant in the MTC. PMID:12570741

  17. Tunable-combinatorial Mechanisms of Acquired Resistance Limit the Efficacy of BRAF/MEK Co-targeting but Result in Melanoma Drug Addiction

    PubMed Central

    Moriceau, Gatien; Hugo, Willy; Hong, Aayoung; Shi, Hubing; Kong, Xiangju; Yu, Clarissa C.; Koya, Richard C.; Samatar, Ahmed A.; Khanlou, Negar; Braun, Jonathan; Ruchalski, Kathleen; Seifert, Heike; Larkin, James; Dahlman, Kimberly B.; Johnson, Douglas B.; Algazi, Alain; Sosman, Jeffrey A.; Ribas, Antoni; Lo, Roger S.

    2014-01-01

    SUMMARY Combined BRAF and MEK targeted therapy improves upon BRAF inhibitor (BRAFi) therapy but is still beset by acquired resistance. We show that melanomas acquire resistance to combined BRAF and MEK inhibition by augmenting or combining mechanisms of single-agent BRAFi resistance. These double-drug resistance-associated genetic configurations significantly altered molecular interactions underlying MAPK pathway reactivation. V600EBRAF, expressed at supra-physiological levels because of V600EBRAF ultra-amplification, dimerized with and activated CRAF. In addition, MEK mutants enhanced interaction with over-expressed V600EBRAF via a regulatory interface at R662 of V600EBRAF. Importantly, melanoma cell lines selected for resistance to BRAFi+MEKi, but not those to BRAFi alone, displayed robust drug addiction, providing a potentially exploitable therapeutic opportunity. PMID:25600339

  18. Identification of acquired antimicrobial resistance genes

    PubMed Central

    Zankari, Ea; Hasman, Henrik; Cosentino, Salvatore; Vestergaard, Martin; Rasmussen, Simon; Lund, Ole; Aarestrup, Frank M.; Larsen, Mette Voldby

    2012-01-01

    Objectives Identification of antimicrobial resistance genes is important for understanding the underlying mechanisms and the epidemiology of antimicrobial resistance. As the costs of whole-genome sequencing (WGS) continue to decline, it becomes increasingly available in routine diagnostic laboratories and is anticipated to substitute traditional methods for resistance gene identification. Thus, the current challenge is to extract the relevant information from the large amount of generated data. Methods We developed a web-based method, ResFinder that uses BLAST for identification of acquired antimicrobial resistance genes in whole-genome data. As input, the method can use both pre-assembled, complete or partial genomes, and short sequence reads from four different sequencing platforms. The method was evaluated on 1862 GenBank files containing 1411 different resistance genes, as well as on 23 de-novo-sequenced isolates. Results When testing the 1862 GenBank files, the method identified the resistance genes with an ID = 100% (100% identity) to the genes in ResFinder. Agreement between in silico predictions and phenotypic testing was found when the method was further tested on 23 isolates of five different bacterial species, with available phenotypes. Furthermore, ResFinder was evaluated on WGS chromosomes and plasmids of 30 isolates. Seven of these isolates were annotated to have antimicrobial resistance, and in all cases, annotations were compatible with the ResFinder results. Conclusions A web server providing a convenient way of identifying acquired antimicrobial resistance genes in completely sequenced isolates was created. ResFinder can be accessed at www.genomicepidemiology.org. ResFinder will continuously be updated as new resistance genes are identified. PMID:22782487

  19. Chemical Proteomics Uncovers EPHA2 as a Mechanism of Acquired Resistance to Small Molecule EGFR Kinase Inhibition.

    PubMed

    Koch, Heiner; Busto, M Estela Del Castillo; Kramer, Karl; Médard, Guillaume; Kuster, Bernhard

    2015-06-01

    Tyrosine kinase inhibitors (TKIs) have become an important therapeutic option for treating several forms of cancer. Gefitinib, an inhibitor of the epidermal growth factor receptor (EGFR), is in clinical use for treating non-small cell lung cancer (NSCLC) harboring activating EGFR mutations. However, despite high initial response rates, many patients develop resistance to gefitinib. The molecular mechanisms of TKI resistance often remain unclear. Here, we describe a chemical proteomic approach comprising kinase affinity purification (kinobeads) and quantitative mass spectrometry for the identification of kinase inhibitor resistance mechanisms in cancer cells. We identified the previously described amplification of MET and found EPHA2 to be more than 10-fold overexpressed (p < 0.001) in gefitinib-resistant HCC827 cells suggesting a potential role in developing resistance. siRNA-mediated EPHA2 knock-down or treating cells with the multikinase inhibitor dasatinib restored sensitivity to gefitinib. Of all dasatinib targets, EPHA2 exhibited the most drastic effect (p < 0.001). In addition, EPHA2 knockdown or ephrin-A1 treatment of resistant cells decreased FAK phosphorylation and cell migration. These findings confirm EPHA2 as an actionable drug target, provide a rational basis for drug combination approaches, and indicate that chemical proteomics is broadly applicable for the discovery of kinase inhibitor resistance. PMID:25963923

  20. Integrated genomic approaches identify upregulation of SCRN1 as a novel mechanism associated with acquired resistance to erlotinib in PC9 cells harboring oncogenic EGFR mutation

    PubMed Central

    Kim, Nayoung; Cho, Ahye; Watanabe, Hideo; Choi, Yoon-La; Aziz, Meraj; Kassner, Michelle; Joung, Je-Gun; Park, Angela KJ; Francis, Joshua M.; Bae, Joon Seol; Ahn, Soo-min; Kim, Kyoung-Mee; Park, Joon Oh; Park, Woong-Yang; Ahn, Myung-Ju; Park, Keunchil; Koo, Jaehyung; Yin, Hongwei Holly; Cho, Jeonghee

    2016-01-01

    Therapies targeting the tyrosine kinase activity of Epidermal Growth Factor Receptor (EGFR) have been proven to be effective in treating a subset of non-small cell lung cancer (NSCLC) patients harboring activating EGFR mutations. Inevitably these patients develop resistance to the EGFR-targeted tyrosine kinase inhibitors (TKIs). Here, we performed integrated genomic analyses using an in vitro system to uncover alternative genomic mechanisms responsible for acquired resistance to EGFR-TKIs. Specifically, we identified 80 genes whose expression is significantly increased in the erlotinib-resistant clones. RNAi-based systematic synthetic lethal screening of these candidate genes revealed that suppression of one upregulated transcript, SCRN1, a secernin family member, restores sensitivity to erlotinib by enhancing inhibition of PI3K/AKT signaling pathway. Furthermore, immunohistochemical analysis revealed increased levels of SCRN1 in 5 of 11 lung tumor specimens from EGFR-TKIs resistant patients. Taken together, we propose that upregulation of SCRN1 is an additional mechanism associated with acquired resistance to EGFR-TKIs and that its suppression serves as a novel therapeutic strategy to overcome drug resistance in these patients. PMID:26883194

  1. Signal regulators of systemic acquired resistance

    PubMed Central

    Gao, Qing-Ming; Zhu, Shifeng; Kachroo, Pradeep; Kachroo, Aardra

    2015-01-01

    Salicylic acid (SA) is an important phytohormone that plays a vital role in a number of physiological responses, including plant defense. The last two decades have witnessed a number of breakthroughs related to biosynthesis, transport, perception and signaling mediated by SA. These findings demonstrate that SA plays a crictical role in both local and systemic defense responses. Systemic acquired resistance (SAR) is one such SA-dependent response. SAR is a long distance signaling mechanism that provides broad spectrum and long-lasting resistance to secondary infections throughout the plant. This unique feature makes SAR a highly desirable trait in crop production. This review summarizes the recent advances in the role of SA in SAR and discusses its relationship to other SAR inducers. PMID:25918514

  2. Acquired resistance to immunotherapy and future challenges.

    PubMed

    Restifo, Nicholas P; Smyth, Mark J; Snyder, Alexandra

    2016-02-01

    Advances in immunotherapy have resulted in remarkable clinical responses in some patients. However, one of the biggest challenges in cancer therapeutics is the development of resistant disease and disease progression on or after therapy. Given that many patients have now received various types of immunotherapy, we asked three scientists to give their views on the current evidence for whether acquired resistance to immunotherapy exists in patients and the future challenges posed by immunotherapy. PMID:26822578

  3. Targets for Combating the Evolution of Acquired Antibiotic Resistance.

    PubMed

    Culyba, Matthew J; Mo, Charlie Y; Kohli, Rahul M

    2015-06-16

    Bacteria possess a remarkable ability to rapidly adapt and evolve in response to antibiotics. Acquired antibiotic resistance can arise by multiple mechanisms but commonly involves altering the target site of the drug, enzymatically inactivating the drug, or preventing the drug from accessing its target. These mechanisms involve new genetic changes in the pathogen leading to heritable resistance. This recognition underscores the importance of understanding how such genetic changes can arise. Here, we review recent advances in our understanding of the processes that contribute to the evolution of antibiotic resistance, with a particular focus on hypermutation mediated by the SOS pathway and horizontal gene transfer. We explore the molecular mechanisms involved in acquired resistance and discuss their viability as potential targets. We propose that additional studies into these adaptive mechanisms not only can provide insights into evolution but also can offer a strategy for potentiating our current antibiotic arsenal. PMID:26016604

  4. Targets for Combating the Evolution of Acquired Antibiotic Resistance

    PubMed Central

    2015-01-01

    Bacteria possess a remarkable ability to rapidly adapt and evolve in response to antibiotics. Acquired antibiotic resistance can arise by multiple mechanisms but commonly involves altering the target site of the drug, enzymatically inactivating the drug, or preventing the drug from accessing its target. These mechanisms involve new genetic changes in the pathogen leading to heritable resistance. This recognition underscores the importance of understanding how such genetic changes can arise. Here, we review recent advances in our understanding of the processes that contribute to the evolution of antibiotic resistance, with a particular focus on hypermutation mediated by the SOS pathway and horizontal gene transfer. We explore the molecular mechanisms involved in acquired resistance and discuss their viability as potential targets. We propose that additional studies into these adaptive mechanisms not only can provide insights into evolution but also can offer a strategy for potentiating our current antibiotic arsenal. PMID:26016604

  5. Tetracycline resistance genes acquired at birth.

    PubMed

    Alicea-Serrano, Angela M; Contreras, Mónica; Magris, Magda; Hidalgo, Glida; Dominguez-Bello, Maria G

    2013-06-01

    Newborns acquire their first microbiota at birth. Maternal vaginal or skin bacteria colonize newborns delivered vaginally or by C-section, respectively (Dominguez-Bello et al. 2010 #884). We aimed to determine differences in the presence of four tetracycline (tet) resistance genes, in the microbes of ten newborns and in the mouth and vagina of their mothers, at the time of birth. DNA was amplified by PCR with primers specific for [tet(M), tet(O), tet(Q), and tet(W)]. Maternal vaginas harbored all four tet resistance genes, but most commonly tet(M) and tet(O) (63 and 38 %, respectively). Genes coding for tet resistance differed by birth mode, with 50 % of vaginally delivered babies had tet(M) and tet(O) and 16 and 13 % of infants born by C-section had tet(O) and tet(W), respectively. Newborns acquire antibiotic resistance genes at birth, and the resistance gene profile varies by mode of delivery. PMID:23483141

  6. Acquired inducible antimicrobial resistance in Gram-positive bacteria

    PubMed Central

    Chancey, Scott T; Zähner, Dorothea; Stephens, David S

    2012-01-01

    A major contributor to the emergence of antibiotic resistance in Gram-positive bacterial pathogens is the expansion of acquired, inducible genetic elements. Although acquired, inducible antibiotic resistance is not new, the interest in its molecular basis has been accelerated by the widening distribution and often ‘silent’ spread of the elements responsible, the diagnostic challenges of such resistance and the mounting limitations of available agents to treat Gram-positive infections. Acquired, inducible antibiotic resistance elements belong to the accessory genome of a species and are horizontally acquired by transformation/recombination or through the transfer of mobile DNA elements. The two key, but mechanistically very different, induction mechanisms are: ribosome-sensed induction, characteristic of the macrolide–lincosamide–streptogramin B antibiotics and tetracycline resistance, leading to ribosomal modifications or efflux pump activation; and resistance by cell surface-associated sensing of β-lactams (e.g., oxacillin), glycopeptides (e.g., vancomycin) and the polypeptide bacitracin, leading to drug inactivation or resistance due to cell wall alterations. PMID:22913355

  7. Inducible and Acquired Clarithromycin Resistance in the Mycobacterium abscessus Complex

    PubMed Central

    Rubio, Marc; March, Francesca; Garrigó, Montserrat; Moreno, Carmen; Español, Montserrat; Coll, Pere

    2015-01-01

    Purpose Clarithromycin was considered the cornerstone for the treatment of Mycobacterium abscessus complex infections. Genetic resistance mechanisms have been described and many experts propose amikacin as an alternative. Nevertheless, clarithromycin has several advantages; therefore, it is necessary to identify the non-functional erm(41) allele to determine the most suitable treatment. The aims of this study were to characterize the molecular mechanisms of clarithromycin resistance in a collection of Mycobacterium abscessus complex isolates and to verify the relationship between these mechanisms and the antibiogram. Materials and Methods Clinical isolates of M. abscessus complex (n = 22) from 16 patients were identified using four housekeeping genes (rpoB, secA1, sodA and hsp65), and their genetic resistance was characterized by studying erm(41) and rrl genes. Nine strains were recovered from the clinical isolates and subjected to E-test and microdilution clarithromycin susceptibility tests, with readings at 3, 7 and 14 days. Results We classified 11/16 (68.8%) M. abscessus subsp. abscessus, 4/16 (25.0%) M. abscessus subsp. bolletii, and 1/16 (6.3%) M. abscessus subsp. massiliense. T28 erm(41) allele was observed in 8 Mycobacterium abscessus subps. abscessus and 3 Mycobacterium abscessus subsp. bolletii. One strain of M. abscessus subsp. bolletii had an erm(41) gene truncated and was susceptible to clarithromycin. No mutations were observed in rrl gene first isolates. In three patients, follow-up of initial rrl wild-type strains showed acquired resistance. Conclusions Most clinical isolates of M. abscessus complex had inducible resistance to clarithromycin and total absence of constitutive resistance. Our findings showed that the acquisition of resistance mutations in rrl gene was associated with functional and non-functional erm(41) gene. Caution is needed when using erm(41) sequencing alone to identify M. abscessus subspecies. This study reports an acquired

  8. Elevated hepatocyte growth factor expression as an autocrine c-Met activation mechanism in acquired resistance to sorafenib in hepatocellular carcinoma cells.

    PubMed

    Firtina Karagonlar, Zeynep; Koc, Dogukan; Iscan, Evin; Erdal, Esra; Atabey, Neşe

    2016-04-01

    Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and the third leading cause of cancer-related deaths worldwide. Limitations in HCC treatment result due to poor prognosis and resistance against traditional radiotherapy and chemotherapies. The multikinase inhibitor sorafenib is the only FDA approved drug available for advanced HCC patients, and development of second-line treatment options for patients who cannot tolerate or develop resistance to sorafenib is an urgent medical need. In this study, we established sorafenib-resistant cells from Huh7 and Mahlavu cell lines by long-term sorafenib exposure. Sorafenib-resistant HCC cells acquired spindle-shape morphology, upregulated mesenchymal markers, and showed significant increase in both migration and invasion abilities compared to their parental counterparts. Moreover, after long-term sorafenib treatment, HCC cells showed induction of hepatocyte growth factor (HGF) synthesis and secretion along with increased levels of c-Met kinase and its active phosphorylated form, indicating autocrine activation of HGF/c-Met signaling. Importantly, the combined treatment of the resistant cells with c-Met kinase inhibitor SU11274 and HGF neutralizing antibody significantly reversed the increased invasion ability of the cells. The combined treatment also significantly augmented sorafenib-induced apoptosis, suggesting restoration of sorafenib sensitivity. These results describe, for the first time, compensatory upregulation of HGF synthesis leading to autocrine activation of HGF/c-Met signaling as a novel cellular strategy in the acquisition of sorafenib resistance. Therefore, we suggest that combinatorial therapeutic strategies with HGF and c-Met inhibitors comprise promising candidates for overcoming sorafenib resistance. PMID:26790028

  9. Transcriptional plasticity promotes primary and acquired resistance to BET inhibition.

    PubMed

    Rathert, Philipp; Roth, Mareike; Neumann, Tobias; Muerdter, Felix; Roe, Jae-Seok; Muhar, Matthias; Deswal, Sumit; Cerny-Reiterer, Sabine; Peter, Barbara; Jude, Julian; Hoffmann, Thomas; Boryń, Łukasz M; Axelsson, Elin; Schweifer, Norbert; Tontsch-Grunt, Ulrike; Dow, Lukas E; Gianni, Davide; Pearson, Mark; Valent, Peter; Stark, Alexander; Kraut, Norbert; Vakoc, Christopher R; Zuber, Johannes

    2015-09-24

    Following the discovery of BRD4 as a non-oncogene addiction target in acute myeloid leukaemia (AML), bromodomain and extra terminal protein (BET) inhibitors are being explored as a promising therapeutic avenue in numerous cancers. While clinical trials have reported single-agent activity in advanced haematological malignancies, mechanisms determining the response to BET inhibition remain poorly understood. To identify factors involved in primary and acquired BET resistance in leukaemia, here we perform a chromatin-focused RNAi screen in a sensitive MLL-AF9;Nras(G12D)-driven AML mouse model, and investigate dynamic transcriptional profiles in sensitive and resistant mouse and human leukaemias. Our screen shows that suppression of the PRC2 complex, contrary to effects in other contexts, promotes BET inhibitor resistance in AML. PRC2 suppression does not directly affect the regulation of Brd4-dependent transcripts, but facilitates the remodelling of regulatory pathways that restore the transcription of key targets such as Myc. Similarly, while BET inhibition triggers acute MYC repression in human leukaemias regardless of their sensitivity, resistant leukaemias are uniformly characterized by their ability to rapidly restore MYC transcription. This process involves the activation and recruitment of WNT signalling components, which compensate for the loss of BRD4 and drive resistance in various cancer models. Dynamic chromatin immunoprecipitation sequencing and self-transcribing active regulatory region sequencing of enhancer profiles reveal that BET-resistant states are characterized by remodelled regulatory landscapes, involving the activation of a focal MYC enhancer that recruits WNT machinery in response to BET inhibition. Together, our results identify and validate WNT signalling as a driver and candidate biomarker of primary and acquired BET resistance in leukaemia, and implicate the rewiring of transcriptional programs as an important mechanism promoting

  10. Transcriptional plasticity promotes primary and acquired resistance to BET inhibition

    PubMed Central

    Neumann, Tobias; Muerdter, Felix; Roe, Jae-Seok; Muhar, Matthias; Deswal, Sumit; Cerny-Reiterer, Sabine; Peter, Barbara; Jude, Julian; Hoffmann, Thomas; Boryń, Łukasz M.; Axelsson, Elin; Schweifer, Norbert; Tontsch-Grunt, Ulrike; Dow, Lukas E.; Gianni, Davide; Pearson, Mark; Valent, Peter; Stark, Alexander; Kraut, Norbert; Vakoc, Christopher R.; Zuber, Johannes

    2016-01-01

    Summary Following the discovery of BRD4 as a non-oncogene addiction target in acute myeloid leukemia (AML)1,2, BET inhibitors are being explored as promising therapeutic avenue in numerous cancers3–5. While clinical trials have reported single-agent activity in advanced hematologic malignancies6, mechanisms determining the response to BET inhibition remain poorly understood. To identify factors involved in primary and acquired BET resistance in leukemia, we performed a chromatin-focused RNAi screen in a sensitive MLL/AF9; NrasG12D -driven AML model, and investigated dynamic transcriptional profiles in sensitive and resistant murine and human leukemias. Our screen reveals that suppression of the PRC2 complex, contrary to effects in other contexts, promotes BET inhibitor resistance in AML. PRC2 suppression does not directly affect the regulation of Brd4-dependent transcripts, but facilitates the remodeling of regulatory pathways that restore the transcription of key targets such as Myc. Similarly, while BET inhibition triggers acute MYC repression in human leukemias regardless of their sensitivity, resistant leukemias are uniformly characterized by their ability to rapidly restore MYC transcription. This process involves the activation and recruitment of WNT signaling components, which compensate for the loss of BRD4 and drive resistance in various cancer models. Dynamic ChIP- and STARR-seq enhancer profiles reveal that BET-resistant states are characterized by remodeled regulatory landscapes, involving the activation of a focal MYC enhancer that recruits WNT machinery in response to BET inhibition. Together, our results identify and validate WNT signaling as a driver and candidate biomarker of primary and acquired BET resistance in leukemia, and implicate the rewiring of transcriptional programs as an important mechanism promoting resistance to BET inhibitors and, potentially, other chromatin-targeted therapies. PMID:26367798

  11. Mechanisms of acquired resistance to the quinazoline thymidylate synthase inhibitor ZD1694 (Tomudex) in one mouse and three human cell lines.

    PubMed Central

    Jackman, A. L.; Kelland, L. R.; Kimbell, R.; Brown, M.; Gibson, W.; Aherne, G. W.; Hardcastle, A.; Boyle, F. T.

    1995-01-01

    Four cell lines, the mouse L1210 leukaemia, the human W1L2 lymphoblastoid and two human ovarian (CH1 and 41M) cell lines, were made resistant to ZD1694 (Tomudex) by continual exposure to incremental doses of the drug. A 500-fold increase in thymidylate synthase (TS) activity is the primary mechanism of resistance to ZD1694 in the W1L2:RD1694 cell line, which is consequently highly cross-resistant to other folate-based TS inhibitors, including BW1843U89, LY231514 and AG337, but sensitive to antifolates with other enzyme targets. The CH1:RD1694 cell line is 14-fold resistant to ZD1694, largely accounted for by the 4.2-fold increase in TS activity. Cross-resistance was observed to other TS inhibitors, including 5-fluorodeoxyuridine (FdUrd). 41M:RD1694 cells, when exposed to 0.1 microM [3H]ZD1694, accumulated approximately 20-fold less 3H-labelled material over 24 h than the parental line. Data are consistent with this being the result of impaired transport of the drug via the reduced folate/methotrexate carrier. Resistance was therefore observed to methotrexate but not to CB3717, a compound known to use this transport mechanism poorly. The mouse L1210:RD1694 cell line does not accumulate ZD1694 or Methotrexate (MTX) polyglutamates. Folylpolyglutamate synthetase substrate activity (using ZD1694 as the substrate) was decreased to approximately 13% of that observed in the parental line. Cross-resistance was found to those compounds known to be active through polyglutamation. PMID:7537518

  12. Adaptive and Acquired Resistance to EGFR Inhibitors Converge on the MAPK Pathway

    PubMed Central

    Ma, Pengfei; Fu, Yujie; Chen, Minjiang; Jing, Ying; Wu, Jie; Li, Ke; Shen, Ying; Gao, Jian-Xin; Wang, Mengzhao; Zhao, Xiaojing; Zhuang, Guanglei

    2016-01-01

    Both adaptive and acquired resistance significantly limits the efficacy of the epidermal growth factor receptor (EGFR) kinase inhibitors. However, the distinct or common mechanisms of adaptive and acquired resistance have not been fully characterized. Here, through systematic modeling of erlotinib resistance in lung cancer, we found that feedback reactivation of MAPK signaling following erlotinib treatment, which was dependent on the MET receptor, contributed to the adaptive resistance of EGFR inhibitors. Interestingly, acquired resistance to erlotinib was also associated with the MAPK pathway activation as a result of CRAF or NRAS amplification. Consequently, combined inhibition of EGFR and MAPK impeded the development of both adaptive and acquired resistance. These observations demonstrate that adaptive and acquired resistance to EGFR inhibitors can converge on the same pathway and credential cotargeting EGFR and MAPK as a promising therapeutic approach in EGFR mutant tumors. PMID:27279914

  13. Mechanisms of drug resistance: quinolone resistance

    PubMed Central

    Hooper, David C.; Jacoby, George A.

    2015-01-01

    Quinolone antimicrobials are synthetic and widely used in clinical medicine. Resistance emerged with clinical use and became common in some bacterial pathogens. Mechanisms of resistance include two categories of mutation and acquisition of resistance-conferring genes. Resistance mutations in one or both of the two drug target enzymes, DNA gyrase and DNA topoisomerase IV, are commonly in a localized domain of the GyrA and ParE subunits of the respective enzymes and reduce drug binding to the enzyme-DNA complex. Other resistance mutations occur in regulatory genes that control the expression of native efflux pumps localized in the bacterial membrane(s). These pumps have broad substrate profiles that include quinolones as well as other antimicrobials, disinfectants, and dyes. Mutations of both types can accumulate with selection pressure and produce highly resistant strains. Resistance genes acquired on plasmids can confer low-level resistance that promotes the selection of mutational high-level resistance. Plasmid-encoded resistance is due to Qnr proteins that protect the target enzymes from quinolone action, one mutant aminoglycoside-modifying enzyme that also modifies certain quinolones, and mobile efflux pumps. Plasmids with these mechanisms often encode additional antimicrobial resistances and can transfer multidrug resistance that includes quinolones. Thus, the bacterial quinolone resistance armamentarium is large. PMID:26190223

  14. Mechanisms of drug resistance: quinolone resistance.

    PubMed

    Hooper, David C; Jacoby, George A

    2015-09-01

    Quinolone antimicrobials are synthetic and widely used in clinical medicine. Resistance emerged with clinical use and became common in some bacterial pathogens. Mechanisms of resistance include two categories of mutation and acquisition of resistance-conferring genes. Resistance mutations in one or both of the two drug target enzymes, DNA gyrase and DNA topoisomerase IV, are commonly in a localized domain of the GyrA and ParE subunits of the respective enzymes and reduce drug binding to the enzyme-DNA complex. Other resistance mutations occur in regulatory genes that control the expression of native efflux pumps localized in the bacterial membrane(s). These pumps have broad substrate profiles that include quinolones as well as other antimicrobials, disinfectants, and dyes. Mutations of both types can accumulate with selection pressure and produce highly resistant strains. Resistance genes acquired on plasmids can confer low-level resistance that promotes the selection of mutational high-level resistance. Plasmid-encoded resistance is due to Qnr proteins that protect the target enzymes from quinolone action, one mutant aminoglycoside-modifying enzyme that also modifies certain quinolones, and mobile efflux pumps. Plasmids with these mechanisms often encode additional antimicrobial resistances and can transfer multidrug resistance that includes quinolones. Thus, the bacterial quinolone resistance armamentarium is large. PMID:26190223

  15. Evolution of acquired resistance to anti-cancer therapy

    PubMed Central

    Foo, Jasmine; Michor, Franziska

    2014-01-01

    Acquired drug resistance is a major limitation for the successful treatment of cancer. Resistance can emerge due to a variety of reasons including host environmental factors as well as genetic or epigenetic alterations in the cancer cells. Evolutionary theory has contributed to the understanding of the dynamics of resistance mutations in a cancer cell population, the risk of resistance pre-existing before the initiation of therapy, the composition of drug cocktails necessary to prevent the emergence of resistance, and optimum drug administration schedules for patient populations at risk of evolving acquired resistance. Here we review recent advances towards elucidating the evolutionary dynamics of acquired drug resistance and outline how evolutionary thinking can contribute to outstanding questions in the field. PMID:24681298

  16. Nuclear EGFR Contributes to Acquired Resistance to Cetuximab

    PubMed Central

    Li, Chunrong; Iida, Mari; Dunn, Emily F.; Ghia, Amol J.; Wheeler, Deric L.

    2010-01-01

    Epidermal growth factor receptor (EGFR) is a ubiquitously expressed receptor tyrosine kinase involved in the etiology of several human cancers. Cetuximab is an EGFR blocking-antibody that has been approved for the treatment of patients with cancers of the head and neck (HNSCC) and metastatic colorectal cancer (mCRC). Previous reports have shown that EGFR translocation to the nucleus is associated with cell proliferation. Here we investigated mechanisms of acquired resistance to cetuximab using a model derived from the non-small cell lung cancer line H226. We demonstrated that cetuximab-resistant cells overexpress HER family ligands including epidermal growth factor (EGF), amphiregulin (AR), heparin-binding EGF (HB-EGF) and β-cellulin. Overexpression of these ligands is associated with the nuclear translocation of the EGFR and this process was mediated by the Src family kinases (SFK). Treatment of cetuximab-resistant cells with the SFK inhibitor, dasatinib, resulted in loss of nuclear EGFR, increased membrane expression of the EGFR and re-sensitization to cetuximab. In addition, expression of a nuclear localization sequence tagged EGFR in cetuximab-sensitive cells increased resistance to cetuximab both in vitro and in mouse xenografts. Collectively, these data suggest that nuclear expression of EGFR may be an important molecular determinant of resistance to cetuximab therapy and provides a rationale for investigating nuclear EGFR as a biomarker for cetuximab response. Further, these data suggest a rationale for the design of clinical trials that examine the value of treating patients with cetuximab-resistant tumors with inhibitors of SFKs in combination with cetuximab. PMID:19684613

  17. Nuclear EGFR contributes to acquired resistance to cetuximab.

    PubMed

    Li, C; Iida, M; Dunn, E F; Ghia, A J; Wheeler, D L

    2009-10-29

    Epidermal growth factor receptor (EGFR) is a ubiquitously expressed receptor tyrosine kinase involved in the etiology of several human cancers. Cetuximab is an EGFR-blocking antibody that has been approved for the treatment of patients with head and neck squamous cell carcinoma and metastatic colorectal cancer. Previous reports have shown that EGFR translocation to the nucleus is associated with cell proliferation. Here we investigated mechanisms of acquired resistance to cetuximab using a model derived from the non-small cell lung cancer line H226. We demonstrated that cetuximab-resistant cells overexpress HER family ligands including epidermal growth factor (EGF), amphiregulin, heparin-binding EGF and beta-cellulin. Overexpression of these ligands is associated with the nuclear translocation of the EGFR and this process was mediated by the Src family kinases (SFK). Treatment of cetuximab-resistant cells with the SFK inhibitor, dasatinib, resulted in loss of nuclear EGFR, increased membrane expression of the EGFR and resensitization to cetuximab. In addition, expression of a nuclear localization sequence-tagged EGFR in cetuximab-sensitive cells increased resistance to cetuximab both in vitro and in mouse xenografts. Collectively, these data suggest that nuclear expression of EGFR may be an important molecular determinant of resistance to cetuximab therapy and provides a rationale for investigating nuclear EGFR as a biomarker for cetuximab response. Further, these data suggest a rationale for the design of clinical trials that examine the value of treating patients with cetuximab-resistant tumors with inhibitors of SFKs in combination with cetuximab. PMID:19684613

  18. Acquired Drug Resistance in Mycobacterium tuberculosis and Poor Outcomes among Patients with Multidrug-Resistant Tuberculosis

    PubMed Central

    Kipiani, Maia; Mirtskhulava, Veriko; Tukvadze, Nestani; Magee, Matthew J.; Blumberg, Henry M.

    2015-01-01

    Rates and risk factors for acquired drug resistance and association with outcomes among patients with multidrug-resistant tuberculosis (MDR TB) are not well defined. In an MDR TB cohort from the country of Georgia, drug susceptibility testing for second-line drugs (SLDs) was performed at baseline and every third month. Acquired resistance was defined as any SLD whose status changed from susceptible at baseline to resistant at follow-up. Among 141 patients, acquired resistance in Mycobacterium tuberculosis was observed in 19 (14%); prevalence was 9.1% for ofloxacin and 9.8% for capreomycin or kanamycin. Baseline cavitary disease and resistance to >6 drugs were associated with acquired resistance. Patients with M. tuberculosis that had acquired resistance were at significantly increased risk for poor treatment outcome compared with patients without these isolates (89% vs. 36%; p<0.01). Acquired resistance occurs commonly among patients with MDR TB and impedes successful treatment outcomes. PMID:25993036

  19. A Research-Inspired Laboratory Sequence Investigating Acquired Drug Resistance

    ERIC Educational Resources Information Center

    Taylor, Elizabeth Vogel; Fortune, Jennifer A.; Drennan, Catherine L.

    2010-01-01

    Here, we present a six-session laboratory exercise designed to introduce students to standard biochemical techniques in the context of investigating a high impact research topic, acquired resistance to the cancer drug Gleevec. Students express a Gleevec-resistant mutant of the Abelson tyrosine kinase domain, the active domain of an oncogenic…

  20. Dominant mechanisms of primary resistance differ from dominant mechanisms of secondary resistance to targeted therapies.

    PubMed

    Asić, Ksenija

    2016-01-01

    The effectiveness of targeted therapies is currently limited, as almost all patients eventually acquire resistance within year/year and a half from therapy initiation and a small subset of a patients fail to respond at all, demonstrating intrinsic resistance. The aim of this review was to determine the potential common features and differences between the mechanisms of intrinsic and acquired resistance to targeted therapies by analyzing established resistance-generating alterations for ten FDA-approved targeted drugs. The frequency of alterations underlying intrinsic and acquired resistance shows distinctive pattern, where dominant mechanisms of intrinsic resistance include aberrations of signals downstream or upstream of the targeted protein and dominant mechanisms of acquired resistance refer to lesions in the target itself or alterations of signals at target-level that can mimic or compensate for target function. It appears that during the evolution of acquired resistance, the tumor cell is inclined to preserve the same oncogene addiction on a targeted protein it had prior to drug administration. On the other hand, intrinsic resistance develops early in tumorogenesis and is based on randomly selected mutated signals between targeted and non-targeted signaling pathways, leading to the acquisition of cancer hallmarks. In general, there is an overlap between the mechanisms of intrinsic and acquired resistance, but the occurrence frequency and distribution of alterations underlying intrinsic and acquired resistance to targeted therapies are significantly different. Focus should be placed on different group of genes in pursuing predictive markers for intrinsic and acquired resistance to targeted therapies. PMID:26364890

  1. Overcoming acquired resistance to kinase inhibition: the cases of EGFR, ALK and BRAF.

    PubMed

    Giroux, Simon

    2013-01-15

    In the past decade, several kinase inhibitors have been approved based on their clinical benefit for cancer patients. Unfortunately, in many cases, patients develop resistance to these agents via secondary mutations and alternative mechanisms. This review will focus on the cases of acquired resistance to EGFR and ALK inhibitors for non-small cell lung cancer patients and BRAF inhibitors for melanoma patients. I will overview the main causes of acquired resistance, and explore the chemical scaffolds as well as combination of drugs, used to tackle these major causes of resistance. PMID:23245516

  2. Signaling by small metabolites in systemic acquired resistance.

    PubMed

    Shah, Jyoti; Chaturvedi, Ratnesh; Chowdhury, Zulkarnain; Venables, Barney; Petros, Robby A

    2014-08-01

    Plants can retain the memory of a prior encounter with a pest. This memory confers upon a plant the ability to subsequently activate defenses more robustly when challenged by a pest. In plants that have retained the memory of a prior, localized, foliar infection by a pathogen, the pathogen-free distal organs develop immunity against subsequent infections by a broad-spectrum of pathogens. The long-term immunity conferred by this mechanism, which is termed systemic acquired resistance (SAR), is inheritable over a few generations. Signaling mediated by the phenolic metabolite salicylic acid (SA) is critical for the manifestation of SAR. Recent studies have described the involvement of additional small metabolites in SAR signaling, including methyl salicylate, the abietane diterpenoid dehydroabietinal, the lysine catabolite pipecolic acid, a glycerol-3-phosphate-dependent factor and the dicarboxylic acid azelaic acid. Many of these metabolites can be systemically transported through the plant and probably facilitate communication by the primary infected tissue with the distal tissues, which is essential for the activation of SAR. Some of these metabolites have been implicated in the SAR-associated rapid activation of defenses in response to subsequent exposure to the pathogen, a mechanism termed priming. Here, we summarize the role of these signaling metabolites in SAR, and the relationship between them and SA signaling in SAR. PMID:24506415

  3. Staphylococci in community-acquired infections: Increased resistance to penicillin.

    PubMed

    Hughes, G B; Chidi, C C; Macon, W L

    1976-04-01

    One hundred patients with community-acquired staphylococcal infections of the skin and soft tissues were treated in the Emergency Ward of Cleveland Metropolitan General Hospital from June to October of 1974. Each staphylococcal infection was considered community-acquired if, within two weeks prior to being treated for the first time, the patient had not received antibiotics, had not been hospitalized, and had not been in contact with other recently hospitalized persons. Of 100 community-acquired staphylococcal infections, 85 were resistant to penicillin. Almost no resistance to other tested antibiotics was observed. Unless indicated otherwise by bacteriologic testing, penicillin is a poor drug of choice in those skin and soft tissue infections suspected of harboring staphylococci. PMID:1267491

  4. Irreversible inhibitors of the EGF receptor may circumvent acquired resistance to gefitinib

    PubMed Central

    Kwak, Eunice L.; Sordella, Raffaella; Bell, Daphne W.; Godin-Heymann, Nadia; Okimoto, Ross A.; Brannigan, Brian W.; Harris, Patricia L.; Driscoll, David R.; Fidias, Panos; Lynch, Thomas J.; Rabindran, Sridhar K.; McGinnis, John P.; Wissner, Allan; Sharma, Sreenath V.; Isselbacher, Kurt J.; Settleman, Jeffrey; Haber, Daniel A.

    2005-01-01

    Non-small cell lung cancers (NSCLCs) with activating mutations in the kinase domain of the epidermal growth factor receptor (EGFR) demonstrate dramatic, but transient, responses to the reversible tyrosine kinase inhibitors gefitinib (Iressa) and erlotinib (Tarceva). Some recurrent tumors have a common secondary mutation in the EGFR kinase domain, T790M, conferring drug resistance, but in other cases the mechanism underlying acquired resistance is unknown. In studying multiple sites of recurrent NSCLCs, we detected T790M in only a small percentage of tumor cells. To identify additional mechanisms of acquired resistance to gefitinib, we used NSCLC cells harboring an activating EGFR mutation to generate multiple resistant clones in vitro. These drug-resistant cells demonstrate continued dependence on EGFR and ERBB2 signaling for their viability and have not acquired secondary EGFR mutations. However, they display increased internalization of ligand-activated EGFR, consistent with altered receptor trafficking. Although gefitinib-resistant clones are cross-resistant to related anilinoquinazolines, they demonstrate sensitivity to a class of irreversible inhibitors of EGFR. These inhibitors also show effective inhibition of signaling by T790M-mutant EGFR and killing of NSCLC cells with the T790M mutation. Both mechanisms of gefitinib resistance are therefore circumvented by irreversible tyrosine kinase inhibitors. Our findings suggest that one of these, HKI-272, may prove highly effective in the treatment of EGFR-mutant NSCLCs, including tumors that have become resistant to gefitinib or erlotinib. PMID:15897464

  5. Response and Acquired Resistance to Everolimus in Anaplastic Thyroid Cancer

    PubMed Central

    Wagle, Nikhil; Grabiner, Brian C.; Van Allen, Eliezer M.; Amin-Mansour, Ali; Taylor-Weiner, Amaro; Rosenberg, Mara; Gray, Nathanael; Barletta, Justine A.; Guo, Yanan; Swanson, Scott J.; Ruan, Daniel T.; Hanna, Glenn J.; Haddad, Robert I.; Getz, Gad; Kwiatkowski, David J.; Carter, Scott L.; Sabatini, David M.; Jänne, Pasi A.; Garraway, Levi A.; Lorch, Jochen H.

    2015-01-01

    SUMMARY Everolimus, an inhibitor of the mammalian target of rapamycin (mTOR), is effective in treating tumors harboring alterations in the mTOR pathway. Mechanisms of resistance to everolimus remain undefined. Resistance developed in a patient with metastatic anaplastic thyroid carcinoma after an extraordinary 18-month response. Whole-exome sequencing of pretreatment and drug-resistant tumors revealed a nonsense mutation in TSC2, a negative regulator of mTOR, suggesting a mechanism for exquisite sensitivity to everolimus. The resistant tumor also harbored a mutation in MTOR that confers resistance to allosteric mTOR inhibition. The mutation remains sensitive to mTOR kinase inhibitors. PMID:25295501

  6. Extensive Drug Resistance Acquired During Treatment of Multidrug-Resistant Tuberculosis

    PubMed Central

    Cegielski, J. Peter; Dalton, Tracy; Yagui, Martin; Wattanaamornkiet, Wanpen; Volchenkov, Grigory V.; Via, Laura E.; Van Der Walt, Martie; Tupasi, Thelma; Smith, Sarah E.; Odendaal, Ronel; Leimane, Vaira; Kvasnovsky, Charlotte; Kuznetsova, Tatiana; Kurbatova, Ekaterina; Kummik, Tiina; Kuksa, Liga; Kliiman, Kai; Kiryanova, Elena V.; Kim, HeeJin; Kim, Chang-ki; Kazennyy, Boris Y.; Jou, Ruwen; Huang, Wei-Lun; Ershova, Julia; Erokhin, Vladislav V.; Diem, Lois; Contreras, Carmen; Cho, Sang Nae; Chernousova, Larisa N.; Chen, Michael P.; Caoili, Janice Campos; Bayona, Jaime; Akksilp, Somsak; Calahuanca, Gloria Yale; Wolfgang, Melanie; Viiklepp, Piret; Vasilieva, Irina A.; Taylor, Allison; Tan, Kathrine; Suarez, Carmen; Sture, Ingrida; Somova, Tatiana; Smirnova, Tatyana G.; Sigman, Erika; Skenders, Girts; Sitti, Wanlaya; Shamputa, Isdore C.; Riekstina, Vija; Pua, Kristine Rose; Therese, M.; Perez, C.; Park, Seungkyu; Norvaisha, Inga; Nemtsova, Evgenia S.; Min, Seonyeong; Metchock, Beverly; Levina, Klavdia; Lei, Yung-Chao; Lee, Jongseok; Larionova, Elena E.; Lancaster, Joey; Jeon, Doosoo; Jave, Oswaldo; Khorosheva, Tatiana; Hwang, Soo Hee; Huang, Angela Song-En; Gler, M. Tarcela; Dravniece, Gunta; Eum, Seokyong; Demikhova, Olga V.; Degtyareva, Irina; Danilovits, Manfred; Cirula, Anda; Cho, Eunjin; Cai, Ying; Brand, Jeanette; Bonilla, Cesar; Barry, Clifton E.; Asencios, Luis; Andreevskaya, Sofia N.; Akksilp, Rattanawadee

    2014-01-01

    Background. Increasing access to drugs for the treatment of multidrug-resistant (MDR) tuberculosis is crucial but could lead to increasing resistance to these same drugs. In 2000, the international Green Light Committee (GLC) initiative began to increase access while attempting to prevent acquired resistance. Methods. To assess the GLC's impact, we followed adults with pulmonary MDR tuberculosis from the start to the end of treatment with monthly sputum cultures, drug susceptibility testing, and genotyping. We compared the frequency and predictors of acquired resistance to second-line drugs (SLDs) in 9 countries that volunteered to participate, 5 countries that met GLC criteria, and 4 countries that did not apply to the GLC. Results. In total, 832 subjects were enrolled. Of those without baseline resistance to specific SLDs, 68 (8.9%) acquired extensively drug-resistant (XDR) tuberculosis, 79 (11.2%) acquired fluoroquinolone (FQ) resistance, and 56 (7.8%) acquired resistance to second-line injectable drugs (SLIs). The relative risk (95% confidence interval [CI]) of acquired resistance was lower at GLC-approved sites: 0.27 (.16–.47) for XDR tuberculosis, 0.28 (.17–.45) for FQ, and 0.15 (.06–.39) to 0.60 (.34–1.05) for 3 different SLIs. The risk increased as the number of potentially effective drugs decreased. Controlling for baseline drug resistance and differences between sites, the odds ratios (95% CIs) were 0.21 (.07–.62) for acquired XDR tuberculosis and 0.23 (.09–.59) for acquired FQ resistance. Conclusions. Treatment of MDR tuberculosis involves substantial risk of acquired resistance to SLDs, increasing as baseline drug resistance increases. The risk was significantly lower in programs documented by the GLC to meet specific standards. PMID:25057101

  7. EPHA2 Blockade Overcomes Acquired Resistance to EGFR Kinase Inhibitors in Lung Cancer.

    PubMed

    Amato, Katherine R; Wang, Shan; Tan, Li; Hastings, Andrew K; Song, Wenqiang; Lovly, Christine M; Meador, Catherine B; Ye, Fei; Lu, Pengcheng; Balko, Justin M; Colvin, Daniel C; Cates, Justin M; Pao, William; Gray, Nathanael S; Chen, Jin

    2016-01-15

    Despite the success of treating EGFR-mutant lung cancer patients with EGFR tyrosine kinase inhibitors (TKI), all patients eventually acquire resistance to these therapies. Although various resistance mechanisms have been described, there are currently no FDA-approved therapies that target alternative mechanisms to treat lung tumors with acquired resistance to first-line EGFR TKI agents. Here we found that EPHA2 is overexpressed in EGFR TKI-resistant tumor cells. Loss of EPHA2 reduced the viability of erlotinib-resistant tumor cells harboring EGFR(T790M) mutations in vitro and inhibited tumor growth and progression in an inducible EGFR(L858R+T790M)-mutant lung cancer model in vivo. Targeting EPHA2 in erlotinib-resistant cells decreased S6K1-mediated phosphorylation of cell death agonist BAD, resulting in reduced tumor cell proliferation and increased apoptosis. Furthermore, pharmacologic inhibition of EPHA2 by the small-molecule inhibitor ALW-II-41-27 decreased both survival and proliferation of erlotinib-resistant tumor cells and inhibited tumor growth in vivo. ALW-II-41-27 was also effective in decreasing viability of cells with acquired resistance to the third-generation EGFR TKI AZD9291. Collectively, these data define a role for EPHA2 in the maintenance of cell survival of TKI-resistant, EGFR-mutant lung cancer and indicate that EPHA2 may serve as a useful therapeutic target in TKI-resistant tumors. PMID:26744526

  8. Characterization of a human colorectal carcinoma cell line with acquired resistance to flavopiridol.

    PubMed

    Smith, V; Raynaud, F; Workman, P; Kelland, L R

    2001-11-01

    Flavopiridol is a broad-spectrum inhibitor of cyclin-dependent kinases (cdks) and represents the first in this anticancer class to enter clinical trials. In anticipation of the likelihood that, as with other cancer drugs, acquired resistance may limit the drug's efficacy, an acquired resistance model has been established by in vitro drug exposure of the human colon carcinoma cell line HCT116. This stably resistant line, possessing 8-fold resistance to flavopiridol, showed a lack of cross-resistance to the anticancer agents etoposide, doxorubicin, paclitaxel, topotecan, and cisplatin, and notably to other chemical classes of cdk inhibitors: the aminopurines roscovitine and purvalanol A, 9-nitropaullone, and hymenialdisine. Resistance did not seem to be related to differences in the levels of multidrug resistance drug efflux proteins, P-glycoprotein, and MRP1. Moreover, there were no changes in overall drug accumulation between the resistant and sensitive cell lines. Flavopiridol induced cell cycle arrest, apoptosis, and inhibition of retinoblastoma gene product phosphorylation on serine 780 in both parental and resistant lines, but the latter required 8-fold higher concentrations to achieve these effects. Cyclin E protein levels and cyclin E-associated kinase activity were increased in the resistant line, suggesting that overexpression of cyclin E may be the mechanism of resistance to flavopiridol. However, transfection of cyclin E to increase expression of this protein did not result in an increase in resistance to flavopiridol. Thus, up-regulation of cyclin E alone does not seem to cause resistance to this cdk inhibitor. PMID:11641415

  9. Acquired resistance to 17-allylamino-17-demethoxygeldanamycin (17-AAG, tanespimycin) in glioblastoma cells

    PubMed Central

    Gaspar, Nathalie; Sharp, Swee Y; Pacey, Simon; Jones, Chris; Walton, Michael; Vassal, Gilles; Eccles, Suzanne; Pearson, Andrew; Workman, Paul

    2009-01-01

    HSP90 inhibitors, such as 17-allylamino-17-demethoxygeldanamycin (17-AAG, tanespimycin) which is currently in phase II/III clinical trials, are promising new anticancer agents. Here, we explored acquired resistance to HSP90 inhibitors in glioblastoma, a primary brain tumor with poor prognosis. Glioblastoma cells were exposed continuously to increased 17-AAG concentrations. Four 17-AAG-resistant glioblastoma cell lines were generated. High resistance levels with resistance indices (RI=resistant line IC50/parental line IC50) of 20-137 were obtained rapidly (2-8 weeks). After cessation of 17-AAG exposure, RI decreased and then stabilised. Cross-resistance was found with other ansamycin benzoquinones but not with the structurally unrelated HSP90 inhibitors, radicicol, the purine BIIB021 and the resorcinylic pyrazole/isoxazole amide compounds VER-49009, VER-50589, and NVP-AUY922. An inverse correlation between NQO1 expression/activity and 17-AAG IC50 was observed in the resistant lines. The NQO1 inhibitor ES936 abrogated the differential effects of 17-AAG sensitivity between the parental and resistant lines. NQO1 mRNA levels and NQO1 DNA polymorphism analysis indicated different underlying mechanisms: reduced expression and selection of the inactive NQO1*2 polymorphism. Decreased NQO1 expression was also observed in a melanoma line with acquired resistance to 17-AAG. No resistance was generated with VER-50589 and NVP-AUY922. In conclusion, low NQO1 activity is a likely mechanism of acquired resistance to 17-AAG in glioblastoma, melanoma and possibly other tumor types. Such resistance can be overcome with novel HSP90 inhibitors. PMID:19244114

  10. Erlotinib is a viable treatment for tumors with acquired resistance to cetuximab.

    PubMed

    Brand, Toni M; Dunn, Emily F; Iida, Mari; Myers, Rebecca A; Kostopoulos, Kellie T; Li, Chunrong; Peet, Chimera R; Wheeler, Deric L

    2011-09-01

    The epidermal growth factor receptor (EGFR) is a ubiquitously expressed receptor tyrosine kinase (RTK) and is recognized as a key mediator of tumorigenesis in many human tumors. Currently there are five EGFR inhibitors used in oncology, two monoclonal antibodies (panitumumab, and cetuximab) and three tyrosine kinase inhibitors (erlotinib, gefitinib, and lapatinib). Both strategies of EGFR inhibition have demonstrated clinical successes, however many tumors remain non-responsive or acquire resistance during therapy. To explore potential molecular mechanisms of acquired resistance to cetuximab we previously established a series of cetuximab-resistant clones by chronically exposing the NCI-H226 NSCLC cell line to escalating doses of cetuximab. Cetuximab-resistant clones exhibited a dramatic increase in steady-state expression of EGFR, HER2, and HER3 receptors as well as increased signaling through the MAPK and AKT pathways. RNAi studies demonstrated dependence of cetuximab-resistant clones on the EGFR signaling network. These findings prompted investigation on whether or not cells with acquired resistance to cetuximab would be sensitive to the EGFR targeted TKI erlotinib. In vitro, erlotinib was able to decrease signaling through the EGFR axis, decrease cellular proliferation, and induce apoptosis. To determine if erlotinib could have therapeutic benefit in vivo, we established cetuximab-resistant NCI-H226 mouse xenografts, and subsequently treated them with erlotinib. Mice harboring cetuximab-resistant tumors treated with erlotinib exhibited either a tumor regression or growth delay as compared to vehicle controls. Analysis of the erlotinib treated tumors demonstrated a decrease in cell proliferation and increase rates of apoptosis. The work presented herein suggests that 1) cells with acquired resistance to cetuximab maintain their dependence on EGFR and 2) tumors developing resistance to cetuximab can benefit from subsequent treatment with erlotinib, providing

  11. A Convenient Cell Culture Model for CML Acquired Resistance Through BCR-ABL Mutations.

    PubMed

    Wang, Zhiqiang; Chen, WenYong

    2016-01-01

    Tyrosine kinase inhibitors (TKIs) are the effective treatments for chronic myeloid leukemia (CML). However, clinical resistance to TKIs that leads to patient relapse remains a challenge. Acquisition of BCR-ABL mutations is crucial in the resistance but the underlying molecular mechanisms are poorly understood. Here we describe a cell culture model for CML acquired resistance in which blast crisis CML cells undergo initial apoptosis upon treatment with therapeutically effective doses of TKIs, but the cells regrow quickly with development of resistance through BCR-ABL mutations. This model mimics the clinical process of acquisition of BCR-ABL mutations and will be an important tool to dissect molecular mechanisms of CML drug resistance and to explore strategies to overcome resistance. PMID:27581146

  12. Inhibition of mitochondrial glutaminase activity reverses acquired erlotinib resistance in non-small cell lung cancer

    PubMed Central

    Xie, Caifeng; Jin, Jiangbo; Bao, Xujie; Zhan, Wei-Hua; Han, Tian-Yu; Gan, Mingxi; Zhang, Chengfu; Wang, Jianbin

    2016-01-01

    The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) erlotinib has been approved based on the clinical benefit in non-small cell lung cancer (NSCLC) patients over the past decade. Unfortunately, cancer cells become resistant to this agent via various mechanisms, and this limits the improvement in patient outcomes. Thus, it is urgent to develop novel agents to overcome erlotinib resistance. Here, we propose a novel strategy to overcome acquired erlotinib resistance in NSCLC by inhibiting glutaminase activity. Compound 968, an inhibitor of the glutaminase C (GAC), when combined with erlotinib potently inhibited the cell proliferation of erlotinib-resistant NSCLC cells HCC827ER and NCI-H1975. The combination of compound 968 and erlotinib not only decreased GAC and EGFR protein expression but also inhibited GAC activity in HCC827ER cells. The growth of erlotinib-resistant cells was glutamine-dependent as proved by GAC gene knocked down and rescue experiment. More importantly, compound 968 combined with erlotinib down-regulated the glutamine and glycolysis metabolism in erlotinib-resistant cells. Taken together, our study provides a valuable approach to overcome acquired erlotinib resistance by blocking glutamine metabolism and suggests that combination of EGFR-TKI and GAC inhibitor maybe a potential treatment strategy for acquired erlotinib-resistant NSCLC. PMID:26575584

  13. Mechanisms of Antibiotic Resistance.

    PubMed

    Munita, Jose M; Arias, Cesar A

    2016-04-01

    Emergence of resistance among the most important bacterial pathogens is recognized as a major public health threat affecting humans worldwide. Multidrug-resistant organisms have not only emerged in the hospital environment but are now often identified in community settings, suggesting that reservoirs of antibiotic-resistant bacteria are present outside the hospital. The bacterial response to the antibiotic "attack" is the prime example of bacterial adaptation and the pinnacle of evolution. "Survival of the fittest" is a consequence of an immense genetic plasticity of bacterial pathogens that trigger specific responses that result in mutational adaptations, acquisition of genetic material, or alteration of gene expression producing resistance to virtually all antibiotics currently available in clinical practice. Therefore, understanding the biochemical and genetic basis of resistance is of paramount importance to design strategies to curtail the emergence and spread of resistance and to devise innovative therapeutic approaches against multidrug-resistant organisms. In this chapter, we will describe in detail the major mechanisms of antibiotic resistance encountered in clinical practice, providing specific examples in relevant bacterial pathogens. PMID:27227291

  14. Aminoglycoside Resistance: The Emergence of Acquired 16S Ribosomal RNA Methyltransferases.

    PubMed

    Doi, Yohei; Wachino, Jun-Ichi; Arakawa, Yoshichika

    2016-06-01

    Aminoglycoside-producing Actinobacteria are known to protect themselves from their own aminoglycoside metabolites by producing 16S ribosomal RNA methyltransferase (16S-RMTase), which prevents them from binding to the 16S rRNA targets. Ten acquired 16S-RMTases have been reported from gram-negative pathogens. Most of them posttranscriptionally methylate residue G1405 of 16S rRNA resulting in high-level resistance to gentamicin, tobramycin, amikacin, and plazomicin. Strains that produce 16S-RMTase are frequently multidrug-resistant or even extensively drug-resistant. Although the direct clinical impact of high-level aminoglycoside resistance resulting from production of 16S-RMTase is yet to be determined, ongoing spread of this mechanism will further limit treatment options for multidrug-resistant and extensively drug-resistant gram-negative infections. PMID:27208771

  15. Increased Mitochondrial DNA Induces Acquired Docetaxel Resistance in Head and Neck Cancer Cells

    PubMed Central

    Mizumachi, T; Suzuki, S; Naito, A; Carcel-Trullols, J; Evans, TT; Spring, PM; Oridate, N; Furuta, Y; Fukuda, S; Higuchi, M

    2008-01-01

    Docetaxel is one of the most effective chemotherapeutic agents against cancer; nevertheless, some patients develop resistance. Unfortunately, their causes and mechanisms remain unknown. We created docetaxel-resistant DRHEp2 from human laryngeal cancer HEp2 and investigated the roles of mitochondrial DNA (mtDNA) and ROS on docetaxel resistance. DRHEp2 had greatly increased mtDNA content. Reduction of mtDNA content in DRHEp2 by ethidium bromide treatment reduced the resistance. These results indicate the possible roles of mtDNA-coded enzymes in mitochondrial respiratory chain (MRC) in resistant mechanisms. Oligomycin A, an Fo-ATPase inhibitor, eliminated docetaxel resistance in DRHEp2. In contrast, inhibitors of other MRC did not. RNA interference targeted to Fo-ATPase d-subunit restored docetaxel-induced cytotoxicity to DRHEp2. These results indicate the roles of Fo-ATPase for resistant mechanisms. Docetaxel induced ROS generation in HEp2 but not in DRHEp2 and antioxidant pyrrolidine dithiocarbamate eliminated docetaxel-induced cytotoxicity, suggesting roles of ROS in docetaxel-induced cell death. Furthermore, inhibition of Fo-ATPase by Oligomycin A induced docetaxel–mediated ROS generation in DRHEp2. Taken together, DRHEp2 acquired docetaxel resistance through increasing Fo-ATPase, which led to diminish docetaxel-induced ROS generation and subsequently inhibited cell death. In conclusion, mtDNA plays an important role in developing docetaxel resistance through the reduction of ROS generation by regulating Fo-ATPase. PMID:17637738

  16. Acquired antifungal drug resistance in Aspergillus fumigatus: epidemiology and detection.

    PubMed

    Howard, Susan Julie; Arendrup, Maiken Cavling

    2011-04-01

    Voriconazole is the recommended agent for invasive aspergillosis, with lipid amphotericin B or caspofungin as second line treatment choices. Being the only agents available in oral formulation, azoles are used in chronic infections and often over longer time periods. In addition to being used in clinical medicine, azoles are employed extensively in agriculture. Azole-resistant Aspergillus has been isolated in azole naïve patients, in azole exposed patients and in the environment. The primary underlying mechanism of resistance is as a result of alterations in the cyp51A target gene, with a variety of mutations found in clinical isolates but just one identified in a environmental strain (a point mutation at codon 98 accompanied by a tandem repeat in the promoter region). Much less is currently known about echinocandin resistance in Aspergillus, in part because susceptibility testing is not routinely performed and because the methods suffer from technical difficulties and suboptimal reproducibility. Clinical breakthrough cases have been reported however, and resistance has been confirmed in vivo. In this paper we review the current knowledge on epidemiology, susceptibility testing and underlying mechanisms involved in azole and echinocandin resistance in Aspergillus. PMID:20795765

  17. Community-Acquired Methicillin-Resistant Pyogenic Liver Abscess

    PubMed Central

    Cherian, Joel; Singh, Rahul; Varma, Muralidhar; Vidyasagar, Sudha; Mukhopadhyay, Chiranjay

    2016-01-01

    Pyogenic liver abscesses are rare with an incidence of 0.5% to 0.8% and are mostly due to hepatobiliary causes (40% to 60%). Most are polymicrobial with less than 10% being caused by Staphylococcus aureus. Of these, few are caused by methicillin-resistant Staphylococcus aureus (MRSA) and fewer still by a community-acquired strain. Here we present a case study of a patient with a community-acquired MRSA liver abscess. The patient presented with fever since 1 month and tender hepatomegaly. Blood tests revealed elevated levels of alkaline phosphatase, C-reactive protein, erythrocyte sedimentation rate, and neutrophilic leukocytosis. Blood cultures were sterile. Ultrasound of the abdomen showed multiple abscesses, from which pus was drained and MRSA isolated. Computed tomography of the abdomen did not show any source of infection, and an amebic serology was negative. The patient was started on vancomycin for 2 weeks, following which he became afebrile and was discharged on oral linezolid for 4 more weeks. Normally a liver abscess is treated empirically with ceftriaxone for pyogenic liver abscess and metronidazole for amebic liver abscess. However, if the patient has risk factors for a Staphylococcal infection, it is imperative that antibiotics covering gram-positive organisms be added while waiting for culture reports. PMID:27540556

  18. PP2A inhibition overcomes acquired resistance to HER2 targeted therapy

    PubMed Central

    2014-01-01

    Background HER2 targeted therapies including trastuzumab and more recently lapatinib have significantly improved the prognosis for HER2 positive breast cancer patients. However, resistance to these agents is a significant clinical problem. Although several mechanisms have been proposed for resistance to trastuzumab, the mechanisms of lapatinib resistance remain largely unknown. In this study we generated new models of acquired resistance to HER2 targeted therapy and investigated mechanisms of resistance using phospho-proteomic profiling. Results Long-term continuous exposure of SKBR3 cells to low dose lapatinib established a cell line, SKBR3-L, which is resistant to both lapatinib and trastuzumab. Phospho-proteomic profiling and immunoblotting revealed significant alterations in phospho-proteins involved in key signaling pathways and molecular events. In particular, phosphorylation of eukaryotic elongation factor 2 (eEF2), which inactivates eEF2, was significantly decreased in SKBR3-L cells compared to the parental SKBR3 cells. SKBR3-L cells exhibited significantly increased activity of protein phosphatase 2A (PP2A), a phosphatase that dephosphorylates eEF2. SKBR3-L cells showed increased sensitivity to PP2A inhibition, with okadaic acid, compared to SKBR3 cells. PP2A inhibition significantly enhanced response to lapatinib in both the SKBR3 and SKBR3-L cells. Furthermore, treatment of SKBR3 parental cells with the PP2A activator, FTY720, decreased sensitivity to lapatinib. The alteration in eEF2 phosphorylation, PP2A activity and sensitivity to okadaic acid were also observed in a second HER2 positive cell line model of acquired lapatinib resistance, HCC1954-L. Conclusions Our data suggests that decreased eEF2 phosphorylation, mediated by increased PP2A activity, contributes to resistance to HER2 inhibition and may provide novel targets for therapeutic intervention in HER2 positive breast cancer which is resistant to HER2 targeted therapies. PMID:24958351

  19. Mutations in the tyrosine kinase domain of FLT3 define a new molecular mechanism of acquired drug resistance to PTK inhibitors in FLT3-ITD-transformed hematopoietic cells.

    PubMed

    Bagrintseva, Ksenia; Schwab, Ruth; Kohl, Tobias M; Schnittger, Susanne; Eichenlaub, Sabine; Ellwart, Joachim W; Hiddemann, Wolfgang; Spiekermann, Karsten

    2004-03-15

    Activating mutations in the juxtamembrane domain (FLT3-length mutations, FLT3-LM) and in the protein tyrosine kinase domain (TKD) of FLT3 (FLT3-TKD) represent the most frequent genetic alterations in acute myeloid leukemia (AML) and define a molecular target for therapeutic interventions by protein tyrosine kinase (PTK) inhibitors. We could show that distinct activating FLT3-TKD mutations at position D835 mediate primary resistance to FLT3 PTK inhibitors in FLT3-transformed cell lines. In the presence of increasing concentrations of the FLT3 PTK inhibitor SU5614, we generated inhibitor resistant Ba/F3 FLT3-internal tandem duplication (ITD) cell lines (Ba/F3 FLT3-ITD-R1-R4) that were characterized by a 7- to 26-fold higher IC50 (concentration that inhibits 50%) to SU5614 compared with the parental ITD cells. The molecular characterization of ITD-R1-4 cells demonstrated that specific TKD mutations (D835N and Y842H) on the ITD background were acquired during selection with SU5614. Introduction of these dual ITD-TKD, but not single D835N or Y842H FLT3 mutants, in Ba/F3 cells restored the FLT3 inhibitor resistant phenotype. Our data show that preexisting or acquired mutations in the PTK domain of FLT3 can induce drug resistance to FLT3 PTK inhibitors in vitro. These findings provide a molecular basis for the evaluation of clinical resistance to FLT3 PTK inhibitors in patients with AML. PMID:14604974

  20. Impaired 2',3'-dideoxy-3'-thiacytidine accumulation in T-lymphoblastoid cells as a mechanism of acquired resistance independent of multidrug resistant protein 4 with a possible role for ATP-binding cassette C11.

    PubMed Central

    Turriziani, O; Schuetz, J D; Focher, F; Scagnolari, C; Sampath, J; Adachi, M; Bambacioni, F; Riva, E; Antonelli, G

    2002-01-01

    Cellular factors may contribute to the decreased efficacy of chemotherapy in HIV infection. Indeed, prolonged treatment with nucleoside analogues, such as azidothymidine (AZT), 2',3'-deoxycytidine or 9-(2-phosphonylmethoxyethyl)adenine, induces cellular resistance. We have developed a human T lymphoblastoid cell line (CEM 3TC) that is selectively resistant to the antiproliferative effect of 2',3'-dideoxy-3'-thiacytidine (3TC) because the CEM 3TC cells were equally sensitive to AZT, as well as the antimitotic agent, vinblastine. The anti-retroviral activity of 3TC against HIV-1 was also severely impaired in the CEM 3TC cells. Despite similar deoxycytidine kinase activity and unchanged uptake of nucleosides such as AZT and 2'-deoxycytidine, CEM 3TC had profoundly impaired 3TC accumulation. Further studies indicated that CEM 3TC retained much less 3TC. However, despite a small overexpression of multidrug resistance protein (MRP) 4, additional studies with cells specifically engineered to overexpress MRP4 demonstrated there was no impact on either 3TC accumulation or efflux. Finally, an increased expression of the MRP5 homologue, ATP-binding cassette C11 (ABCC11) was observed in the CEM 3TC cells. We speculate that the decreased 3TC accumulation in the CEM 3TC might be due to the upregulation of ABCC11. PMID:12133003

  1. Activation of Alternate Prosurvival Pathways Accounts for Acquired Sunitinib Resistance in U87MG Glioma Xenografts

    PubMed Central

    Lv, Hua; Mazloom, Amin R.; Xu, Huilei; Ma'ayan, Avi; Gallo, James M.

    2012-01-01

    Acquired drug resistance represents a major obstacle to using sunitinib for the treatment of solid tumors. Here, we examined the cellular and molecular alterations in tumors that are associated with acquired brain tumor resistance to sunitinib by using an in vivo model. U87MG tumors obtained from nude mice that received sunitinib (40 mg/kg/day) for 30 days were classified into sunitinib-sensitive and -resistant groups based on tumor volume and underwent targeted gene microarray and protein array analyses. The expression of several angiogenesis-associated genes was significantly modulated in sunitinib-treated tumors compared with those in control tumors (p < 0.05), whereas no significant differences were observed between sunitinib-sensitive and -resistant tumors (p > 0.05). Tumor vasculature based on microvessel density, neurogenin 2 chondroitin sulfate proteoglycan density, and α-smooth muscle actin density was also similar in sunitinib-treatment groups (p > 0.05). The moderate increase in unbound sunitinib tumor-to-plasma area-under-the-curve ratio in sunitinib-resistant mice was accompanied by up-regulated ATP-binding cassette G2 expression in tumor. The most profound difference between the sunitinib-sensitive and -resistant groups was found in the expression of several phosphorylated proteins involved in intracellular signaling. In particular, phospholipase C-γ1 phosphorylation in sunitinib-resistant tumors was up-regulated by 2.6-fold compared with that in sunitinib-sensitive tumors (p < 0.05). In conclusion, acquired sunitinib resistance in U87MG tumors is not associated with revascularization in tumors, but rather with the activation of alternate prosurvival pathways involved in an escape mechanism facilitating tumor growth and possibly insufficient drug uptake in tumor cells caused by an up-regulated membrane efflux transporter. PMID:22869928

  2. Acquired PIK3CA amplification causes resistance to selective phosphoinositide 3-kinase inhibitors in breast cancer.

    PubMed

    Huw, L-Y; O'Brien, C; Pandita, A; Mohan, S; Spoerke, J M; Lu, S; Wang, Y; Hampton, G M; Wilson, T R; Lackner, M R

    2013-01-01

    Agents targeting the PI3K/mTOR signaling axis have shown promise in early-phase clinical trials and are currently being studied in later stages of clinical development in multiple indications. Experience with other targeted agents suggests that clinical responses may be short-lived because of acquired resistance to therapy. Here, we report preclinical modeling of acquired resistance in a HER2-positive, PIK3CA mutant breast cancer cell line, KPL-4. We identified a heretofore-unreported mechanism of resistance, specifically high-level amplification of the mutant allele of PIK3CA, which resulted in a marked upregulation of PI3K signaling, enabling resistant cells to regain proliferative capacity at clinically relevant concentrations of the PI3K inhibitor, GDC-0941. We show that knockdown of the amplified PIK3CA mutant allele in these cells by small interfering RNA restored pathway signaling and sensitivity to PI3K inhibition at levels comparable to parental cells. These novel preclinical findings suggest that, in addition to assessment of other previously reported mechanisms of resistance, evaluation of PI3K copy number variation should be integrated into the exploratory analysis of biopsies obtained at disease progression. PMID:24366379

  3. Acquired Resistance to EGFR Inhibitors Is Associated with a Manifestation of Stem cell–like Properties in Cancer Cells

    PubMed Central

    Shien, Kazuhiko; Toyooka, Shinichi; Yamamoto, Hiromasa; Soh, Junichi; Jida, Masaru; Thu, Kelsie L.; Hashida, Shinsuke; Maki, Yuho; Ichihara, Eiki; Asano, Hiroaki; Tsukuda, Kazunori; Takigawa, Nagio; Kiura, Katsuyuki; Gazdar, Adi F.; Lam, Wan L.; Miyoshi, Shinichiro

    2015-01-01

    Acquired resistance to EGF receptor (EGFR) tyrosine kinase inhibitor (TKI) is a critical problem in the treatment of lung cancer. Although several mechanisms have been shown to be responsible for acquired resistance, all mechanisms have not been uncovered. In this study, we investigated the molecular and cellular profiles of the acquired resistant cells to EGFR-TKI in EGFR-mutant lung cancers. Four EGFR-mutant cell lines were exposed to gefitinib by stepwise escalation and high-concentration exposure methods, and resistant sublines to gefitinib were established. The molecular profiles and cellular phenotypes of these resistant sublines were characterized. Although previously reported, alterations including secondary EGFR T790M mutation, MET amplification, and appearance of epithelial-to-mesenchymal transition (EMT) features were observed, these 2 drug-exposure methods revealed different resistance mechanisms. The resistant cells with EMT features exhibited downregulation of miRNA-200c by DNA methylation. Furthermore, the HCC827-derived subline characterized by the high-concentration exposure method exhibited not only EMT features but also stem cell–like properties, including aldehyde dehydrogenase isoform 1 (ALDH1A1) overexpression, increase of side-population, and self-renewal capability. Resistant sublines with stem cell–like properties were resistant to conventional chemotherapeutic agents but equally sensitive to histone deacetylase and proteasome inhibitors, compared with their parental cells. ALDH1A1 was upregulated in clinical samples with acquired resistance to gefitinib. In conclusion, our study indicates that the manner of EGFR-TKI exposure influences the mechanism of acquired resistance and the appearance of stem cell–like property with EGFR-TKI treatment. PMID:23542356

  4. Acquired resistance to EGFR inhibitors is associated with a manifestation of stem cell-like properties in cancer cells.

    PubMed

    Shien, Kazuhiko; Toyooka, Shinichi; Yamamoto, Hiromasa; Soh, Junichi; Jida, Masaru; Thu, Kelsie L; Hashida, Shinsuke; Maki, Yuho; Ichihara, Eiki; Asano, Hiroaki; Tsukuda, Kazunori; Takigawa, Nagio; Kiura, Katsuyuki; Gazdar, Adi F; Lam, Wan L; Miyoshi, Shinichiro

    2013-05-15

    Acquired resistance to EGF receptor (EGFR) tyrosine kinase inhibitor (TKI) is a critical problem in the treatment of lung cancer. Although several mechanisms have been shown to be responsible for acquired resistance, all mechanisms have not been uncovered. In this study, we investigated the molecular and cellular profiles of the acquired resistant cells to EGFR-TKI in EGFR-mutant lung cancers. Four EGFR-mutant cell lines were exposed to gefitinib by stepwise escalation and high-concentration exposure methods, and resistant sublines to gefitinib were established. The molecular profiles and cellular phenotypes of these resistant sublines were characterized. Although previously reported, alterations including secondary EGFR T790M mutation, MET amplification, and appearance of epithelial-to-mesenchymal transition (EMT) features were observed, these 2 drug-exposure methods revealed different resistance mechanisms. The resistant cells with EMT features exhibited downregulation of miRNA-200c by DNA methylation. Furthermore, the HCC827-derived subline characterized by the high-concentration exposure method exhibited not only EMT features but also stem cell-like properties, including aldehyde dehydrogenase isoform 1 (ALDH1A1) overexpression, increase of side-population, and self-renewal capability. Resistant sublines with stem cell-like properties were resistant to conventional chemotherapeutic agents but equally sensitive to histone deacetylase and proteasome inhibitors, compared with their parental cells. ALDH1A1 was upregulated in clinical samples with acquired resistance to gefitinib. In conclusion, our study indicates that the manner of EGFR-TKI exposure influences the mechanism of acquired resistance and the appearance of stem cell-like property with EGFR-TKI treatment. PMID:23542356

  5. Radiation-resistant acquired immunity of vaccinated mice to Schistosoma mansoni

    SciTech Connect

    Aitken, R.; Coulson, P.S.; Dixon, B.; Wilson, R.A.

    1987-11-01

    Vaccination of mice with attenuated cercariae of Schistosoma mansoni induces specific acquired resistance to challenge infection. This resistance is immunologically-mediated, possibly via a delayed-type hypersensitivity. Studies of parasite migration have shown that the protective mechanism operates most effectively in the lungs of vaccinated mice. We have probed the mechanism by exposing mice to 500 rads of gamma radiation before challenge infection. Our results show that the effector mechanism operative against challenge larvae is resistant to radiation. In contrast, classical immune responses are markedly suppressed by the same treatment. While leukocyte populations in the blood fall dramatically after irradiation, numbers of cells recoverable by bronchoalveolar lavage are unaffected. We suggest that vaccination with attenuated cercariae establishes populations of sensitized cells in the lungs which trigger the mechanism of resistance when challenge schistosomula migrate through pulmonary capillary beds. Although the cells may be partially disabled by irradiation, they remain responsive to worm antigens and thereby capable of initiating the elimination mechanism. This hypothesis would explain the radiation resistance of vaccine-induced immunity to S. mansoni.

  6. Prolongation of acquired cellular resistance to Listeria monocytogenes

    PubMed Central

    Willers, J. M. N.; Hofhuis, F. M. A.; Meer, C. Vander

    1982-01-01

    Intracutaneous immunization of mice with 105 or 106 viable listeria resulted in acquired cellular resistance (ACR) of short duration (7 days) and in delayed-type hypersensitivity (DH) lasting at least 27 days. The ACR was partially non-specific, as 50% of the mice were also protected against a lethal challenge with Salmonella enteritidis. The specific element of the ACR could be transferred by non-adherent spleen cells from immune mice to normal recipient mice. Such transfer was not possible with adherent spleen cells from immune mice or with spleen cells from normal mice. Two systems of multiple immunizations to extend the period during which mice were protected against a challenge with 50 LD50 listeria were used. In the first system, mice were immunized with 106 viable listeria and subsequently challenged with 50 LD50 (= 107) viable listeria. Mice surviving the challenge were actually boosted at the challenge injection for ACR. In the second system mice were immunized and boosted with 108 killed listeria mixed with the adjuvant dimethyl dioctadecyl ammonium bromide (DDA). In the former system after each booster injection with viable listeria the interval during which the mice were protected doubled and reached a maximum of 31 days. In the latter system all intervals between two booster injections were equally long and never exceeded 28 days. In both systems the existence of immunological memory was suggested. The difference in results obtained after immunization with viable listeria and killed listeria mixed with DDA are discussed. PMID:6809603

  7. Molecular mechanisms for tumour resistance to chemotherapy.

    PubMed

    Pan, Shu-Ting; Li, Zhi-Ling; He, Zhi-Xu; Qiu, Jia-Xuan; Zhou, Shu-Feng

    2016-08-01

    Chemotherapy is one of the prevailing methods used to treat malignant tumours, but the outcome and prognosis of tumour patients are not optimistic. Cancer cells gradually generate resistance to almost all chemotherapeutic drugs via a variety of distinct mechanisms and pathways. Chemotherapeutic resistance, either intrinsic or acquired, is caused and sustained by reduced drug accumulation and increased drug export, alterations in drug targets and signalling transduction molecules, increased repair of drug-induced DNA damage, and evasion of apoptosis. In order to better understand the mechanisms of chemoresistance, this review highlights our current knowledge of the role of altered drug metabolism and transport and deregulation of apoptosis and autophagy in the development of tumour chemoresistance. Reduced intracellular activation of prodrugs (e.g. thiotepa and tegafur) or enhanced drug inactivation by Phase I and II enzymes contributes to the development of chemoresistance. Both primary and acquired resistance can be caused by alterations in the transport of anticancer drugs which is mediated by a variety of drug transporters such as P-glycoprotein (P-gp), multidrug resistance associated proteins, and breast cancer resistance protein. Presently there is a line of evidence indicating that deregulation of programmed cell death including apoptosis and autophagy is also an important mechanism for tumour resistance to anticancer drugs. Reversal of chemoresistance is likely via pharmacological and biological approaches. Further studies are warranted to grasp the full picture of how each type of cancer cells develop resistance to anticancer drugs and to identify novel strategies to overcome it. PMID:27097837

  8. Acquisition of cancer stem cell-like properties in non-small cell lung cancer with acquired resistance to afatinib

    PubMed Central

    Hashida, Shinsuke; Yamamoto, Hiromasa; Shien, Kazuhiko; Miyoshi, Yuichiro; Ohtsuka, Tomoaki; Suzawa, Ken; Watanabe, Mototsugu; Maki, Yuho; Soh, Junichi; Asano, Hiroaki; Tsukuda, Kazunori; Miyoshi, Shinichiro; Toyooka, Shinichi

    2015-01-01

    Afatinib is an irreversible epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) that is known to be effective against the EGFR T790M variant, which accounts for half of the mechanisms of acquired resistance to reversible EGFR-TKIs. However, acquired resistance to afatinib was also observed in clinical use. Thus, elucidating and overcoming the mechanisms of resistance are important issues in the treatment of non-small cell lung cancer. In this study, we established various afatinib-resistant cell lines and investigated the resistance mechanisms. EGFR T790M mutations were not detected using direct sequencing in established resistant cells. Several afatinib-resistant cell lines displayed MET amplification, and these cells were sensitive to the combination of afatinib plus crizotinib. As a further investigation, a cell line that acquired resistance to afatinib plus crizotinib, HCC827-ACR, was established from one of the MET amplified-cell lines. Several afatinib-resistant cell lines including HCC827-ACR displayed epithelial-to-mesenchymal transition (EMT) features and epigenetic silencing of miR-200c, which is a suppresser of EMT. In addition, these cell lines also exhibited overexpression of ALDH1A1 and ABCB1, which are putative stem cell markers, and resistance to docetaxel. In conclusion, we established afatinib-resistant cells and found that MET amplification, EMT, and stem cell-like features are observed in cells with acquired resistance to EGFR-TKIs. This finding may provide clues to overcoming resistance to EGFR-TKIs. PMID:26202045

  9. Acquisition of cancer stem cell-like properties in non-small cell lung cancer with acquired resistance to afatinib.

    PubMed

    Hashida, Shinsuke; Yamamoto, Hiromasa; Shien, Kazuhiko; Miyoshi, Yuichiro; Ohtsuka, Tomoaki; Suzawa, Ken; Watanabe, Mototsugu; Maki, Yuho; Soh, Junichi; Asano, Hiroaki; Tsukuda, Kazunori; Miyoshi, Shinichiro; Toyooka, Shinichi

    2015-10-01

    Afatinib is an irreversible epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) that is known to be effective against the EGFR T790M variant, which accounts for half of the mechanisms of acquired resistance to reversible EGFR-TKIs. However, acquired resistance to afatinib was also observed in clinical use. Thus, elucidating and overcoming the mechanisms of resistance are important issues in the treatment of non-small cell lung cancer. In this study, we established various afatinib-resistant cell lines and investigated the resistance mechanisms. EGFR T790M mutations were not detected using direct sequencing in established resistant cells. Several afatinib-resistant cell lines displayed MET amplification, and these cells were sensitive to the combination of afatinib plus crizotinib. As a further investigation, a cell line that acquired resistance to afatinib plus crizotinib, HCC827-ACR, was established from one of the MET amplified-cell lines. Several afatinib-resistant cell lines including HCC827-ACR displayed epithelial-to-mesenchymal transition (EMT) features and epigenetic silencing of miR-200c, which is a suppresser of EMT. In addition, these cell lines also exhibited overexpression of ALDH1A1 and ABCB1, which are putative stem cell markers, and resistance to docetaxel. In conclusion, we established afatinib-resistant cells and found that MET amplification, EMT, and stem cell-like features are observed in cells with acquired resistance to EGFR-TKIs. This finding may provide clues to overcoming resistance to EGFR-TKIs. PMID:26202045

  10. Bordetella pertussis Acquires Resistance to Complement-Mediated Killing In Vivo

    PubMed Central

    Pishko, Elizabeth J.; Betting, David J.; Hutter, Christina S.; Harvill, Eric T.

    2003-01-01

    In order to initially colonize a host, bacteria must avoid various components of the innate immune system, one of which is complement. The genus Bordetella includes three closely related species that differ in their ability to resist complement-mediated killing. Bordetella parapertussis and Bordetella bronchiseptica resist killing in naïve serum, a characteristic that may aid in efficient respiratory tract colonization and has been attributed to expression of O antigen. Bordetella pertussis lacks O antigen and is sensitive to naïve serum in vitro, yet it also efficiently colonizes the respiratory tract. Based on these observations, we hypothesized that B. pertussis may have an alternate mechanism to resist complement in vivo. While a number of reports on serum sensitivity of the bordetellae have been published, we show here that serum concentration and growth conditions can greatly alter the observed level of sensitivity to complement and that all but one strain of B. pertussis observed were sensitive to some level of naïve serum in vitro, particularly when there was excess complement. However, B. pertussis rapidly acquires increased resistance in vivo to naïve serum that is specific to the alternative pathway. Resistance is not efficiently acquired by B. parapertussis and B. bronchiseptica mutants lacking O antigen. This B. pertussis-specific mechanism of complement resistance does not appear to be dependent on either brkA or other genes expressed specifically in the Bvg+ phase. This in vivo acquisition of alternative pathway resistance suggests that there is a novel O antigen-independent method by which B. pertussis evades complement-mediated killing. PMID:12933835

  11. Bordetella pertussis acquires resistance to complement-mediated killing in vivo.

    PubMed

    Pishko, Elizabeth J; Betting, David J; Hutter, Christina S; Harvill, Eric T

    2003-09-01

    In order to initially colonize a host, bacteria must avoid various components of the innate immune system, one of which is complement. The genus Bordetella includes three closely related species that differ in their ability to resist complement-mediated killing. Bordetella parapertussis and Bordetella bronchiseptica resist killing in naïve serum, a characteristic that may aid in efficient respiratory tract colonization and has been attributed to expression of O antigen. Bordetella pertussis lacks O antigen and is sensitive to naïve serum in vitro, yet it also efficiently colonizes the respiratory tract. Based on these observations, we hypothesized that B. pertussis may have an alternate mechanism to resist complement in vivo. While a number of reports on serum sensitivity of the bordetellae have been published, we show here that serum concentration and growth conditions can greatly alter the observed level of sensitivity to complement and that all but one strain of B. pertussis observed were sensitive to some level of naïve serum in vitro, particularly when there was excess complement. However, B. pertussis rapidly acquires increased resistance in vivo to naïve serum that is specific to the alternative pathway. Resistance is not efficiently acquired by B. parapertussis and B. bronchiseptica mutants lacking O antigen. This B. pertussis-specific mechanism of complement resistance does not appear to be dependent on either brkA or other genes expressed specifically in the Bvg(+) phase. This in vivo acquisition of alternative pathway resistance suggests that there is a novel O antigen-independent method by which B. pertussis evades complement-mediated killing. PMID:12933835

  12. Overcoming acquired BRAF inhibitor resistance in melanoma via targeted inhibition of Hsp90 with ganetespib.

    PubMed

    Acquaviva, Jaime; Smith, Donald L; Jimenez, John-Paul; Zhang, Chaohua; Sequeira, Manuel; He, Suqin; Sang, Jim; Bates, Richard C; Proia, David A

    2014-02-01

    Activating BRAF kinase mutations serve as oncogenic drivers in over half of all melanomas, a feature that has been exploited in the development of new molecularly targeted approaches to treat this disease. Selective BRAF(V600E) inhibitors, such as vemurafenib, typically induce initial, profound tumor regressions within this group of patients; however, durable responses have been hampered by the emergence of drug resistance. Here, we examined the activity of ganetespib, a small-molecule inhibitor of Hsp90, in melanoma lines harboring the BRAF(V600E) mutation. Ganetespib exposure resulted in the loss of mutant BRAF expression and depletion of mitogen-activated protein kinase and AKT signaling, resulting in greater in vitro potency and antitumor efficacy compared with targeted BRAF and MAP-ERK kinase (MEK) inhibitors. Dual targeting of Hsp90 and BRAF(V600E) provided combinatorial benefit in vemurafenib-sensitive melanoma cells in vitro and in vivo. Importantly, ganetespib overcame mechanisms of intrinsic and acquired resistance to vemurafenib, the latter of which was characterized by reactivation of extracellular signal-regulated kinase (ERK) signaling. Continued suppression of BRAF(V600E) by vemurafenib potentiated sensitivity to MEK inhibitors after acquired resistance had been established. Ganetespib treatment reduced, but not abolished, elevations in steady-state ERK activity. Profiling studies revealed that the addition of a MEK inhibitor could completely abrogate ERK reactivation in the resistant phenotype, with ganetespib displaying superior combinatorial activity over vemurafenib. Moreover, ganetespib plus the MEK inhibitor TAK-733 induced tumor regressions in vemurafenib-resistant xenografts. Overall these data highlight the potential of ganetespib as a single-agent or combination treatment in BRAF(V600E)-driven melanoma, particularly as a strategy to overcome acquired resistance to selective BRAF inhibitors. PMID:24398428

  13. CRISPR provides acquired resistance against viruses in prokaryotes.

    PubMed

    Barrangou, Rodolphe; Fremaux, Christophe; Deveau, Hélène; Richards, Melissa; Boyaval, Patrick; Moineau, Sylvain; Romero, Dennis A; Horvath, Philippe

    2007-03-23

    Clustered regularly interspaced short palindromic repeats (CRISPR) are a distinctive feature of the genomes of most Bacteria and Archaea and are thought to be involved in resistance to bacteriophages. We found that, after viral challenge, bacteria integrated new spacers derived from phage genomic sequences. Removal or addition of particular spacers modified the phage-resistance phenotype of the cell. Thus, CRISPR, together with associated cas genes, provided resistance against phages, and resistance specificity is determined by spacer-phage sequence similarity. PMID:17379808

  14. Two novel ALK mutations mediate acquired resistance to the next generation ALK inhibitor alectinib

    PubMed Central

    Katayama, Ryohei; Friboulet, Luc; Koike, Sumie; Lockerman, Elizabeth L.; Khan, Tahsin M.; Gainor, Justin F.; Iafrate, A. John; Takeuchi, Kengo; Taiji, Makoto; Okuno, Yasushi; Fujita, Naoya; Engelman, Jeffrey A.; Shaw, Alice T.

    2014-01-01

    Purpose The first-generation ALK tyrosine kinase inhibitor (TKI) crizotinib is a standard therapy for patients with ALK-rearranged NSCLC. Several next-generation ALK-TKIs have entered the clinic and have shown promising activity in crizotinib-resistant patients. As patients still relapse even on these next-generation ALK-TKIs, we examined mechanisms of resistance to the next-generation ALK-TKI alectinib and potential strategies to overcome this resistance. Experimental Design We established a cell line model of alectinib resistance, and analyzed a resistant tumor specimen from a patient who had relapsed on alectinib. We developed Ba/F3 models harboring alectinib-resistant ALK mutations and evaluated the potency of other next-generation ALK-TKIs in these models. We tested the antitumor activity of the next-generation ALK-TKI ceritinib in the patient with acquired resistance to alectinib. To elucidate structure-activity-relationships of ALK mutations, we performed computational thermodynamic simulation with MP-CAFEE. Results We identified a novel V1180L gatekeeper mutation from the cell line model and a second novel I1171T mutation from the patient who developed resistance to alectinib. Both ALK mutations conferred resistance to alectinib as well as to crizotinib, but were sensitive to ceritinib and other next-generation ALK-TKIs. Treatment of the patient with ceritinib led to a marked response. Thermodynamics simulation suggests that both mutations lead to distinct structural alterations that decrease the binding affinity with alectinib. Conclusions We have identified two novel ALK mutations arising after alectinib exposure which are sensitive to other next generation ALK-TKIs. The ability of ceritinib to overcome alectinib-resistance mutations suggests a potential role for sequential therapy with multiple next-generation ALK-TKIs. PMID:25228534

  15. Multidrug efflux pumps as main players in intrinsic and acquired resistance to antimicrobials.

    PubMed

    Hernando-Amado, Sara; Blanco, Paula; Alcalde-Rico, Manuel; Corona, Fernando; Reales-Calderón, Jose A; Sánchez, María B; Martínez, José L

    2016-09-01

    Multidrug efflux pumps constitute a group of transporters that are ubiquitously found in any organism. In addition to other functions with relevance for the cell physiology, efflux pumps contribute to the resistance to compounds used for treating different diseases, including resistance to anticancer drugs, antibiotics or antifungal compounds. In the case of antimicrobials, efflux pumps are major players in both intrinsic and acquired resistance to drugs currently in use for the treatment of infectious diseases. One important aspect not fully explored of efflux pumps consists on the identification of effectors able to induce their expression. Indeed, whereas the analysis of clinical isolates have shown that mutants overexpressing these resistance elements are frequently found, less is known on the conditions that may trigger expression of efflux pumps, hence leading to transient induction of resistance in vivo, a situation that is barely detectable using classical susceptibility tests. In the current article we review the structure and mechanisms of regulation of the expression of bacterial and fungal efflux pumps, with a particular focus in those for which a role in clinically relevant resistance has been reported. PMID:27620952

  16. Mechanisms of echinocandin antifungal drug resistance

    PubMed Central

    Perlin, David S.

    2015-01-01

    Fungal infections due to Candida and Aspergillus species cause extensive morbidity and mortality, especially among immunosuppressed patients, and antifungal therapy is critical to patient management. Yet only a few drug classes are available to treat invasive fungal diseases, and this problem is compounded by the emergence of antifungal resistance. Echinocandin drugs are the preferred choice to treat candidiasis. They are the first cell wall–active agents and target the fungal-specific enzyme glucan synthase, which catalyzes the biosynthesis of β-1,3-glucan, a key cell wall polymer. Therapeutic failures occur rarely among common Candida species, with the exception of Candida glabrata, which are frequently multidrug resistant. Echinocandin resistance in susceptible species is always acquired during therapy. The mechanism of resistance involves amino acid changes in hot-spot regions of Fks subunits of glucan synthase, which decrease the sensitivity of the enzyme to drug. Cellular stress response pathways lead to drug adaptation, which promote the formation of resistant fks strains. Clinical factors promoting echinocandin resistance include empiric therapy, prophylaxis, gastrointestinal reservoirs, and intra-abdominal infections. A better understanding of the echinocandin resistance mechanism, along with cellular and clinical factors promoting resistance, will promote more effective strategies to overcome and prevent echinocandin resistance. PMID:26190298

  17. Socioeconomic and behavioral factors leading to acquired bacterial resistance to antibiotics in developing countries.

    PubMed Central

    Okeke, I. N.; Lamikanra, A.; Edelman, R.

    1999-01-01

    In developing countries, acquired bacterial resistance to antimicrobial agents is common in isolates from healthy persons and from persons with community-acquired infections. Complex socioeconomic and behavioral factors associated with antibiotic resistance, particularly regarding diarrheal and respiratory pathogens, in developing tropical countries, include misuse of antibiotics by health professionals, unskilled practitioners, and laypersons; poor drug quality; unhygienic conditions accounting for spread of resistant bacteria; and inadequate surveillance. PMID:10081668

  18. Effects of Sorafenib Dose on Acquired Reversible Resistance and Toxicity in Hepatocellular Carcinoma.

    PubMed

    Kuczynski, Elizabeth A; Lee, Christina R; Man, Shan; Chen, Eric; Kerbel, Robert S

    2015-06-15

    Acquired evasive resistance is a major limitation of hepatocellular carcinoma (HCC) treatment with the tyrosine kinase inhibitor (TKI) sorafenib. Recent findings suggest that resistance to sorafenib may have a reversible phenotype. In addition, loss of responsiveness has been proposed to be due to a gradual decrease in sorafenib plasma levels in patients. Here, the possible mechanisms underlying reversible sorafenib resistance were investigated using a Hep3B-hCG orthotopic human xenograft model of locally advanced HCC. Tissue and plasma sorafenib and metabolite levels, downstream antitumor targets, and toxicity were assessed during standard and dose-escalated sorafenib treatment. Drug levels were found to decline significantly over time in mice treated with 30 mg/kg sorafenib, coinciding with the onset of resistance but a greater magnitude of change was observed in tissues compared with plasma. Skin rash also correlated with drug levels and tended to decrease in severity over time. Drug level changes appeared to be partially tumor dependent involving induction of tumoral CYP3A4 metabolism, with host pretreatment alone unable to generate resistance. Escalation from 30 to 60 mg/kg sorafenib improved antitumor efficacy but worsened survival due to excessive body weight loss. Microvessel density was inhibited by sorafenib treatment but remained suppressed over time and dose increase. In conclusion, tumor CYP3A4 induction by sorafenib is a novel mechanism to account for variability in systemic drug levels; however, declining systemic sorafenib levels may only be a minor resistance mechanism. Escalating the dose may be an effective treatment strategy, provided toxicity can be controlled. PMID:25908587

  19. Association between Mycobacterium tuberculosis Complex Phylogenetic Lineage and Acquired Drug Resistance

    PubMed Central

    Yuen, Courtney M.; Kurbatova, Ekaterina V.; Click, Eleanor S.; Cavanaugh, J. Sean; Cegielski, J. Peter

    2013-01-01

    Background Development of resistance to antituberculosis drugs during treatment (i.e., acquired resistance) can lead to emergence of resistant strains and consequent poor clinical outcomes. However, it is unknown whether Mycobacterium tuberculosis complex species and lineage affects the likelihood of acquired resistance. Methods We analyzed data from the U.S. National Tuberculosis Surveillance System and National Tuberculosis Genotyping Service for tuberculosis cases during 2004–2011 with assigned species and lineage and both initial and final drug susceptibility test results. We determined univariate associations between species and lineage of Mycobacterium tuberculosis complex bacteria and acquired resistance to isoniazid, rifamycins, fluoroquinolones, and second-line injectables. We used Poisson regression with backward elimination to generate multivariable models for acquired resistance to isoniazid and rifamycins. Results M. bovis was independently associated with acquired resistance to isoniazid (adjusted prevalence ratio = 8.46, 95% CI 2.96–24.14) adjusting for HIV status, and with acquired resistance to rifamycins (adjusted prevalence ratio = 4.53, 95% CI 1.29–15.90) adjusting for homelessness, HIV status, initial resistance to isoniazid, site of disease, and administration of therapy. East Asian lineage was associated with acquired resistance to fluoroquinolones (prevalence ratio = 6.10, 95% CI 1.56–23.83). Conclusions We found an association between mycobacterial species and lineage and acquired drug resistance using U.S. surveillance data. Prospective clinical studies are needed to determine the clinical significance of these findings, including whether rapid genotyping of isolates at the outset of treatment may benefit patient management. PMID:24376623

  20. Fibrocyte-like cells mediate acquired resistance to anti-angiogenic therapy with bevacizumab

    PubMed Central

    Mitsuhashi, Atsushi; Goto, Hisatsugu; Saijo, Atsuro; Trung, Van The; Aono, Yoshinori; Ogino, Hirokazu; Kuramoto, Takuya; Tabata, Sho; Uehara, Hisanori; Izumi, Keisuke; Yoshida, Mitsuteru; Kobayashi, Hiroaki; Takahashi, Hidefusa; Gotoh, Masashi; Kakiuchi, Soji; Hanibuchi, Masaki; Yano, Seiji; Yokomise, Hiroyasu; Sakiyama, Shoji; Nishioka, Yasuhiko

    2015-01-01

    Bevacizumab exerts anti-angiogenic effects in cancer patients by inhibiting vascular endothelial growth factor (VEGF). However, its use is still limited due to the development of resistance to the treatment. Such resistance can be regulated by various factors, although the underlying mechanisms remain incompletely understood. Here we show that bone marrow-derived fibrocyte-like cells, defined as alpha-1 type I collagen-positive and CXCR4-positive cells, contribute to the acquired resistance to bevacizumab. In mouse models of malignant pleural mesothelioma and lung cancer, fibrocyte-like cells mediate the resistance to bevacizumab as the main producer of fibroblast growth factor 2. In clinical specimens of lung cancer, the number of fibrocyte-like cells is significantly increased in bevacizumab-treated tumours, and correlates with the number of treatment cycles, as well as CD31-positive vessels. Our results identify fibrocyte-like cells as a promising cell biomarker and a potential therapeutic target to overcome resistance to anti-VEGF therapy. PMID:26635184

  1. Fibrocyte-like cells mediate acquired resistance to anti-angiogenic therapy with bevacizumab.

    PubMed

    Mitsuhashi, Atsushi; Goto, Hisatsugu; Saijo, Atsuro; Trung, Van The; Aono, Yoshinori; Ogino, Hirokazu; Kuramoto, Takuya; Tabata, Sho; Uehara, Hisanori; Izumi, Keisuke; Yoshida, Mitsuteru; Kobayashi, Hiroaki; Takahashi, Hidefusa; Gotoh, Masashi; Kakiuchi, Soji; Hanibuchi, Masaki; Yano, Seiji; Yokomise, Hiroyasu; Sakiyama, Shoji; Nishioka, Yasuhiko

    2015-01-01

    Bevacizumab exerts anti-angiogenic effects in cancer patients by inhibiting vascular endothelial growth factor (VEGF). However, its use is still limited due to the development of resistance to the treatment. Such resistance can be regulated by various factors, although the underlying mechanisms remain incompletely understood. Here we show that bone marrow-derived fibrocyte-like cells, defined as alpha-1 type I collagen-positive and CXCR4-positive cells, contribute to the acquired resistance to bevacizumab. In mouse models of malignant pleural mesothelioma and lung cancer, fibrocyte-like cells mediate the resistance to bevacizumab as the main producer of fibroblast growth factor 2. In clinical specimens of lung cancer, the number of fibrocyte-like cells is significantly increased in bevacizumab-treated tumours, and correlates with the number of treatment cycles, as well as CD31-positive vessels. Our results identify fibrocyte-like cells as a promising cell biomarker and a potential therapeutic target to overcome resistance to anti-VEGF therapy. PMID:26635184

  2. Hippo pathway effector YAP inhibition restores the sensitivity of EGFR-TKI in lung adenocarcinoma having primary or acquired EGFR-TKI resistance.

    PubMed

    Lee, Jeong Eun; Park, Hee Sun; Lee, Dahye; Yoo, Geon; Kim, Tackhoon; Jeon, Haeyon; Yeo, Min-Kyung; Lee, Choong-Sik; Moon, Jae Young; Jung, Sung Soo; Kim, Ju Ock; Kim, Sun Young; Park, Dong Il; Park, Yeon Hee; Lee, Jae Cheol; Oh, In-Jae; Lim, Dae Sik; Chung, Chaeuk

    2016-05-20

    The efficacy of EGFR-tyrosine kinase inhibitors (TKIs) is significantly limited by various resistance mechanisms to those drugs. The resistance to EGFR-TKI is largely divided by two classes; acquired resistance after EGFR-TKI treatment, and primary resistance marked by cancer cell's dependence on other oncogene, such as KRAS. YAP has emerged as critical oncogene in conferring drug resistance against targeted therapy. In this study, we evaluated the role of YAP in primary and acquired EGFR-TKI resistance using gefitinib-resistant A549 and PC9 cells and their parental cell lines. Our study revealed that EGFR-TKI resistance is associated with enhanced YAP activity. Notably, YAP activation was independent of the Hippo pathway. We confirmed that AXL is a downstream target of YAP that confers EGFR-TKI resistance. And our results showed that YAP can induce ERK activation in lung adenocarcinoma. The combination of YAP inhibition with EGFR-TKI overcomes primary and acquired EGFR-TKI resistance. We also found increased YAP expression in human lung cancer after acquiring EGFR-TKI resistance. Collectively, we suggest a novel EGFR-TKI resistance mechanism involving YAP activation and suggest targeting YAP and EGFR simultaneously may be a breakthrough treatment of primary and acquired EGFR-TKI resistant lung cancer. PMID:27105908

  3. Acquired Multidrug Antifungal Resistance in Candida lusitaniae during Therapy

    PubMed Central

    Asner, Sandra A.; Giulieri, Stefano; Diezi, Manuel; Marchetti, Oscar

    2015-01-01

    Candida lusitaniae is usually susceptible to echinocandins. Beta-1,3-glucan synthase encoded by FKS genes is the target of echinocandins. A few missense mutations in the C. lusitaniae FKS1 hot spot 1 (HS1) have been reported. We report here the rapid emergence of antifungal resistance in C. lusitaniae isolated during therapy with amphotericin B (AMB), caspofungin (CAS), and azoles for treatment of persistent candidemia in an immunocompromised child with severe enterocolitis and visceral adenoviral disease. As documented from restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) analysis, the five C. lusitaniae isolates examined were related to each other. From antifungal susceptibility and molecular analyses, 5 different profiles (P) were obtained. These profiles included the following: profile 1 (P1) (CAS MIC [μg/ml], 0.5; fluconazole [FLC] MIC, 0.25), determined while the patient was being treated with liposomal AMB for 3 months; P2 (FLC MIC [μg/ml], 0.25; CAS MIC, 4), while the patient was being treated with CAS for 2 weeks; P3 (CAS MIC [μg/ml], 0.5; FLC MIC, 32), while the patient was being treated with azoles and CAS initially followed by azoles alone for a week; P4 (CAS MIC [μg/ml], 8; FLC MIC, 8), while the patient was being treated with both drugs for 3 weeks; and P5 (AMB MIC [μg/ml], 0.125; CAS MIC, 8), while the patient was being treated with AMB and FLC for 2 weeks. CAS resistance was associated with resistance not only to micafungin and anidulafungin but also to AMB. Analysis of CAS resistance revealed 3 novel FKS1 mutations in CAS-resistant isolates (S638Y in P2; S631Y in P4; S638P in P5). While S638Y and -P are within HS1, S631Y is in close proximity to this domain but was confirmed to confer candin resistance using a site-directed mutagenesis approach. FLC resistance could be linked with overexpression of major facilitator gene 7 (MFS7) in C. lusitaniae P2 and P4 and was associated with resistance to 5

  4. Mechanisms of Resistance to Aminoglycoside Antibiotics: Overview and Perspectives

    PubMed Central

    Garneau-Tsodikova, Sylvie

    2015-01-01

    Aminoglycoside (AG) antibiotics are used to treat many Gram-negative and some Gram-positive infections and, importantly, multidrug-resistant tuberculosis. Among various bacterial species, resistance to AGs arises through a variety of intrinsic and acquired mechanisms. The bacterial cell wall serves as a natural barrier for small molecules such as AGs and may be further fortified via acquired mutations. Efflux pumps work to expel AGs from bacterial cells, and modifications here too may cause further resistance to AGs. Mutations in the ribosomal target of AGs, while rare, also contribute to resistance. Of growing clinical prominence is resistance caused by ribosome methyltransferases. By far the most widespread mechanism of resistance to AGs is the inactivation of these antibiotics by AG-modifying enzymes. We provide here an overview of these mechanisms by which bacteria become resistant to AGs and discuss their prevalence and potential for clinical relevance. PMID:26877861

  5. Influence of infection of cotton by Rotylenchulus Reniformis and Meloidogyne Incognita on the production of enzymes involved in systemic acquired resistance.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Systemic acquired resistance (SAR), which results in enhanced defense mechanisms in plants, can be elicited by virulent and avirulent strains of pathogens including nematodes. Recent studies of nematode reproduction strongly suggest that Meloidogyne incognita and Rotylenchulus reniformis induce SAR ...

  6. Non-Small Cell Lung Cancer Cells Acquire Resistance to the ALK Inhibitor Alectinib by Activating Alternative Receptor Tyrosine Kinases.

    PubMed

    Isozaki, Hideko; Ichihara, Eiki; Takigawa, Nagio; Ohashi, Kadoaki; Ochi, Nobuaki; Yasugi, Masayuki; Ninomiya, Takashi; Yamane, Hiromichi; Hotta, Katsuyuki; Sakai, Katsuya; Matsumoto, Kunio; Hosokawa, Shinobu; Bessho, Akihiro; Sendo, Toshiaki; Tanimoto, Mitsune; Kiura, Katsuyuki

    2016-03-15

    Crizotinib is the standard of care for advanced non-small cell lung cancer (NSCLC) patients harboring the anaplastic lymphoma kinase (ALK) fusion gene, but resistance invariably develops. Unlike crizotinib, alectinib is a selective ALK tyrosine kinase inhibitor (TKI) with more potent antitumor effects and a favorable toxicity profile, even in crizotinib-resistant cases. However, acquired resistance to alectinib, as for other TKIs, remains a limitation of its efficacy. Therefore, we investigated the mechanisms by which human NSCLC cells acquire resistance to alectinib. We established two alectinib-resistant cell lines that did not harbor the secondary ALK mutations frequently occurring in crizotinib-resistant cells. One cell line lost the EML4-ALK fusion gene, but exhibited increased activation of insulin-like growth factor-1 receptor (IGF1R) and human epidermal growth factor receptor 3 (HER3), and overexpressed the HER3 ligand neuregulin 1. Accordingly, pharmacologic inhibition of IGF1R and HER3 signaling overcame resistance to alectinib in this cell line. The second alectinib-resistant cell line displayed stimulated HGF autocrine signaling that promoted MET activation and remained sensitive to crizotinib treatment. Taken together, our findings reveal two novel mechanisms underlying alectinib resistance that are caused by the activation of alternative tyrosine kinase receptors rather than by secondary ALK mutations. These studies may guide the development of comprehensive treatment strategies that take into consideration the various approaches ALK-positive lung tumors use to withstand therapeutic insult. PMID:26719536

  7. Activation of the Met kinase confers acquired drug resistance in FGFR-targeted lung cancer therapy.

    PubMed

    Kim, S-M; Kim, H; Yun, M R; Kang, H N; Pyo, K-H; Park, H J; Lee, J M; Choi, H M; Ellinghaus, P; Ocker, M; Paik, S; Kim, H R; Cho, B C

    2016-01-01

    Aberrant fibroblast growth factor receptor (FGFR) activation/expression is a common feature in lung cancer (LC). In this study, we evaluated the antitumor activity of and the mechanisms underlying acquired resistance to two potent selective FGFR inhibitors, AZD4547 and BAY116387, in LC cell lines. The antitumor activity of AZD4547 and BAY1163877 was screened in 24 LC cell lines, including 5 with FGFR1 amplification. Two cell lines containing FGFR1 amplifications, H1581 and DMS114, were sensitive to FGFR inhibitors (IC50<250 nm). Clones of FGFR1-amplified H1581 cells resistant to AZD4547 or BAY116387 (H1581AR and H1581BR cells, respectively) were established. Receptor tyrosine kinase (RTK) array and immunoblotting analyses showed strong overexpression and activation of Met in H1581AR/BR cells, compared with that in the parental cells. Gene set enrichment analysis against the Kyoto Encyclopedia of Genes and Genomes (KEGG) database showed that cytokine-cytokine receptor interaction pathways were significantly enriched in H1581AR/BR cells, with Met contributing significantly to the core enrichment. Genomic DNA quantitative PCR and fluorescent in situ hybridization analyses showed MET amplification in H1581AR, but not in H1581BR, cells. Met amplification drives acquired resistance to AZD4547 in H1581AR cells by activating ErbB3. Combination treatment with FGFR inhibitors and an anaplastic lymphoma kinase (ALK)/Met inhibitor, crizotinib, or Met-specific short interfering RNA (siRNA) synergistically inhibited cell proliferation in both H1581AR and H1581BR cells. Conversely, ectopic expression of Met in H1581 cells conferred resistance to AZD4547 and BAY1163877. Acquired resistance to FGFR inhibitors not only altered cellular morphology, but also promoted migration and invasion of resistant clones, in part by inducing epithelial-to-mesenchymal transition. Taken together, our data suggest that Met activation is sufficient to bypass dependency on FGFR signaling. Concurrent

  8. Mechanisms of Drug Resistance: Daptomycin Resistance

    PubMed Central

    Tran, Truc T.; Munita, Jose M.; Arias, Cesar A.

    2016-01-01

    Daptomycin (DAP) is a cyclic lipopeptide with in vitro activity against a variety of Gram-positive pathogens, including multidrug-resistant organisms. Since its introduction in clinical practice in 2003, DAP has become an important key front-line antibiotic for severe or deep-seated infections caused by Gram-positive organisms. Unfortunately, DAP-resistance (R) has been extensively documented in clinically important organisms such as Staphylococcus aureus, Enterococcus spp, and Streptococcus spp. Studies on the mechanisms of DAP-R in Bacillus subtilis and other Gram-positive bacteria indicate that the genetic pathways of DAP resistance are diverse and complex. However, a common phenomenon emerging from these mechanistic studies is that DAP-R is associated with important adaptive changes in cell wall and cell membrane homeostasis with critical changes in cell physiology. Findings related to these adaptive changes have offered novel insights into the genetics and molecular mechanisms of bacterial cell envelope stress response and the manner in which Gram-positive bacteria cope with the antimicrobial peptide attack and protect vital structures of the cell envelope such as the cell membrane. In this review, we will examine the most recent findings related to the molecular mechanisms of resistance to DAP in relevant Gram-positive pathogens and discuss the clinical implications for therapy against these important bacteria. PMID:26495887

  9. Acquired resistance to the 16-membered macrolides tylosin and tilmicosin by Mycoplasma bovis.

    PubMed

    Lerner, Uri; Amram, Eytan; Ayling, Roger D; Mikula, Inna; Gerchman, Irena; Harrus, Shimon; Teff, Dina; Yogev, David; Lysnyansky, Inna

    2014-01-31

    The molecular mechanism of acquired resistance to the 16-membered macrolides tylosin (Ty) and tilmicosin (Tm) was investigated in Mycoplasma bovis field isolates. Sequence analysis of domains II and V of the two 23S rRNA alleles and ribosomal proteins L4 and L22 was performed on 54 M. bovis isolates showing different minimal inhibitory concentrations (MIC). The presence of any one of the point mutations G748A, C752T, A2058G, A2059G or A2059C (Escherichia coli numbering) in one or both alleles of the 23S rRNAs was correlated with decreased susceptibility to Ty (8-1024 μg/ml) and to Tm (32 to >256 μg/ml) in 27/27 and 27/31 M. bovis isolates, respectively. Although a single mutation in domain II or V could be sufficient to cause decreased susceptibility to Ty, our data imply that a combination of mutations in two domains is necessary to achieve higher MICs (≥ 128 μg/ml). The influence of a combination of mutations in two domains II and V on enhancement of resistance to Tm was less clear. In addition, the amino acid (aa) substitution L22-Q90H was found in 24/32 representative M. bovis isolates with different MICs, but no correlation with decreased susceptibility to Ty or Tm was identified. Multiple aa substitutions were also identified in the L4 protein, including at positions 185-186 (positions 64 and 65 in E. coli) which are adjacent to the macrolide-binding site. This is the first description of the molecular mechanism of acquired resistance to the 16-membered macrolides in M. bovis. PMID:24393633

  10. Acquired resistance and clonal evolution in melanoma during BRAF inhibitor therapy

    PubMed Central

    Kong, Xiangju; Hong, Aayoung; Koya, Richard C.; Moriceau, Gatien; Chodon, Thinle; Guo, Rongqing; Johnson, Douglas B.; Dahlman, Kimberly B.; Kelley, Mark C.; Kefford, Richard F.; Chmielowski, Bartosz; Glaspy, John A.; Sosman, Jeffrey A.; van Baren, Nicolas; Long, Georgina V.; Ribas, Antoni; Lo, Roger S.

    2013-01-01

    BRAF inhibitors elicit rapid anti-tumor responses in the majority of patients with V600BRAF mutant melanoma, but acquired drug resistance is almost universal. We sought to identify the core resistance pathways and the extent of tumor heterogeneity during disease progression. We show that MAPK reactivation mechanisms were detected among 70% of disease-progressive tissues, with RAS mutations, mutant BRAF amplification and alternative splicing being most common. We also detected PI3K-PTEN-AKT-upregulating genetic alterations among 22% of progressive melanomas. Distinct molecular lesions, in both core drug escape pathways, were commonly detected concurrently in the same tumor or among multiple tumors from the same patient. Beyond harboring extensively heterogeneous resistance mechanisms, melanoma re-growth emerging from BRAF inhibitor selection displayed branched evolution marked by altered mutational spectra/signatures and increased fitness. Thus, melanoma genomic heterogeneity contributes significantly to BRAF inhibitor treatment failure, implying upfront, co-targeting of two core pathways as an essential strategy for durable responses. PMID:24265155

  11. Interconnection between flowering time control and activation of systemic acquired resistance

    PubMed Central

    Banday, Zeeshan Z.; Nandi, Ashis K.

    2015-01-01

    The ability to avoid or neutralize pathogens is inherent to all higher organisms including plants. Plants recognize pathogens through receptors, and mount resistance against the intruders, with the help of well-elaborated defense arsenal. In response to some localinfections, plants develop systemic acquired resistance (SAR), which provides heightened resistance during subsequent infections. Infected tissues generate mobile signaling molecules that travel to the systemic tissues, where they epigenetically modify expression o a set of genes to initiate the manifestation of SAR in distant tissues. Immune responses are largely regulated at transcriptional level. Flowering is a developmental transition that occurs as a result of the coordinated action of large numbers of transcription factors that respond to intrinsic signals and environmental conditions. The plant hormone salicylic acid (SA) which is required for SAR activation positively regulates flowering. Certain components of chromatin remodeling complexes that are recruited for suppression of precocious flowering are also involved in suppression of SAR in healthy plants. FLOWERING LOCUS D, a putative histone demethylase positively regulates SAR manifestation and flowering transition in Arabidopsis. Similarly, incorporation of histone variant H2A.Z in nucleosomes mediated by PHOTOPERIOD-INDEPENDENT EARLY FLOWERING 1, an ortholog of yeast chromatin remodeling complex SWR1, concomitantly influences SAR and flowering time. SUMO conjugation and deconjugation mechanisms also similarly affect SAR and flowering in an SA-dependent manner. The evidences suggest a common underlying regulatory mechanism for activation of SAR and flowering in plants. PMID:25852723

  12. Interconnection between flowering time control and activation of systemic acquired resistance.

    PubMed

    Banday, Zeeshan Z; Nandi, Ashis K

    2015-01-01

    The ability to avoid or neutralize pathogens is inherent to all higher organisms including plants. Plants recognize pathogens through receptors, and mount resistance against the intruders, with the help of well-elaborated defense arsenal. In response to some localinfections, plants develop systemic acquired resistance (SAR), which provides heightened resistance during subsequent infections. Infected tissues generate mobile signaling molecules that travel to the systemic tissues, where they epigenetically modify expression o a set of genes to initiate the manifestation of SAR in distant tissues. Immune responses are largely regulated at transcriptional level. Flowering is a developmental transition that occurs as a result of the coordinated action of large numbers of transcription factors that respond to intrinsic signals and environmental conditions. The plant hormone salicylic acid (SA) which is required for SAR activation positively regulates flowering. Certain components of chromatin remodeling complexes that are recruited for suppression of precocious flowering are also involved in suppression of SAR in healthy plants. FLOWERING LOCUS D, a putative histone demethylase positively regulates SAR manifestation and flowering transition in Arabidopsis. Similarly, incorporation of histone variant H2A.Z in nucleosomes mediated by PHOTOPERIOD-INDEPENDENT EARLY FLOWERING 1, an ortholog of yeast chromatin remodeling complex SWR1, concomitantly influences SAR and flowering time. SUMO conjugation and deconjugation mechanisms also similarly affect SAR and flowering in an SA-dependent manner. The evidences suggest a common underlying regulatory mechanism for activation of SAR and flowering in plants. PMID:25852723

  13. Managing acquired resistance in EGFR-mutated non-small cell lung cancer.

    PubMed

    Forde, Patrick M; Ettinger, David S

    2015-08-01

    Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) deliver high response rates with relatively modest toxicity in patients with advanced EGFR-mutated non-small cell lung cancer. Despite this, nearly all tumors eventually develop resistance to first-line therapy. At present, the only standard treatment option for patients with acquired resistance is cytotoxic chemotherapy. In this article, we review the latest research into methods of targeting acquired resistance to EGFR TKI therapy, including third-generation EGFR TKIs that target the T790M resistance mutation and other novel agents in development. PMID:26351816

  14. Co-option of Liver Vessels and Not Sprouting Angiogenesis Drives Acquired Sorafenib Resistance in Hepatocellular Carcinoma

    PubMed Central

    Kuczynski, Elizabeth A.; Yin, Melissa; Bar-Zion, Avinoam; Lee, Christina R.; Butz, Henriett; Man, Shan; Daley, Frances; Vermeulen, Peter B.; Yousef, George M.; Foster, F. Stuart

    2016-01-01

    Background: The anti-angiogenic Sorafenib is the only approved systemic therapy for advanced hepatocellular carcinoma (HCC). However, acquired resistance limits its efficacy. An emerging theory to explain intrinsic resistance to other anti-angiogenic drugs is ‘vessel co-option,’ ie, the ability of tumors to hijack the existing vasculature in organs such as the lungs or liver, thus limiting the need for sprouting angiogenesis. Vessel co-option has not been evaluated as a potential mechanism for acquired resistance to anti-angiogenic agents. Methods: To study sorafenib resistance mechanisms, we used an orthotopic human HCC model (n = 4-11 per group), where tumor cells are tagged with a secreted protein biomarker to monitor disease burden and response to therapy. Histopathology, vessel perfusion assessed by contrast-enhanced ultrasound, and miRNA sequencing and quantitative real-time polymerase chain reaction were used to monitor changes in tumor biology. Results: While sorafenib initially inhibited angiogenesis and stabilized tumor growth, no angiogenic ‘rebound’ effect was observed during development of resistance unless therapy was stopped. Instead, resistant tumors became more locally infiltrative, which facilitated extensive incorporation of liver parenchyma and the co-option of liver-associated vessels. Up to 75% (±10.9%) of total vessels were provided by vessel co-option in resistant tumors relative to 23.3% (±10.3%) in untreated controls. miRNA sequencing implicated pro-invasive signaling and epithelial-to-mesenchymal-like transition during resistance development while functional imaging further supported a shift from angiogenesis to vessel co-option. Conclusions: This is the first documentation of vessel co-option as a mechanism of acquired resistance to anti-angiogenic therapy and could have important implications including the potential therapeutic benefits of targeting vessel co-option in conjunction with vascular endothelial growth factor

  15. Acquired Antibiotic Resistance: Are We Born with It? ▿

    PubMed Central

    Zhang, Lu; Kinkelaar, Daniel; Huang, Ying; Li, Yingli; Li, Xiaojing; Wang, Hua H.

    2011-01-01

    The rapid emergence of antibiotic resistance (AR) is a major public health concern. Recent findings on the prevalence of food-borne antibiotic-resistant (ART) commensal bacteria in ready-to-consume food products suggested that daily food consumption likely serves as a major avenue for dissemination of ART bacteria from the food chain to human hosts. To properly assess the impact of various factors, including the food chain, on AR development in hosts, it is important to determine the baseline of ART bacteria in the human gastrointestinal (GI) tract. We thus examined the gut microbiota of 16 infant subjects, from the newborn stage to 1 year of age, who fed on breast milk and/or infant formula during the early stages of development and had no prior exposure to antibiotics. Predominant bacterial populations resistant to several antibiotics and multiple resistance genes were found in the infant GI tracts within the first week of age. Several ART population transitions were also observed in the absence of antibiotic exposure and dietary changes. Representative AR gene pools including tet(M), ermB, sul2, and blaTEM were detected in infant subjects. Enterococcus spp., Staphylococcus spp., Klebsiella spp., Streptococcus spp., and Escherichia coli/Shigella spp. were among the identified AR gene carriers. ART bacteria were not detected in the infant formula and infant foods examined, but small numbers of skin-associated ART bacteria were found in certain breast milk samples. The data suggest that the early development of AR in the human gut microbiota is independent of infants' exposure to antibiotics but is likely impacted by exposure to maternal and environmental microbes during and after delivery and that the ART population is significantly amplified within the host even in the absence of antibiotic selective pressure. PMID:21821748

  16. Early Adaptation and Acquired Resistance to CDK4/6 Inhibition in Estrogen Receptor-Positive Breast Cancer.

    PubMed

    Herrera-Abreu, Maria Teresa; Palafox, Marta; Asghar, Uzma; Rivas, Martín A; Cutts, Rosalind J; Garcia-Murillas, Isaac; Pearson, Alex; Guzman, Marta; Rodriguez, Olga; Grueso, Judit; Bellet, Meritxell; Cortés, Javier; Elliott, Richard; Pancholi, Sunil; Baselga, José; Dowsett, Mitch; Martin, Lesley-Ann; Turner, Nicholas C; Serra, Violeta

    2016-04-15

    Small-molecule inhibitors of the CDK4/6 cell-cycle kinases have shown clinical efficacy in estrogen receptor (ER)-positive metastatic breast cancer, although their cytostatic effects are limited by primary and acquired resistance. Here we report that ER-positive breast cancer cells can adapt quickly to CDK4/6 inhibition and evade cytostasis, in part, via noncanonical cyclin D1-CDK2-mediated S-phase entry. This adaptation was prevented by cotreatment with hormone therapies or PI3K inhibitors, which reduced the levels of cyclin D1 (CCND1) and other G1-S cyclins, abolished pRb phosphorylation, and inhibited activation of S-phase transcriptional programs. Combined targeting of both CDK4/6 and PI3K triggered cancer cell apoptosis in vitro and in patient-derived tumor xenograft (PDX) models, resulting in tumor regression and improved disease control. Furthermore, a triple combination of endocrine therapy, CDK4/6, and PI3K inhibition was more effective than paired combinations, provoking rapid tumor regressions in a PDX model. Mechanistic investigations showed that acquired resistance to CDK4/6 inhibition resulted from bypass of cyclin D1-CDK4/6 dependency through selection of CCNE1 amplification or RB1 loss. Notably, although PI3K inhibitors could prevent resistance to CDK4/6 inhibitors, they failed to resensitize cells once resistance had been acquired. However, we found that cells acquiring resistance to CDK4/6 inhibitors due to CCNE1 amplification could be resensitized by targeting CDK2. Overall, our results illustrate convergent mechanisms of early adaptation and acquired resistance to CDK4/6 inhibitors that enable alternate means of S-phase entry, highlighting strategies to prevent the acquisition of therapeutic resistance to these agents. Cancer Res; 76(8); 2301-13. ©2016 AACR. PMID:27020857

  17. Molecular mechanisms of drug resistance and its reversal in cancer.

    PubMed

    Kartal-Yandim, Melis; Adan-Gokbulut, Aysun; Baran, Yusuf

    2016-08-01

    Chemotherapy is the main strategy for the treatment of cancer. However, the main problem limiting the success of chemotherapy is the development of multidrug resistance. The resistance can be intrinsic or acquired. The resistance phenotype is associated with the tumor cells that gain a cross-resistance to a large range of drugs that are structurally and functionally different. Multidrug resistance arises via many unrelated mechanisms, such as overexpression of energy-dependent efflux proteins, decrease in uptake of the agents, increase or alteration in drug targets, modification of cell cycle checkpoints, inactivation of the agents, compartmentalization of the agents, inhibition of apoptosis and aberrant bioactive sphingolipid metabolism. Exact elucidation of resistance mechanisms and molecular and biochemical approaches to overcome multidrug resistance have been a major goal in cancer research. This review comprises the mechanisms guiding multidrug resistance in cancer chemotherapy and also touches on approaches for reversing the resistance. PMID:25757878

  18. Glioblastoma Multiforme Therapy and Mechanisms of Resistance

    PubMed Central

    Ramirez, Yulian P.; Weatherbee, Jessica L.; Wheelhouse, Richard T.; Ross, Alonzo H.

    2013-01-01

    Glioblastoma multiforme (GBM) is a grade IV brain tumor characterized by a heterogeneous population of cells that are highly infiltrative, angiogenic and resistant to chemotherapy. The current standard of care, comprised of surgical resection followed by radiation and the chemotherapeutic agent temozolomide, only provides patients with a 12–14 month survival period post-diagnosis. Long-term survival for GBM patients remains uncommon as cells with intrinsic or acquired resistance to treatment repopulate the tumor. In this review we will describe the mechanisms of resistance, and how they may be overcome to improve the survival of GBM patients by implementing novel chemotherapy drugs, new drug combinations and new approaches relating to DNA damage, angiogenesis and autophagy. PMID:24287492

  19. Acquired Resistance to Clinical Cancer Therapy: A Twist in Physiological Signaling.

    PubMed

    Wicki, Andreas; Mandalà, Mario; Massi, Daniela; Taverna, Daniela; Tang, Huifang; Hemmings, Brian A; Xue, Gongda

    2016-07-01

    Although modern therapeutic strategies have brought significant progress to cancer care in the last 30 years, drug resistance to targeted monotherapies has emerged as a major challenge. Aberrant regulation of multiple physiological signaling pathways indispensable for developmental and metabolic homeostasis, such as hyperactivation of pro-survival signaling axes, loss of suppressive regulations, and impaired functionalities of the immune system, have been extensively investigated aiming to understand the diversity of molecular mechanisms that underlie cancer development and progression. In this review, we intend to discuss the molecular mechanisms of how conventional physiological signal transduction confers to acquired drug resistance in cancer patients. We will particularly focus on protooncogenic receptor kinase inhibition-elicited tumor cell adaptation through two major core downstream signaling cascades, the PI3K/Akt and MAPK pathways. These pathways are crucial for cell growth and differentiation and are frequently hyperactivated during tumorigenesis. In addition, we also emphasize the emerging roles of the deregulated host immune system that may actively promote cancer progression and attenuate immunosurveillance in cancer therapies. Understanding these mechanisms may help to develop more effective therapeutic strategies that are able to keep the tumor in check and even possibly turn cancer into a chronic disease. PMID:27142452

  20. Mechanisms of resistance to cabazitaxel.

    PubMed

    Duran, George E; Wang, Yan C; Francisco, E Brian; Rose, John C; Martinez, Francisco J; Coller, John; Brassard, Diana; Vrignaud, Patricia; Sikic, Branimir I

    2015-01-01

    We studied mechanisms of resistance to the novel taxane cabazitaxel in established cellular models of taxane resistance. We also developed cabazitaxel-resistant variants from MCF-7 breast cancer cells by stepwise selection in drug alone (MCF-7/CTAX) or drug plus the transport inhibitor PSC-833 (MCF-7/CTAX-P). Among multidrug-resistant (MDR) variants, cabazitaxel was relatively less cross-resistant than paclitaxel and docetaxel (15- vs. 200-fold in MES-SA/Dx5 and 9- vs. 60-fold in MCF-7/TxT50, respectively). MCF-7/TxTP50 cells that were negative for MDR but had 9-fold resistance to paclitaxel were also 9-fold resistant to cabazitaxel. Selection with cabazitaxel alone (MCF-7/CTAX) yielded 33-fold resistance to cabazitaxel, 52-fold resistance to paclitaxel, activation of ABCB1, and 3-fold residual resistance to cabazitaxel with MDR inhibition. The MCF-7/CTAX-P variant did not express ABCB1, nor did it efflux rhodamine-123, BODIPY-labeled paclitaxel, and [(3)H]-docetaxel. These cells are hypersensitive to depolymerizing agents (vinca alkaloids and colchicine), have reduced baseline levels of stabilized microtubules, and impaired tubulin polymerization in response to taxanes (cabazitaxel or docetaxel) relative to MCF-7 parental cells. Class III β-tubulin (TUBB3) RNA and protein were elevated in both MCF-7/CTAX and MCF-7/CTAX-P. Decreased BRCA1 and altered epithelial-mesenchymal transition (EMT) markers are also associated with cabazitaxel resistance in these MCF-7 variants, and may serve as predictive biomarkers for its activity in the clinical setting. In summary, cabazitaxel resistance mechanisms include MDR (although at a lower level than paclitaxel and docetaxel), and alterations in microtubule dynamicity, as manifested by higher expression of TUBB3, decreased BRCA1, and by the induction of EMT. PMID:25416788

  1. Mutations Associated with Acquired Resistance to PD-1 Blockade in Melanoma.

    PubMed

    Zaretsky, Jesse M; Garcia-Diaz, Angel; Shin, Daniel S; Escuin-Ordinas, Helena; Hugo, Willy; Hu-Lieskovan, Siwen; Torrejon, Davis Y; Abril-Rodriguez, Gabriel; Sandoval, Salemiz; Barthly, Lucas; Saco, Justin; Homet Moreno, Blanca; Mezzadra, Riccardo; Chmielowski, Bartosz; Ruchalski, Kathleen; Shintaku, I Peter; Sanchez, Phillip J; Puig-Saus, Cristina; Cherry, Grace; Seja, Elizabeth; Kong, Xiangju; Pang, Jia; Berent-Maoz, Beata; Comin-Anduix, Begoña; Graeber, Thomas G; Tumeh, Paul C; Schumacher, Ton N M; Lo, Roger S; Ribas, Antoni

    2016-09-01

    Background Approximately 75% of objective responses to anti-programmed death 1 (PD-1) therapy in patients with melanoma are durable, lasting for years, but delayed relapses have been noted long after initial objective tumor regression despite continuous therapy. Mechanisms of immune escape in this context are unknown. Methods We analyzed biopsy samples from paired baseline and relapsing lesions in four patients with metastatic melanoma who had had an initial objective tumor regression in response to anti-PD-1 therapy (pembrolizumab) followed by disease progression months to years later. Results Whole-exome sequencing detected clonal selection and outgrowth of the acquired resistant tumors and, in two of the four patients, revealed resistance-associated loss-of-function mutations in the genes encoding interferon-receptor-associated Janus kinase 1 (JAK1) or Janus kinase 2 (JAK2), concurrent with deletion of the wild-type allele. A truncating mutation in the gene encoding the antigen-presenting protein beta-2-microglobulin (B2M) was identified in a third patient. JAK1 and JAK2 truncating mutations resulted in a lack of response to interferon gamma, including insensitivity to its antiproliferative effects on cancer cells. The B2M truncating mutation led to loss of surface expression of major histocompatibility complex class I. Conclusions In this study, acquired resistance to PD-1 blockade immunotherapy in patients with melanoma was associated with defects in the pathways involved in interferon-receptor signaling and in antigen presentation. (Funded by the National Institutes of Health and others.). PMID:27433843

  2. Long-distance communication and signal amplification in systemic acquired resistance.

    PubMed

    Shah, Jyoti; Zeier, Jürgen

    2013-01-01

    Systemic acquired resistance (SAR) is an inducible defense mechanism in plants that confers enhanced resistance against a variety of pathogens. SAR is activated in the uninfected systemic (distal) organs in response to a prior (primary) infection elsewhere in the plant. SAR is associated with the activation of salicylic acid (SA) signaling and the priming of defense responses for robust activation in response to subsequent infections. The activation of SAR requires communication by the primary infected tissues with the distal organs. The vasculature functions as a conduit for the translocation of factors that facilitate long-distance intra-plant communication. In recent years, several metabolites putatively involved in long-distance signaling have been identified. These include the methyl ester of SA (MeSA), the abietane diterpenoid dehydroabietinal (DA), the dicarboxylic acid azelaic acid (AzA), and a glycerol-3-phosphate (G3P)-dependent factor. Long-distance signaling by some of these metabolites also requires the lipid-transfer protein DIR1 (DEFECTIVE IN INDUCED RESISTANCE 1). The relative contribution of these factors in long-distance signaling is likely influenced by environmental conditions, for example light. In the systemic leaves, the AGD2-LIKE DEFENSE RESPONSE PROTEIN1 (ALD1)-dependent production of the lysine catabolite pipecolic acid (Pip), FLAVIN-DEPENDENT MONOOXYGENASE1 (FMO1) signaling, as well as SA synthesis and downstream signaling are required for the activation of SAR. This review summarizes the involvement and interaction between long-distance SAR signals and details the recently discovered role of Pip in defense amplification and priming that allows plants to acquire immunity at the systemic level. Recent advances in SA signaling and perception are also highlighted. PMID:23440336

  3. Overexpression of Specific CD44 Isoforms Is Associated with Aggressive Cell Features in Acquired Endocrine Resistance

    PubMed Central

    Bellerby, Rebecca; Smith, Chris; Kyme, Sue; Gee, Julia; Günthert, Ursula; Green, Andy; Rakha, Emad; Barrett-Lee, Peter; Hiscox, Stephen

    2016-01-01

    While endocrine therapy is the mainstay of ER+ breast cancer, the clinical effectiveness of these agents is limited by the phenomenon of acquired resistance that is associated with disease relapse and poor prognosis. Our previous studies revealed that acquired resistance is accompanied by a gain in cellular invasion and migration and also that CD44 family proteins are overexpressed in the resistant phenotype. Given the association of CD44 with tumor progression, we hypothesized that its overexpression may act to promote the aggressive behavior of endocrine-resistant breast cancers. Here, we have investigated further the role of two specific CD44 isoforms, CD44v3 and CD44v6, in the endocrine-resistant phenotype. Our data revealed that overexpression of CD44v6, but not CD44v3, in endocrine-sensitive MCF-7 cells resulted in a gain in EGFR signaling, enhanced their endogenous invasive capacity, and attenuated their response to endocrine treatment. Suppression of CD44v6 in endocrine-resistant cell models was associated with a reduction in their invasive capacity. Our data suggest that upregulation of CD44v6 in acquired resistant breast cancer may contribute to a gain in the aggressive phenotype of these cells and loss of endocrine response through transactivation of the EGFR pathway. Future therapeutic targeting of CD44v6 may prove to be an effective strategy alongside EGFR-targeted agents in delaying/preventing acquired resistance in breast cancer. PMID:27379207

  4. Community-Acquired Methicillin-Resistant "Staphylococcus aureus": Considerations for School Nurses

    ERIC Educational Resources Information Center

    Alex, Aniltta; Letizia, MariJo

    2007-01-01

    Methicillin-resistant "Staphylococcus aureus" (MRSA) is a disease-causing organism that has been present in hospital settings since the 1960s. However, a genetically distinct strain of MRSA, called community-acquired methicillin-resistant "Staphylococcus aureus" (CA-MRSA), has emerged in recent years in community settings among healthy…

  5. Acquired resistance to ABT-737 in lymphoma cells that up-regulate MCL-1 and BFL-1

    PubMed Central

    Yecies, Derek; Carlson, Nicole E.; Deng, Jing

    2010-01-01

    ABT-737 is a small-molecule antagonist of BCL-2 currently under evaluation in clinical trials in the oral form of ABT-263. We anticipate that acquired resistance to this promising drug will inevitably arise. To study potential mechanisms of resistance to ABT-737, we derived resistant lines from initially sensitive OCI-Ly1 and SU-DHL-4 lymphoma cell lines via long-term exposure. Resistance was based in the mitochondria and not due to an inability of the drug to bind BCL-2. Resistant cells had increased levels of BFL-1 and/or MCL-1 proteins, which are not targeted by ABT-737. Proapoptotic BIM was displaced from BCL-2 by ABT-737 in both parental and resistant cells, but in resistant cells, BIM was sequestered by the additional BFL-1 and/or MCL-1. Decreasing MCL-1 levels with flavopiridol, PHA 767491, or shRNA restored sensitivity to ABT-737 resistant cells. MCL-1 was up-regulated not by protein stabilization but rather by increased transcript levels. Surprisingly, in addition to stable increases in MCL-1 transcript and protein in resistant cells, there was a dynamic increase within hours after ABT-737 treatment. BFL-1 protein and transcript levels in resistant cells were similarly dynamically up-regulated. This dynamic increase suggests a novel mechanism whereby modulation of antiapoptotic protein function communicates with nuclear transcriptional machinery. PMID:20197552

  6. (Mechanisms of tolerance and resistance)

    SciTech Connect

    Waters, L.C.

    1990-08-28

    The traveler participated in the Seventh International Congress of Pesticide Chemistry by presenting a poster entitled Studies on the Expression of Insecticide Resistance-Associated Cytochrome P450 in Drosophila Using Cloned DNA'' and as an invited speaker in the Workshop Session on Insecticide Resistance. The Congress covered a wide range of topics, including studies of new syntheic compounds and natural products with crop protecting properties, modes of action of pesticides, mechanisms of pesticide resistance, environmental fate of pesticides and estimates of risk to pesticide exposure. Several presentations on the potential role of cytochrome P450 in resistance to insecticides and herbicides were relevant to our work at ORNL's Biology Division on molecular mechanisms of P450 expression.

  7. Endemic carbapenem-resistant Pseudomonas aeruginosa with acquired metallo-beta-lactamase determinants in European hospital.

    PubMed

    Lagatolla, Cristina; Tonin, Enrico A; Monti-Bragadin, Carlo; Dolzani, Lucilla; Gombac, Francesca; Bearzi, Claudia; Edalucci, Elisabetta; Gionechetti, Fabrizia; Rossolini, Gian Maria

    2004-03-01

    Acquired metallo-beta-lactamases (MBLs) can confer broad-spectrum beta-lactam resistance (including carbapenems) not reversible by conventional beta-lactamase inhibitors and are emerging resistance determinants of remarkable clinical importance. In 2001, multidrug-resistant Pseudomonas aeruginosa carrying bla(VIM) MBL genes were found to be widespread (approximately 20% of all P. aeruginosa isolates and 70% of the carbapenem-resistant isolates) at Trieste University Hospital. Clonal diversity and heterogeneity of resistance determinants (either bla(VIM-1)-like or bla(VIM-2)-like) were detected among MBL producers. This evidence is the first that acquired MBLs can rapidly emerge and establish a condition of endemicity in certain epidemiologic settings. PMID:15109432

  8. Collateral Chemoresistance to Anti-Microtubule Agents in a Lung Cancer Cell Line with Acquired Resistance to Erlotinib

    PubMed Central

    Mizuuchi, Hiroshi; Suda, Kenichi; Sato, Katsuaki; Tomida, Shuta; Fujita, Yoshihiko; Kobayashi, Yoshihisa; Maehara, Yoshihiko; Sekido, Yoshitaka; Nishio, Kazuto; Mitsudomi, Tetsuya

    2015-01-01

    Various alterations underlying acquired resistance to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) have been described. Although treatment strategies specific for these mechanisms are under development, cytotoxic agents are currently employed to treat many patients following failure of EGFR-TKIs. However, the effect of TKI resistance on sensitivity to these cytotoxic agents is mostly unclear. This study investigated the sensitivity of erlotinib-resistant tumor cells to five cytotoxic agents using an in vitro EGFR-TKI-resistant model. Four erlotinib-sensitive lung adenocarcinoma cell lines and their resistant derivatives were tested. Of the resistant cell lines, all but one showed a similar sensitivity to the tested drugs as their parental cells. HCC4006ER cells with epithelial mesenchymal transition features acquired resistance to the three microtubule-targeting agents, docetaxel, paclitaxel and vinorelbine, but not to cisplatin and gemcitabine. Gene expression array and immunoblotting demonstrated that ATP-binding cassette subfamily B, member 1 (ABCB1) was up-regulated in HCC4006ER cells. ABCB1 knockdown by siRNA partially restored sensitivity to the anti-microtubule agents but not to erlotinib. Moreover, the histone deacetylase inhibitor entinostat sensitized HCC4006ER cells to anti-microtubule agents through ABCB1 suppression. Our study indicates that sensitivity of tumor cells to cytotoxic agents in general does not change before and after failure of EGFR-TKIs. However, we describe that two different molecular alterations confer acquired resistance to EGFR-TKIs and cytotoxic agents, respectively. This phenomenon should be kept in mind in selection of subsequent therapy after failure of EGFR-TKIs. PMID:25875914

  9. Collateral chemoresistance to anti-microtubule agents in a lung cancer cell line with acquired resistance to erlotinib.

    PubMed

    Mizuuchi, Hiroshi; Suda, Kenichi; Sato, Katsuaki; Tomida, Shuta; Fujita, Yoshihiko; Kobayashi, Yoshihisa; Maehara, Yoshihiko; Sekido, Yoshitaka; Nishio, Kazuto; Mitsudomi, Tetsuya

    2015-01-01

    Various alterations underlying acquired resistance to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) have been described. Although treatment strategies specific for these mechanisms are under development, cytotoxic agents are currently employed to treat many patients following failure of EGFR-TKIs. However, the effect of TKI resistance on sensitivity to these cytotoxic agents is mostly unclear. This study investigated the sensitivity of erlotinib-resistant tumor cells to five cytotoxic agents using an in vitro EGFR-TKI-resistant model. Four erlotinib-sensitive lung adenocarcinoma cell lines and their resistant derivatives were tested. Of the resistant cell lines, all but one showed a similar sensitivity to the tested drugs as their parental cells. HCC4006ER cells with epithelial mesenchymal transition features acquired resistance to the three microtubule-targeting agents, docetaxel, paclitaxel and vinorelbine, but not to cisplatin and gemcitabine. Gene expression array and immunoblotting demonstrated that ATP-binding cassette subfamily B, member 1 (ABCB1) was up-regulated in HCC4006ER cells. ABCB1 knockdown by siRNA partially restored sensitivity to the anti-microtubule agents but not to erlotinib. Moreover, the histone deacetylase inhibitor entinostat sensitized HCC4006ER cells to anti-microtubule agents through ABCB1 suppression. Our study indicates that sensitivity of tumor cells to cytotoxic agents in general does not change before and after failure of EGFR-TKIs. However, we describe that two different molecular alterations confer acquired resistance to EGFR-TKIs and cytotoxic agents, respectively. This phenomenon should be kept in mind in selection of subsequent therapy after failure of EGFR-TKIs. PMID:25875914

  10. A novel acquired ALK F1245C mutation confers resistance to crizotinib in ALK-positive NSCLC but is sensitive to ceritinib.

    PubMed

    Kodityal, Sandeep; Elvin, Julia A; Squillace, Rachel; Agarwal, Nikita; Miller, Vincent A; Ali, Siraj M; Klempner, Samuel J; Ou, Sai-Hong Ignatius

    2016-02-01

    The emergence of acquired anaplastic lymphoma kinase (ALK) resistant mutations is a common molecular mechanism underpinning disease progression during crizotinib treatment of ALK-positive (ALK+) non-small cell lung cancer (NSCLC) patients. Identifying acquired resistance mutations in ALK is paramount for tailoring future therapy with second generation ALK inhibitors and beyond. Comprehensive genomic profiling using hybrid-capture next generation sequencing has been successful in identifying acquired ALK resistance mutations. Here we described the emergence of an ALK F1245C mutation in an advanced ALK+ NSCLC patient (EML4-ALK variant 3a/b) who developed slow disease progression after a durable response to crizotinib. The patient was eventually switched to ceritinib with on-going clinical response. This is the first patient report that ALK F1245C is an acquired resistance mutation to crizotinib that can be overcome by ceritinib. PMID:26775591

  11. Imaging the urokinase plasminongen activator receptor in preclinical breast cancer models of acquired drug resistance.

    PubMed

    LeBeau, Aaron M; Sevillano, Natalia; King, Mandy L; Duriseti, Sai; Murphy, Stephanie T; Craik, Charles S; Murphy, Laura L; VanBrocklin, Henry F

    2014-01-01

    Subtype-targeted therapies can have a dramatic impact on improving the quality and quantity of life for women suffering from breast cancer. Despite an initial therapeutic response, cancer recurrence and acquired drug-resistance are commonplace. Non-invasive imaging probes that identify drug-resistant lesions are urgently needed to aid in the development of novel drugs and the effective utilization of established therapies for breast cancer. The protease receptor urokinase plasminogen activator receptor (uPAR) is a target that can be exploited for non-invasive imaging. The expression of uPAR has been associated with phenotypically aggressive breast cancer and acquired drug-resistance. Acquired drug-resistance was modeled in cell lines from two different breast cancer subtypes, the uPAR negative luminal A subtype and the uPAR positive triple negative subtype cell line MDA-MB-231. MCF-7 cells, cultured to be resistant to tamoxifen (MCF-7 TamR), were found to significantly over-express uPAR compared to the parental cell line. uPAR expression was maintained when resistance was modeled in triple-negative breast cancer by generating doxorubicin and paclitaxel resistant MDA-MB-231 cells (MDA-MB-231 DoxR and MDA-MB-231 TaxR). Using the antagonistic uPAR antibody 2G10, uPAR was imaged in vivo by near-infrared (NIR) optical imaging and (111)In-single photon emission computed tomography (SPECT). Tumor uptake of the (111)In-SPECT probe was high in the three drug-resistant xenografts (> 46 %ID/g) and minimal in uPAR negative xenografts at 72 hours post-injection. This preclinical study demonstrates that uPAR can be targeted for imaging breast cancer models of acquired resistance leading to potential clinical applications. PMID:24505235

  12. Acquisition of a single EZH2 D1 domain mutation confers acquired resistance to EZH2-targeted inhibitors

    PubMed Central

    Baker, Theresa; Nerle, Sujata; Pritchard, Justin; Zhao, Boyang; Rivera, Victor M.

    2015-01-01

    Although targeted therapies have revolutionized cancer treatment, overcoming acquired resistance remains a major clinical challenge. EZH2 inhibitors (EZH2i), EPZ-6438 and GSK126, are currently in the early stages of clinical evaluation and the first encouraging signs of efficacy have recently emerged in the clinic. To anticipate mechanisms of resistance to EZH2i, we used a forward genetic platform combining a mutagenesis screen with next generation sequencing technology and identified a hotspot of secondary mutations in the EZH2 D1 domain (Y111 and I109). Y111D mutation within the WT or A677G EZH2 allele conferred robust resistance to both EPZ-6438 and GSK126, but it only drove a partial resistance within the Y641F allele. EZH2 mutants required histone methyltransferase (HMT) catalytic activity and the polycomb repressive complex 2 (PRC2) components, SUZ12 and EED, to drive drug resistance. Furthermore, D1 domain mutations not only blocked the ability of EZH2i to bind to WT and A677G mutant, but also abrogated drug binding to the Y641F mutant. These data provide the first cellular validation of the mechanistic model underpinning the oncogenic function of WT and mutant EZH2. Importantly, our findings suggest that acquired-resistance to EZH2i may arise in WT and mutant EZH2 patients through a single mutation that remains targetable by second generation EZH2i. PMID:26360609

  13. Antimicrobial Resistance Mechanisms among Campylobacter

    PubMed Central

    2013-01-01

    Campylobacter jejuni and Campylobacter coli are recognized as the most common causative agents of bacterial gastroenteritis in the world. Humans most often become infected by ingesting contaminated food, especially undercooked chicken, but also other sources of bacteria have been described. Campylobacteriosis is normally a self-limiting disease. Antimicrobial treatment is needed only in patients with more severe disease and in those who are immunologically compromised. The most common antimicrobial agents used in the treatment of Campylobacter infections are macrolides, such as erythromycin, and fluoroquinolones, such as ciprofloxacin. Tetracyclines have been suggested as an alternative choice in the treatment of clinical campylobacteriosis but in practice are not often used. However, during the past few decades an increasing number of resistant Campylobacter isolates have developed resistance to fluoroquinolones and other antimicrobials such as macrolides, aminoglycosides, and beta-lactams. Trends in antimicrobial resistance have shown a clear correlation between use of antibiotics in the veterinary medicine and animal production and resistant isolates of Campylobacter in humans. In this review, the patterns of emerging resistance to the antimicrobial agents useful in treatment of the disease are presented and the mechanisms of resistance to these drugs in Campylobacter are discussed. PMID:23865047

  14. Characterization of naturally acquired multiple-drug resistance of Yoshida rat ascites hepatoma AH66 cell line.

    PubMed

    Miyamoto, K; Wakabayashi, D; Minamino, T; Nomura, M; Wakusawa, S; Nakamura, S

    1996-01-01

    Characteristics of multiple-drug resistance of rat ascites hepatoma AH66, a cell line induced by dimethylaminoazobenzene and established as a transplantable tumor, were compared with those of AH66F, a drug sensitive line obtained from AH66. The AH66 cell line was resistant to vinblastine, adriamycin, SN-38 an active form of camptothesine, etoposide, and clorambucil by 10-fold or more than the AH66F cell line. The resistance of AH66 cells to vinblastine, adriamycin, and SN-38 was closely related to P-glycoprotein overexpression in the plasma membrane, because the resistance was significantly inhibited by verapamil. AH66 cells contained much glutahione and had a high activity of glutathione S-transferase P-form (GST-P), compared with AH66F cells, and resistance to clorambucil was decreased by treatment with buthionine sulfoximine, an inhibitor of glutathione synthesis. AH66 cells have a similar topoisomerase I activity, but about 6 times lower topoisomerase II activity than AH66F cells. Therefore, the resistance to etoposide and a part of the resistance to adriamycin of AH66 cells seems to depend upon this low topoisomerase II activity. These results, show that the AH66 cell line has high multiple-drug resistance compared with the AH66F cell line, by several mechanisms. Consequently, the AH66 and AH66F cell lines are useful to study naturally acquired multiple-drug resistance of hepatomas. PMID:8702243

  15. A Nexus Consisting of Beta-Catenin and Stat3 Attenuates BRAF Inhibitor Efficacy and Mediates Acquired Resistance to Vemurafenib.

    PubMed

    Sinnberg, Tobias; Makino, Elena; Krueger, Marcel A; Velic, Ana; Macek, Boris; Rothbauer, Ulrich; Groll, Nicola; Pötz, Oliver; Czemmel, Stefan; Niessner, Heike; Meier, Friedegund; Ikenberg, Kristian; Garbe, Claus; Schittek, Birgit

    2016-06-01

    Acquired resistance to second generation BRAF inhibitors (BRAFis), like vemurafenib is limiting the benefits of long term targeted therapy for patients with malignant melanomas that harbor BRAF V600 mutations. Since many resistance mechanisms have been described, most of them causing a hyperactivation of the MAPK- or PI3K/AKT signaling pathways, one potential strategy to overcome BRAFi resistance in melanoma cells would be to target important common signaling nodes. Known factors that cause secondary resistance include the overexpression of receptor tyrosine kinases (RTKs), alternative splicing of BRAF or the occurrence of novel mutations in MEK1 or NRAS. In this study we show that β-catenin is stabilized and translocated to the nucleus in approximately half of the melanomas that were analyzed and which developed secondary resistance towards BRAFi. We further demonstrate that β-catenin is involved in the mediation of resistance towards vemurafenib in vitro and in vivo. Unexpectedly, β-catenin acts mainly independent of the TCF/LEF dependent canonical Wnt-signaling pathway in resistance development, which partly explains previous contradictory results about the role of β-catenin in melanoma progression and therapy resistance. We further demonstrate that β-catenin interacts with Stat3 after chronic vemurafenib treatment and both together cooperate in the acquisition and maintenance of resistance towards BRAFi. PMID:27428425

  16. Axl mediates acquired resistance of head and neck cancer cells to the epidermal growth factor receptor inhibitor erlotinib.

    PubMed

    Giles, Keith M; Kalinowski, Felicity C; Candy, Patrick A; Epis, Michael R; Zhang, Priscilla M; Redfern, Andrew D; Stuart, Lisa M; Goodall, Gregory J; Leedman, Peter J

    2013-11-01

    Elevated expression and activity of the epidermal growth factor receptor (EGFR) is associated with development and progression of head and neck cancer (HNC) and a poor prognosis. Clinical trials with EGFR tyrosine kinase inhibitors (e.g., erlotinib) have been disappointing in HNC. To investigate the mechanisms mediating resistance to these agents, we developed an HNC cell line (HN5-ER) with acquired erlotinib resistance. In contrast to parental HN5 HNC cells, HN5-ER cells exhibited an epithelial-mesenchymal (EMT) phenotype with increased migratory potential, reduced E-cadherin and epithelial-associated microRNAs (miRNA), and elevated vimentin expression. Phosphorylated receptor tyrosine kinase profiling identified Axl activation in HN5-ER cells. Growth and migration of HN5-ER cells were blocked with a specific Axl inhibitor, R428, and R428 resensitized HN5-ER cells to erlotinib. Microarray analysis of HN5-ER cells confirmed the EMT phenotype associated with acquired erlotinib resistance, and identified activation of gene expression associated with cell migration and inflammation pathways. Moreover, increased expression and secretion of interleukin (IL)-6 and IL-8 in HN5-ER cells suggested a role for inflammatory cytokine signaling in EMT and erlotinib resistance. Expression of the tumor suppressor miR-34a was reduced in HN5-ER cells and increasing its expression abrogated Axl expression and reversed erlotinib resistance. Finally, analysis of 302 HNC patients revealed that high tumor Axl mRNA expression was associated with poorer survival (HR = 1.66, P = 0.007). In summary, our results identify Axl as a key mediator of acquired erlotinib resistance in HNC and suggest that therapeutic inhibition of Axl by small molecule drugs or specific miRNAs might overcome anti-EGFR therapy resistance. PMID:24026012

  17. Acquired Resistance of Lung Adenocarcinomas to Gefitinib or Erlotinib Is Associated with a Second Mutation in the EGFR Kinase Domain

    PubMed Central

    2005-01-01

    Background Lung adenocarcinomas from patients who respond to the tyrosine kinase inhibitors gefitinib (Iressa) or erlotinib (Tarceva) usually harbor somatic gain-of-function mutations in exons encoding the kinase domain of the epidermal growth factor receptor (EGFR). Despite initial responses, patients eventually progress by unknown mechanisms of “acquired” resistance. Methods and Findings We show that in two of five patients with acquired resistance to gefitinib or erlotinib, progressing tumors contain, in addition to a primary drug-sensitive mutation in EGFR, a secondary mutation in exon 20, which leads to substitution of methionine for threonine at position 790 (T790M) in the kinase domain. Tumor cells from a sixth patient with a drug-sensitive EGFR mutation whose tumor progressed on adjuvant gefitinib after complete resection also contained the T790M mutation. This mutation was not detected in untreated tumor samples. Moreover, no tumors with acquired resistance had KRAS mutations, which have been associated with primary resistance to these drugs. Biochemical analyses of transfected cells and growth inhibition studies with lung cancer cell lines demonstrate that the T790M mutation confers resistance to EGFR mutants usually sensitive to either gefitinib or erlotinib. Interestingly, a mutation analogous to T790M has been observed in other kinases with acquired resistance to another kinase inhibitor, imatinib (Gleevec). Conclusion In patients with tumors bearing gefitinib- or erlotinib-sensitive EGFR mutations, resistant subclones containing an additional EGFR mutation emerge in the presence of drug. This observation should help guide the search for more effective therapy against a specific subset of lung cancers. PMID:15737014

  18. Acquired antimicrobial resistance in the intestinal microbiota of diverse cat populations.

    PubMed

    Moyaert, H; De Graef, E M; Haesebrouck, F; Decostere, A

    2006-08-01

    The aim of this study was to investigate the prevalence of acquired antimicrobial resistance in the resident intestinal microbiota of cats and to identify significant differences between various cat populations. Escherichia coli, Enterococcus faecalis, E. faecium and Streptococcus canis were isolated as faecal indicator bacteria from rectal swabs of 47 individually owned cats, 47 cattery cats and 18 hospitalised cats, and submitted through antimicrobial sensitivity tests. The results revealed that bacteria isolated from hospitalised and/or cattery cats were more frequently resistant than those from individually owned cats. E. coli isolates from hospitalised cats were particularly resistant to ampicillin, tetracycline and sulfonamide. Both enterococci and streptococci showed high resistance to tetracycline and in somewhat lesser extent to erythromycin and tylosin. Most E. faecium isolates were resistant to lincomycin and penicillin. One E. faecalis as well as one E. faecium isolate from hospitalised cats showed 'high-level resistance' (MIC > 500 microg/ml) against gentamicin, a commonly used antimicrobial agent in case of human enterococcal infections. The results of this research demonstrate that the extent of acquired antimicrobial resistance in the intestinal microbiota of cats depends on the social environment of the investigated population. It is obvious that the flora of healthy cats may act as a reservoir of resistance genes. PMID:16330058

  19. Resistant mechanisms to BRAF inhibitors in melanoma.

    PubMed

    Manzano, José Luís; Layos, Laura; Bugés, Cristina; de Los Llanos Gil, María; Vila, Laia; Martínez-Balibrea, Eva; Martínez-Cardús, Anna

    2016-06-01

    Patients with advanced melanoma have traditionally had very poor prognosis. However, since 2011 better understanding of the biology and epidemiology of this disease has revolutionized its treatment, with newer therapies becoming available. These newer therapies can be classified into immunotherapy and targeted therapy. The immunotherapy arsenal includes inhibitors of CTLA4, PD-1 and PDL-1, while targeted therapy focuses on BRAF and MEK. BRAF inhibitors (vemurafenib, dabrafenib) have shown benefit in terms of overall survival (OS) compared to chemotherapy, and their combination with MEK inhibitors has recently been shown to improve progression-free survival (PFS), compared with monotherapy with BRAF inhibitors. However, almost 20% of patients initially do not respond, due to intrinsic resistance to therapy and, of those who do, most eventually develop mechanisms of acquired resistance, including reactivation of the MAP kinase pathway, persistent activation of receptor tyrosine kinase (RTKS) receptor, activation of phosphatidyinositol-3OH kinase, overexpression of epidermal growth factor receptor (EGFR), and interactions with the tumor microenvironment. Herein we comment in detail on mechanisms of resistance to targeted therapy and discuss the strategies to overcome them. PMID:27429963

  20. Resistant mechanisms to BRAF inhibitors in melanoma

    PubMed Central

    Layos, Laura; Bugés, Cristina; de los Llanos Gil, María; Vila, Laia; Martínez-Balibrea, Eva; Martínez-Cardús, Anna

    2016-01-01

    Patients with advanced melanoma have traditionally had very poor prognosis. However, since 2011 better understanding of the biology and epidemiology of this disease has revolutionized its treatment, with newer therapies becoming available. These newer therapies can be classified into immunotherapy and targeted therapy. The immunotherapy arsenal includes inhibitors of CTLA4, PD-1 and PDL-1, while targeted therapy focuses on BRAF and MEK. BRAF inhibitors (vemurafenib, dabrafenib) have shown benefit in terms of overall survival (OS) compared to chemotherapy, and their combination with MEK inhibitors has recently been shown to improve progression-free survival (PFS), compared with monotherapy with BRAF inhibitors. However, almost 20% of patients initially do not respond, due to intrinsic resistance to therapy and, of those who do, most eventually develop mechanisms of acquired resistance, including reactivation of the MAP kinase pathway, persistent activation of receptor tyrosine kinase (RTKS) receptor, activation of phosphatidyinositol-3OH kinase, overexpression of epidermal growth factor receptor (EGFR), and interactions with the tumor microenvironment. Herein we comment in detail on mechanisms of resistance to targeted therapy and discuss the strategies to overcome them. PMID:27429963

  1. Mechanisms for nonprofit hospitals to acquire new equipment.

    PubMed

    Cotora, C

    1985-01-01

    The expense of new technologies and current high costs of capital financing have combined to encourage hospitals to acquire the use of new equipment by having a group of private investors purchase the equipment and make it available for use by the hospital. However, tax exempt healthcare providers are inhibited from pursuing this alternative because of current Internal Revenue Service policies prohibiting Investment Tax Credit (ITC) for property used by tax exempt organizations. This article discusses some approaches a nonprofit hospital and a group of potential investors can take to enable the investors to claim ITC. PMID:10299873

  2. Kinetics and maintenance of acquired resistance in mice to Listeria monocytogenes.

    PubMed

    Kearns, R J; Hinrichs, D J

    1977-06-01

    In the mouse system, acquired resistance to Listeria monocytogenes can only be demonstrated after immunization with viable microorganisms. A successful state of immunity cannot be elicited with formalin-killed organisms or bacterial cell-derived products. Viable, serologically cross-reactive organisms (not mouse pathogenic) do not induce a state of immunity as measured by acquired resistance. The duration of immunity, once established, is dose independent, and the absolute interval of its existence is not extended by secondary challenge with large numbers of viable organisms. The decline of immunity in actively immunized animals is not altered by antigenic challenge with formalin-killed cells or cell products. This indicates that the cellular requirements for the development of host resistance are similar for induction as well as maintenance. In vitro measurements of cellular immunity by migration inhibition indicate that formalin-killed organisms as well as cell products were recognized by actively sensitized lymphocytes obtained from immune animals. PMID:408273

  3. Lung and chest wall mechanics in patients with acquired immunodeficiency syndrome and severe Pneumocystis carinii pneumonia.

    PubMed

    D'Angelo, E; Calderini, E; Robatto, F M; Puccio, P; Milic-Emili, J

    1997-10-01

    The aim of this study was to assess the mechanical characteristics of the respiratory system in patients with acquired immune deficiency syndrome (AIDS) and acute respiratory distress syndrome (ARDS) caused by Pneumocystis carinii pneumonia (PCP). In 12 mechanically ventilated patients, total respiratory system mechanics was assessed using the technique of rapid airway occlusion during constant flow inflation, and was partitioned into lung and chest wall components using the oesophageal balloon technique. We measured interrupter resistance (Rint), which mainly reflects airway resistance, additional resistance (deltaR) due to viscoelastic behaviour and time constant inequalities, and static elastance (Est). In addition, the static inflation volume-pressure (V-P) curve was assessed. In eight patients, computed tomography scans were performed within 2 days of the assessment of respiratory mechanics. Compared to values reported in the literature for normal subjects, Est and deltaR were markedly increased in AIDS patients with PCP, whilst Rint exhibited a relatively smaller increase. These changes, which involved only the lung and airways, were mainly due to the reduction of ventilated lung units, but additional factors were involved to cause independent modifications of lung stiffness, airway calibre, and viscoelastic properties. The changes in Rint, deltaR, and Est were similar to those observed in other studies on patients with ARDS of different aetiologies. At variance with common observations in the latter patients, none of the AIDS patients with PCP exhibited an inflection point on the static inflation V-P curve, suggesting little or no alveolar recruitment during lung inflation. This finding could be related to the distinctive histopathology of Pneumocystis carinii pneumonia. Indeed, computed tomography revealed homogeneous diffuse interstitial and alveolar infiltration rather than the dense, dependent opacities observed in other studies on acute respiratory

  4. CIPROFLOXACIN RESISTANCE PATTERN AMONG BACTERIA ISOLATED FROM PATIENTS WITH COMMUNITY-ACQUIRED URINARY TRACT INFECTION

    PubMed Central

    REIS, Ana Carolina Costa; SANTOS, Susana Regia da Silva; de SOUZA, Siane Campos; SALDANHA, Milena Góes; PITANGA, Thassila Nogueira; OLIVEIRA, Ricardo Riccio

    2016-01-01

    SUMMARY Objective: To identify the main bacterial species associated with community-acquired urinary tract infection (UTI) and to assess the pattern of ciprofloxacin susceptibility among bacteria isolated from urine cultures. Methods: We conducted a retrospective study in all the patients with community-acquired UTI seen in Santa Helena Laboratory, Camaçari, Bahia, Brazil during five years (2010-2014). All individuals who had a positive urine culture result were included in this study. Results: A total of 1,641 individuals met the inclusion criteria. Despite the fact that participants were female, we observed a higher rate of resistance to ciprofloxacin in males. The most frequent pathogens identified in urine samples were Escherichia coli, Klebsiella pneumoniae and Staphylococcus saprophyticus. Antimicrobial resistance has been observed mainly for ampicillin, sulfamethoxazole + trimethoprim and ciprofloxacin. Moreover, E. coli has shown the highest rate of ciprofloxacin resistance, reaching 36% of ciprofloxacin resistant strains in 2014. Conclusion: The rate of bacterial resistance to ciprofloxacin observed in the studied population is much higher than expected, prompting the need for rational use of this antibiotic, especially in infections caused by E. coli. Prevention of bacterial resistance can be performed through control measures to limit the spread of resistant microorganisms and a rational use of antimicrobial policy. PMID:27410913

  5. Amphibians acquire resistance to live and dead fungus overcoming fungal immunosuppression.

    PubMed

    McMahon, Taegan A; Sears, Brittany F; Venesky, Matthew D; Bessler, Scott M; Brown, Jenise M; Deutsch, Kaitlin; Halstead, Neal T; Lentz, Garrett; Tenouri, Nadia; Young, Suzanne; Civitello, David J; Ortega, Nicole; Fites, J Scott; Reinert, Laura K; Rollins-Smith, Louise A; Raffel, Thomas R; Rohr, Jason R

    2014-07-10

    Emerging fungal pathogens pose a greater threat to biodiversity than any other parasitic group, causing declines of many taxa, including bats, corals, bees, snakes and amphibians. Currently, there is little evidence that wild animals can acquire resistance to these pathogens. Batrachochytrium dendrobatidis is a pathogenic fungus implicated in the recent global decline of amphibians. Here we demonstrate that three species of amphibians can acquire behavioural or immunological resistance to B. dendrobatidis. Frogs learned to avoid the fungus after just one B. dendrobatidis exposure and temperature-induced clearance. In subsequent experiments in which B. dendrobatidis avoidance was prevented, the number of previous exposures was a negative predictor of B. dendrobatidis burden on frogs and B. dendrobatidis-induced mortality, and was a positive predictor of lymphocyte abundance and proliferation. These results suggest that amphibians can acquire immunity to B. dendrobatidis that overcomes pathogen-induced immunosuppression and increases their survival. Importantly, exposure to dead fungus induced a similar magnitude of acquired resistance as exposure to live fungus. Exposure of frogs to B. dendrobatidis antigens might offer a practical way to protect pathogen-naive amphibians and facilitate the reintroduction of amphibians to locations in the wild where B. dendrobatidis persists. Moreover, given the conserved nature of vertebrate immune responses to fungi and the fact that many animals are capable of learning to avoid natural enemies, these results offer hope that other wild animal taxa threatened by invasive fungi might be rescued by management approaches based on herd immunity. PMID:25008531

  6. Induced PD-L1 expression mediates acquired resistance to agonistic anti-CD40 treatment.

    PubMed

    Zippelius, Alfred; Schreiner, Jens; Herzig, Petra; Müller, Philipp

    2015-03-01

    CD40 stimulation on antigen-presenting cells (APC) allows direct activation of CD8(+) cytotoxic T cells, independent of CD4⁺ T-cell help. Agonistic anti-CD40 antibodies have been demonstrated to induce beneficial antitumor T-cell responses in mouse models of cancer and early clinical trials. We report here that anti-CD40 treatment induces programmed death ligand-1 (PD-L1) upregulation on tumor-infiltrating monocytes and macrophages, which was strictly dependent on T cells and IFNγ. PD-L1 expression could be counteracted by coadministration of antibodies blocking the PD-1 (programmed death-1)/PD-L1 axis as shown for T cells from tumor models and human donors. The combined treatment was highly synergistic and induced complete tumor rejection in about 50% of mice bearing MC-38 colon and EMT-6 breast tumors. Mechanistically, this was reflected by a strong increase of IFNγ and granzyme-B production in intratumoral CD8⁺ T cells. Concomitant CTLA-4 blockade further improved rejection of established tumors in mice. This study uncovers a novel mechanism of acquired resistance upon agonistic CD40 stimulation and proposes that the concomitant blockade of the PD-1/PD-L1 axis is a viable therapeutic strategy to optimize clinical outcomes. PMID:25623164

  7. Lung cancers with acquired resistance to EGFR inhibitors occasionally harbor BRAF gene mutations but lack mutations in KRAS, NRAS, or MEK1.

    PubMed

    Ohashi, Kadoaki; Sequist, Lecia V; Arcila, Maria E; Moran, Teresa; Chmielecki, Juliann; Lin, Ya-Lun; Pan, Yumei; Wang, Lu; de Stanchina, Elisa; Shien, Kazuhiko; Aoe, Keisuke; Toyooka, Shinichi; Kiura, Katsuyuki; Fernandez-Cuesta, Lynnette; Fidias, Panos; Yang, James Chih-Hsin; Miller, Vincent A; Riely, Gregory J; Kris, Mark G; Engelman, Jeffrey A; Vnencak-Jones, Cindy L; Dias-Santagata, Dora; Ladanyi, Marc; Pao, William

    2012-07-31

    Acquired resistance to EGF receptor (EGFR) tyrosine kinase inhibitors (TKIs) is inevitable in metastatic EGFR-mutant lung cancers. Here, we modeled disease progression using EGFR-mutant human tumor cell lines. Although five of six models displayed alterations already found in humans, one harbored an unexpected secondary NRAS Q61K mutation; resistant cells were sensitive to concurrent EGFR and MEK inhibition but to neither alone. Prompted by this finding and because RAS/RAF/MEK mutations are known mediators of acquired resistance in other solid tumors (colon cancers, gastrointestinal stromal tumors, and melanomas) responsive to targeted therapies, we analyzed the frequency of secondary KRAS/NRAS/BRAF/MEK1 gene mutations in the largest collection to date of lung cancers with acquired resistance to EGFR TKIs. No recurrent NRAS, KRAS, or MEK1 mutations were found in 212, 195, or 146 patient samples, respectively, but 2 of 195 (1%) were found to have mutations in BRAF (G469A and V600E). Ectopic expression of mutant NRAS or BRAF in drug-sensitive EGFR-mutant cells conferred resistance to EGFR TKIs that was overcome by addition of a MEK inhibitor. Collectively, these positive and negative results provide deeper insight into mechanisms of acquired resistance to EGFR TKIs in lung cancer and inform ongoing clinical trials designed to overcome resistance. In the context of emerging knowledge about mechanisms of acquired resistance to targeted therapies in various cancers, our data highlight the notion that, even though solid tumors share common signaling cascades, mediators of acquired resistance must be elucidated for each disease separately in the context of treatment. PMID:22773810

  8. Clinical Significance of Community- and Healthcare-Acquired Carbapenem-Resistant Enterobacteriaceae Isolates

    PubMed Central

    Tang, Hung-Jen; Hsieh, Cheng-Fang; Chang, Ping-Chin; Chen, Jyh-Jou; Lin, Yu-Hsiu; Lai, Chih-Cheng; Chao, Chien-Ming; Chuang, Yin-Ching

    2016-01-01

    This study was conducted to investigate the clinical significance, manifestations, microbiological characteristics and outcomes of carbapenem-resistant Enterobacteriaceae (CRE) isolates, and compare the clinical features of community- and healthcare-acquired CRE isolates. A total of 78 patients were identified to have CRE. Klebsiella pneumoniae was the most common pathogens (n = 42, 53.8%), followed by Enterobacter cloacae (n = 24, 30.8%), and Escherichia coli (n = 11, 14.1%). Most of the patients acquired CRE from healthcare settings (n = 55, 70.5%), and other cases got CRE from community settings (n = 23, 29.5%). Nine cases (11.5%) were classified as CRE colonization. Among the remaining 69 cases of CRE infections, pneumonia (n = 28, 40.6%) was the most common type of infections, followed by urinary tract infection (n = 24, 34.8%), and intra-abdominal infection (n = 16, 23.2%). The patients acquired CRE from community settings were more likely to be elderly, female, and had more urinary tract infections than from healthcare settings. In contrast, the patients acquired CRE from healthcare settings had more intra-abdominal infections, intra-abdominal surgery, and presence of indwelling device than from community settings. In conclusion, community-acquired CRE are not rare, and their associated clinical presentations are different from healthcare-acquired CRE. PMID:26999356

  9. Characterization of in vivo-acquired resistance to macrolides of Mycoplasma gallisepticum strains isolated from poultry

    PubMed Central

    2011-01-01

    The macrolide class of antibiotics, including tylosin and tilmicosin, is widely used in the veterinary field for prophylaxis and treatment of mycoplasmosis. In vitro susceptibility testing of 50 strains of M. gallisepticum isolated in Israel during the period 1997-2010 revealed that acquired resistance to tylosin as well as to tilmicosin was present in 50% of them. Moreover, 72% (13/18) of the strains isolated from clinical samples since 2006 showed acquired resistance to enrofloxacin, tylosin and tilmicosin. Molecular typing of the field isolates, performed by gene-target sequencing (GTS), detected 13 molecular types (I-XIII). Type II was the predominant type prior to 2006 whereas type X, first detected in 2008, is currently prevalent. All ten type X strains were resistant to both fluoroquinolones and macrolides, suggesting selective pressure leading to clonal dissemination of resistance. However, this was not a unique event since resistant strains with other GTS molecular types were also found. Concurrently, the molecular basis for macrolide resistance in M. gallisepticum was identified. Our results revealed a clear-cut correlation between single point mutations A2058G or A2059G in domain V of the gene encoding 23S rRNA (rrnA, MGA_01) and acquired macrolide resistance in M. gallisepticum. Indeed, all isolates with MIC ≥ 0.63 μg/mL to tylosin and with MIC ≥ 1.25 μg/mL to tilmicosin possess one of these mutations, suggesting an essential role in decreased susceptibility of M. gallisepticum to 16-membered macrolides. PMID:21810258

  10. Characterization of in vivo-acquired resistance to macrolides of Mycoplasma gallisepticum strains isolated from poultry.

    PubMed

    Gerchman, Irena; Levisohn, Sharon; Mikula, Inna; Manso-Silván, Lucía; Lysnyansky, Inna

    2011-01-01

    The macrolide class of antibiotics, including tylosin and tilmicosin, is widely used in the veterinary field for prophylaxis and treatment of mycoplasmosis. In vitro susceptibility testing of 50 strains of M. gallisepticum isolated in Israel during the period 1997-2010 revealed that acquired resistance to tylosin as well as to tilmicosin was present in 50% of them. Moreover, 72% (13/18) of the strains isolated from clinical samples since 2006 showed acquired resistance to enrofloxacin, tylosin and tilmicosin. Molecular typing of the field isolates, performed by gene-target sequencing (GTS), detected 13 molecular types (I-XIII). Type II was the predominant type prior to 2006 whereas type X, first detected in 2008, is currently prevalent. All ten type X strains were resistant to both fluoroquinolones and macrolides, suggesting selective pressure leading to clonal dissemination of resistance. However, this was not a unique event since resistant strains with other GTS molecular types were also found. Concurrently, the molecular basis for macrolide resistance in M. gallisepticum was identified. Our results revealed a clear-cut correlation between single point mutations A2058G or A2059G in domain V of the gene encoding 23S rRNA (rrnA, MGA_01) and acquired macrolide resistance in M. gallisepticum. Indeed, all isolates with MIC ≥ 0.63 μg/mL to tylosin and with MIC ≥ 1.25 μg/mL to tilmicosin possess one of these mutations, suggesting an essential role in decreased susceptibility of M. gallisepticum to 16-membered macrolides. PMID:21810258

  11. Inherent and Acquired Resistance to Paclitaxel in Hepatocellular Carcinoma: Molecular Events Involved

    PubMed Central

    Meena, Avtar Singh; Sharma, Aanchal; Kumari, Ratna; Mohammad, Naoshad; Singh, Shivendra Vikram; Bhat, Manoj Kumar

    2013-01-01

    Hepatocellular carcinoma (HCC) is a primary malignancy of the liver and is a major cause of cancer related deaths worldwide. Only 10 to 20% of HCC can be surgically excised. Therefore, chemotherapeutic intervention and treatment is essential for achieving favorable prognosis. However, therapeutic outcome of chemotherapy is generally poor owing to inherent resistance of cancer cells to the treatment or due to development of acquired resistance. To differentiate and delineate the molecular events, we developed drug resistant Hep3B cells (DRC) by treating cells with the increasing concentration of paclitaxel. We also developed a unique single cell clone of Hep3B cells (SCC) by selecting single cell colonies and screening them for resistant phenotype. Interestingly, both DRC and SCC were resistant to paclitaxel in comparison to parental Hep3B cells. We analyzed the contributory factors that may be involved in the development of resistance. As expected, level of P-glycoprotein (P-gp) was elevated in DRC. In addition, Caveolin-1 (Cav-1), Fatty acid synthase (FASN) and Cytochrome P450 (CYP450) protein levels were elevated in DRC whereas in SCC, FASN and CYP450 levels were elevated. Downregulation of these molecules by respective siRNAs and/or by specific pharmacological inhibitors resensitized cells to paclitaxel. Interestingly, these drug resistant cells were also less sensitive to vinblastine, doxorubicin and methotrexate with the exception of cisplatin. Our results suggested that differential levels of P-gp, Cav-1 and FASN play a major role in acquired resistant phenotype whereas FASN level was associated with the presentation of inherent resistant phenotype in HCC. PMID:23613870

  12. ZEB1 Mediates Acquired Resistance to the Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors in Non-Small Cell Lung Cancer

    PubMed Central

    Yoshida, Takeshi; Song, Lanxi; Bai, Yun; Kinose, Fumi; Li, Jiannong; Ohaegbulam, Kim C.; Muñoz-Antonia, Teresita; Qu, Xiaotao; Eschrich, Steven; Uramoto, Hidetaka; Tanaka, Fumihiro; Nasarre, Patrick; Gemmill, Robert M.; Roche, Joëlle; Drabkin, Harry A.; Haura, Eric B.

    2016-01-01

    Epithelial-mesenchymal transition (EMT) is one mechanism of acquired resistance to inhibitors of the epidermal growth factor receptor-tyrosine kinases (EGFR-TKIs) in non-small cell lung cancer (NSCLC). The precise mechanisms of EMT-related acquired resistance to EGFR-TKIs in NSCLC remain unclear. We generated erlotinib-resistant HCC4006 cells (HCC4006ER) by chronic exposure of EGFR-mutant HCC4006 cells to increasing concentrations of erlotinib. HCC4006ER cells acquired an EMT phenotype and activation of the TGF-β/SMAD pathway, while lacking both T790M secondary EGFR mutation and MET gene amplification. We employed gene expression microarrays in HCC4006 and HCC4006ER cells to better understand the mechanism of acquired EGFR-TKI resistance with EMT. At the mRNA level, ZEB1 (TCF8), a known regulator of EMT, was >20-fold higher in HCC4006ER cells than in HCC4006 cells, and increased ZEB1 protein level was also detected. Furthermore, numerous ZEB1 responsive genes, such as CDH1 (E-cadherin), ST14, and vimentin, were coordinately regulated along with increased ZEB1 in HCC4006ER cells. We also identified ZEB1 overexpression and an EMT phenotype in several NSCLC cells and human NSCLC samples with acquired EGFR-TKI resistance. Short-interfering RNA against ZEB1 reversed the EMT phenotype and, importantly, restored erlotinib sensitivity in HCC4006ER cells. The level of micro-RNA-200c, which can negatively regulate ZEB1, was significantly reduced in HCC4006ER cells. Our results suggest that increased ZEB1 can drive EMT-related acquired resistance to EGFR-TKIs in NSCLC. Attempts should be made to explore targeting ZEB1 to resensitize TKI-resistant tumors. PMID:26789630

  13. An Oral Formulation of YK-4-279: Preclinical Efficacy and Acquired Resistance Patterns in Ewing Sarcoma.

    PubMed

    Lamhamedi-Cherradi, Salah-Eddine; Menegaz, Brian A; Ramamoorthy, Vandhana; Aiyer, Ramani A; Maywald, Rebecca L; Buford, Adrianna S; Doolittle, Dannette K; Culotta, Kirk S; O'Dorisio, James E; Ludwig, Joseph A

    2015-07-01

    Ewing sarcoma is a transcription factor-mediated pediatric bone tumor caused by a chromosomal translocation of the EWSR1 gene and one of several genes in the ETS family of transcription factors, typically FLI1 or ERG. Full activity of the resulting oncogenic fusion protein occurs only after binding RNA helicase A (RHA), and novel biologically targeted small molecules designed to interfere with that interaction have shown early promise in the preclinical setting. Herein, we demonstrate marked preclinical antineoplastic activity of an orally bioavailable formulation of YK-4-279 and identify mechanisms of acquired chemotherapy resistance that may be exploited to induce collateral sensitivity. Daily enteral administration of YK-4-279 led to significant delay in Ewing sarcoma tumor growth within a murine model. In advance of anticipated early-phase human clinical trials, we investigated both de novo and acquired mechanism(s) by which Ewing sarcoma cells evade YK-4-279-mediated cell death. Drug-resistant clones, formed by chronic in vitro exposure to steadily increased levels of YK-4-279, overexpressed c-Kit, cyclin D1, pStat3(Y705), and PKC isoforms. Interestingly, cross-resistance to imatinib and enzastaurin (selective inhibitors of c-Kit and PKC-β, respectively), was observed and the use of YK-4-279 with enzastaurin in vitro led to marked drug synergy, suggesting a potential role for combination therapies in the future. By advancing an oral formulation of YK-4-279 and identifying prominent mechanisms of resistance, this preclinical research takes us one step closer to a shared goal of curing adolescents and young adults afflicted by Ewing sarcoma. PMID:25964201

  14. [A mathematical model for the chemical control of Aedes aegypti (Diptera: Culicidae) having acquired chemical resistance].

    PubMed

    Restrepo-Alape, Leonardo D; Toro-Zapata, Hernán D; Muñoz-Loaiza, Aníbal

    2010-12-01

    Dengue fever is a common vector-borne disease in tropical and subtropical areas. It is transmitted to humans by the bite of an infected female Aedes mosquito. Since no vaccines are currently available which can protect against infection, disease control relies on controlling the mosquito population. This work was aimed at modelling such mosquito's population dynamics regarding chemical control of the adult population and its acquired resistance to chemicals. The model was analysed by using classical dynamic system theory techniques and mosquito growth threshold was determined as this establishes when a particular population may prosper in the environment or when it is likely to disappear. A suitable chemical control strategy was developed from such threshold. Simulations were made in control and non-control scenarios; this determined the degree of control application effectiveness against different levels of acquired resistance. PMID:22030690

  15. Naturally occurring dominant drug resistance mutations occur infrequently in the setting of recently acquired hepatitis C

    PubMed Central

    Applegate, Tanya L; Gaudieri, Silvana; Plauzolles, Anne; Chopra, Abha; Grebely, Jason; Lucas, Michaela; Hellard, Margaret; Luciani, Fabio; Dore, Gregory J; Matthews, Gail V

    2014-01-01

    Background Directly Acting Antivirals (DAAs) are predicted to transform hepatitis C (HCV) therapy, yet little is known about the prevalence of naturally occurring resistance mutations in recently acquired HCV. This study aimed to determine the prevalence and frequency of drug resistance mutations in the viral quasispecies among HIV positive and negative individuals with recent HCV. Methods The NS3 protease, NS5A and NS5B polymerase genes were amplified from fifty genotype 1a participants of the Australian Trial in Acute Hepatitis C. Amino acid variations at sites known to be associated with possible drug resistance were analysed by ultra-deep pyrosequencing. Results Twelve percent of individuals harboured dominant resistance mutations, while 36% demonstrated non dominant resistant variants below that detectable by bulk sequencing (ie < 20%) but above a threshold of 1%. Resistance variants (< 1%) were observed at most sites associated with DAA resistance from all classes, with the exception of sofosbuvir. Conclusions Dominant resistant mutations were uncommonly observed in the setting of recent HCV. However, low level mutations to all DAA classes were observed by deep sequencing at the majority of sites, and in most individuals. The significance of these variants and impact on future treatment options remains to be determined. PMID:25105742

  16. A family cluster of tuberculosis cases, including a case of acquired multidrug resistant tuberculosis.

    PubMed

    Holden, Julie; Trachtman, Louis

    2012-01-01

    Although the number of tuberculosis cases in the US is at an all-time low, with progressive declines seen for the past 17 years, many goals in the tuberculosis elimination process remain unrealized. This report describes a cluster of four tuberculosis cases in a family, including one case of acquired multidrug resistant tuberculosis. It also underscores some important issues in tuberculosis control today, including significant disparities in the foreign-born population with multidrug resistant tuberculosis as a looming problem, as well as utilization of therapeutic drug level monitoring in complicated cases. PMID:22533114

  17. Physiological and Molecular Characteristics of Elicitin-Induced Systemic Acquired Resistance in Tobacco.

    PubMed Central

    Keller, H.; Blein, J. P.; Bonnet, P.; Ricci, P.

    1996-01-01

    Elicitins are low molecular weight proteins secreted by all Phytophthora species analyzed so far. Application of the purified proteins to tobacco Nicotiana tabacum leads to the induction of resistance to subsequent inoculations with the black shank-causing agent, Phytophthora parasitica var nicotianae. In this paper, we describe the systemic characteristics of elicitin-induced acquired resistance in tobacco. Elicitin application is followed by the rapid translocation of the protein in the plant. The basic elicitin, cryptogein, induces necrosis formation in the leaves, which results from accumulation of the protein in these organs. Necrosis does not seem to be essential for the establishment of systemic acquired resistance (SAR), since resistance induced by the acidic elicitin, capsicein, is not accompanied by the development of visible symptoms on the leaves. Both elicitins trigger the coordinate accumulation of transcripts from nine genes, previously described to be expressed during establishment of SAR. Additionally, elicitin treatment leads to the activation of the multiple response gene str 246. In leaves, transcript accumulation was found to be higher in all cases in response to cryptogein compared to capsicein treatment. These results, along with northern hybridization analysis following infiltration of leaves with cryptogein, indicate that SAR genes appear to be expressed locally, corresponding to necrosis formation as well as systemically during induction of resistance. To our knowledge, elicitins are the only well-characterized, pathogen-derived molecules that trigger SAR in a plant. PMID:12226188

  18. Epidermal growth factor receptor cooperates with Src family kinases in acquired resistance to cetuximab.

    PubMed

    Wheeler, Deric L; Iida, Mari; Kruser, Tim J; Nechrebecki, Meghan M; Dunn, Emily F; Armstrong, Eric A; Huang, Shyhmin; Harari, Paul M

    2009-04-01

    The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase that plays a major role in oncogenesis. Cetuximab is an EGFR-blocking antibody that is FDA approved for use in patients with metastatic colorectal cancer (mCRC) and head and neck squamous cell carcinoma (HNSCC). Although cetuximab has shown strong clinical benefit for a subset of cancer patients, most become refractory to cetuximab therapy. We reported that cetuximab-resistant NSCLC line NCI-H226 cells have increased steady-state expression and activity of EGFR secondary to altered trafficking/degradation and this increase in EGFR expression and activity lead to hyper-activation of HER3 and down stream signals to survival. We now present data that Src family kinases (SFKs) are highly activated in cetuximab-resistant cells and enhance EGFR activation of HER3 and PI(3)K/Akt. Studies using the Src kinase inhibitor dasatinib decreased HER3 and PI(3)K/Akt activity. In addition, cetuximab-resistant cells were resensitized to cetuximab when treated with dasatinib. These results indicate that SFKs and EGFR cooperate in acquired resistance to cetuximab and suggest a rationale for clinical strategies that investigate combinatorial therapy directed at both the EGFR and SFKs in patients with acquired resistance to cetuximab. PMID:19276677

  19. Identification of novel therapeutic target genes in acquired lapatinib-resistant breast cancer by integrative meta-analysis.

    PubMed

    Lee, Young Seok; Hwang, Sun Goo; Kim, Jin Ki; Park, Tae Hwan; Kim, Young Rae; Myeong, Ho Sung; Choi, Jong Duck; Kwon, Kang; Jang, Cheol Seong; Ro, Young Tae; Noh, Yun Hee; Kim, Sung Young

    2016-02-01

    Acquired resistance to lapatinib is a highly problematic clinical barrier that has to be overcome for a successful cancer treatment. Despite efforts to determine the mechanisms underlying acquired lapatinib resistance (ALR), no definitive genetic factors have been reported to be solely responsible for the acquired resistance in breast cancer. Therefore, we performed a cross-platform meta-analysis of three publically available microarray datasets related to breast cancer with ALR, using the R-based RankProd package. From the meta-analysis, we were able to identify a total of 990 differentially expressed genes (DEGs, 406 upregulated, 584 downregulated) that are potentially associated with ALR. Gene ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of the DEGs showed that "response to organic substance" and "p53 signaling pathway" may be largely involved in ALR process. Of these, many of the top 50 upregulated and downregulated DEGs were found in oncogenesis of various tumors and cancers. For the top 50 DEGs, we constructed the gene coexpression and protein-protein interaction networks from a huge database of well-known molecular interactions. By integrative analysis of two systemic networks, we condensed the total number of DEGs to six common genes (LGALS1, PRSS23, PTRF, FHL2, TOB1, and SOCS2). Furthermore, these genes were confirmed in functional module eigens obtained from the weighted gene correlation network analysis of total DEGs in the microarray datasets ("GSE16179" and "GSE52707"). Our integrative meta-analysis could provide a comprehensive perspective into complex mechanisms underlying ALR in breast cancer and a theoretical support for further chemotherapeutic studies. PMID:26361955

  20. Amphibians acquire resistance to live and dead fungus overcoming fungal immunosuppression

    PubMed Central

    McMahon, Taegan A.; Sears, Brittany F.; Venesky, Matthew D.; Bessler, Scott M.; Brown, Jenise M.; Deutsch, Kaitlin; Halstead, Neal T.; Lentz, Garrett; Tenouri, Nadia; Young, Suzanne; Civitello, David J.; Ortega, Nicole; Fites, J. Scott; Reinert, Laura K.; Rollins-Smith, Louise A.; Raffel, Thomas R.; Rohr, Jason R.

    2015-01-01

    Emerging fungal pathogens pose a greater threat to biodiversity than any other parasitic group1, causing declines of many taxa, including bats, corals, bees, snakes and amphibians1–4. Currently, there is little evidence that wild animals can acquire resistance to these pathogens5. Batrachochytrium dendrobatidis is a pathogenic fungus implicated in the recent global decline of amphibians6. Here we demonstrate that three species of amphibians can acquire behavioural or immunological resistance to B. dendrobatidis. Frogs learned to avoid the fungus after just one B. dendrobatidis exposure and temperature-induced clearance. In subsequent experiments in which B. dendrobatidis avoidance was prevented, the number of previous exposures was a negative predictor of B. dendrobatidis burden on frogs and B. dendrobatidis-induced mortality, and was a positive predictor of lymphocyte abundance and proliferation. These results suggest that amphibians can acquire immunity to B. dendrobatidis that overcomes pathogen-induced immunosuppression7–9 and increases their survival. Importantly, exposure to dead fungus induced a similar magnitude of acquired resistance as exposure to live fungus. Exposure of frogs to B. dendrobatidis antigens might offer a practical way to protect pathogen-naive amphibians and facilitate the reintroduction of amphibians to locations in the wild where B. dendrobatidis persists. Moreover, given the conserved nature of vertebrate immune responses to fungi5 and the fact that many animals are capable of learning to avoid natural enemies10, these results offer hope that other wild animal taxa threatened by invasive fungi might be rescued by management approaches based on herd immunity. PMID:25008531

  1. Bacteraemia and antibiotic-resistant pathogens in community acquired pneumonia: risk and prognosis.

    PubMed

    Torres, Antoni; Cillóniz, Catia; Ferrer, Miquel; Gabarrús, Albert; Polverino, Eva; Villegas, Santiago; Marco, Francesc; Mensa, Josep; Menéndez, Rosario; Niederman, Michael

    2015-05-01

    The sensitivity of blood cultures in the diagnosis of bacteraemia for community-acquired pneumonia is low. Recommendations, by guidelines, to perform blood cultures are discordant. We aimed to determine the incidence, microbial aetiology, risk factors and outcomes of bacteraemic patients with community-acquired pneumonia, including cases with antibiotic-resistant pathogens (ARP). A prospective, observational study was undertaken on consecutive adult patients admitted to the Hospital Clinic of Barcelona (Barcelona, Spain) with community-acquired pneumonia and blood cultures were obtained. Of the 2892 patients included, bacteraemia was present in 297 (10%) patients; 30 (10%) of whom had ARP (multidrug-resistant Streptococcus pneumoniae, methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, and an extended spectrum of beta-lactamase producing Enterobacteriaceae). In multivariate analyses, pleuritic pain, C-reactive protein ≥21.6 mg·dL(-1) and intensive care unit admissions were independently associated with bacteraemia, while prior antibiotic treatment and pneumococcal vaccine were protective factors. The risk factors for ARP bacteraemia were previous antibiotics and C-reactive protein <22.2 mg·dL(-1), while pleuritic pain was the only protective factor in the multivariate analysis. Bacteraemia (excluding ARP), appropriate empiric treatment, neurological disease, arterial oxygen tension/inspiratory oxygen fraction <250, pneumonia severity index risk classes IV and V, and intensive care unit admission were independently associated with a 30-day hospital mortality in the multivariate analysis. Inappropriate therapy was more frequent in ARP bacteraemia, compared with other bacteraemias (27% versus 3%, respectively, p<0.001). Antibiotic therapy protected against bacteraemia, but increased specifically the risk of bacteraemia from ARP due to the inappropriate coverage of these pathogens. Identifying patients at risk of ARP bacteraemia would help in

  2. Acquired-resistance of bevacizumab treatment for radiation brain necrosis: a case report

    PubMed Central

    Sun, Dayong; Bian, Jianliang; Chang, Joe Y.; Yuan, Zhiyong; Wang, Ping

    2016-01-01

    The case study reported on acquired bevacizumab resistance in one patient receiving re-treatment with bevacizumab following radiation brain necrosis progression after bevacizumab was discontinued. This case offers novel and additional insight for bevacizumab treatment. Low-dose bevacizumab is effective for radiation brain necrosis, and radiation brain necrosis may progress after bevacizumab discontinuation, whereas too many cycles of bevacizumab treatment may induce drug-resistance and re-treatment failure following the progression. Therefore, more rational administration for radiation brain necrosis with bevacizumab may include three aspects: short-course treatment, timely discontinuation upon obtaining satisfactory effects (to prevent long-term medication associated resistance) and re-treatment after brain necrosis progression. PMID:26933810

  3. Postpartum patient with thrombosis of mechanical prostheses and acquired supravalvular aortic stenosis.

    PubMed

    Benfatti, Ricardo Adala; Martins Júnior, Carlos Roberto; Silva, Guilherme Viotto Rodrigues da; Pontes, José Carlos Dorsa Vieira

    2011-01-01

    The blood hypercoagulability in pregnancy increases significantly the incidence of thrombosis of mechanical valves. Acquired supravalvular aortic stenosis is extremely rare. We report the case of an immediate postpartum patient with aortic mechanical prostheses and acquired supravalvular aortic stenosis who underwent emergency heart surgery, with severe hemodynamic instability, using adapted surgical technique for correction of supravalvular stenosis with satisfactory clinical and echocardiography results. PMID:21894422

  4. Sym004, a novel EGFR antibody mixture, can overcome acquired resistance to cetuximab.

    PubMed

    Iida, Mari; Brand, Toni M; Starr, Megan M; Li, Chunrong; Huppert, Evan J; Luthar, Neha; Pedersen, Mikkel W; Horak, Ivan D; Kragh, Michael; Wheeler, Deric L

    2013-10-01

    The epidermal growth factor receptor (EGFR) is a central regulator of tumor progression in a variety of human cancers. Cetuximab is an anti-EGFR monoclonal antibody that has been approved for head and neck and colorectal cancer treatment, but many patients treated with cetuximab don't respond or eventually acquire resistance. To determine how tumor cells acquire resistance to cetuximab, we previously developed a model of acquired resistance using the non-small cell lung cancer line NCI-H226. These cetuximab-resistant (Ctx(R)) cells exhibit increased steady-state EGFR expression secondary to alterations in EGFR trafficking and degradation and, further, retained dependence on EGFR signaling for enhanced growth potential. Here, we examined Sym004, a novel mixture of antibodies directed against distinct epitopes on the extracellular domain of EGFR, as an alternative therapy for Ctx(R) tumor cells. Sym004 treatment of Ctx(R) clones resulted in rapid EGFR degradation, followed by robust inhibition of cell proliferation and down-regulation of several mitogen-activated protein kinase pathways. To determine whether Sym004 could have therapeutic benefit in vivo, we established de novo Ctx(R) NCI-H226 mouse xenografts and subsequently treated Ctx(R) tumors with Sym004. Sym004 treatment of mice harboring Ctx(R) tumors resulted in growth delay compared to mice continued on cetuximab. Levels of total and phospho-EGFR were robustly decreased in Ctx(R) tumors treated with Sym004. Immunohistochemical analysis of these Sym004-treated xenograft tumors further demonstrated decreased expression of Ki67, and phospho-rpS6, as well as a modest increase in cleaved caspase-3. These results indicate that Sym004 may be an effective targeted therapy for Ctx(R) tumors. PMID:24204198

  5. ACE2 overexpression inhibits acquired platinum resistance-induced tumor angiogenesis in NSCLC.

    PubMed

    Cheng, Qijian; Zhou, Ling; Zhou, Jianping; Wan, Huanying; Li, Qingyun; Feng, Yun

    2016-09-01

    Angiotensin II (AngII) is a multifunctional bioactive peptide in the renin-angiotensin system (RAS). Angiotensin-converting enzyme 2 (ACE2) is a newly identified component of RAS. We previously reported that ACE2 overexpression may inhibit cell growth and vascular endothelial growth factor (VEGF) production in vitro and in vivo. In the present study, we investigated the effect of ACE2 on tumor-associated angiogen-esis after the development of acquired platinum resistance in non-small cell lung cancer (NSCLC). Four NSCLC cell lines, A549, LLC, A549-DDP and LLC-DDP, were used in vitro, while A549 and A549-DDP cells were used in vivo. A549-DDP and LLC-DDP cells were newly established at our institution as acquired platinum-resistant sublines by culturing the former parent cells in cisplatin (CDDP)-containing conditioned medium for 6 months. These platinum-resistant cells showed significantly higher angiotensin II type 1 receptor (AT1R), ACE and VEGF production and lower ACE2 expression than their corresponding parent cells. We showed that ACE2 overexpression inhibited the production of VEGF in vitro and in vivo compared to their corresponding parent cells. We also found that ACE2 overexpression reduced the expression of AT1R and ACE. Additionally, we confirmed that ACE2 overexpres-sion inhibited cell growth and VEGF production while simultaneously suppressing ACE and AT1R expression in human lung cancer xenografts. Our findings indicate that ACE2 overexpression may potentially suppress angiogenesis in NSCLC after the development of acquired platinum resistance. PMID:27460845

  6. MicroRNA-138 promotes acquired alkylator resistance in glioblastoma by targeting the Bcl-2-interacting mediator BIM

    PubMed Central

    Stojcheva, Nina; Schechtmann, Gennadi; Sass, Steffen; Roth, Patrick; Florea, Ana-Maria; Stefanski, Anja; Stühler, Kai; Wolter, Marietta; Müller, Nikola S.; Theis, Fabian J.; Weller, Michael; Reifenberger, Guido; Happold, Caroline

    2016-01-01

    Glioblastoma is the most aggressive brain tumor in adults with a median survival below 12 months in population-based studies. The main reason for tumor recurrence and progression is constitutive or acquired resistance to the standard of care of surgical resection followed by radiotherapy with concomitant and adjuvant temozolomide (TMZ/RT→TMZ). Here, we investigated the role of microRNA (miRNA) alterations as mediators of alkylator resistance in glioblastoma cells. Using microarray-based miRNA expression profiling of parental and TMZ-resistant cultures of three human glioma cell lines, we identified a set of differentially expressed miRNA candidates. From these, we selected miR-138 for further functional analyses as this miRNA was not only upregulated in TMZ-resistant versus parental cells, but also showed increased expression in vivo in recurrent glioblastoma tissue samples after TMZ/RT→TMZ treatment. Transient transfection of miR-138 mimics in glioma cells with low basal miR-138 expression increased glioma cell proliferation. Moreover, miR-138 overexpression increased TMZ resistance in long-term glioblastoma cell lines and glioma initiating cell cultures. The apoptosis regulator BIM was identified as a direct target of miR-138, and its silencing mediated the induced TMZ resistance phenotype. Altered sensitivity to apoptosis played only a minor role in this resistance mechanism. Instead, we identified the induction of autophagy to be regulated downstream of the miR-138/BIM axis and to promote cell survival following TMZ exposure. Our data thus define miR-138 as a glioblastoma cell survival-promoting miRNA associated with resistance to TMZ therapy in vitro and with tumor progression in vivo. PMID:26887050

  7. MicroRNA-138 promotes acquired alkylator resistance in glioblastoma by targeting the Bcl-2-interacting mediator BIM.

    PubMed

    Stojcheva, Nina; Schechtmann, Gennadi; Sass, Steffen; Roth, Patrick; Florea, Ana-Maria; Stefanski, Anja; Stühler, Kai; Wolter, Marietta; Müller, Nikola S; Theis, Fabian J; Weller, Michael; Reifenberger, Guido; Happold, Caroline

    2016-03-15

    Glioblastoma is the most aggressive brain tumor in adults with a median survival below 12 months in population-based studies. The main reason for tumor recurrence and progression is constitutive or acquired resistance to the standard of care of surgical resection followed by radiotherapy with concomitant and adjuvant temozolomide (TMZ/RT→TMZ). Here, we investigated the role of microRNA (miRNA) alterations as mediators of alkylator resistance in glioblastoma cells. Using microarray-based miRNA expression profiling of parental and TMZ-resistant cultures of three human glioma cell lines, we identified a set of differentially expressed miRNA candidates. From these, we selected miR-138 for further functional analyses as this miRNA was not only upregulated in TMZ-resistant versus parental cells, but also showed increased expression in vivo in recurrent glioblastoma tissue samples after TMZ/RT→TMZ treatment. Transient transfection of miR-138 mimics in glioma cells with low basal miR-138 expression increased glioma cell proliferation. Moreover, miR-138 overexpression increased TMZ resistance in long-term glioblastoma cell lines and glioma initiating cell cultures. The apoptosis regulator BIM was identified as a direct target of miR-138, and its silencing mediated the induced TMZ resistance phenotype. Altered sensitivity to apoptosis played only a minor role in this resistance mechanism. Instead, we identified the induction of autophagy to be regulated downstream of the miR-138/BIM axis and to promote cell survival following TMZ exposure. Our data thus define miR-138 as a glioblastoma cell survival-promoting miRNA associated with resistance to TMZ therapy in vitro and with tumor progression in vivo. PMID:26887050

  8. Acquired Genetic Mechanisms of a Multiresistant Bacterium Isolated from a Treatment Plant Receiving Wastewater from Antibiotic Production

    PubMed Central

    Johnning, Anna; Moore, Edward R. B.; Svensson-Stadler, Liselott; Shouche, Yogesh S.; Larsson, D. G. Joakim

    2013-01-01

    The external environment, particularly wastewater treatment plants (WWTPs), where environmental bacteria meet human commensals and pathogens in large numbers, has been highlighted as a potential breeding ground for antibiotic resistance. We have isolated the extensively drug-resistant Ochrobactrum intermedium CCUG 57381 from an Indian WWTP receiving industrial wastewater from pharmaceutical production contaminated with high levels of quinolones. Antibiotic susceptibility testing against 47 antibiotics showed that the strain was 4 to >500 times more resistant to sulfonamides, quinolones, tetracyclines, macrolides, and the aminoglycoside streptomycin than the type strain O. intermedium LMG 3301T. Whole-genome sequencing identified mutations in the Indian strain causing amino acid substitutions in the target enzymes of quinolones. We also characterized three acquired regions containing resistance genes to sulfonamides (sul1), tetracyclines [tet(G) and tetR], and chloramphenicol/florfenicol (floR). Furthermore, the Indian strain harbored acquired mechanisms for horizontal gene transfer, including a type I mating pair-forming system (MPFI), a MOBP relaxase, and insertion sequence transposons. Our results highlight that WWTPs serving antibiotic manufacturing may provide nearly ideal conditions for the recruitment of resistance genes into human commensal and pathogenic bacteria. PMID:24038701

  9. The changing face of community-acquired methicillin-resistant Staphylococcus aureus.

    PubMed

    Kale, P; Dhawan, B

    2016-01-01

    Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of infection, both in hospitalised patients with significant healthcare exposure and in patients without healthcare risk factors. Community-acquired methicillin-resistant S. aureus (CA-MRSA) are known for their rapid community transmission and propensity to cause aggressive skin and soft tissue infections and community-acquired pneumonia. The distinction between the healthcare-associated (HA)-MRSA and CA-MRSA is gradually fading owing to the acquisition of multiple virulence factors and genetic elements. The movement of CA-MRSA strains into the nosocomial setting limits the utility of using clinical risk factors alone to designate community or HA status. Identification of unique genetic characteristics and genotyping are valuable tools for MRSA epidemiological studies. Although the optimum pharmacotherapy for CA-MRSA infections has not been determined, many CA-MRSA strains remain broadly susceptible to several non-β-lactam antibacterial agents. This review aimed at illuminating the characteristic features of CA-MRSA, virulence factors, changing clinical settings and molecular epidemiology, insurgence into the hospital settings and therapy with drug resistance. PMID:27514947

  10. Selinexor is effective in acquired resistance to ibrutinib and synergizes with ibrutinib in chronic lymphocytic leukemia.

    PubMed

    Hing, Zachary A; Mantel, Rose; Beckwith, Kyle A; Guinn, Daphne; Williams, Erich; Smith, Lisa L; Williams, Katie; Johnson, Amy J; Lehman, Amy M; Byrd, John C; Woyach, Jennifer A; Lapalombella, Rosa

    2015-05-14

    Despite the therapeutic efficacy of ibrutinib in chronic lymphocytic leukemia (CLL), complete responses are infrequent, and acquired resistance to Bruton agammaglobulinemia tyrosine kinase (BTK) inhibition is being observed in an increasing number of patients. Combination regimens that increase frequency of complete remissions, accelerate time to remission, and overcome single agent resistance are of considerable interest. We previously showed that the XPO1 inhibitor selinexor is proapoptotic in CLL cells and disrupts B-cell receptor signaling via BTK depletion. Herein we show the combination of selinexor and ibrutinib elicits a synergistic cytotoxic effect in primary CLL cells and increases overall survival compared with ibrutinib alone in a mouse model of CLL. Selinexor is effective in cells isolated from patients with prolonged lymphocytosis following ibrutinib therapy. Finally, selinexor is effective in ibrutinib-refractory mice and in a cell line harboring the BTK C481S mutation. This is the first report describing the combined activity of ibrutinib and selinexor in CLL, which represents a new treatment paradigm and warrants further evaluation in clinical trials of CLL patients including those with acquired ibrutinib resistance. PMID:25838351

  11. Drug Resistance Mechanisms in Mycobacterium tuberculosis

    PubMed Central

    Palomino, Juan Carlos; Martin, Anandi

    2014-01-01

    Tuberculosis (TB) is a serious public health problem worldwide. Its situation is worsened by the presence of multidrug resistant (MDR) strains of Mycobacterium tuberculosis, the causative agent of the disease. In recent years, even more serious forms of drug resistance have been reported. A better knowledge of the mechanisms of drug resistance of M. tuberculosis and the relevant molecular mechanisms involved will improve the available techniques for rapid drug resistance detection and will help to explore new targets for drug activity and development. This review article discusses the mechanisms of action of anti-tuberculosis drugs and the molecular basis of drug resistance in M. tuberculosis. PMID:27025748

  12. DNA-PK mediates AKT activation and apoptosis inhibition in clinically acquired platinum resistance.

    PubMed

    Stronach, Euan A; Chen, Michelle; Maginn, Elaina N; Agarwal, Roshan; Mills, Gordon B; Wasan, Harpreet; Gabra, Hani

    2011-11-01

    Clinical resistance to chemotherapy is a frequent event in cancer treatment and is closely linked to poor outcome. High-grade serous (HGS) ovarian cancer is characterized by p53 mutation and high levels of genomic instability. Treatment includes platinum-based chemotherapy and initial response rates are high; however, resistance is frequently acquired, at which point treatment options are largely palliative. Recent data indicate that platinum-resistant clones exist within the sensitive primary tumor at presentation, implying resistant cell selection after treatment with platinum chemotherapy. The AKT pathway is central to cell survival and has been implicated in platinum resistance. Here, we show that platinum exposure induces an AKT-dependent, prosurvival, DNA damage response in clinically platinum-resistant but not platinum-sensitive cells. AKT relocates to the nucleus of resistant cells where it is phosphorylated specifically on S473 by DNA-dependent protein kinase (DNA-PK), and this activation inhibits cisplatin-mediated apoptosis. Inhibition of DNA-PK or AKT, but not mTORC2, restores platinum sensitivity in a panel of clinically resistant HGS ovarian cancer cell lines: we also demonstrate these effects in other tumor types. Resensitization is associated with prevention of AKT-mediated BAD phosphorylation. Strikingly, in patient-matched sensitive cells, we do not see enhanced apoptosis on combining cisplatin with AKT or DNA-PK inhibition. Insulin-mediated activation of AKT is unaffected by DNA-PK inhibitor treatment, suggesting that this effect is restricted to DNA damage-mediated activation of AKT and that, clinically, DNA-PK inhibition might prevent platinum-induced AKT activation without interfering with normal glucose homeostasis, an unwanted toxicity of direct AKT inhibitors. PMID:22131882

  13. DNA-PK Mediates AKT Activation and Apoptosis Inhibition in Clinically Acquired Platinum Resistance12

    PubMed Central

    Stronach, Euan A; Chen, Michelle; Maginn, Elaina N; Agarwal, Roshan; Mills, Gordon B; Wasan, Harpreet; Gabra, Hani

    2011-01-01

    Clinical resistance to chemotherapy is a frequent event in cancer treatment and is closely linked to poor outcome. High-grade serous (HGS) ovarian cancer is characterized by p53 mutation and high levels of genomic instability. Treatment includes platinum-based chemotherapy and initial response rates are high; however, resistance is frequently acquired, at which point treatment options are largely palliative. Recent data indicate that platinum-resistant clones exist within the sensitive primary tumor at presentation, implying resistant cell selection after treatment with platinum chemotherapy. The AKT pathway is central to cell survival and has been implicated in platinum resistance. Here, we show that platinum exposure induces an AKT-dependent, prosurvival, DNA damage response in clinically platinum-resistant but not platinum-sensitive cells. AKT relocates to the nucleus of resistant cells where it is phosphorylated specifically on S473 by DNA-dependent protein kinase (DNA-PK), and this activation inhibits cisplatin-mediated apoptosis. Inhibition of DNA-PK or AKT, but not mTORC2, restores platinum sensitivity in a panel of clinically resistant HGS ovarian cancer cell lines: we also demonstrate these effects in other tumor types. Resensitization is associated with prevention of AKT-mediated BAD phosphorylation. Strikingly, in patient-matched sensitive cells, we do not see enhanced apoptosis on combining cisplatin with AKT or DNA-PK inhibition. Insulin-mediated activation of AKT is unaffected by DNA-PK inhibitor treatment, suggesting that this effect is restricted to DNA damage-mediated activation of AKT and that, clinically, DNA-PK inhibition might prevent platinum-induced AKT activation without interfering with normal glucose homeostasis, an unwanted toxicity of direct AKT inhibitors. PMID:22131882

  14. Protein arginine methyltransferase 1 may be involved in pregnane x receptor-activated overexpression of multidrug resistance 1 gene during acquired multidrug resistant

    PubMed Central

    Li, Tingting; Kong, Ah-Ng Tony; Ma, Zhiqiang; Liu, Haiyan; Liu, Pinghua; Xiao, Yu; Jiang, Xuehua; Wang, Ling

    2016-01-01

    Purpose Pregnane x receptor (PXR) - activated overexpression of the multidrug resistance 1 (MDR1) gene is an important way for tumor cells to acquire drug resistance. However, the detailed mechanism still remains unclear. In the present study, we aimed to investigate whether protein arginine methyl transferase 1(PRMT1) is involved in PXR - activated overexpression of MDR1 during acquired multidrug resistant. Experimental Design Arginine methyltransferase inhibitor 1 (AMI-1) was used to pharmacologically block PRMT1 in resistant breast cancer cells (MCF7/adr). The mRNA and protein levels of MDR1 were detected by real-time PCR and western blotting analysis. Immunofluorescence microscopy and co-immunoprecipitation were used to investigate the physical interaction between PXR and PRMT1. Then, 136 candidate compounds were screened for PRMT1 inhibitors. Lastly, luciferase reporter gene and nude mice bearing resistant breast cancer xenografts were adopted to investigate the anti-tumor effect of PRMT1 inhibitors when combined with adriamycin. Results AMI-1 significantly suppressed the expression of MDR1 in MCF7/adr cells and increased cells sensitivity of MCF7/adr to adriamycin. Physical interaction between PRMT1 and PXR exists in MCF7/adr cells, which could be disrupted by AMI-1. Those results suggest that PRMT1 may be involved in PXR-activated overexpression of MDR1 in resistant breast cancer cells, and AMI-1 may suppress MDR1 by disrupting the interaction between PRMT1 and PXR. Then, five compounds including rutin, isoquercitrin, salvianolic acid A, naproxen, and felodipline were identified to be PRMT1 inhibitors. Finally, those PRMT1 inhibitors were observed to significantly decrease MDR1 promoter activity in vitro and enhance the antitumor effect of adriamycin in nude mice that bearing resistant breast cancer xenografts. Conclusions PRMT1 may be an important co-activator of PXR in activating MDR1 gene during acquired resistance, and PRMT1 inhibitor combined with

  15. Antiviral Drug Resistance: Mechanisms and Clinical Implications

    PubMed Central

    Chou, Sunwen

    2010-01-01

    Summary Antiviral drug resistance is an increasing concern in immunocompromised patient populations, where ongoing viral replication and prolonged drug exposure lead to the selection of resistant strains. Rapid diagnosis of resistance can be made by associating characteristic viral mutations with resistance to various drugs as determined by phenotypic assays. Management of drug resistance includes optimization of host factors and drug delivery, selection of alternative therapies based on knowledge of mechanisms of resistance, and the development of new antivirals. This article discusses drug resistance in herpesviruses and hepatitis B. PMID:20466277

  16. Antiangiogenic therapy of experimental cancer does not induce acquired drug resistance

    NASA Astrophysics Data System (ADS)

    Boehm, Thomas; Folkman, Judah; Browder, Timothy; O'Reilly, Michael S.

    1997-11-01

    Acquired drug resistance is a major problem in the treatment of cancer. Of the more than 500,000 annual deaths from cancer in the United States, many follow the development of resistance to chemotherapy. The emergence of resistance depends in part on the genetic instability, heterogeneity and high mutational rate of tumour cells. In contrast, endothelial cells are genetically stable, homogenous and have a low mutational rate. Therefore, antiangiogenic therapy directed against a tumour's endothelial cells should, in principle, induce little or no drug resistance. Endostatin, a potent angiogenesis inhibitor, was administered to mice bearing Lewis lung carcinoma, T241 fibrosarcoma or B16F10 melanoma. Treatment was stopped when tumours had regressed. Tumours were then allowed to re-grow and endostatin therapy was resumed. After 6, 4 or 2 treatment cycles, respectively, no tumours recurred after discontinuation of therapy. These experiments show that drug resistance does not develop in three tumour types treated with a potent angiogenesis inhibitor. An unexpected finding is that repeated cycles of antiangiogenic therapy are followed by prolonged tumour dormancy without further therapy.

  17. Surveillance for Travel and Domestically Acquired Multidrug-Resistant Human Shigella Infections-Pennsylvania, 2006-2014.

    PubMed

    Li, Yu Lung; Tewari, Deepanker; Yealy, Courtney C; Fardig, David; M'ikanatha, Nkuchia M

    2016-01-01

    Shigellosis is a leading cause of enteric infections in the United States. We compared antimicrobial resistance in Shigella infections related to overseas travel (travel-associated) and in those acquired domestically by analyzing antimicrobial resistance patterns, geographic distributions, and pulsed-field gel electrophoresis (PFGE) patterns. We tested samples (n = 204) from a collection of isolates recovered from patients in Pennsylvania between 2006 and 2014. Isolates were grouped into travel- and non-travel-associated categories. Eighty-one (79.4%) of the Shigella isolates acquired during international travel were resistant to multiple antibiotics compared to 53 (52.1%) of the infections transmitted in domestic settings. A majority (79.4%) of isolates associated with international travel demonstrated resistance to aminoglycosides and tetracyclines, whereas 47 (46.1%) of the infections acquired domestically were resistant to tetracycline. Almost all isolates (92.2%) transmitted in domestic settings were resistant to aminoglycosides, and 5 isolates from adult male patients were resistant to azithromycin, a drug often used for empiric treatment of severe shigellosis. Twenty (19.6%) isolates associated with illnesses acquired during overseas travel in 4 countries were resistant to quinolones. One S. sonnei PFGE pattern was traced to a multidrug-resistant isolate acquired overseas that had caused a multistate outbreak of shigellosis, suggesting global dissemination of a drug-resistant species. Resistance to certain drugs-for example, tetracycline-increased in both overseas- and domestic-acquired infections during the study period. The prevalence of resistance to macrolides (azithromycin) and third-generation cephalosporins (ceftriaxone) was less than 1%; however, efforts to better monitor changes in drug resistance over time combined with increased antimicrobial stewardship are essential at the local, national, and global levels. PMID:27314654

  18. Facet joint septic arthritis due to community acquired methicillin resistant Staphylococcus aureus (MRSA) - A case report.

    PubMed

    Purushothaman, Rajesh; Inassi, Jojo; Marthya, Anwar

    2015-10-01

    Septic arthritis of facet joint (SAFJ) is extremely rare. Only about sixty cases have been reported so far. A single case of SAFJ in a series of 491 cases of spinal infections was first reported by David-Chaussé in 1981. A case report of SAFJ was published by Halpin in 1987. With the growing availability and use of MRI, more and more cases are being reported. The most common organism that causes SAFJ is Staphylococcus aureus. We are reporting a case of SAFJ caused by community acquired, methicillin resistant S aureus (MRSA) successfully treated by Linezolid. PMID:26719620

  19. Systemic loxoscelism in the age of community-acquired methicillin-resistant Staphylococcus aureus.

    PubMed

    Rogers, Karen M; Klotz, Carrie R; Jack, Meg; Seger, Donna

    2011-02-01

    The increase in cases of community-acquired methicillin-resistant Staphylococcus aureus (MRSA), as well as its isolation from the majority of skin and soft tissue abscesses in the emergency department, requires the emergency physician to consider this diagnosis in all skin or soft tissue infections. However, making the diagnosis of MRSA when the wound is actually a cutaneous lesion of a brown recluse spider bite may have untoward consequences. Furthermore, the clinical manifestations of systemic loxoscelism may be misdiagnosed as a systemic staphylococcal infection. We present a patient with systemic loxoscelism who was diagnosed with a systemic infection and received an unnecessary surgical procedure. PMID:20817348

  20. Resistance to caspase-8 and -9 fragments in a malignant pleural mesothelioma cell line with acquired cisplatin-resistance

    PubMed Central

    Janson, V; Johansson, A; Grankvist, K

    2010-01-01

    Apoptotic cysteine–aspartate proteases (caspases) are essential for the progression and execution of apoptosis, and detection of caspase fragmentation or activity is often used as markers of apoptosis. Cisplatin (cis-diamminedichloroplatinum (II)) is a chemotherapeutic drug that is clinically used for the treatment of solid tumours. We compared a cisplatin-resistant pleural malignant mesothelioma cell line (P31res1.2) with its parental cell line (P31) regarding the consequences of in vitro acquired cisplatin-resistance on basal and cisplatin-induced (equitoxic and equiapoptotic cisplatin concentrations) caspase-3, -8 and -9 fragmentation and proteolytic activity. Acquisition of cisplatin-resistance resulted in basal fragmentation of caspase-8 and -9 without a concomitant increase in proteolytic activity, and there was an increased basal caspase-3/7 activity. Similarly, cisplatin-resistant non-small-cell lung cancer cells, H1299res, had increased caspase-3 and -9 content compared with the parental H1299 cells. In P31 cells, cisplatin exposure resulted in caspase-9-mediated caspase-3/7 activation, but in P31res1.2 cells the cisplatin-induced caspase-3/7 activation occurred before caspase-8 or -9 activation. We therefore concluded that in vitro acquisition of cisplatin-resistance rendered P31res1.2 cells resistant to caspase-8 and caspase-9 fragments and that cisplatin-induced, initiator-caspase independent caspase-3/7 activation was necessary to overcome this resistance. Finally, the results demonstrated that detection of cleaved caspase fragments alone might be insufficient as a marker of caspase activity and ensuing apoptosis induction. PMID:21364680

  1. Risk Factors for Acquired Rifamycin and Isoniazid Resistance: A Systematic Review and Meta-Analysis

    PubMed Central

    Rockwood, Neesha; Abdullahi, Leila H.; Wilkinson, Robert J.; Meintjes, Graeme

    2015-01-01

    Background Studies looking at acquired drug resistance (ADR) are diverse with respect to geographical distribution, HIV co-infection rates, retreatment status and programmatic factors such as regimens administered and directly observed therapy. Our objective was to examine and consolidate evidence from clinical studies of the multifactorial aetiology of acquired rifamycin and/or isoniazid resistance within the scope of a single systematic review. This is important to inform policy and identify key areas for further studies. Methods Case-control and cohort studies and randomised controlled trials that reported ADR as an outcome during antitubercular treatment regimens including a rifamycin and examined the association of at least 1 risk factor were included. Post hoc, we carried out random effects Mantel-Haenszel weighted meta-analyses of the impact of 2 key risk factors 1) HIV and 2) baseline drug resistance on the binary outcome of ADR. Heterogeneity was assessed used I2 statistic. As a secondary outcome, we calculated median cumulative incidence of ADR, weighted by the sample size of the studies. Results Meta-analysis of 15 studies showed increased risk of ADR with baseline mono- or polyresistance (RR 4.85 95% CI 3.26 to 7.23, heterogeneity I2 58%, 95% CI 26 to 76%). Meta-analysis of 8 studies showed that HIV co-infection was associated with increased risk of ADR (RR 3.02, 95% CI 1.28 to 7.11); there was considerable heterogeneity amongst these studies (I2 81%, 95% CI 64 to 90%). Non-adherence, extrapulmonary/disseminated disease and advanced immunosuppression in HIV co-infection were other risk factors noted. The weighted median cumulative incidence of acquired multi drug resistance calculated in 24 studies (assuming whole cohort as denominator, regardless of follow up DST) was 0.1% (5th to 95th percentile 0.07 to 3.2%). Conclusion Baseline drug resistance and HIV co-infection were significant risk factors for ADR. There was a trend of positive association with

  2. Non-invasive analysis of acquired resistance to cancer therapy by sequencing of plasma DNA.

    PubMed

    Murtaza, Muhammed; Dawson, Sarah-Jane; Tsui, Dana W Y; Gale, Davina; Forshew, Tim; Piskorz, Anna M; Parkinson, Christine; Chin, Suet-Feung; Kingsbury, Zoya; Wong, Alvin S C; Marass, Francesco; Humphray, Sean; Hadfield, James; Bentley, David; Chin, Tan Min; Brenton, James D; Caldas, Carlos; Rosenfeld, Nitzan

    2013-05-01

    Cancers acquire resistance to systemic treatment as a result of clonal evolution and selection. Repeat biopsies to study genomic evolution as a result of therapy are difficult, invasive and may be confounded by intra-tumour heterogeneity. Recent studies have shown that genomic alterations in solid cancers can be characterized by massively parallel sequencing of circulating cell-free tumour DNA released from cancer cells into plasma, representing a non-invasive liquid biopsy. Here we report sequencing of cancer exomes in serial plasma samples to track genomic evolution of metastatic cancers in response to therapy. Six patients with advanced breast, ovarian and lung cancers were followed over 1-2 years. For each case, exome sequencing was performed on 2-5 plasma samples (19 in total) spanning multiple courses of treatment, at selected time points when the allele fraction of tumour mutations in plasma was high, allowing improved sensitivity. For two cases, synchronous biopsies were also analysed, confirming genome-wide representation of the tumour genome in plasma. Quantification of allele fractions in plasma identified increased representation of mutant alleles in association with emergence of therapy resistance. These included an activating mutation in PIK3CA (phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha) following treatment with paclitaxel; a truncating mutation in RB1 (retinoblastoma 1) following treatment with cisplatin; a truncating mutation in MED1 (mediator complex subunit 1) following treatment with tamoxifen and trastuzumab, and following subsequent treatment with lapatinib, a splicing mutation in GAS6 (growth arrest-specific 6) in the same patient; and a resistance-conferring mutation in EGFR (epidermal growth factor receptor; T790M) following treatment with gefitinib. These results establish proof of principle that exome-wide analysis of circulating tumour DNA could complement current invasive biopsy approaches to identify

  3. Community-acquired methicillin-resistant Staphylococcus aureus in a Malaysian tertiary centre.

    PubMed

    Rashid, Zetti Zainol; Bahari, Norazlah; Othman, Amizah; Jaafar, Roslinda; Mohamed, Nurul Azmawati; Jabbari, Idimaz; Sulong, Anita; Hashim, Rohaidah; Ahmad, Norazah

    2013-01-01

    Abstract. Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is a pathogen recognized to be distinct in both phenotype and genotype from hospital-acquired MRSA. We have identified CA-MRSA cases in Universiti Kebangsaan Malaysia Medical Centre, Kuala Lumpur, Malaysia, including their antibiotic susceptibility patterns and genotypic characteristics. Cases were identified during January to December 2009 from routine clinical specimens, where culture and antibiotic susceptibility results yielded pauci-resistant MRSA isolates suspected as being CA-MRSA. The patients' clinical data were collected and their specimens were sent for molecular confirmation and analysis. Five cases of CA-MRSA were identified, which had a multi-sensitive pattern on antibiotic susceptibility tests and were resistant to only penicillin and oxacillin. All cases were skin and soft-tissue infections, including diabetic foot with gangrene, infected scalp hematoma, philtrum abscess in a healthcare worker, thrombophlebitis complicated with abscess and infected bedsore. All five cases were confirmed MRSA by detection of mecA. SCCmec typing (ccr and mec complex) revealed SCCmec type IV for all cases except the infected bedsore case. Panton-Valentine leukocidin gene was positive in all isolates. As clinical features among methicillin-sensitive Staphylococcus aureus, CA-MRSA and "nosocomial CA-MRSA" are indistinct, early recognition is necessary in order to initiate appropriate antibiotics and infection control measures. Continual surveillance of pauci-resistant MRSA and molecular analysis are necessary in order to identify emerging strains as well as their epidemiology and transmission, both in the community and in healthcare setting. PMID:23682444

  4. Long-term persistence of acquired resistance to 5-fluorouracil in the colon cancer cell line SW620

    SciTech Connect

    Tentes, I.K.; Schmidt, W.M.; Krupitza, G.; Steger, G.G.; Mikulits, W.; Kortsaris, A.; Mader, R.M.

    2010-11-15

    Treatment resistance to antineoplastic drugs represents a major clinical problem. Here, we investigated the long-term stability of acquired resistance to 5-fluorouracil (FU) in an in vitro colon cancer model, using four sub-clones characterised by increasing FU-resistance derived from the cell line SW620. The resistance phenotype was preserved after FU withdrawal for 15 weeks ({approx} 100 cell divisions) independent of the established level of drug resistance and of epigenetic silencing. Remarkably, resistant clones tolerated serum deprivation, adopted a CD133{sup +} CD44{sup -} phenotype, and further exhibited loss of membrane-bound E-cadherin together with predominant nuclear {beta}-catenin localisation. Thus, we provide evidence for a long-term memory of acquired drug resistance, driven by multiple cellular strategies (epithelial-mesenchymal transition and selective propagation of CD133{sup +} cells). These resistance phenomena, in turn, accentuate the malignant phenotype.

  5. Arabidopsis TTR1 causes LRR-dependent lethal systemic necrosis, rather than systemic acquired resistance, to Tobacco ringspot virus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Most Arabidopsis ecotypes display tolerance to the Tobacco ringspot virus (TRSV), but a subset of Arabidopsis ecotypes, including Estland (Est), develop lethal systemic necrosis (LSN), which differs from the localized hypersensitive responses (HRs) or systemic acquired resistance (SAR) characteristi...

  6. Acquired EGFR C797S mutation mediates resistance to AZD9291 in non-small cell lung cancer harboring EGFR T790M.

    PubMed

    Thress, Kenneth S; Paweletz, Cloud P; Felip, Enriqueta; Cho, Byoung Chul; Stetson, Daniel; Dougherty, Brian; Lai, Zhongwu; Markovets, Aleksandra; Vivancos, Ana; Kuang, Yanan; Ercan, Dalia; Matthews, Sarah E; Cantarini, Mireille; Barrett, J Carl; Jänne, Pasi A; Oxnard, Geoffrey R

    2015-06-01

    Here we studied cell-free plasma DNA (cfDNA) collected from subjects with advanced lung cancer whose tumors had developed resistance to the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) AZD9291. We first performed next-generation sequencing of cfDNA from seven subjects and detected an acquired EGFR C797S mutation in one; expression of this mutant EGFR construct in a cell line rendered it resistant to AZD9291. We then performed droplet digital PCR on serial cfDNA specimens collected from 15 AZD9291-treated subjects. All were positive for the T790M mutation before treatment, but upon developing AZD9291 resistance three molecular subtypes emerged: six cases acquired the C797S mutation, five cases maintained the T790M mutation but did not acquire the C797S mutation and four cases lost the T790M mutation despite the presence of the underlying EGFR activating mutation. Our findings provide insight into the diversity of mechanisms through which tumors acquire resistance to AZD9291 and highlight the need for therapies that are able to overcome resistance mediated by the EGFR C797S mutation. PMID:25939061

  7. Acquired EGFR C797S mediates resistance to AZD9291 in advanced non-small cell lung cancer harboring EGFR T790M

    PubMed Central

    Thress, Kenneth S.; Paweletz, Cloud P.; Felip, Enriqueta; Cho, Byoung Chul; Stetson, Daniel; Dougherty, Brian; Lai, Zhongwu; Markovets, Aleksandra; Vivancos, Ana; Kuang, Yanan; Ercan, Dalia; Matthews, Sarah; Cantarini, Mireille; Barrett, J. Carl; Jänne, Pasi A.; Oxnard, Geoffrey R.

    2015-01-01

    Here we studied cell-free plasma DNA (cfDNA) collected from subjects with advanced lung cancer whose tumors had developed resistance to the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) AZD9291. We first performed next-generation sequencing of cfDNA from seven subjects and detected an acquired EGFR C797S mutation in one; expression of this mutant EGFR construct in a cell line rendered it resistant to AZD9291. We then performed droplet digital PCR on serial cfDNA specimens collected from 15 AZD9291-treated subjects. All were positive for T790M prior to treatment, but at resistance three molecular subtypes emerged: 6 cases acquired the C797S mutation, 5 cases maintained the T790M mutation but did not acquire the C797S mutation, and 4 cases lost the T790M mutation despite detecting of the underlying EGFR activating mutation. Our findings provide insight into the diversity of mechanisms through which tumors acquire resistance to AZD9291 and highlight the need for therapies able to overcome resistance mediated by EGFR C797S. PMID:25939061

  8. NF-κB drives acquired resistance to a novel mutant-selective EGFR inhibitor

    PubMed Central

    Galvani, Elena; Sun, Jing; Leon, Leticia G.; Sciarrillo, Rocco; Narayan, Ravi S.; Tjin Tham Sjin, Robert; Lee, Kwangho; Ohashi, Kadoaki; Heideman, Daniëlle A.M.; Alfieri, Roberta R.; Heynen, Guus J.; Bernards, René; Smit, Egbert F.; Pao, William; Peters, Godefridus J.; Giovannetti, Elisa

    2015-01-01

    The clinical efficacy of EGFR tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC) harbouring activating EGFR mutations is limited by the emergence of acquired resistance, mostly ascribed to the secondary EGFR-T790M mutation. Selective EGFR-T790M inhibitors have been proposed as a new, extremely relevant therapeutic approach. Here, we demonstrate that the novel irreversible EGFR-TKI CNX-2006, a structural analog of CO-1686, currently tested in a phase-1/2 trial, is active against in vitro and in vivo NSCLC models expressing mutant EGFR, with minimal effect on the wild-type receptor. By integration of genetic and functional analyses in isogenic cell pairs we provide evidence of the crucial role played by NF-κB1 in driving CNX-2006 acquired resistance and show that NF-κB activation may replace the oncogenic EGFR signaling in NSCLC when effective and persistent inhibition of the target is achieved in the presence of the T790M mutation. In this context, we demonstrate that the sole, either genetic or pharmacologic, inhibition of NF-κB is sufficient to reduce the viability of cells that adapted to EGFR-TKIs. Overall, our findings support the rational inhibition of members of the NF-κB pathway as a promising therapeutic option for patients who progress after treatment with novel mutant-selective EGFR-TKIs. PMID:26015408

  9. Infection control implications of heterogeneous resistance mechanisms in carbapenem-resistant Enterobacteriaceae (CRE).

    PubMed

    Goodman, K E; Simner, P J; Tamma, P D; Milstone, A M

    2016-01-01

    The Centers for Disease Control and Prevention (CDC) defines carbapenem-resistant Enterobacteriaceae (CRE) based upon a phenotypic demonstration of carbapenem resistance. However, considerable heterogeneity exists within this definitional umbrella. CRE may mechanistically differ by whether they do or do not produce carbapenemases. Moreover, patients can acquire CRE through multiple pathways: endogenously through antibiotic selective pressure on intestinal microbiota, exogenously through horizontal transmission or through a combination of these factors. Some evidence suggests that non-carbapenemase-producing CRE may be more frequently acquired by antibiotic exposure and carbapenemase-producing CRE via horizontal transmission, but definitive data are lacking. This review examines types of CRE resistance mechanisms, antibiotic exposure and horizontal transmission pathways of CRE acquisition, and the implications of these heterogeneities to the development of evidence-based CRE healthcare epidemiology policies. In our Expert Commentary & Five-Year View, we outline specific nosocomial CRE knowledge gaps and potential methodological approaches for their resolution. PMID:26535959

  10. Reaction Mechanism of Extreme Ultraviolet Resists

    NASA Astrophysics Data System (ADS)

    Toriumi, Minoru; Kaneyama, Koji; Itani, Toshiro

    2008-06-01

    Molecular resist of polyphenol was evaluated as an extreme-ultraviolet resist compared with a polymer resist of poly(tert-butoxycarbonylhydroxystyrene). X-ray reflectometry was used to determine the resist-film density and measurement accuracy was improved. The molecular resist shows higher sensitivity of 3 mJ/cm2 than the polymer resist of 4 mJ/cm2. The deprotection mechanism was approximated by simple reaction equations and Fourier-transform infrared spectra was interpreted to give the products of a quantum yield and a deprotection rate constant as 9.7×10-8 and 8.1×10-8 cm3 molecule-1 s-1 for molecular and polymer resists. The higher sensitivity of the molecular resist is due to the larger efficiency of the reaction mechanism.

  11. Antibiotic resistance mechanisms in M. tuberculosis: an update.

    PubMed

    Nguyen, Liem

    2016-07-01

    Treatment of tuberculosis (TB) has been a therapeutic challenge because of not only the naturally high resistance level of Mycobacterium tuberculosis to antibiotics but also the newly acquired mutations that confer further resistance. Currently standardized regimens require patients to daily ingest up to four drugs under direct observation of a healthcare worker for a period of 6-9 months. Although they are quite effective in treating drug susceptible TB, these lengthy treatments often lead to patient non-adherence, which catalyzes for the emergence of M. tuberculosis strains that are increasingly resistant to the few available anti-TB drugs. The rapid evolution of M. tuberculosis, from mono-drug-resistant to multiple drug-resistant, extensively drug-resistant and most recently totally drug-resistant strains, is threatening to make TB once again an untreatable disease if new therapeutic options do not soon become available. Here, I discuss the molecular mechanisms by which M. tuberculosis confers its profound resistance to antibiotics. This knowledge may help in developing novel strategies for weakening drug resistance, thus enhancing the potency of available antibiotics against both drug susceptible and resistant M. tuberculosis strains. PMID:27161440

  12. Clinical approaches to treat patients with non-small cell lung cancer and epidermal growth factor receptor tyrosine kinase inhibitor acquired resistance.

    PubMed

    Tartarone, Alfredo; Lerose, Rosa

    2015-10-01

    The discovery of epidermal growth factor receptor activating mutations (EGFR Mut+) has determined a paradigm shift in the treatment of non-small cell lung cancer (NSCLC). In several phase III studies, patients with NSCLC EGFR Mut+ achieved a significantly better progression-free survival when treated with a first- (gefitinib, erlotinib) or second-generation (afatinib) EGFR tyrosine kinase inhibitor (TKI) compared with standard chemotherapy. However, despite these impressive results, most patients with NSCLC EGFR Mut+ develop acquired resistance to TKIs. This review will discuss both the mechanisms of resistance to TKIs and the therapeutic strategies to overcome resistance, including emerging data on third-generation TKIs. PMID:26016841

  13. Macrolide-resistant Mycoplasma pneumoniae in adolescents with community-acquired pneumonia

    PubMed Central

    2012-01-01

    Background Although the prevalence of macrolide-resistant Mycoplasma pneumoniae isolates in Japanese pediatric patients has increased rapidly, there have been no reports concerning macrolide-resistant M. pneumoniae infection in adolescents aged 16 to 19 years old. The purpose of this study was to clarify the prevalence and clinical characteristics of macrolide-resistant M. pneumoniae in adolescent patients with community-acquired pneumonia. Methods A total of 99 cases with M. pneumoniae pneumonia confirmed by polymerase chain reaction (PCR) and culture were analyzed. Forty-five cases were pediatric patients less than 16 years old, 26 cases were 16 to 19-year-old adolescent patients and 28 cases were adult patients. Primers for domain V of 23S rRNA were used and DNA sequences of the PCR products were compared with the sequence of an M. pneumoniae reference strain. Results Thirty of 45 pediatric patients (66%), 12 of 26 adolescent patients (46%) and seven of 28 adult patients (25%) with M. pneumoniae pneumonia were found to be infected with macrolide-resistant M. pneumoniae (MR patients). Although the prevalence of resistant strains was similar in pediatric patients between 2008 and 2011, an increase in the prevalence of resistant strains was observed in adolescent patients. Among 30 pediatric MR patients, 26 had an A-to-G transition at position 2063 (A2063G) and four had an A-to-G transition at position 2064 (A2064G). In 12 adolescent MR patients, 10 showed an A2063G transition and two showed an A2064G transition, and in seven adult MR patients, six showed an A2063G transition and one showed an A2064G transition. Conclusions The prevalence of macrolide-resistant M. pneumoniae is high among adolescent patients as well as pediatric patients less than 16-years old. To prevent outbreaks of M. pneumoniae infection, especially macrolide-resistant M. pneumoniae, in closed populations including among families, in schools and in university students, physicians should pay

  14. Bacterial resistance to tetracycline: mechanisms, transfer, and clinical significance.

    PubMed Central

    Speer, B S; Shoemaker, N B; Salyers, A A

    1992-01-01

    Tetracycline has been a widely used antibiotic because of its low toxicity and broad spectrum of activity. However, its clinical usefulness has been declining because of the appearance of an increasing number of tetracycline-resistant isolates of clinically important bacteria. Two types of resistance mechanisms predominate: tetracycline efflux and ribosomal protection. A third mechanism of resistance, tetracycline modification, has been identified, but its clinical relevance is still unclear. For some tetracycline resistance genes, expression is regulated. In efflux genes found in gram-negative enteric bacteria, regulation is via a repressor that interacts with tetracycline. Gram-positive efflux genes appear to be regulated by an attenuation mechanism. Recently it was reported that at least one of the ribosome protection genes is regulated by attenuation. Tetracycline resistance genes are often found on transmissible elements. Efflux resistance genes are generally found on plasmids, whereas genes involved in ribosome protection have been found on both plasmids and self-transmissible chromosomal elements (conjugative transposons). One class of conjugative transposon, originally found in streptococci, can transfer itself from streptococci to a variety of recipients, including other gram-positive bacteria, gram-negative bacteria, and mycoplasmas. Another class of conjugative transposons has been found in the Bacteroides group. An unusual feature of the Bacteroides elements is that their transfer is enhanced by preexposure to tetracycline. Thus, tetracycline has the double effect of selecting for recipients that acquire a resistance gene and stimulating transfer of the gene. PMID:1423217

  15. Small cell lung cancer transformation and T790M mutation: complimentary roles in acquired resistance to kinase inhibitors in lung cancer

    PubMed Central

    Suda, Kenichi; Murakami, Isao; Sakai, Kazuko; Mizuuchi, Hiroshi; Shimizu, Shigeki; Sato, Katsuaki; Tomizawa, Kenji; Tomida, Shuta; Yatabe, Yasushi; Nishio, Kazuto; Mitsudomi, Tetsuya

    2015-01-01

    Lung cancers often harbour a mutation in the epidermal growth factor receptor (EGFR) gene. Because proliferation and survival of lung cancers with EGFR mutation solely depend on aberrant signalling from the mutated EGFR, these tumours often show dramatic responses to EGFR tyrosine kinase inhibitors (TKIs). However, acquiring resistance to these drugs is almost inevitable, thus a better understanding of the underlying resistance mechanisms is critical. Small cell lung cancer (SCLC) transformation is a relatively rare acquired resistance mechanism that has lately attracted considerable attention. In the present study, through an in-depth analysis of multiple EGFR-TKI refractory lesions obtained from an autopsy case, we observed a complementary relationship between SCLC transformation and EGFR T790M secondary mutation (resistance mutation). We also identified analogies and differences in genetic aberration between a TKI-refractory lesion with SCLC transformation and one with EGFR T790M mutation. In particular, target sequencing revealed a TP53 P151S mutation in all pre- and post-treatment lesions. PTEN M264I mutation was identified only in a TKI-refractory lesion with SCLC transformation, while PIK3CA and RB1 mutations were identified only in pre-treatment primary tumour samples. These results provide the groundwork for understanding acquired resistance to EGFR-TKIs via SCLC transformation. PMID:26400668

  16. Small cell lung cancer transformation and T790M mutation: complimentary roles in acquired resistance to kinase inhibitors in lung cancer.

    PubMed

    Suda, Kenichi; Murakami, Isao; Sakai, Kazuko; Mizuuchi, Hiroshi; Shimizu, Shigeki; Sato, Katsuaki; Tomizawa, Kenji; Tomida, Shuta; Yatabe, Yasushi; Nishio, Kazuto; Mitsudomi, Tetsuya

    2015-01-01

    Lung cancers often harbour a mutation in the epidermal growth factor receptor (EGFR) gene. Because proliferation and survival of lung cancers with EGFR mutation solely depend on aberrant signalling from the mutated EGFR, these tumours often show dramatic responses to EGFR tyrosine kinase inhibitors (TKIs). However, acquiring resistance to these drugs is almost inevitable, thus a better understanding of the underlying resistance mechanisms is critical. Small cell lung cancer (SCLC) transformation is a relatively rare acquired resistance mechanism that has lately attracted considerable attention. In the present study, through an in-depth analysis of multiple EGFR-TKI refractory lesions obtained from an autopsy case, we observed a complementary relationship between SCLC transformation and EGFR T790M secondary mutation (resistance mutation). We also identified analogies and differences in genetic aberration between a TKI-refractory lesion with SCLC transformation and one with EGFR T790M mutation. In particular, target sequencing revealed a TP53 P151S mutation in all pre- and post-treatment lesions. PTEN M264I mutation was identified only in a TKI-refractory lesion with SCLC transformation, while PIK3CA and RB1 mutations were identified only in pre-treatment primary tumour samples. These results provide the groundwork for understanding acquired resistance to EGFR-TKIs via SCLC transformation. PMID:26400668

  17. Acquired resistance to EGFR tyrosine kinase inhibitors alters the metabolism of human head and neck squamous carcinoma cells and xenograft tumours

    PubMed Central

    Beloueche-Babari, M; Box, C; Arunan, V; Parkes, H G; Valenti, M; De Haven Brandon, A; Jackson, L E; Eccles, S A; Leach, M O

    2015-01-01

    Background: Acquired resistance to molecularly targeted therapeutics is a key challenge in personalised cancer medicine, highlighting the need for identifying the underlying mechanisms and early biomarkers of relapse, in order to guide subsequent patient management. Methods: Here we use human head and neck squamous cell carcinoma (HNSCC) models and nuclear magnetic resonance (NMR) spectroscopy to assess the metabolic changes that follow acquired resistance to EGFR tyrosine kinase inhibitors (TKIs), and which could serve as potential metabolic biomarkers of drug resistance. Results: Comparison of NMR metabolite profiles obtained from control (CALS) and EGFR TKI-resistant (CALR) cells grown as 2D monolayers, 3D spheroids or xenograft tumours in athymic mice revealed a number of differences between the sensitive and drug-resistant models. In particular, we observed elevated levels of glycerophosphocholine (GPC) in CALR relative to CALS monolayers, spheroids and tumours, independent of the growth rate or environment. In addition, there was an increase in alanine, aspartate and creatine+phosphocreatine in resistant spheroids and xenografts, and increased levels of lactate, branched-chain amino acids and a fall in phosphoethanolamine only in xenografts. The xenograft lactate build-up was associated with an increased expression of the glucose transporter GLUT-1, whereas the rise in GPC was attributed to inhibition of GPC phosphodiesterase. Reduced glycerophosphocholine (GPC) and phosphocholine were observed in a second HNSCC model probably indicative of a different drug resistance mechanism. Conclusions: Our studies reveal metabolic signatures associated not only with acquired EGFR TKI resistance but also growth pattern, microenvironment and contributing mechanisms in HNSCC models. These findings warrant further investigation as metabolic biomarkers of disease relapse in the clinic. PMID:25742484

  18. 14-3-3σ regulation of and interaction with YAP1 in acquired gemcitabine resistance via promoting ribonucleotide reductase expression

    PubMed Central

    Qin, Li; Dong, Zizheng; Zhang, Jian-Ting

    2016-01-01

    Gemcitabine is an important anticancer therapeutics approved for treatment of several human cancers including locally advanced or metastatic pancreatic ductal adenocarcinoma (PDAC). Its clinical effectiveness, however, is hindered by existence of intrinsic and development of acquired resistances. Previously, it was found that 14-3-3σ expression associates with poor clinical outcome of PDAC patients. It was also found that 14-3-3σ expression is up-regulated in gemcitabine resistant PDAC cells and contributes to the acquired gemcitabine resistance. In this study, we investigated the molecular mechanism of 14-3-3σ function in gemcitabine resistance and found that 14-3-3σ up-regulates YAP1 expression and then binds to YAP1 to inhibit gemcitabine-induced caspase 8 activation and apoptosis. 14-3-3σ association with YAP1 up-regulates the expression of ribonucleotide reductase M1 and M2, which may mediate 14-3-3σ/YAP1 function in the acquired gemcitabine resistance. These findings suggest a possible role of YAP1 signaling in gemcitabine resistance. PMID:26894857

  19. Mechanisms of Antimicrobial Resistance in ESKAPE Pathogens

    PubMed Central

    Santajit, Sirijan; Indrawattana, Nitaya

    2016-01-01

    The ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) are the leading cause of nosocomial infections throughout the world. Most of them are multidrug resistant isolates, which is one of the greatest challenges in clinical practice. Multidrug resistance is amongst the top three threats to global public health and is usually caused by excessive drug usage or prescription, inappropriate use of antimicrobials, and substandard pharmaceuticals. Understanding the resistance mechanisms of these bacteria is crucial for the development of novel antimicrobial agents or other alternative tools to combat these public health challenges. Greater mechanistic understanding would also aid in the prediction of underlying or even unknown mechanisms of resistance, which could be applied to other emerging multidrug resistant pathogens. In this review, we summarize the known antimicrobial resistance mechanisms of ESKAPE pathogens. PMID:27274985

  20. Methylbenzene-Containing Polyketides from a Streptomyces that Spontaneously Acquired Rifampicin Resistance: Structural Elucidation and Biosynthesis.

    PubMed

    Thong, Wei Li; Shin-Ya, Kazuo; Nishiyama, Makoto; Kuzuyama, Tomohisa

    2016-04-22

    Conventional screening for novel bioactive compounds in actinomycetes often results in the rediscovery of known compounds. In contrast, recent genome sequencing revealed that most of the predicted gene clusters for secondary metabolisms are not expressed under standard cultivation conditions. To explore the potential metabolites produced by these gene clusters, we implemented a cryptic gene activation strategy by screening mutants that acquire resistance to rifampicin. The induction of rifampicin resistance in 11 actinomycete strains generated 164 rifampicin-resistant mutants (rif mutants). The comparison of the metabolic profiles between the rif mutants and their wild-type strains indicated that one mutant (TW-R50-13) overproduced an unidentified metabolite (1). During the isolation and structural elucidation of metabolite 1, an additional metabolite was found; both are unprecedented compounds featuring a C5N unit and a methylbenzene moiety. Of these partial structures, the biosynthesis of the latter has not been reported. A feeding experiment using (13)C-labeled precursors demonstrated that the methylbenzene moiety is most likely synthesized by the action of polyketide synthase. The gene deletion experiments revealed that the genes for the methylbenzene moiety are located at a different locus than the genes for the C5N unit. PMID:26905826

  1. Direct pharmacological assessment of clinically acquired models as a strategy to overcome resistance to tyrosine kinase inhibitors

    PubMed Central

    Benes, Cyril H

    2015-01-01

    We have performed a study using cell lines established from biopsies of clinically resistant non-small cell lung cancers with the aim of discovering therapeutic strategies to overcome acquired resistance. Our results indicate that pharmacological assessment of tumor material might efficiently complement genetic profiling in the future path toward personalized medicine. PMID:27308520

  2. Direct pharmacological assessment of clinically acquired models as a strategy to overcome resistance to tyrosine kinase inhibitors.

    PubMed

    Benes, Cyril H

    2015-01-01

    We have performed a study using cell lines established from biopsies of clinically resistant non-small cell lung cancers with the aim of discovering therapeutic strategies to overcome acquired resistance. Our results indicate that pharmacological assessment of tumor material might efficiently complement genetic profiling in the future path toward personalized medicine. PMID:27308520

  3. The phenomenon of acquired resistance to metformin in breast cancer cells: The interaction of growth pathways and estrogen receptor signaling.

    PubMed

    Scherbakov, Alexander M; Sorokin, Danila V; Tatarskiy, Victor V; Prokhorov, Nikolay S; Semina, Svetlana E; Berstein, Lev M; Krasil'nikov, Mikhail A

    2016-04-01

    Metformin, a biguanide antidiabetic drug, is used to decrease hyperglycemia in patients with type 2 diabetes. Recently, the epidemiological studies revealed the potential of metformin as an anti-tumor drug for several types of cancer, including breast cancer. Anti-tumor metformin action was found to be mediated, at least in part, via activation of adenosine monophosphate-activated protein kinase (AMPK)-intracellular energy sensor, which inhibits the mammalian target of rapamycin (mTOR) and some other signaling pathways. Nevertheless, some patients can be non-sensitive or resistant to metformin action. Here we analyzed the mechanism of the formation of metformin-resistant phenotype in breast cancer cells and its role in estrogen receptor (ER) regulation. The experiments were performed on the ER-positive MCF-7 breast cancer cells and metformin-resistant MCF-7 subline (MCF-7/M) developed due to long-term metformin treatment. The transcriptional activity of NF-κB and ER was measured by the luciferase reporter gene analysis. The protein expression was determined by immunoblotting (Snail1, (phospho)AMPK, (phospho)IκBα, (phospho)mTOR, cyclin D1, (phospho)Akt and ERα) and immunohistochemical analysis (E-cadherin). We have found that: 1) metformin treatment of MCF-7 cells is accompanied with the stimulation of AMPK and inhibition of growth-related proteins including IκBα, NF-κB, cyclin D1 and ERα; 2) long-term metformin treatment lead to the appearance and progression of cross-resistance to metformin and tamoxifen; the resistant cells are characterized with the unaffected AMPK activity, but the irreversible ER suppression and constitutive activation of Akt/Snail1 signaling; 3) Akt/Snail1 signaling is involved into progression of metformin resistance. The results presented may be considered as the first evidence of the progression of cross-resistance to metformin and tamoxifen in breast cancer cells. Importantly, the acquired resistance to both drugs is based on the

  4. CYP3A5 mediates basal and acquired therapy resistance in different subtypes of pancreatic ductal adenocarcinoma.

    PubMed

    Noll, Elisa M; Eisen, Christian; Stenzinger, Albrecht; Espinet, Elisa; Muckenhuber, Alexander; Klein, Corinna; Vogel, Vanessa; Klaus, Bernd; Nadler, Wiebke; Rösli, Christoph; Lutz, Christian; Kulke, Michael; Engelhardt, Jan; Zickgraf, Franziska M; Espinosa, Octavio; Schlesner, Matthias; Jiang, Xiaoqi; Kopp-Schneider, Annette; Neuhaus, Peter; Bahra, Marcus; Sinn, Bruno V; Eils, Roland; Giese, Nathalia A; Hackert, Thilo; Strobel, Oliver; Werner, Jens; Büchler, Markus W; Weichert, Wilko; Trumpp, Andreas; Sprick, Martin R

    2016-03-01

    Although subtypes of pancreatic ductal adenocarcinoma (PDAC) have been described, this malignancy is clinically still treated as a single disease. Here we present patient-derived models representing the full spectrum of previously identified quasi-mesenchymal (QM-PDA), classical and exocrine-like PDAC subtypes, and identify two markers--HNF1A and KRT81--that enable stratification of tumors into different subtypes by using immunohistochemistry. Individuals with tumors of these subtypes showed substantial differences in overall survival, and their tumors differed in drug sensitivity, with the exocrine-like subtype being resistant to tyrosine kinase inhibitors and paclitaxel. Cytochrome P450 3A5 (CYP3A5) metabolizes these compounds in tumors of the exocrine-like subtype, and pharmacological or short hairpin RNA (shRNA)-mediated CYP3A5 inhibition sensitizes tumor cells to these drugs. Whereas hepatocyte nuclear factor 4, alpha (HNF4A) controls basal expression of CYP3A5, drug-induced CYP3A5 upregulation is mediated by the nuclear receptor NR1I2. CYP3A5 also contributes to acquired drug resistance in QM-PDA and classical PDAC, and it is highly expressed in several additional malignancies. These findings designate CYP3A5 as a predictor of therapy response and as a tumor cell-autonomous detoxification mechanism that must be overcome to prevent drug resistance. PMID:26855150

  5. CYP3A5 mediates basal and acquired therapy resistance in different subtypes of pancreatic ductal adenocarcinoma

    PubMed Central

    Noll, Elisa M.; Eisen, Christian; Stenzinger, Albrecht; Espinet, Elisa; Muckenhuber, Alexander; Klein, Corinna; Vogel, Vanessa; Klaus, Bernd; Nadler, Wiebke; Rösli, Christoph; Lutz, Christian; Kulke, Michael; Engelhardt, Jan; Zickgraf, Franziska M.; Espinosa, Octavio; Schlesner, Matthias; Jiang, Xiaoqi; Kopp-Schneider, Annette; Neuhaus, Peter; Bahra, Marcus; Sinn, Bruno V.; Eils, Roland; Giese, Nathalia A.; Hackert, Thilo; Strobel, Oliver; Werner, Jens; Büchler, Markus W.; Weichert, Wilko; Trumpp, Andreas; Sprick, Martin R.

    2016-01-01

    Although subtypes of pancreatic ductal adenocarcinoma (PDAC) were described, this malignancy is clinically still treated as a single disease. Here, we present patient-derived models representing the full spectrum of previously identified quasi-mesenchymal (QM-PDA), classical and exocrine-like PDAC subtypes, and identify two markers—HNF1A and KRT81—that enable stratification of tumors into different subtypes by immunohistochemistry. Individuals bearing tumors of these subtypes show significant differences in overall survival and their tumors differ in drug sensitivity, with the exocrine-like subtype being resistant to tyrosine kinase inhibitors and paclitaxel. Cytochrome P450 3A5 (CYP3A5) metabolizes these compounds in tumors of the exocrine-like subtype, and pharmacological or shRNA-mediated CYP3A5 inhibition sensitizes tumor cells to these drugs. Whereas hepatocyte nuclear factor 4 alpha (HNF4A) controls basal expression of CYP3A5, drug-induced CYP3A5 upregulation is mediated by the nuclear receptor NR1I2. CYP3A5 also contributes to acquired drug resistance in QM-PDA and classical PDAC, and is highly expressed in several additional malignancies. These findings designate CYP3A5 as predictor of therapy response and as a tumor cell-autonomous detoxification mechanism that must be overcome to prevent drug resistance. PMID:26855150

  6. IKK phosphorylation of NF-κB at serine 536 contributes to acquired cisplatin resistance in head and neck squamous cell cancer

    PubMed Central

    Li, Zhipeng; Yang, Zejia; Lapidus, Rena G; Liu, Xuefeng; Cullen, Kevin J; Dan, Han C

    2015-01-01

    Current treatment methods for advanced head and neck squamous cell carcinoma (HNSCC) include surgery, radiation therapy and chemotherapy. For recurrent and metastatic HNSCC, cisplatin is the most common treatment option, but most of patients will eventually develop cisplatin resistance. Therefore, it is imperative to define the mechanisms involved in cisplatin resistance and find novel therapeutic strategies to overcome this deadly disease. In order to determine the role of nuclear factor-kappa B (NF-κB) in contributing to acquired cisplatin resistance in HNSCC, the expression and activity of NF-κB and its upstream kinases, IKKα and IKKβ, were evaluated and compared in three pairs of cisplatin sensitive and resistant HNSCC cell lines, including a pair of patient derived HNSCC cell line. The experiments revealed that NF-κB p65 activity was elevated in cisplatin resistant HNSCC cells compared to that in their parent cells. Importantly, the phosphorylation of NF-κB p65 at serine 536 and the phosphorylation of IKKα and IKKβ at their activation loops were dramatically elevated in the resistant cell lines. Furthermore, knockdown of NF-κB or overexpression of p65-S536 alanine (p65-S536A) mutant sensitizes resistant cells to cisplatin. Additionally, the novel IKKβ inhibitor CmpdA has been shown to consistently block the phosphorylation of NF-κB at serine 536 while also dramatically improving the efficacy of cisplatin in inhibition of cell proliferation and induction of apoptosis in the cisplatin resistant cancer cells. These results indicated that IKK/NF-κB plays a pivotal role in controlling acquired cisplatin resistance and that targeting the IKK/NF-κB signaling pathway may provide a possible therapeutic method to overcome the acquired resistance to cisplatin in HNSCC. PMID:26693062

  7. Acquired resistance to Giardia muris in X-linked immunodeficient mice.

    PubMed Central

    Skea, D L; Underdown, B J

    1991-01-01

    A previous study from this laboratory (D. P. Snider, D. Skea, and B. J. Underdown, Infect. Immun. 56:2838-2842, 1988) indicated that immunodeficient mice expressing the xid gene develop prolonged infections with Giardia muris, unlike immunocompetent mice, which eliminate the intestinal protozoan parasite in 8 to 10 weeks. In this study, CBA/N (xid) and CBA/Ca mice were infected with G. muris cysts and at various times following this primary infection were cured by treatment with metronidazole. In contrast to the marked differences in the ability of xid and normal mice to eliminate a primary infection, mice of both strains were resistant to a secondary challenge of G. muris cysts. These data imply that the mechanism(s) responsible for elimination of a primary infection is not identical to those required to resist a secondary challenge infection. Splenocytes from immunocompetent CBA/Ca mice (but not immunodeficient CBA/N mice) could transfer the ability to eliminate a primary G. muris infection to irradiated mice of either strain. In contrast, splenocytes from previously infected CBA/Ca mice could not transfer resistance to a challenge infection, further supporting the hypothesis that there are differences between mechanisms required to eliminate a primary infection and those necessary to resist a second challenge infection. PMID:2019439

  8. Impaired acquired resistance of mice to Klebsiella pneumoniae infection induced by acute NO/sub 2/ exposure

    SciTech Connect

    Bouley, G.; Azoulay-Dupuis, E.; Gaudebout, C.

    1985-12-01

    The natural resistance of nonimmunized C57B1/6 mice to an intraperitoneal Klebsiella pneumoniae challenge was not significantly affected by prior continuous exposure to 20 ppm NO/sub 2/ for 4 days. In contrast, the acquired resistance of mice immunized just before and infected just after NO/sub 2/ exposure was seriously impaired. This could not be explained by the loss of appetite (about 30%) observed in NO/sub 2/ treated mice, for neither the natural nor acquired resistance of control air exposure mice given approximately 70% ad libitum food and water were significantly modified.

  9. Genomic and Molecular Characterization of Miltefosine Resistance in Leishmania infantum Strains with Either Natural or Acquired Resistance through Experimental Selection of Intracellular Amastigotes

    PubMed Central

    Hendrickx, Sarah; Eberhardt, Eline; Garcia-Hernandez, Raquel; Lachaud, Laurence; Cotton, James; Sanders, Mandy; Cuypers, Bart; Imamura, Hideo; Dujardin, Jean-Claude; Delputte, Peter; Cos, Paul; Caljon, Guy; Gamarro, Francisco; Castanys, Santiago

    2016-01-01

    During the last decade miltefosine (MIL) has been used as first-line treatment for visceral leishmaniasis in endemic areas with antimonial resistance, but a decline in clinical effectiveness is now being reported. While only two MIL-resistant Leishmania infantum strains from HIV co-infected patients have been documented, phenotypic MIL-resistance for L. donovani has not yet been identified in the laboratory. Hence, a better understanding of the factors contributing to increased MIL-treatment failure is necessary. Given the paucity of defined MIL-resistant L. donovani clinical isolates, this study used an experimental amastigote-selected MIL-resistant L. infantum isolate (LEM3323). In-depth exploration of the MIL-resistant phenotype was performed by coupling genomic with phenotypic data to gain insight into gene function and the mutant phenotype. A naturally MIL-resistant L. infantum clinical isolate (LEM5159) was included to compare both datasets. Phenotypically, resistance was evaluated by determining intracellular amastigote susceptibility in vitro and actual MIL-uptake. Genomic analysis provided supportive evidence that the resistance selection model on intracellular amastigotes can be a good proxy for the in vivo field situation since both resistant strains showed mutations in the same inward transporter system responsible for the acquired MIL-resistant phenotype. In line with previous literature findings in promastigotes, our data confirm a defective import machinery through inactivation of the LiMT/LiRos3 protein complex as the main mechanism for MIL-resistance also in intracellular amastigotes. Whole genome sequencing analysis of LEM3323 revealed a 2 base pair deletion in the LiMT gene that led to the formation an early stop codon and a truncation of the LiMT protein. Interestingly, LEM5159 revealed mutations in both the LiMT and LiRos3 genes, resulting in an aberrant expression of the LiMT protein. To verify that these mutations were indeed accountable for

  10. Genomic and Molecular Characterization of Miltefosine Resistance in Leishmania infantum Strains with Either Natural or Acquired Resistance through Experimental Selection of Intracellular Amastigotes.

    PubMed

    Mondelaers, Annelies; Sanchez-Cañete, Maria P; Hendrickx, Sarah; Eberhardt, Eline; Garcia-Hernandez, Raquel; Lachaud, Laurence; Cotton, James; Sanders, Mandy; Cuypers, Bart; Imamura, Hideo; Dujardin, Jean-Claude; Delputte, Peter; Cos, Paul; Caljon, Guy; Gamarro, Francisco; Castanys, Santiago; Maes, Louis

    2016-01-01

    During the last decade miltefosine (MIL) has been used as first-line treatment for visceral leishmaniasis in endemic areas with antimonial resistance, but a decline in clinical effectiveness is now being reported. While only two MIL-resistant Leishmania infantum strains from HIV co-infected patients have been documented, phenotypic MIL-resistance for L. donovani has not yet been identified in the laboratory. Hence, a better understanding of the factors contributing to increased MIL-treatment failure is necessary. Given the paucity of defined MIL-resistant L. donovani clinical isolates, this study used an experimental amastigote-selected MIL-resistant L. infantum isolate (LEM3323). In-depth exploration of the MIL-resistant phenotype was performed by coupling genomic with phenotypic data to gain insight into gene function and the mutant phenotype. A naturally MIL-resistant L. infantum clinical isolate (LEM5159) was included to compare both datasets. Phenotypically, resistance was evaluated by determining intracellular amastigote susceptibility in vitro and actual MIL-uptake. Genomic analysis provided supportive evidence that the resistance selection model on intracellular amastigotes can be a good proxy for the in vivo field situation since both resistant strains showed mutations in the same inward transporter system responsible for the acquired MIL-resistant phenotype. In line with previous literature findings in promastigotes, our data confirm a defective import machinery through inactivation of the LiMT/LiRos3 protein complex as the main mechanism for MIL-resistance also in intracellular amastigotes. Whole genome sequencing analysis of LEM3323 revealed a 2 base pair deletion in the LiMT gene that led to the formation an early stop codon and a truncation of the LiMT protein. Interestingly, LEM5159 revealed mutations in both the LiMT and LiRos3 genes, resulting in an aberrant expression of the LiMT protein. To verify that these mutations were indeed accountable for

  11. Community-Acquired Methicillin-Resistant Pyogenic Liver Abscess: A Case Report.

    PubMed

    Cherian, Joel; Singh, Rahul; Varma, Muralidhar; Vidyasagar, Sudha; Mukhopadhyay, Chiranjay

    2016-01-01

    Pyogenic liver abscesses are rare with an incidence of 0.5% to 0.8% and are mostly due to hepatobiliary causes (40% to 60%). Most are polymicrobial with less than 10% being caused by Staphylococcus aureus. Of these, few are caused by methicillin-resistant Staphylococcus aureus (MRSA) and fewer still by a community-acquired strain. Here we present a case study of a patient with a community-acquired MRSA liver abscess. The patient presented with fever since 1 month and tender hepatomegaly. Blood tests revealed elevated levels of alkaline phosphatase, C-reactive protein, erythrocyte sedimentation rate, and neutrophilic leukocytosis. Blood cultures were sterile. Ultrasound of the abdomen showed multiple abscesses, from which pus was drained and MRSA isolated. Computed tomography of the abdomen did not show any source of infection, and an amebic serology was negative. The patient was started on vancomycin for 2 weeks, following which he became afebrile and was discharged on oral linezolid for 4 more weeks. Normally a liver abscess is treated empirically with ceftriaxone for pyogenic liver abscess and metronidazole for amebic liver abscess. However, if the patient has risk factors for a Staphylococcal infection, it is imperative that antibiotics covering gram-positive organisms be added while waiting for culture reports. PMID:27540556

  12. Antibiotic Resistance Pattern of Community Acquired Uropathogens at a Tertiary Care Hospital in Jaipur, Rajasthan

    PubMed Central

    Sood, Smita; Gupta, Ravi

    2012-01-01

    Background: Urinary tract infections (UTIs) are amongst the most common infections described in outpatients setting. Objectives: A study was conducted to evaluate the uropathogenic bacterial flora and its antimicrobial susceptibility profile among patients presenting to the out-patient clinics of a tertiary care hospital at Jaipur, Rajasthan. Materials and Methods: 2012 consecutive urine specimens from symptomatic UTI cases attending to the outpatient clinics were processed in the Microbiology lab. Bacterial isolates obtained were identified using biochemical reactions. Antimicrobial susceptibility testing was performed by the Kirby-Bauer disc diffusion method. Extended spectrum beta lactamase (ESBL) production was determined by the double disk approximation test and the Clinical and Laboratory Standards Institute (formerly NCCLS) confirmatory method. Results: Pathogens were isolated from 346 (17.16%) of the 2012 patients who submitted a urine sample. Escherichia coli was the most frequently isolated community acquired uropathogen accounting for 61.84% of the total isolates. ESBL production was observed in 23.83% of E. coli strains and 8.69% of Klebsiella strains. With the exception of Nitrofurantoin, resistance to agents commonly used as empiric oral treatments for UTI was quite high. Conclusion: The study revealed E. coli as the predominant bacterial pathogen for the community acquired UTIs in Jaipur, Rajasthan. An increasing trend in the production ESBLs among UTI pathogens in the community was noted. Nitrofurantoin should be used as empirical therapy for primary, uncomplicated UTIs. PMID:22529539

  13. Increased thymidylate synthase in L1210 cells possessing acquired resistance to N10-propargyl-5,8-dideazafolic acid (CB3717): development, characterization, and cross-resistance studies

    SciTech Connect

    Jackman, A.L.; Alison, D.L.; Calvert, A.H.; Harrap, K.R.

    1986-06-01

    The properties are described of a mutant L1210 cell line (L1210:C15) with acquired resistance (greater than 200-fold) to the thymidylate synthase (TS) inhibitor N10-propargyl-5,8-dideazafolic acid. TS was overproduced 45-fold and was accompanied by a small increase in the activity of dihydrofolate reductase (2.6-fold). Both the level of resistance and enzyme activities were maintained in drug-free medium (greater than 300 generations). Failure of N10-propargyl-5,8-dideazafolic acid to suppress the (/sup 3/H)-2'-deoxyuridine incorporation into the acid-precipitable material of the resistant line supported the evidence that TS overproduction was the mechanism of resistance; consequently the L1210:C15 cells were largely cross-resistant to another (but weaker) TS inhibitor, 5,8-dideazafolic acid. Minimal cross-resistance was observed to the dihydrofolate reductase inhibitors methotrexate and 5-methyl-5,8-dideazaaminopterin (5- and 2-fold, respectively). L1210 and L1210:C15 cells were, however, equally sensitive to 5-fluorodeoxyuridine (FdUrd), an unexpected finding since a metabolite, 5-fluorodeoxyuridine monophosphate, is a potent TS inhibitor; however, this cytotoxicity against the L1210:C15 cells was antagonized by coincubation with 5 microM folinic acid although folinic acid potentiated the cytotoxicity of FdUrd to the N10-propargyl-5,8-dideazafolic acid-sensitive L1210 line. Thymidine was much less effective as a FdUrd protecting agent in the L1210:C15 when compared with the L1210 cells; however, a combination of thymidine plus hypoxanthine was without any additional effect (compared with thymidine alone) against the sensitive line but effectively protected L1210:C15 cells.

  14. The insulin-like growth factor 1 receptor causes acquired resistance to erlotinib in lung cancer cells with the wild-type epidermal growth factor receptor.

    PubMed

    Suda, Kenichi; Mizuuchi, Hiroshi; Sato, Katsuaki; Takemoto, Toshiki; Iwasaki, Takuya; Mitsudomi, Tetsuya

    2014-08-15

    Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) therapy often provides a dramatic response in lung cancer patients with EGFR mutations. In addition, moderate clinical efficacy of the EGFR-TKI, erlotinib, has been shown in lung cancer patients with the wild-type EGFR. Numerous molecular mechanisms that cause acquired resistance to EGFR-TKIs have been identified in lung cancers with the EGFR mutations; however, few have been reported in lung cancers with the wild-type EGFR. We used H358 lung adenocarcinoma cells lacking EGFR mutations that showed modest sensitivity to erlotinib. The H358 cells acquired resistance to erlotinib via chronic exposure to the drug. The H358 erlotinib-resistant (ER) cells do not have a secondary EGFR mutation, neither MET gene amplification nor PTEN downregulation; these have been identified in lung cancers with the EGFR mutations. From comprehensive screening of receptor tyrosine kinase phosphorylation, we observed increased phosphorylation of insulin-like growth factor 1 receptor (IGF1R) in H358ER cells compared with parental H358 cells. H358ER cells responded to combined therapy with erlotinib and NVP-AEW541, an IGF1R-TKI. Our results indicate that IGF1R activation is a molecular mechanism that confers acquired resistance to erlotinib in lung cancers with the wild-type EGFR. PMID:24458568

  15. [MOLECULAR MECHANISMS OF DRUG RESISTANCE NEISSERIA GONORRHOEAE HISTORY AND PROSPECTS].

    PubMed

    Bodoev, I N; Il'ina, E N

    2015-01-01

    Neisseria gonorrhoeae (gonococcus) is a strict human pathogen, which causes gonorrhea--an infectious disease, whose origin dates back to more than two thousand years. Due to the unique plasticity of the genetic material, these bacteria have acquired the capacity to adapt to the host immune system, cause repeated infections, as well as withstand antimicrobials. Since the introduction of antibiotics in 1930s, gonococcus has displayed its propensity to develop resistance to all clinically useful antibiotics. It is important to note that the known resistance determinants of N. gonorrhoeae were acquired through horizontal gene transfer, recombination and spontaneous mutagenesis, and may be located both in the chromosome and on the plasmid. After introduction of a new antimicrobial drug, gonococcus becomes resistant within two decades and replaces sensitive bacterial population. Currently Ceftriaxone is the last remaining antibiotic for first-line treatment of gonorrhea. However, the first gonococcus displaying high-level resistance to Ceftriaxone was isolated in Japan a few years ago. Therefore, in the near future, gonorrhea may become untreatable. In the present review, we discuss the chronology of the anti-gonorrhea drugs (antibiotics) replacement, the evolution of resistance mechanisms emergence and future perspectives of N. gonorrhoeae treatment. PMID:26665738

  16. Disease resistance: Molecular mechanisms and biotechnological applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This special issue “Disease resistance: molecular mechanisms and biotechnological applications” contains 11 review articles and four original research papers. Research in the area of engineering for disease resistance continues to progress although only 10% of the transgenic plants registered for ...

  17. Nitric oxide and reactive oxygen species are required for systemic acquired resistance in plants

    PubMed Central

    El-Shetehy, Mohamed; Wang, Caixia; Shine, M B; Yu, Keshun; Kachroo, Aardra; Kachroo, Pradeep

    2015-01-01

    Systemic acquired resistance (SAR) is a form of broad-spectrum disease resistance that is induced in response to primary infection and that protects uninfected portions of the plant against secondary infections by related or unrelated pathogens. SAR is associated with an increase in chemical signals that operate in a collective manner to confer protection against secondary infections. These include, the phytohormone salicylic acid (SA), glycerol-3-phosphate (G3P), azelaic acid (AzA) and more recently identified signals nitric oxide (NO) and reactive oxygen species (ROS). NO, ROS, AzA and G3P function in the same branch of the SAR pathway, and in parallel to the SA-regulated branch. NO and ROS function upstream of AzA/G3P and different reactive oxygen species functions in an additive manner to mediate chemical cleavage of the C9 double bond on C18 unsaturated fatty acids to generate AzA. The parallel and additive functioning of various chemical signals provides important new insights in the overlapping pathways leading to SAR. PMID:26375184

  18. Acquired resistance to mutant-selective EGFR inhibitor AZD9291 is associated with increased dependence on RAS signaling in preclinical models

    PubMed Central

    Eberlein, Catherine A.; Stetson, Daniel; Markovets, Aleksandra A.; Al-Kadhimi, Katherine J.; Lai, Zhongwu; Fisher, Paul R.; Meador, Catherine B.; Spitzler, Paula; Ichihara, Eiki; Ross, Sarah J.; Ahdesmaki, Miika J.; Ahmed, Ambar; Ratcliffe, Laura E.; Christey O’Brien, Elizabeth L.; Barnes, Claire H.; Brown, Henry; Smith, Paul D.; Dry, Jonathan R.; Beran, Garry; Thress, Kenneth S.; Dougherty, Brian; Pao, William; Cross, Darren A. E.

    2015-01-01

    Resistance to targeted EGFR inhibitors is likely to develop in EGFR mutant lung cancers. Early identification of innate or acquired resistance mechanisms to these agents is essential to direct development of future therapies. We describe the detection of heterogeneous mechanisms of resistance within populations of EGFR mutant cells (PC9 and/or NCI-H1975) with acquired resistance to current and newly developed EGFR TKIs including AZD9291. We report the detection of NRAS mutations, including a novel E63K mutation, and a gain of copy number of WT NRAS or WT KRAS in cell populations resistant to gefitinib, afatinib, WZ4002 or AZD9291. Compared to parental cells, a number of resistant cell populations were more sensitive to inhibition by the MEK inhibitor selumetinib (AZD6244; ARRY-142886) when treated in combination with the originating EGFR inhibitor. In vitro, a combination of AZD9291 with selumetinib prevented emergence of resistance in PC9 cells and delayed resistance in NCI-H1975 cells. In vivo, concomitant dosing of AZD9291 with selumetinib caused regression of AZD9291-resistant tumours in an EGFRm/T790M transgenic model. Our data support the use of a combination of AZD9291 with a MEK inhibitor to delay or prevent resistance to AZD9291 in EGFRm and/or EGFRm/T790M tumours. Further, these findings suggest that NRAS modifications in tumour samples from patients who have progressed on current or EGFR inhibitors in development may support subsequent treatment with a combination of EGFR and MEK inhibition. PMID:25870145

  19. Acquired Resistance to the Mutant-Selective EGFR Inhibitor AZD9291 Is Associated with Increased Dependence on RAS Signaling in Preclinical Models.

    PubMed

    Eberlein, Catherine A; Stetson, Daniel; Markovets, Aleksandra A; Al-Kadhimi, Katherine J; Lai, Zhongwu; Fisher, Paul R; Meador, Catherine B; Spitzler, Paula; Ichihara, Eiki; Ross, Sarah J; Ahdesmaki, Miika J; Ahmed, Ambar; Ratcliffe, Laura E; O'Brien, Elizabeth L Christey; Barnes, Claire H; Brown, Henry; Smith, Paul D; Dry, Jonathan R; Beran, Garry; Thress, Kenneth S; Dougherty, Brian; Pao, William; Cross, Darren A E

    2015-06-15

    Resistance to targeted EGFR inhibitors is likely to develop in EGFR-mutant lung cancers. Early identification of innate or acquired resistance mechanisms to these agents is essential to direct development of future therapies. We describe the detection of heterogeneous mechanisms of resistance within populations of EGFR-mutant cells (PC9 and/or NCI-H1975) with acquired resistance to current and newly developed EGFR tyrosine kinase inhibitors, including AZD9291. We report the detection of NRAS mutations, including a novel E63K mutation, and a gain of copy number of WT NRAS or WT KRAS in cell populations resistant to gefitinib, afatinib, WZ4002, or AZD9291. Compared with parental cells, a number of resistant cell populations were more sensitive to inhibition by the MEK inhibitor selumetinib (AZD6244; ARRY-142886) when treated in combination with the originating EGFR inhibitor. In vitro, a combination of AZD9291 with selumetinib prevented emergence of resistance in PC9 cells and delayed resistance in NCI-H1975 cells. In vivo, concomitant dosing of AZD9291 with selumetinib caused regression of AZD9291-resistant tumors in an EGFRm/T790M transgenic model. Our data support the use of a combination of AZD9291 with a MEK inhibitor to delay or prevent resistance to AZD9291 in EGFRm and/or EGFRm/T790M tumors. Furthermore, these findings suggest that NRAS modifications in tumor samples from patients who have progressed on current or EGFR inhibitors in development may support subsequent treatment with a combination of EGFR and MEK inhibition. PMID:25870145

  20. A Novel Plant Sesquiterpene Lactone Derivative, DETD-35, Suppresses BRAFV600E Mutant Melanoma Growth and Overcomes Acquired Vemurafenib Resistance in Mice.

    PubMed

    Feng, Jia-Hua; Nakagawa-Goto, Kyoko; Lee, Kuo-Hsiung; Shyur, Lie-Fen

    2016-06-01

    Acquired resistance to vemurafenib develops through reactivation of RAF/MEK/ERK signaling or bypass mechanisms. Recent combination therapies such as a MEK inhibitor combined with vemurafenib show improvement in major clinical end points, but the percentage of patients with adverse toxic events is higher than with vemurafenib monotherapy and most patients ultimately relapse. Therefore, there is an urgent need to develop new antimelanoma drugs and/or adjuvant agents for vemurafenib therapy. In this study, we created a novel semiorganically modified derivative, DETD-35, from deoxyelephantopin (DET), a plant sesquiterpene lactone demonstrated as an anti-inflammatory and anti-mammary tumor agent. Our results show that DETD-35 inhibited proliferation of a panel of melanoma cell lines, including acquired vemurafenib resistance A375 cells (A375-R) established in this study, with superior activities to DET and no cytotoxicity to normal melanocytes. DETD-35 suppressed tumor growth and reduced tumor mass as effectively as vemurafenib in A375 xenograft study. Furthermore, DETD-35 also reduced tumor growth in both acquired (A375-R) and intrinsic (A2058) vemurafenib resistance xenograft models, where vemurafenib showed no antitumor activity. Notably, the combination of DETD-35 and vemurafenib exhibited the most significant effects in both in vitro and in vivo xenograft studies due to synergism of the compound and the drug. Mechanistic studies suggested that DETD-35 overcame acquired vemurafenib resistance at least in part through deregulating MEK-ERK, Akt, and STAT3 signaling pathways and promoting apoptosis of cancer cells. Overall, our results suggest that DETD-35 may be useful as a therapeutic or adjuvant agent against BRAF(V600E) mutant and acquired vemurafenib resistance melanoma. Mol Cancer Ther; 15(6); 1163-76. ©2016 AACR. PMID:27048951

  1. Increased CD271 expression by the NF-kB pathway promotes melanoma cell survival and drives acquired resistance to BRAF inhibitor vemurafenib

    PubMed Central

    Lehraiki, Abdelali; Cerezo, Michael; Rouaud, Florian; Abbe, Patricia; Allegra, Marilyne; Kluza, Jerome; Marchetti, Philippe; Imbert, Veronique; Cheli, Yann; Bertolotto, Corine; Ballotti, Robert; Rocchi, Stéphane

    2015-01-01

    Specific BRAFV600E inhibitors (BRAFi) are highly effective in the treatment of melanoma. However, acquired drug resistances invariably develop after the initial response. Therefore, the identification of new mechanisms of acquired resistance gives important clues towards the development of therapies that could elicit long lasting responses. Here we report that CD271 confers resistance to BRAFi in melanoma cells. The expression of CD271 is increased by BRAFi through a stimulation of tumor necrosis factor-alpha (TNFα) secretion that leads to NF-κB signaling pathway activation. CD271 is upregulated in a subset of BRAFi-resistant melanoma cells. The inhibition of TNFα/NF-κB pathway and CD271 silencing restore the BRAFi sensitivity of resistant melanoma cells. Finally, increase of CD271 expression is validated in BRAFi-resistant xenografts tumors and also in tumors from the patients who relapsed under BRAFi. In summary, these results reveal a novel TNFα/NF-κB/CD271 axis whose activation contributes to the acquisition of resistance to BRAFi and therefore may represent a novel therapeutic target to improve the efficacy of therapy in melanoma.

  2. Overcoming acquired drug resistance in colorectal cancer cells by targeted delivery of 5-FU with EGF grafted hollow mesoporous silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Chen, Lijue; She, Xiaodong; Wang, Tao; He, Li; Shigdar, Sarah; Duan, Wei; Kong, Lingxue

    2015-08-01

    Acquired drug resistance (ADR) can be developed in colorectal cancer cells after 5-fluorouracil (5-FU) treatment and diminish the effectiveness of chemotherapy. In this work, acquired 5-FU resistance in the colorectal cancer cell line SW480 was obtained with the up-regulation of dihydropyrimidine dehydrogenase (DPYD) gene expression which can convert 5-FU to its inactive metabolite. To overcome ADR in colorectal cancer, hollow mesoporous silica nanoparticles (HMSNs) grafted with epidermal growth factor (EGF) were used as nanocarriers to deliver 5-FU to colorectal cancer cells with acquired drug resistance. The effect and mechanism of 5-FU loaded EGF grafted HMSNs (EGF-HMSNs-5-FU) in overcoming acquired drug resistance in SW480/ADR cells were studied. The EGF-HMSNs were demonstrated to be specifically internalized in EGFR overexpressed SW480/ADR cells via a receptor-mediated endocytosis and can escape from endo-lysosomes. The EGF-HMSNs-5-FU exhibited much higher cytotoxicity on SW480/ADR cells than HMSNs-5-FU and free 5-FU while the plain HMSNs did not show significant cytotoxicity. The mechanism of EGF-HMSNs-5-FU in overcoming drug resistance in SW480/ADR cells could be attributed to the specific internalization of EGF-HMSNs-5-FU in EGFR overexpressed cells which can lead to high intracellular drug accumulation and cause cell death through S phase arrest.Acquired drug resistance (ADR) can be developed in colorectal cancer cells after 5-fluorouracil (5-FU) treatment and diminish the effectiveness of chemotherapy. In this work, acquired 5-FU resistance in the colorectal cancer cell line SW480 was obtained with the up-regulation of dihydropyrimidine dehydrogenase (DPYD) gene expression which can convert 5-FU to its inactive metabolite. To overcome ADR in colorectal cancer, hollow mesoporous silica nanoparticles (HMSNs) grafted with epidermal growth factor (EGF) were used as nanocarriers to deliver 5-FU to colorectal cancer cells with acquired drug resistance. The

  3. Nasal colonization in children with community acquired methicillin-resistant Staphylococcus aureus

    PubMed Central

    Davoodabadi, Fazlollah; Mobasherizadeh, Sina; Mostafavizadeh, Kamyar; Shojaei, Hasan; Havaei, Seyed Asghar; Koushki, Ali Mehrabi; Moghadasizadeh, Zahra; Meidani, Mohsen; Shirani, Kiana

    2016-01-01

    Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a frequent cause of infections. The changing epidemiology of MRSA became evident in the 1990s when CA-MRSA cases were first reported. Nasal carriage of CA-MRSA is associated with an increased risk for development of infections in various populations. Materials and Methods: Anterior nares culture for the presence of methicillin-susceptible Staphylococcus aureus (MSSA) and MRSA was taken from 345 children attending kindergartens, who didn’t have any known risk factor for MRSA colonization. Also, children demographic variables were recorded. Identification of SA and community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) with standard microbiological test was performed. Finally, the susceptibility of isolated to various antibiotics determined. The data were analyzed with Whonet 5.6 software. Results: Of 345 children, 20 children (5.8%) were colonized with CA-MRSA, 86 children (24.9%) with MSSA and 239 cases (69.3%) didn’t have SA colonization. The highest rate of MSSA and MRSA colonization was obtained at the age of 6 years. The frequency distribution of SA (MSSA and MRSA) colonization prevalence didn’t have any significant differences based on age, gender and the admission time (P > 0.05); but it was significantly different in the urban areas (P < 0.001). The lowest resistance rate of CA-MRSA isolates, with a frequency of 10%, was detected with gentamicin, rifampin, and trimethoprim-sulfamethoxazole. Conclusions: In summary, CA-MRSA colonization was observed in child care centers remarkably. Therefore, by facing various infections due to SA especially in areas of low socio-economic status, it must be considered. Based on antibiogram test, empirical treatment with rifampin, gentamicin and ciprofloxacin is recommended during CA-MRSA infections. PMID:27274501

  4. Origin and Evolution of European Community-Acquired Methicillin-Resistant Staphylococcus aureus

    PubMed Central

    Wirth, Thierry; Andersen, Paal S.; Skov, Robert L.; De Grassi, Anna; Simões, Patricia Martins; Tristan, Anne; Petersen, Andreas; Aziz, Maliha; Kiil, Kristoffer; Cirković, Ivana; Udo, Edet E.; del Campo, Rosa; Vuopio-Varkila, Jaana; Ahmad, Norazah; Tokajian, Sima; Peters, Georg; Schaumburg, Frieder; Olsson-Liljequist, Barbro; Givskov, Michael; Driebe, Elizabeth E.; Vigh, Henrik E.; Shittu, Adebayo; Ramdani-Bougessa, Nadjia; Rasigade, Jean-Philippe; Price, Lance B.; Vandenesch, Francois; Larsen, Anders R.; Laurent, Frederic

    2014-01-01

    ABSTRACT Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) was recognized in Europe and worldwide in the late 1990s. Within a decade, several genetically and geographically distinct CA-MRSA lineages carrying the small SCCmec type IV and V genetic elements and the Panton-Valentine leukocidin (PVL) emerged around the world. In Europe, the predominant CA-MRSA strain belongs to clonal complex 80 (CC80) and is resistant to kanamycin/amikacin and fusidic acid. CC80 was first reported in 1993 but was relatively rare until the late 1990s. It has since been identified throughout North Africa, the Middle East, and Europe, with recent sporadic reports in sub-Saharan Africa. While strongly associated with skin and soft tissue infections, it is rarely found among asymptomatic carriers. Methicillin-sensitive S. aureus (MSSA) CC80 strains are extremely rare except in sub-Saharan Africa. In the current study, we applied whole-genome sequencing to a global collection of both MSSA and MRSA CC80 isolates. Phylogenetic analyses strongly suggest that the European epidemic CA-MRSA lineage is derived from a PVL-positive MSSA ancestor from sub-Saharan Africa. Moreover, the tree topology suggests a single acquisition of both the SCCmec element and a plasmid encoding the fusidic acid resistance determinant. Four canonical SNPs distinguish the derived CA-MRSA lineage and include a nonsynonymous mutation in accessory gene regulator C (agrC). These changes were associated with a star-like expansion into Europe, the Middle East, and North Africa in the early 1990s, including multiple cases of cross-continent imports likely driven by human migrations. PMID:25161186

  5. Comparative Proteomics Analysis of Phloem Exudates Collected during the Induction of Systemic Acquired Resistance1[OPEN

    PubMed Central

    Wilson, Daniel C.; Dey, Sanjukta; Hauck, Stefanie M.; Vlot, A. Corina; Cameron, Robin K.

    2016-01-01

    Systemic acquired resistance (SAR) is a plant defense response that provides long-lasting, broad-spectrum pathogen resistance to uninfected systemic leaves following an initial localized infection. In Arabidopsis (Arabidopsis thaliana), local infection with virulent or avirulent strains of Pseudomonas syringae pv tomato generates long-distance SAR signals that travel from locally infected to distant leaves through the phloem to establish SAR. In this study, a proteomics approach was used to identify proteins that accumulate in phloem exudates in response to the induction of SAR. To accomplish this, phloem exudates collected from mock-inoculated or SAR-induced leaves of wild-type Columbia-0 plants were subjected to label-free quantitative liquid chromatography-tandem mass spectrometry proteomics. Comparing mock- and SAR-induced phloem exudate proteomes, 16 proteins were enriched in phloem exudates collected from SAR-induced plants, while 46 proteins were suppressed. SAR-related proteins THIOREDOXIN h3, ACYL-COENZYME A-BINDING PROTEIN6, and PATHOGENESIS-RELATED1 were enriched in phloem exudates of SAR-induced plants, demonstrating the strength of this approach and suggesting a role for these proteins in the phloem during SAR. To identify novel components of SAR, transfer DNA mutants of differentially abundant phloem proteins were assayed for SAR competence. This analysis identified a number of new proteins (m-type thioredoxins, major latex protein-like protein, ULTRAVIOLET-B RESISTANCE8 photoreceptor) that contribute to the SAR response. The Arabidopsis SAR phloem proteome is a valuable resource for understanding SAR long-distance signaling and the dynamic nature of the phloem during plant-pathogen interactions. PMID:27208255

  6. Comparative Proteomics Analysis of Phloem Exudates Collected during the Induction of Systemic Acquired Resistance.

    PubMed

    Carella, Philip; Merl-Pham, Juliane; Wilson, Daniel C; Dey, Sanjukta; Hauck, Stefanie M; Vlot, A Corina; Cameron, Robin K

    2016-06-01

    Systemic acquired resistance (SAR) is a plant defense response that provides long-lasting, broad-spectrum pathogen resistance to uninfected systemic leaves following an initial localized infection. In Arabidopsis (Arabidopsis thaliana), local infection with virulent or avirulent strains of Pseudomonas syringae pv tomato generates long-distance SAR signals that travel from locally infected to distant leaves through the phloem to establish SAR In this study, a proteomics approach was used to identify proteins that accumulate in phloem exudates in response to the induction of SAR To accomplish this, phloem exudates collected from mock-inoculated or SAR-induced leaves of wild-type Columbia-0 plants were subjected to label-free quantitative liquid chromatography-tandem mass spectrometry proteomics. Comparing mock- and SAR-induced phloem exudate proteomes, 16 proteins were enriched in phloem exudates collected from SAR-induced plants, while 46 proteins were suppressed. SAR-related proteins THIOREDOXIN h3, ACYL-COENZYME A-BINDING PROTEIN6, and PATHOGENESIS-RELATED1 were enriched in phloem exudates of SAR-induced plants, demonstrating the strength of this approach and suggesting a role for these proteins in the phloem during SAR To identify novel components of SAR, transfer DNA mutants of differentially abundant phloem proteins were assayed for SAR competence. This analysis identified a number of new proteins (m-type thioredoxins, major latex protein-like protein, ULTRAVIOLET-B RESISTANCE8 photoreceptor) that contribute to the SAR response. The Arabidopsis SAR phloem proteome is a valuable resource for understanding SAR long-distance signaling and the dynamic nature of the phloem during plant-pathogen interactions. PMID:27208255

  7. JAK2-related pathway induces acquired erlotinib resistance in lung cancer cells harboring an epidermal growth factor receptor-activating mutation.

    PubMed

    Harada, Daijiro; Takigawa, Nagio; Ochi, Nobuaki; Ninomiya, Takashi; Yasugi, Masayuki; Kubo, Toshio; Takeda, Hiromasa; Ichihara, Eiki; Ohashi, Kadoaki; Takata, Saburo; Tanimoto, Mitsune; Kiura, Katsuyuki

    2012-10-01

    Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors, such as gefitinib and erlotinib, are effective for non-small cell lung cancer with activating EGFR mutations. However, even in patients with an initial dramatic response to such a drug, acquired resistance develops after 6-12 months. A secondary mutation of T790M in EGFR and amplification of the MET gene account for this resistance; however, the mechanism(s) of approximately 30% of acquired resistance cases remain unknown. We established an erlotinib-resistant lung cancer cell line named PC-9/ER3 that harbors an EGFR mutation after continuously exposing PC-9 cells to erlotinib. PC-9/ER3 cells were 136-fold more resistant to erlotinib than the parental cells. Although the PC-9/ER3 cells did not carry the T790M mutation or MET amplification and had similar levels of phosphorylated (p) STAT3, pJAK2 increased in the resistant cells. It was found in the present study that 3-12 h of exposure to erlotinib in both cell lines did not affect pJAK2 expression, but did result in increased pSTAT3 expression. pAkt in PC-9/ER3 cells was less suppressed than in PC-9 cells, although pEGFR and pMAPK were markedly suppressed in both cell lines. The combined treatment of erlotinib plus a JAK2 inhibitor (JSI-124) suppressed pAkt in PC-9/ER3 cells. Similarly, the combination of erlotinib plus JSI-124 or siRNA against JAK2 restored sensitivity to erlotinib in PC-9/ER3 cells. The combination of erlotinib plus JSI-124 was also effective for reducing PC-9/ER3 tumors in a murine xenograft model. Our results suggest that the activation of JAK2 partially accounts for acquired erlotinib resistance. PMID:22712764

  8. Mechanisms of antibiotic resistance in enterococci

    PubMed Central

    Miller, William R; Munita, Jose M; Arias, Cesar A

    2015-01-01

    Multidrug-resistant (MDR) enterococci are important nosocomial pathogens and a growing clinical challenge. These organisms have developed resistance to virtually all antimicrobials currently used in clinical practice using a diverse number of genetic strategies. Due to this ability to recruit antibiotic resistance determinants, MDR enterococci display a wide repertoire of antibiotic resistance mechanisms including modification of drug targets, inactivation of therapeutic agents, overexpression of efflux pumps and a sophisticated cell envelope adaptive response that promotes survival in the human host and the nosocomial environment. MDR enterococci are well adapted to survive in the gastrointestinal tract and can become the dominant flora under antibiotic pressure, predisposing the severely ill and immunocompromised patient to invasive infections. A thorough understanding of the mechanisms underlying antibiotic resistance in enterococci is the first step for devising strategies to control the spread of these organisms and potentially establish novel therapeutic approaches. PMID:25199988

  9. Antibiotic resistance mechanisms of Myroides sp.*

    PubMed Central

    Hu, Shao-hua; Yuan, Shu-xing; Qu, Hai; Jiang, Tao; Zhou, Ya-jun; Wang, Ming-xi; Ming, De-song

    2016-01-01

    Bacteria of the genus Myroides (Myroides spp.) are rare opportunistic pathogens. Myroides sp. infections have been reported mainly in China. Myroides sp. is highly resistant to most available antibiotics, but the resistance mechanisms are not fully elucidated. Current strain identification methods based on biochemical traits are unable to identify strains accurately at the species level. While 16S ribosomal RNA (rRNA) gene sequencing can accurately achieve this, it fails to give information on the status and mechanisms of antibiotic resistance, because the 16S rRNA sequence contains no information on resistance genes, resistance islands or enzymes. We hypothesized that obtaining the whole genome sequence of Myroides sp., using next generation sequencing methods, would help to clarify the mechanisms of pathogenesis and antibiotic resistance, and guide antibiotic selection to treat Myroides sp. infections. As Myroides sp. can survive in hospitals and the environment, there is a risk of nosocomial infections and pandemics. For better management of Myroides sp. infections, it is imperative to apply next generation sequencing technologies to clarify the antibiotic resistance mechanisms in these bacteria. PMID:26984839

  10. Mechanisms of Resistance to Photodynamic Therapy

    PubMed Central

    Casas, Adriana; Di Venosa, Gabriela; Hasan, Tayyaba; Batlle, Alcira

    2013-01-01

    Photodynamic therapy (PDT) involves the administration of a photosensitizer (PS) followed by illumination with visible light, leading to generation of reactive oxygen species. The mechanisms of resistance to PDT ascribed to the PS may be shared with the general mechanisms of drug resistance, and are related to altered drug uptake and efflux rates or altered intracellular trafficking. As a second step, an increased inactivation of oxygen reactive species is also associated to PDT resistance via antioxidant detoxifying enzymes and activation of heat shock proteins. Induction of stress response genes also occurs after PDT, resulting in modulation of proliferation, cell detachment and inducing survival pathways among other multiple extracellular signalling events. In addition, an increased repair of induced damage to proteins, membranes and occasionally to DNA may happen. PDT-induced tissue hypoxia as a result of vascular damage and photochemical oxygen consumption may also contribute to the appearance of resistant cells. The structure of the PS is believed to be a key point in the development of resistance, being probably related to its particular subcellular localization. Although most of the features have already been described for chemoresistance, in many cases, no cross-resistance between PDT and chemotherapy has been reported. These findings are in line with the enhancement of PDT efficacy by combination with chemotherapy. The study of cross resistance in cells with developed resistance against a particular PS challenged against other PS is also highly complex and comprises different mechanisms. In this review we will classify the different features observed in PDT resistance, leading to a comparison with the mechanisms most commonly found in chemo resistant cells. PMID:21568910

  11. Mechanisms of biofilm resistance to antimicrobial agents.

    PubMed

    Mah, T F; O'Toole, G A

    2001-01-01

    Biofilms are communities of microorganisms attached to a surface. It has become clear that biofilm-grown cells express properties distinct from planktonic cells, one of which is an increased resistance to antimicrobial agents. Recent work has indicated that slow growth and/or induction of an rpoS-mediated stress response could contribute to biocide resistance. The physical and/or chemical structure of exopolysaccharides or other aspects of biofilm architecture could also confer resistance by exclusion of biocides from the bacterial community. Finally, biofilm-grown bacteria might develop a biofilm-specific biocide-resistant phenotype. Owing to the heterogeneous nature of the biofilm, it is likely that there are multiple resistance mechanisms at work within a single community. Recent research has begun to shed light on how and why surface-attached microbial communities develop resistance to antimicrobial agents. PMID:11166241

  12. Nitroheterocyclic drug resistance mechanisms in Trypanosoma brucei

    PubMed Central

    Wyllie, Susan; Foth, Bernardo J.; Kelner, Anna; Sokolova, Antoaneta Y.; Berriman, Matthew; Fairlamb, Alan H.

    2016-01-01

    Objectives The objective of this study was to identify the mechanisms of resistance to nifurtimox and fexinidazole in African trypanosomes. Methods Bloodstream-form Trypanosoma brucei were selected for resistance to nifurtimox and fexinidazole by stepwise exposure to increasing drug concentrations. Clones were subjected to WGS to identify putative resistance genes. Transgenic parasites modulating expression of genes of interest were generated and drug susceptibility phenotypes determined. Results Nifurtimox-resistant (NfxR) and fexinidazole-resistant (FxR) parasites shared reciprocal cross-resistance suggestive of a common mechanism of action. Previously, a type I nitroreductase (NTR) has been implicated in nitro drug activation. WGS of resistant clones revealed that NfxR parasites had lost >100 kb from one copy of chromosome 7, rendering them hemizygous for NTR as well as over 30 other genes. FxR parasites retained both copies of NTR, but lost >70 kb downstream of one NTR allele, decreasing NTR transcription by half. A single knockout line of NTR displayed 1.6- and 1.9-fold resistance to nifurtimox and fexinidazole, respectively. Since NfxR and FxR parasites are ∼6- and 20-fold resistant to nifurtimox and fexinidazole, respectively, additional factors must be involved. Overexpression and knockout studies ruled out a role for a putative oxidoreductase (Tb927.7.7410) and a hypothetical gene (Tb927.1.1050), previously identified in a genome-scale RNAi screen. Conclusions NTR was confirmed as a key resistance determinant, either by loss of one gene copy or loss of gene expression. Further work is required to identify which of the many dozens of SNPs identified in the drug-resistant cell lines contribute to the overall resistance phenotype. PMID:26581221

  13. Evidence for the role of microRNA 374b in acquired cisplatin resistance in pancreatic cancer cells

    PubMed Central

    Schreiber, R; Mezencev, R; Matyunina, L V; McDonald, J F

    2016-01-01

    Recent evidence has implicated microRNAs (miRNAs) as potentially significant players in the acquisition of cancer-drug resistance in pancreatic and other cancers. To evaluate the potential contribution of miRNAs in acquired resistance to cisplatin in pancreatic cancer, we compared levels of more than 2000 human miRNAs in a cisplatin-resistant cell line (BxPC3-R) derived from parental (BxPC3) cells by step-wise exposure to increasing concentrations of the drug over more than 20 passages. The acquired drug resistance was accompanied by significant changes in the expression of 57 miRNAs, of which 23 were downregulated and 34 were upregulated. Employing a hidden Markov model (HMM) algorithm, we identified downregulation of miR-374b as likely being directly involved in acquisition of the drug-resistant phenotype. Consistent with this prediction, ectopic overexpression of miR-374b in the resistant BxPC3-R cells restored cisplatin sensitivity to levels approaching those displayed by the BxPC3 parental cells. The results are consistent with a growing body of evidence implicating miRNAs in acquired cancer-drug resistance and with the potential therapeutic value of these small regulatory RNAs in blocking and/or reversing the process. PMID:27229158

  14. Increased interleukin-6 expression is associated with poor prognosis and acquired cisplatin resistance in head and neck squamous cell carcinoma.

    PubMed

    Gao, Jian; Zhao, Sen; Halstensen, Trond S

    2016-06-01

    Increased expression of interleukin 6 (IL-6) is associated with poor prognosis and chemoresistance in many different carcinomas, but its role in head and neck squamous cell carcinoma (HNSCC) is still unsettled. Analyzing tumorous mRNA expression data from 399 HNSCC patients revealed that high IL-6 expression predicted poor prognosis. Similar tendency was observed in platinum treated patients, suggesting an IL-6 associated cisplatin resistance. IL-6 increase was also found in two in-house acquired cisplatin‑resistant HNSCC cell lines (both basaloid and conventional squamous cell carcinoma) by using microarray analysis. However, although the in-house acquired cisplatin-resistant cell lines had higher basal and markedly increased cisplatin-induced IL-6 expression, IL-6 did not mediate the cisplatin resistance as neither exogenous IL-6 nor IL-6R/gp130 inhibitors affected cisplatin sensitivity. Moreover, the IL-6/STAT3 pathway was impaired in the resistant cell lines, partly due to decreased IL-6R expression. Thus, high IL-6 expression correlated to poor prognosis and acquired cisplatin resistance, but it did not mediate cisplatin resistance in the HNSCC cell lines. PMID:27108527

  15. Evidence for the role of microRNA 374b in acquired cisplatin resistance in pancreatic cancer cells.

    PubMed

    Schreiber, R; Mezencev, R; Matyunina, L V; McDonald, J F

    2016-08-01

    Recent evidence has implicated microRNAs (miRNAs) as potentially significant players in the acquisition of cancer-drug resistance in pancreatic and other cancers. To evaluate the potential contribution of miRNAs in acquired resistance to cisplatin in pancreatic cancer, we compared levels of more than 2000 human miRNAs in a cisplatin-resistant cell line (BxPC3-R) derived from parental (BxPC3) cells by step-wise exposure to increasing concentrations of the drug over more than 20 passages. The acquired drug resistance was accompanied by significant changes in the expression of 57 miRNAs, of which 23 were downregulated and 34 were upregulated. Employing a hidden Markov model (HMM) algorithm, we identified downregulation of miR-374b as likely being directly involved in acquisition of the drug-resistant phenotype. Consistent with this prediction, ectopic overexpression of miR-374b in the resistant BxPC3-R cells restored cisplatin sensitivity to levels approaching those displayed by the BxPC3 parental cells. The results are consistent with a growing body of evidence implicating miRNAs in acquired cancer-drug resistance and with the potential therapeutic value of these small regulatory RNAs in blocking and/or reversing the process. PMID:27229158

  16. Increased interleukin-6 expression is associated with poor prognosis and acquired cisplatin resistance in head and neck squamous cell carcinoma

    PubMed Central

    GAO, JIAN; ZHAO, SEN; HALSTENSEN, TROND S.

    2016-01-01

    Increased expression of interleukin 6 (IL-6) is associated with poor prognosis and chemoresistance in many different carcinomas, but its role in head and neck squamous cell carcinoma (HNSCC) is still unsettled. Analyzing tumorous mRNA expression data from 399 HNSCC patients revealed that high IL-6 expression predicted poor prognosis. Similar tendency was observed in platinum treated patients, suggesting an IL-6 associated cisplatin resistance. IL-6 increase was also found in two in-house acquired cisplatin-resistant HNSCC cell lines (both basaloid and conventional squamous cell carcinoma) by using microarray analysis. However, although the in-house acquired cisplatin-resistant cell lines had higher basal and markedly increased cisplatin-induced IL-6 expression, IL-6 did not mediate the cisplatin resistance as neither exogenous IL-6 nor IL-6R/gp130 inhibitors affected cisplatin sensitivity. Moreover, the IL-6/STAT3 pathway was impaired in the resistant cell lines, partly due to decreased IL-6R expression. Thus, high IL-6 expression correlated to poor prognosis and acquired cisplatin resistance, but it did not mediate cisplatin resistance in the HNSCC cell lines. PMID:27108527

  17. Mechanisms of resistance in castration-resistant prostate cancer (CRPC).

    PubMed

    Chandrasekar, Thenappan; Yang, Joy C; Gao, Allen C; Evans, Christopher P

    2015-06-01

    Despite advances in prostate cancer diagnosis and management, morbidity from prostate cancer remains high. Approximately 20% of men present with advanced or metastatic disease, while 29,000 men continue to die of prostate cancer each year. Androgen deprivation therapy (ADT) has been the standard of care for initial management of advanced or metastatic prostate cancer since Huggins and Hodges first introduced the concept of androgen-dependence in 1972, but progression to castration-resistant prostate cancer (CRPC) occurs within 2-3 years of initiation of ADT. CRPC, previously defined as hormone-refractory prostate cancer, is now understood to still be androgen dependent. Multiple mechanisms of resistance help contribute to the progression to castration resistant disease, and the androgen receptor (AR) remains an important driver in this progression. These mechanisms include AR amplification and hypersensitivity, AR mutations leading to promiscuity, mutations in coactivators/corepressors, androgen-independent AR activation, and intratumoral and alternative androgen production. More recently, identification of AR variants (ARVs) has been established as another mechanism of progression to CRPC. Docetaxel chemotherapy has historically been the first-line treatment for CRPC, but in recent years, newer agents have been introduced that target some of these mechanisms of resistance, thereby providing additional survival benefit. These include AR signaling inhibitors such as enzalutamide (Xtandi, ENZA, MDV-3100) and CYP17A1 inhibitors such as abiraterone acetate (Zytiga). Ultimately, these agents will also fail to suppress CRPC. While some of the mechanisms by which these agents fail are unique, many share similarities to the mechanisms contributing to CRPC progression. Understanding these mechanisms of resistance to ADT and currently approved CRPC treatments will help guide future research into targeted therapies. PMID:26814148

  18. Mechanisms of resistance in castration-resistant prostate cancer (CRPC)

    PubMed Central

    Chandrasekar, Thenappan; Yang, Joy C.; Gao, Allen C.

    2015-01-01

    Despite advances in prostate cancer diagnosis and management, morbidity from prostate cancer remains high. Approximately 20% of men present with advanced or metastatic disease, while 29,000 men continue to die of prostate cancer each year. Androgen deprivation therapy (ADT) has been the standard of care for initial management of advanced or metastatic prostate cancer since Huggins and Hodges first introduced the concept of androgen-dependence in 1972, but progression to castration-resistant prostate cancer (CRPC) occurs within 2-3 years of initiation of ADT. CRPC, previously defined as hormone-refractory prostate cancer, is now understood to still be androgen dependent. Multiple mechanisms of resistance help contribute to the progression to castration resistant disease, and the androgen receptor (AR) remains an important driver in this progression. These mechanisms include AR amplification and hypersensitivity, AR mutations leading to promiscuity, mutations in coactivators/corepressors, androgen-independent AR activation, and intratumoral and alternative androgen production. More recently, identification of AR variants (ARVs) has been established as another mechanism of progression to CRPC. Docetaxel chemotherapy has historically been the first-line treatment for CRPC, but in recent years, newer agents have been introduced that target some of these mechanisms of resistance, thereby providing additional survival benefit. These include AR signaling inhibitors such as enzalutamide (Xtandi, ENZA, MDV-3100) and CYP17A1 inhibitors such as abiraterone acetate (Zytiga). Ultimately, these agents will also fail to suppress CRPC. While some of the mechanisms by which these agents fail are unique, many share similarities to the mechanisms contributing to CRPC progression. Understanding these mechanisms of resistance to ADT and currently approved CRPC treatments will help guide future research into targeted therapies. PMID:26814148

  19. Curcumin mediates oxaliplatin-acquired resistance reversion in colorectal cancer cell lines through modulation of CXC-Chemokine/NF-κB signalling pathway

    PubMed Central

    Ruiz de Porras, Vicenç; Bystrup, Sara; Martínez-Cardús, Anna; Pluvinet, Raquel; Sumoy, Lauro; Howells, Lynne; James, Mark I.; Iwuji, Chinenye; Manzano, José Luis; Layos, Laura; Bugés, Cristina; Abad, Albert; Martínez-Balibrea, Eva

    2016-01-01

    Resistance to oxaliplatin (OXA) is a complex process affecting the outcomes of metastatic colorectal cancer (CRC) patients treated with this drug. De-regulation of the NF-κB signalling pathway has been proposed as an important mechanism involved in this phenomenon. Here, we show that NF-κB was hyperactivated in in vitro models of OXA-acquired resistance but was attenuated by the addition of Curcumin, a non-toxic NF-κB inhibitor. The concomitant combination of Curcumin + OXA was more effective and synergistic in cell lines with acquired resistance to OXA, leading to the reversion of their resistant phenotype, through the inhibition of the NF-κB signalling cascade. Transcriptomic profiling revealed the up-regulation of three NF-κB-regulated CXC-chemokines, CXCL8, CXCL1 and CXCL2, in the resistant cells that were more efficiently down-regulated after OXA + Curcumin treatment as compared to the sensitive cells. Moreover, CXCL8 and CXCL1 gene silencing made resistant cells more sensitive to OXA through the inhibition of the Akt/NF-κB pathway. High expression of CXCL1 in FFPE samples from explant cultures of CRC patients-derived liver metastases was associated with response to OXA + Curcumin. In conclusion, we suggest that combination of OXA + Curcumin could be an effective treatment, for which CXCL1 could be used as a predictive marker, in CRC patients. PMID:27091625

  20. EGFR-TKI resistance in NSCLC patients: mechanisms and strategies

    PubMed Central

    Lin, Yuxin; Wang, Xian; Jin, Hongchuan

    2014-01-01

    The epidermal growth factor receptor (EGFR) is a kind of receptor tyrosine kinase (RTK) that plays a critical role in the initiation and development of malignant tumors via modulating downstream signaling pathways. In non-small cell lung cancer (NSCLC), the activating mutations located in the tyrosine kinase domains of EGFR have been demonstrated in multiple researches as the “Achilles’ heel” of this deadly disease since they could be well-targeted by epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs). However, it’s still too early to celebrate since the first-generation EGFR-TKIs such as gefitinib and erlotinib have only achieved limited clinical benefits and acquired resistance to this kind of drugs occurred inevitably in almost all the NSCLC patients. In order to make the most of EGFR-TKIs and develop more effective regimens for the NSCLC patients, researchers majoring in different aspects start a battle against EGFR-TKI resistance. Challenging as it is, we still progress stably and step firmly toward the final victory. This review will summarize the major mechanisms of acquired resistance to EGFR-TKIs, and then discuss the development of rationally designed molecular target drugs in accordance with each mechanism, in the hope of shedding light on the great achievements we have obtained and tough obstacles we have to overcome in the battle against this deadly disease. PMID:25232485

  1. BIIB021, a synthetic Hsp90 inhibitor, has broad application against tumors with acquired multidrug resistance.

    PubMed

    Zhang, Hong; Neely, Laura; Lundgren, Karen; Yang, Yong-Ching; Lough, Rachel; Timple, Noel; Burrows, Francis

    2010-03-01

    17-AAG, the first-generation clinical Hsp90 inhibitor, exhibits promising antitumor activity in clinical studies, but is limited by poor solubility and hepatotoxicity. To pursue compounds with better biopharmaceutical properties, we have developed a series of fully synthetic orally bioavailable inhibitors of Hsp90. Here, we report that 17-AAG and other ansamycin derivatives are inactive in P-gp and/or MRP-1 expressing cell lines and sensitivity could be restored by coadministration of P-gp or MRP inhibitors. In contrast, the synthetic Hsp90 inhibitor, BIIB021 was active in these models. Accordingly, BIIB021 was considerably more active than 17-AAG against adrenocortical carcinoma, a tumor that naturally expresses P-gp, both in vitro and in vivo. This efflux pump-mediated resistance is manifested in both cytotoxicity assays and measurements of target inhibition, such as client protein degradation. Other than this, the cytotoxic activity of BIIB021 was also not influenced by loss of NQO1 or Bcl-2 overexpression, molecular lesions that do not prevent client loss but are nonetheless associated with reduced cell killing by 17-AAG. Our results indicate that the activity of 17-AAG and other ansamycins may be curtailed in tumors that have upregulated efflux pumps or antiapoptotic proteins or other genetic alterations. These data indicate that the new generation of synthetic anti-Hsp90 drugs, exemplified by BIIB021 that is currently undergoing Phase II testing, may have broader application against tumors with acquired multidrug resistance or tumors located in organs protected by MDR proteins, such as the adrenal glands, brain and testis. PMID:19676042

  2. Carbapenem-resistant Acinetobacter baumannii acquired before liver transplantation: Impact on recipient outcomes.

    PubMed

    Freire, Maristela Pinheiro; Pierrotti, Ligia Câmera; Oshiro, Isabel Cristina Villela Soares; Bonazzi, Patrícia Rodrigues; Oliveira, Larissa Marques de; Machado, Anna Silva; Van Der Heijden, Inneke Marie; Rossi, Flavia; Costa, Silvia Figueiredo; D'Albuquerque, Luiz Augusto Carneiro; Abdala, Edson

    2016-05-01

    Infection with carbapenem-resistant Acinetobacter baumannii (CRAB) after liver transplantation (LT) is associated with high mortality. This study aimed to identify risk factors for post-LT CRAB infection, as well as to evaluate the impact of pre-LT CRAB acquisition on the incidence of post-LT CRAB infection. This was a prospective cohort study of all patients undergoing LT at our facility between October 2009 and October 2011. Surveillance cultures (SCs) were collected immediately before LT and weekly thereafter, until discharge. We analyzed 196 patients who were submitted to 222 LTs. CRAB was identified in 105 (53.6%); 24 (22.9%) of these patients were found to have acquired CRAB before LT, and 85 (81.0%) tested positive on SCs. Post-LT CRAB infection occurred in 56 (28.6%), the most common site being the surgical wound. Multivariate analysis showed that the risk factors for developing CRAB infection were prolonged cold ischemia, post-LT dialysis, LT due to fulminant hepatitis, and pre-LT CRAB acquisition with pre-LT CRAB acquisition showing a considerable trend toward significance (P = 0.06). Among the recipients with CRAB infection, 60-day mortality was 46.4%, significantly higher than among those without (P < 0.001). Mortality risk factors were post-LT infection with multidrug-resistant bacteria, LT performed because of fulminant hepatitis, retransplantation, prolonged cold ischemia, longer LT surgical time, and pre-LT CRAB acquisition, the last showing a trend toward significance (P = 0.08). In conclusion, pre-LT CRAB acquisition appears to increase the risk of post-LT CRAB infection, which has a negative impact on recipient survival. Liver Transplantation 22 615-626 2016 AASLD. PMID:26684547

  3. Drug Targets and Mechanisms of Resistance in the Anaerobic Protozoa

    PubMed Central

    Upcroft, Peter; Upcroft, Jacqueline A.

    2001-01-01

    The anaerobic protozoa Giardia duodenalis, Trichomonas vaginalis, and Entamoeba histolytica infect up to a billion people each year. G. duodenalis and E. histolytica are primarily pathogens of the intestinal tract, although E. histolytica can form abscesses and invade other organs, where it can be fatal if left untreated. T. vaginalis infection is a sexually transmitted infection causing vaginitis and acute inflammatory disease of the genital mucosa. T. vaginalis has also been reported in the urinary tract, fallopian tubes, and pelvis and can cause pneumonia, bronchitis, and oral lesions. Respiratory infections can be acquired perinatally. T. vaginalis infections have been associated with preterm delivery, low birth weight, and increased mortality as well as predisposing to human immunodeficiency virus infection, AIDS, and cervical cancer. All three organisms lack mitochondria and are susceptible to the nitroimidazole metronidazole because of similar low-redox-potential anaerobic metabolic pathways. Resistance to metronidazole and other drugs has been observed clinically and in the laboratory. Laboratory studies have identified the enzyme that activates metronidazole, pyruvate:ferredoxin oxidoreductase, to its nitroso form and distinct mechanisms of decreasing drug susceptibility that are induced in each organism. Although the nitroimidazoles have been the drug family of choice for treating the anaerobic protozoa, G. duodenalis is less susceptible to other antiparasitic drugs, such as furazolidone, albendazole, and quinacrine. Resistance has been demonstrated for each agent, and the mechanism of resistance has been investigated. Metronidazole resistance in T. vaginalis is well documented, and the principal mechanisms have been defined. Bypass metabolism, such as alternative oxidoreductases, have been discovered in both organisms. Aerobic versus anaerobic resistance in T. vaginalis is discussed. Mechanisms of metronidazole resistance in E. histolytica have recently

  4. Length of stay an important mediator of hospital-acquired methicillin-resistant Staphylococcus aureus.

    PubMed

    Wong, J G; Chen, M I; Win, M K; Ng, P Y; Chow, A

    2016-04-01

    Hospital-acquired methicillin-resistant Staphylococcus aureus (HA-MRSA) is becoming increasingly established in Asian hospitals. The primary aim of this study was to decompose the risk factors for HA-MRSA based on conceptual clinical pathways. The secondary aim was to show the amount of effect attributable to antibiotic exposure and total length of stay before outcome (LBO) so that institutions can manage at-risk patients accordingly. A case-control study consisting of 1200 inpatients was conducted in a large tertiary hospital in Singapore between January and December 2006. Results from the generalized structural equation model (GSEM) show that LBO [adjusted odds ratio (aOR) 14·9, 95% confidence interval (CI) 8·7-25·5], prior hospitalization (aOR 6·2, 95% CI 3·3-11·5), and cumulative antibiotic exposure (aOR 3·5, 95% CI 2·3-5·3), directly affected HA-MRSA acquisition. LBO accounted for the majority of the effects due to age (100%), immunosuppression (67%), and surgery (96%), and to a lesser extent for male gender (22%). Our model enabled us to account and quantify effects of intermediaries. LBO was found to be an important mediator of age, immunosuppression and surgery on MRSA infection. Traditional regression approaches will not only give different conclusions but also underestimate the effects. Hospitals should minimize the hospital stay when possible to reduce the risk of MRSA. PMID:26538070

  5. Surveillance of Antibiotic Resistance among Hospital- and Community-Acquired Toxigenic Clostridium difficile Isolates over 5-Year Period in Kuwait

    PubMed Central

    Jamal, Wafaa Y.; Rotimi, Vincent O.

    2016-01-01

    Clostridium difficile infection (CDI) is a leading and an important cause of diarrhea in a healthcare setting especially in industrialized countries. Community-associated CDI appears to add to the burden on healthcare setting problems. The aim of the study was to investigate the antimicrobial resistance of healthcare-associated and community-acquired C. difficile infection over 5 years (2008–2012) in Kuwait. A total of 111 hospital-acquired (HA-CD) and 35 community-acquired Clostridium difficile (CA-CD) clinical isolates from stool of patients with diarrhoea were studied. Antimicrobial susceptibility testing of 15 antimicrobial agents against these pathogens was performed using E test method. There was no evidence of resistance to amoxicillin-clavulanic acid, daptomycin, linezolid, piperacillin-tazobactam, teicoplanin and vancomycin by both HA-CD and CA-CD isolates. Metronidazole had excellent activity against CA-CD but there was a 2.9% resistance rate against HA-CD isolates. Ampicillin, clindamycin, levofloxacin and imipenem resistance rates among the HC-CD vs. CA-CD isolates were 100 vs. 47.4%; 43 vs. 47.4%; 100 vs. 100% and 100 vs. 89%, respectively. An unexpected high rifampicin resistance rate of 15.7% emerged amongst the HA-CD isolates. In conclusion, vancomycin resistance amongst the HA-CD and CA-CD isolates was not encountered in this series but few metronidazole resistant hospital isolates were isolated. High resistance rates of ampicillin, clindamycin, levofloxacin, and imipenem resistance were evident among both CA-CD and HA-CD isolates. Rifampicin resistance is emerging among the HA-CD isolates. PMID:27536994

  6. The Landscape of Pancreatic Cancer Therapeutic Resistance Mechanisms.

    PubMed

    Chand, Saswati; O'Hayer, Kevin; Blanco, Fernando F; Winter, Jordan M; Brody, Jonathan R

    2016-01-01

    Pancreatic cancer (pancreatic ductal adenocarcinoma, PDA) is infamously moving to the top of the list as one of the most lethal cancers with an overall 5 year survival rate of 7%. Multiple genomic-based and molecular characterization studies of PDA specimens and established animal models have provided the field with multiple targets and a progression model of this disease. Still, to date, the best therapeutic options are surgery and combination cytotoxic therapies. In general, even in the best case scenario (i.e., an early stage diagnosis and a response to a specific therapy), most of these fortunate patients' PDA cells acquire or exert resistance mechanisms and eventually kill the patient. Herein, we touch on a growing field of investigation that focuses on PDA cell therapeutic resistance mechanisms. We examine extrinsic elements (i.e., the tumor microenvironment, hypoxia) to the intrinsic processes within the cell (i.e., post-transcriptional gene regulation and somatic mutations) that are important for therapeutic efficacy and resistance. Even as better targeted and personalized approaches move through the clinical trial pipeline the discussed resistance mechanisms will most likely play a role in the management of this deadly disease. PMID:26929734

  7. The Landscape of Pancreatic Cancer Therapeutic Resistance Mechanisms

    PubMed Central

    Chand, Saswati; O'Hayer, Kevin; Blanco, Fernando F.; Winter, Jordan M.; Brody, Jonathan R.

    2016-01-01

    Pancreatic cancer (pancreatic ductal adenocarcinoma, PDA) is infamously moving to the top of the list as one of the most lethal cancers with an overall 5 year survival rate of 7%. Multiple genomic-based and molecular characterization studies of PDA specimens and established animal models have provided the field with multiple targets and a progression model of this disease. Still, to date, the best therapeutic options are surgery and combination cytotoxic therapies. In general, even in the best case scenario (i.e., an early stage diagnosis and a response to a specific therapy), most of these fortunate patients' PDA cells acquire or exert resistance mechanisms and eventually kill the patient. Herein, we touch on a growing field of investigation that focuses on PDA cell therapeutic resistance mechanisms. We examine extrinsic elements (i.e., the tumor microenvironment, hypoxia) to the intrinsic processes within the cell (i.e., post-transcriptional gene regulation and somatic mutations) that are important for therapeutic efficacy and resistance. Even as better targeted and personalized approaches move through the clinical trial pipeline the discussed resistance mechanisms will most likely play a role in the management of this deadly disease. PMID:26929734

  8. Insulin Resistance and Heart Failure: Molecular Mechanisms

    PubMed Central

    Aroor, Annayya R.; Mandavia, Chirag H.; Sowers, James R.

    2012-01-01

    Insulin resistance and associated reductions in cardiac insulin metabolic signaling is emerging as a major factor for the development of heart failure and assumes more importance because of an epidemic increase in obesity and the cardiorenal metabolic syndrome and our aging population. Major factors contributing to the development of cardiac insulin resistance are oxidative stress, hyperglycemia, hyperlipidemia, dysregulated secretion of adipokines/cytokines and inappropriate activation of renin-angiotensin II-aldosterone system (RAAS) and the sympathetic nervous system. The effects of cardiac insulin resistance are exacerbated by metabolic, endocrine and cytokine alterations associated with systemic insulin resistance. The aggregate of these various alterations leads to an insulin resistant phenotype with metabolic inflexibility, impaired calcium handling, mitochondrial dysfunction and oxidative stress, dysregulated myocardial-endothelial interactions resulting in energy deficiency, impaired diastolic dysfunction, myocardial cell death and cardiac fibrosis. Therefore, understanding the molecular mechanisms linking insulin resistance and heart failure may help to design new and more effective mechanism-based drugs to improve myocardial and systemic insulin resistance. PMID:22999243

  9. An intact cuticle in distal tissues is essential for the induction of systemic acquired resistance in plants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Systemic acquired resistance (SAR) immunizes distal tissues of plants against secondary infections. We report that an acyl carrier protein, ACP4, is essential for perception but not generation of the SAR signal in Arabidopsis. A mutation in acp4 reduces the fatty acid flux, resulting in impaired cut...

  10. Growth response and acquired resistance of Nile tilapia Orechromis niloticus following infection or vaccination with Streptococcus iniae.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Growth performance and acquired resistance of Nile tilapia, Oreochromis niloticus that survived Streptococcus iniae infection was determined. Tilapia were challenged with three doses of S. iniae (8.8 x 10 to the third power, 8.8 x 10 to the fourth power and 8.8 x 10 to the fifth power CFU fish-1 f...

  11. GROWTH RESPONSE AND ACQUIRED RESISTANCE OF NILE TILAPIA OREOCHROMIS NILOTICUS FOLLOWING INFECTION OR VACCINATION WITH STREPTOCOCCUS INIAE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Growth performance and acquired resistance of Nile tilapia, Oreochromis niloticus (L.) that survived Streptococcus iniae infection was determined. Tilapia were challenged with three doses of S. iniae (8.8 x 10 to the 3rd power, 8.8 x 10 to the 4th power and 8.8 x 10 to the 5th power CFU fish-1 for ...

  12. Saccharin-induced systemic acquired resistance against rust (Phakopsora pachyrhizi) infection in soybean: Effects on growth and development

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We examined the effect of saccharin on the systemic acquired resistance (SAR) response of soybean to the fungus Phakopsora pachyrhizi, the causal agent of soybean rust. Plants were grown hydroponically in half-strength Hoagland’s solution and were challenged with the pathogen 1, 5, 10 and 15 days af...

  13. Growth Response and Acquired Resistance of Nile Tilapia Oreochromis niloticus Following Infection or Vaccination with Streptococcus iniae

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Growth performance and acquired resistance of Nile tilapia, Oreochromis niloticus (L.) that survived Streptococcus iniae infection was determined. Tilapia were challenged with three doses of S. iniae (8.8 x 10 to the 3rd power, 8.8 x 10 to the 4th power and 8.8 x 10 to the 5th power CFU fish-1 for ...

  14. Complement resistance mechanisms of Klebsiella pneumoniae.

    PubMed

    Doorduijn, Dennis J; Rooijakkers, Suzan H M; van Schaik, Willem; Bardoel, Bart W

    2016-10-01

    The current emergence of antibiotic-resistant bacteria causes major problems in hospitals worldwide. To survive within the host, bacterial pathogens exploit several escape mechanisms to prevent detection and killing by the immune system. As a major player in immune defense, the complement system recognizes and destroys bacteria via different effector mechanisms. The complement system can label bacteria for phagocytosis or directly kill Gram-negative bacteria via insertion of a pore-forming complex in the bacterial membrane. The multi-drug resistant pathogen Klebsiella pneumoniae exploits several mechanisms to resist complement. In this review, we present an overview of strategies used by K. pneumoniae to prevent recognition and killing by the complement system. Understanding these complement evasion strategies is crucial for the development of innovative strategies to combat K. pneumoniae. PMID:27364766

  15. New Real-Time PCR Assays for Detection of Inducible and Acquired Clarithromycin Resistance in the Mycobacterium abscessus Group

    PubMed Central

    Shallom, Shamira J.; Moura, Natalia S.; Olivier, Kenneth N.; Sampaio, Elizabeth P.; Holland, Steven M.

    2015-01-01

    Members of the Mycobacterium abscessus group (MAG) cause lung, soft tissue, and disseminated infections. The oral macrolides clarithromycin and azithromycin are commonly used for treatment. MAG can display clarithromycin resistance through the inducible erm(41) gene or via acquired mutations in the rrl (23S rRNA) gene. Strains harboring a truncation or a T28C substitution in erm(41) lose the inducible resistance trait. Phenotypic detection of clarithromycin resistance requires extended incubation (14 days), highlighting the need for faster methods to detect resistance. Two real-time PCR-based assays were developed to assess inducible and acquired clarithromycin resistance and tested on a total of 90 clinical and reference strains. A SYBR green assay was designed to distinguish between a full-length and truncated erm(41) gene by temperature shift in melting curve analysis. Single nucleotide polymorphism (SNP) allele discrimination assays were developed to distinguish T or C at position 28 of erm(41) and 23S rRNA rrl gene mutations at position 2058 and/or 2059. Truncated and full-size erm(41) genes were detected in 21/90 and 69/90 strains, respectively, with 64/69 displaying T at nucleotide position 28 and 5/69 containing C at that position. Fifteen isolates showed rrl mutations conferring clarithromycin resistance, including A2058G (11 isolates), A2058C (3 isolates), and A2059G (1 isolate). Targeted sequencing and phenotypic assessment of resistance concurred with molecular assay results. Interestingly, we also noted cooccurring strains harboring an active erm(41), inactive erm(41), and/or acquired mutational resistance, as well as slowly growing MAG strains and also strains displaying an inducible resistance phenotype within 5 days, long before the recommended 14-day extended incubation. PMID:26269619

  16. Hypermorphic mutation of phospholipase C, γ2 acquired in ibrutinib-resistant CLL confers BTK independency upon B-cell receptor activation

    PubMed Central

    Liu, Ta-Ming; Woyach, Jennifer A.; Zhong, Yiming; Lozanski, Arletta; Lozanski, Gerard; Dong, Shuai; Strattan, Ethan; Lehman, Amy; Zhang, Xiaoli; Jones, Jeffrey A.; Flynn, Joseph; Andritsos, Leslie A.; Maddocks, Kami; Jaglowski, Samantha M.; Blum, Kristie A.; Byrd, John C.; Dubovsky, Jason A.

    2015-01-01

    Ibrutinib has significantly improved the outcome of patients with relapsed chronic lymphocytic leukemia (CLL). Recent reports attribute ibrutinib resistance to acquired mutations in Bruton agammaglobulinemia tyrosine kinase (BTK), the target of ibrutinib, as well as the immediate downstream effector phospholipase C, γ2 (PLCG2). Although the C481S mutation found in BTK has been shown to disable ibrutinib’s capacity to irreversibly bind this primary target, the detailed mechanisms of mutations in PLCG2 have yet to be established. Herein, we characterize the enhanced signaling competence, BTK independence, and surface immunoglobulin dependence of the PLCG2 mutation at R665W, which has been documented in ibrutinib-resistant CLL. Our data demonstrate that this missense alteration elicits BTK-independent activation after B-cell receptor engagement, implying the formation of a novel BTK-bypass pathway. Consistent with previous results, PLCG2R665W confers hypermorphic induction of downstream signaling events. Our studies reveal that proximal kinases SYK and LYN are critical for the activation of mutant PLCG2 and that therapeutics targeting SYK and LYN can combat molecular resistance in cell line models and primary CLL cells from ibrutinib-resistant patients. Altogether, our results engender a molecular understanding of the identified aberration at PLCG2 and explore its functional dependency on BTK, SYK, and LYN, suggesting alternative strategies to combat acquired ibrutinib resistance. PMID:25972157

  17. Leucine Supplementation Improves Acquired Growth Hormone Resistance in Rats with Protein-Energy Malnutrition

    PubMed Central

    Wang, Xinying; Zhao, Jie; Wan, Xiao; Zhang, Li; Wu, Chao; Li, Ning; Li, Jieshou

    2015-01-01

    the MC-L and MC-H groups than in the MC-CON group. Conclusion/Significance Our data are the first to demonstrate that long-term supplementation with leucine improved acquired growth hormone resistance in rats with protein-energy malnutrition. Leucine might promote skeletal muscle protein synthesis by regulating downstream anabolic signaling transduction. PMID:25909895

  18. Regulatory and Functional Aspects of Indolic Metabolism in Plant Systemic Acquired Resistance.

    PubMed

    Stahl, Elia; Bellwon, Patricia; Huber, Stefan; Schlaeppi, Klaus; Bernsdorff, Friederike; Vallat-Michel, Armelle; Mauch, Felix; Zeier, Jürgen

    2016-05-01

    Tryptophan-derived, indolic metabolites possess diverse functions in Arabidopsis innate immunity to microbial pathogen infection. Here, we investigate the functional role and regulatory characteristics of indolic metabolism in Arabidopsis systemic acquired resistance (SAR) triggered by the bacterial pathogen Pseudomonas syringae. Indolic metabolism is broadly activated in both P. syringae-inoculated and distant, non-inoculated leaves. At inoculation sites, camalexin, indol-3-ylmethylamine (I3A), and indole-3-carboxylic acid (ICA) are the major accumulating compounds. Camalexin accumulation is positively affected by MYB122, and the cytochrome P450 genes CYP81F1 and CYP81F2. Local I3A production, by contrast, occurs via indole glucosinolate breakdown by PEN2- dependent and independent pathways. Moreover, exogenous application of the defense hormone salicylic acid stimulates I3A generation at the expense of its precursor indol-3-ylmethylglucosinolate (I3M), and the SAR regulator pipecolic acid primes plants for enhanced P. syringae-induced activation of distinct branches of indolic metabolism. In uninfected systemic tissue, the metabolic response is more specific and associated with enhanced levels of the indolics I3A, ICA, and indole-3-carbaldehyde (ICC). Systemic indole accumulation fully depends on functional CYP79B2/3, PEN2, and MYB34/51/122, and requires functional SAR signaling. Genetic analyses suggest that systemically elevated indoles are dispensable for SAR and associated systemic increases of salicylic acid. However, soil-grown but not hydroponically -cultivated cyp79b2/3 and pen2 plants, both defective in indolic secondary metabolism, exhibit pre-induced immunity, which abrogates their intrinsic ability to induce SAR. PMID:26802249

  19. Comparison of rhizosphere bacterial communities in Arabidopsis thaliana mutants for systemic acquired resistance.

    PubMed

    Hein, John W; Wolfe, Gordon V; Blee, Kristopher A

    2008-02-01

    Systemic acquired resistance (SAR) is an inducible systemic plant defense against a broad spectrum of plant pathogens, with the potential to secrete antimicrobial compounds into the soil. However, its impact on rhizosphere bacteria is not known. In this study, we examined fingerprints of bacterial communities in the rhizosphere of the model plant Arabidopsis thaliana to determine the effect of SAR on bacterial community structure and diversity. We compared Arabidopsis mutants that are constitutive and non-inducible for SAR and verified SAR activation by measuring pathogenesis-related protein activity via a beta-glucoronidase (GUS) reporter construct driven by the beta-1-3 glucanase promoter. We used terminal restriction fragment length polymorphism (T-RFLP) analysis of MspI- and HaeIII-digested 16S rDNA to estimate bacterial rhizosphere community diversity, with Lactobacillus sp. added as internal controls. T-RFLP analysis showed a clear rhizosphere effect on community structure, and diversity analysis of both rhizosphere and bulk soil operational taxonomic units (as defined by terminal restriction fragments) using richness, Shannon-Weiner, and Simpson's diversity indices and evenness confirmed that the presence of Arabidopsis roots significantly altered bacterial communities. This effect of altered soil microbial community structure by plants was also seen upon multivariate cluster analysis of the terminal restriction fragments. We also found visible differences in the rhizosphere community fingerprints of different Arabidopsis SAR mutants; however, there was no clear decrease of rhizosphere diversity because of constitutive SAR expression. Our study suggests that SAR can alter rhizosphere bacterial communities, opening the door to further understanding and application of inducible plant defense as a driving force in structuring soil bacterial assemblages. PMID:17619212

  20. Comparative genomics of community-acquired ST59 methicillin-resistant Staphylococcus aureus in Taiwan: novel mobile resistance structures with IS1216V.

    PubMed

    Hung, Wei-Chun; Takano, Tomomi; Higuchi, Wataru; Iwao, Yasuhisa; Khokhlova, Olga; Teng, Lee-Jene; Yamamoto, Tatsuo

    2012-01-01

    Methicillin-resistant Staphylococcus aureus (MRSA) with ST59/SCCmecV and Panton-Valentine leukocidin gene is a major community-acquired MRSA (CA-MRSA) lineage in Taiwan and has been multidrug-resistant since its initial isolation. In this study, we studied the acquisition mechanism of multidrug resistance in an ST59 CA-MRSA strain (PM1) by comparative genomics. PM1's non-β-lactam resistance was encoded by two unique genetic traits. One was a 21,832-bp composite mobile element structure (MES(PM1)), which was flanked by direct repeats of enterococcal IS1216V and was inserted into the chromosomal sasK gene; the target sequence (att) was 8 bp long and was duplicated at both ends of MES(PM1). MES(PM1) consisted of two regions: the 5'-end side 12.4-kb region carrying Tn551 (with ermB) and Tn5405-like (with aph[3']-IIIa and aadE), similar to an Enterococcus faecalis plasmid, and the 3'-end side 6,587-bp region (MES(cat)) that carries cat and is flanked by inverted repeats of IS1216V. MES(cat) possessed att duplication at both ends and additional two copies of IS1216V inside. MES(PM1) represents the first enterococcal IS1216V-mediated composite transposon emerged in MRSA. IS1216V-mediated deletion likely occurred in IS1216V-rich MES(PM1), resulting in distinct resistance patterns in PM1-derivative strains. Another structure was a 6,025-bp tet-carrying element (MES(tet)) on a 25,961-bp novel mosaic penicillinase plasmid (pPM1); MES(tet) was flanked by direct repeats of IS431, but with no target sequence repeats. Moreover, the PM1 genome was deficient in a copy of the restriction and modification genes (hsdM and hsdS), which might have contributed to the acquisition of enterococcal multidrug resistance. PMID:23071689

  1. New Fks Hot Spot for Acquired Echinocandin Resistance in Saccharomyces cerevisiae and Its Contribution to Intrinsic Resistance of Scedosporium Species▿

    PubMed Central

    Johnson, Michael E.; Katiyar, Santosh K.; Edlind, Thomas D.

    2011-01-01

    Echinocandins represent a new antifungal group with potent activity against Candida species. These lipopeptides inhibit the synthesis of β-1,3-glucan, the major cell wall polysaccharide. Acquired resistance or reduced echinocandin susceptibility (RES) is rare and associated with mutations in two “hot spot” regions of Fks1 or Fks2, the probable β-1,3-glucan synthases. In contrast, many fungi demonstrate intrinsic RES for reasons that remain unclear. We are using Saccharomyces cerevisiae to understand the basis for RES by modeling echinocandin-Fks interaction. Previously characterized mutations confer cross-RES; we screened for mutations conferring differential RES, implying direct interaction of that Fks residue with a variable echinocandin side chain. One mutant (in an fks1Δ background) exhibited ≥16-fold micafungin and anidulafungin versus caspofungin RES. Sequencing identified a novel Fks2 mutation, W714L/Y715N. Equivalent W695L/Y696N and related W695L/F/C mutations in Fks1 generated by site-directed mutagenesis and the isolation of a W695L-equivalent mutation in Candida glabrata confirmed the role of the new “hot spot 3” in RES. Further mutagenesis expanded hot spot 3 to Fks1 residues 690 to 700, yielding phenotypes ranging from cross-RES to differential hypersusceptibility. Fks1 sequences from intrinsically RES Scedosporium species revealed W695F-equivalent substitutions; Fks1 hybrids expressing Scedosporium prolificans hot spot 3 confirmed that this substitution imparts RES. PMID:21576441

  2. Convergence of Acquired Mutations and Alternative Splicing of CD19 Enables Resistance to CART-19 Immunotherapy

    PubMed Central

    Sotillo, Elena; Barrett, David M.; Black, Kathryn L; Bagashev, Asen; Oldridge, Derek; Wu, Glendon; Sussman, Robyn; Lanauze, Claudia; Ruella, Marco; Gazzara, Matthew R.; Martinez, Nicole M.; Harrington, Colleen T.; Chung, Elaine Y.; Perazzelli, Jessica; Hofmann, Ted J.; Maude, Shannon L.; Raman, Pichai; Barrera, Alejandro; Gill, Saar; Lacey, Simon F.; Melenhorst, Jan J.; Allman, David; Jacoby, Elad; Fry, Terry; Mackall, Crystal; Barash, Yoseph; Lynch, Kristen W.; Maris, John M.; Grupp, Stephan A.; Thomas-Tikhonenko, Andrei

    2015-01-01

    The CD19 antigen, expressed on most B-cell acute lymphoblastic leukemias (B-ALL), can be targeted with chimeric antigen receptor–armed T cells (CART-19), but relapses with epitope loss occur in 10% to 20% of pediatric responders. We detected hemizygous deletions spanning the CD19 locus and de novo frameshift and missense mutations in exon 2 of CD19 in some relapse samples. However, we also discovered alternatively spliced CD19 mRNA species, including one lacking exon 2. Pull-down/siRNA experiments identified SRSF3 as a splicing factor involved in exon 2 retention, and its levels were lower in relapsed B-ALL. Using genome editing, we demonstrated that exon 2 skipping bypasses exon 2 mutations in B-ALL cells and allows expression of the N-terminally truncated CD19 variant, which fails to trigger killing by CART-19 but partly rescues defects associated with CD19 loss. Thus, this mechanism of resistance is based on a combination of deleterious mutations and ensuing selection for alternatively spliced RNA isoforms. Significance CART-19 yield 70% response rates in patients with B-ALL, but also produce escape variants. We discovered that the underlying mechanism is the selection for preexisting alternatively spliced CD19 isoforms with the compromised CART-19 epitope. This mechanism suggests a possibility of targeting alternative CD19 ectodomains, which could improve survival of patients with B-cell neoplasms. PMID:26516065

  3. Nanoscale resistive switching devices: mechanisms and modeling

    NASA Astrophysics Data System (ADS)

    Yang, Yuchao; Lu, Wei

    2013-10-01

    Resistive switching devices (also termed memristive devices or memristors) are two-terminal nonlinear dynamic electronic devices that can have broad applications in the fields of nonvolatile memory, reconfigurable logic, analog circuits, and neuromorphic computing. Current rapid advances in memristive devices in turn demand better understanding of the switching mechanism and the development of physics-based as well as simplified device models to guide future device designs and circuit-level applications. In this article, we review the physical processes behind resistive switching (memristive) phenomena and discuss the experimental and modeling efforts to explain these effects. In this article three categories of devices, in which the resistive switching effects are driven by cation migration, anion migration, and electronic effects, will be discussed. The fundamental driving forces and the stochastic nature of resistive switching will also be discussed.

  4. Nanoscale resistive switching devices: mechanisms and modeling.

    PubMed

    Yang, Yuchao; Lu, Wei

    2013-11-01

    Resistive switching devices (also termed memristive devices or memristors) are two-terminal nonlinear dynamic electronic devices that can have broad applications in the fields of nonvolatile memory, reconfigurable logic, analog circuits, and neuromorphic computing. Current rapid advances in memristive devices in turn demand better understanding of the switching mechanism and the development of physics-based as well as simplified device models to guide future device designs and circuit-level applications. In this article, we review the physical processes behind resistive switching (memristive) phenomena and discuss the experimental and modeling efforts to explain these effects. In this article three categories of devices, in which the resistive switching effects are driven by cation migration, anion migration, and electronic effects, will be discussed. The fundamental driving forces and the stochastic nature of resistive switching will also be discussed. PMID:24057010

  5. Antibacterial Mechanisms of Polymyxin and Bacterial Resistance

    PubMed Central

    Qin, Wangrong; Fang, Shisong; Qiu, Juanping

    2015-01-01

    Multidrug resistance in pathogens is an increasingly significant threat for human health. Indeed, some strains are resistant to almost all currently available antibiotics, leaving very limited choices for antimicrobial clinical therapy. In many such cases, polymyxins are the last option available, although their use increases the risk of developing resistant strains. This review mainly aims to discuss advances in unraveling the mechanisms of antibacterial activity of polymyxins and bacterial tolerance together with the description of polymyxin structure, synthesis, and structural modification. These are expected to help researchers not only develop a series of new polymyxin derivatives necessary for future medical care, but also optimize the clinical use of polymyxins with minimal resistance development. PMID:25664322

  6. Mycoplasma bovis: Mechanisms of Resistance and Trends in Antimicrobial Susceptibility.

    PubMed

    Lysnyansky, Inna; Ayling, Roger D

    2016-01-01

    Mycoplasma bovis is a cell-wall-less bacterium and belongs to the class Mollicutes. It is the most important etiological agent of bovine mycoplasmoses in North America and Europe, causing respiratory disease, mastitis, otitis media, arthritis, and reproductive disease. Clinical disease associated with M. bovis is often chronic, debilitating, and poorly responsive to antimicrobial therapy, resulting in significant economic loss, the full extent of which is difficult to estimate. Until M. bovis vaccines are universally available, sanitary control measures and antimicrobial treatment are the only approaches that can be used in attempts to control M. bovis infections. However, in vitro studies show that many of the current M. bovis isolates circulating in Europe have high minimum inhibitory concentrations (MIC) for many of the commercially available antimicrobials. In this review we summarize the current MIC trends indicating the development of antimicrobial resistance in M. bovis as well as the known molecular mechanisms by which resistance is acquired. PMID:27199926

  7. Mycoplasma bovis: Mechanisms of Resistance and Trends in Antimicrobial Susceptibility

    PubMed Central

    Lysnyansky, Inna; Ayling, Roger D.

    2016-01-01

    Mycoplasma bovis is a cell-wall-less bacterium and belongs to the class Mollicutes. It is the most important etiological agent of bovine mycoplasmoses in North America and Europe, causing respiratory disease, mastitis, otitis media, arthritis, and reproductive disease. Clinical disease associated with M. bovis is often chronic, debilitating, and poorly responsive to antimicrobial therapy, resulting in significant economic loss, the full extent of which is difficult to estimate. Until M. bovis vaccines are universally available, sanitary control measures and antimicrobial treatment are the only approaches that can be used in attempts to control M. bovis infections. However, in vitro studies show that many of the current M. bovis isolates circulating in Europe have high minimum inhibitory concentrations (MIC) for many of the commercially available antimicrobials. In this review we summarize the current MIC trends indicating the development of antimicrobial resistance in M. bovis as well as the known molecular mechanisms by which resistance is acquired. PMID:27199926

  8. Alectinib: a novel second generation anaplastic lymphoma kinase (ALK) inhibitor for overcoming clinically-acquired resistance

    PubMed Central

    Song, Zilan; Wang, Meining; Zhang, Ao

    2015-01-01

    The development of inhibitors for the tyrosine anaplastic lymphoma kinase (ALK) has advanced rapidly, driven by biology and medicinal chemistry. The first generation ALK inhibitor crizotinib was granted US FDA approval with only four years of preclinical and clinical testing. Although this drug offers significant clinical benefit to the ALK-positive patients, resistance has been developed through a variety of mechanisms. In addition to ceritinib, alectinib is another second-generation ALK inhibitor launched in 2014 in Japan. This drug has a unique chemical structure bearing a 5H-benzo[b]carbazol-11(6H)-one structural scaffold with an IC50 value of 1.9 nmol/L, and is highly potent against ALK bearing the gatekeeper mutation L1196M with an IC50 of 1.56 nmol/L. In the clinic, alectinib is highly efficacious in treatment of ALK-positive non-small cell lung cancer (NSCLC), and retains potency to combat crizotinib-resistant ALK mutations L1196M, F1174L, R1275Q and C1156Y. PMID:26579422

  9. Mechanisms of Resistance in Bacteria: An Evolutionary Approach

    PubMed Central

    Martins, Ana; Hunyadi, Attila; Amaral, Leonard

    2013-01-01

    Acquisition of resistance is one of the major causes of failure in therapy of bacterial infections. According to the World Health Organization (WHO), thousands of deaths caused by Salmonella sp., Escherichia coli, Staphylococcus aureus or Mycobacteria tuberculosis are due to failure in therapy caused by resistance to the chemotherapeutic agents. Understanding the mechanisms of resistance acquisition by the bacterial strains is therefore essential to prevent and overcome resistance. However, it is very difficult to extrapolate from in vitro studies, where the variables are far less and under constant control, as compared to what happens in vivo where the chosen chemotherapeutic, its effective dose, and the patient’s immune system are variables that differ substantially case-by-case. The aim of this review is to provide a new perspective on the possible ways by which resistance is acquired by the bacterial strains within the patient, with a special emphasis on the adaptive response of the infecting bacteria to the administered antibiotic. PMID:23560029

  10. [Resistance risk, cross-resistance and biochemical resistance mechanism of Laodelphax striatellus to buprofezin].

    PubMed

    Mao, Xu-lian; Liu, Jin; Li, Xu-ke; Chi, Jia-jia; Liu, Yong-jie

    2016-01-01

    In order to investigate the resistance development law and biochemical resistance mechanism of Laodelphax striatellus to buprofezin, spraying rice seedlings was used to continuously screen resistant strains of L. striatellus and dipping rice seedlings was applied to determine the toxicity and cross-resistance of L. striatellus to insecticides. After 32-generation screening with buprofezin, L. striatellus developed 168.49 folds resistance and its reality heritability (h2) was 0.11. If the killing rate was 80%-90%, L. striatellus was expected to develop 10-fold resistance to buprofezin only after 5 to 6 generations breeding. Because the actual reality heritability of field populations was usually lower than that of the resistant strains, the production of field populations increasing with 10-fold resistance would need much longer time. The results of cross-resistance showed that resistant strain had high level cross-resistance with thiamethoxam and imidacloprid, low level cross-resistance with acetamiprid, and no cross-resistance with pymetrozine and chlorpyrifos. The activity of detoxification enzymes of different strains and the syergism of synergist were measured. The results showed that cytochrome P450 monooxygenase played a major role in the resistance of L. striatellus to buprofezin, the esterase played a minor role and the GSH-S-transferase had no effect. Therefore, L. striatellus would have high risk to develop resistance to buprofezin when used in the field and might be delayed by using pymetrozine and chlorpyrifos. PMID:27228617

  11. Genomic profiling of acquired resistance to apoptosis in cells derived from human atherosclerotic lesions: potential role of STATs, cyclinD1, BAD, and Bcl-XL.

    PubMed

    Gagarin, Dmitry; Yang, Zhaoqing; Butler, Jason; Wimmer, Monika; Du, Baoheng; Cahan, Patrick; McCaffrey, Timothy A

    2005-09-01

    Current theories suggest that atherosclerosis, plaque rupture, stroke, and restenosis after angioplasty may involve defective apoptotic mechanisms in vascular cells. Prior work has demonstrated that cells from human atherosclerotic lesions, and cells from the aorta of aged rats, exhibit functional resistance to apoptosis induced by TGF-beta and glucocorticoids. The present studies demonstrate that human lesion-derived cells (LDC) are also resistant to apoptosis induced by fas ligation compared to cells derived from the adjacent media, and that in vitro expansion of LDC causes acquired resistance to apoptosis. Microarray profiling of fas-resistant versus sensitive cells identified a set of genes including STATs, caspase 1, cyclin D1, Bcl-xL, VDAC2, and BAD. The STAT proteins have been implicated in resistance to apoptosis, potentially via their ability to modulate caspase 1 (ICE), Bcl-xL, and cyclin D1 expression. Western blot analysis of sensitive and resistant LDC clonal lines confirmed increases in cyclin D1, STAT6, Bcl-xL, and BAD, with decreased expression of caspase 1. Thus, transcript profiling has identified a potential pathway of apoptotic regulation in subsets of lesion cells. The resistant phenotype may contribute to plaque stability and excessive vascular repair, while sensitive cells may be involved in plaque rupture and infarction. The data suggests both genetic interventions and novel small-molecule inhibitors that may be effective modulators of apoptosis in atherosclerosis, angina, and in-stent restenosis. PMID:16005468

  12. Comparison of local and systemic induction of acquired disease resistance in cucumber plants treated with benzothiadiazoles or salicylic acid.

    PubMed

    Narusaka, Y; Narusaka, M; Horio, T; Ishii, H

    1999-04-01

    The accumulation of chitinase and its involvement in systemic acquired disease resistance was analyzed using acibenzolar-S-methyl and salicylic acid (SA). Resistance against scab (pathogen: Cladosporium cucumerinum) and the accumulation of chitinase were rapidly induced in cucumber plants after treatment with acibenzolar-S-methyl. In contrast, SA protected the plants from C. cucumerinum and the accumulation of chitinase was induced only on the treated leaves. The accumulation of chitinase in response to inoculation with the pathogen was induced more rapidly in cucumber plants previously treated with acibenzolar-S-methyl than in plants pretreated with SA or water. Thus, it appears that a prospective signal(s), that induces systemic resistance, can be transferred from leaves treated with acibenzolar-S-methyl to the untreated upper and lower leaves where systemic resistance is elicited. In contrast, exogenously applied SA is not likely to function as a mobile, systemic resistance-inducing signal, because SA only induces localized acquired resistance. PMID:10394634

  13. Benznidazole-Resistance in Trypanosoma cruzi Is a Readily Acquired Trait That Can Arise Independently in a Single Population

    PubMed Central

    Mejia, Ana Maria; Hall, Belinda S.; Taylor, Martin C.; Gómez-Palacio, Andrés; Wilkinson, Shane R.; Triana-Chávez, Omar; Kelly, John M.

    2012-01-01

    Benznidazole is the frontline drug used against Trypanosoma cruzi, the causative agent of Chagas disease. However, treatment failures are often reported. Here, we demonstrate that independently acquired mutations in the gene encoding a mitochondrial nitroreductase (TcNTR) can give rise to distinct drug-resistant clones within a single population. Following selection of benznidazole-resistant parasites, all clones examined had lost one of the chromosomes containing the TcNTR gene. Sequence analysis of the remaining TcNTR allele revealed 3 distinct mutant genes in different resistant clones. Expression studies showed that these mutant proteins were unable to activate benznidazole. This correlated with loss of flavin mononucleotide binding. The drug-resistant phenotype could be reversed by transfection with wild-type TcNTR. These results identify TcNTR as a central player in acquired resistance to benznidazole. They also demonstrate that T. cruzi has a propensity to undergo genetic changes that can lead to drug resistance, a finding that has implications for future therapeutic strategies. PMID:22551809

  14. Current perspectives on tigecycline resistance in Enterobacteriaceae: susceptibility testing issues and mechanisms of resistance.

    PubMed

    Pournaras, Spyros; Koumaki, Vasiliki; Spanakis, Nicholas; Gennimata, Vasiliki; Tsakris, Athanassios

    2016-07-01

    During the past decades, rates of multidrug-resistant (MDR) and carbapenem-resistant (CR) Enterobacteriaceae clinical isolates, mainly Klebsiella spp., Escherichia coli, Enterobacter spp., Proteus spp. and Serratia marcescens, have increased, considerably restricting effective antimicrobial treatments. Tigecycline, the first member of the glycylcyclines, has been approved by the US Food and Drug Administration (FDA) for the treatment of complicated skin and soft-tissue, complicated intra-abdominal and community-acquired bacterial respiratory infections and is increasingly administered against MDR Enterobacteriaceae. Although resistance has gradually appeared, tigecycline still remains relatively active among Enterobacteriaceae, with resistance rates largely <10% in most wide-scale surveillance studies. Tigecycline resistance has been reported in some studies to be elevated among extended-spectrum β-lactamase (ESBL)-producing, MDR, extensively drug-resistant and CR isolates. Broth microdilution (BMD) is the reference method for tigecycline susceptibility testing, but disagreements have been reported between the methods applied for routine tigecycline susceptibility testing. Therefore, confirmation of daily tigecycline susceptibility testing with BMD appears important in order to avoid misclassification of isolates. Various mechanisms have been reported to confer tigecycline resistance, with RND-type transporters, mainly the AcrAB efflux pump, playing an important role. Other pumps and various control pathways are also implicated in tigecycline resistance. Overall, tigecycline is a potent therapeutic option for enterobacterial infections. Accurate detection of tigecycline susceptibility status and surveillance of resistant organisms in the hospital environment is necessary in order to optimise its use and to preserve tigecycline in our therapeutic arsenal. PMID:27256586

  15. Differential involvement of glutathione S-transferase mu 1 and multidrug resistance protein 1 in melanoma acquired resistance to vinca alkaloids.

    PubMed

    Attaoua, Chaker; Vincent, Laure-Anaïs; Abdel Jaoued, Aida; Hadj-Kaddour, Kamel; Baï, Qiang; De Vos, John; Vian, Laurence; Cuq, Pierre

    2015-02-01

    On account of its extreme intrinsic resistance to apoptosis and of its strong ability to become chemoresistant after a primary response to drugs, malignant melanoma (MM) is still a therapeutic challenge. We previously showed that glutathione S-transferase mu 1 (GSTM1) acts in synergy with multidrug resistance protein 1 (MRP1) to protect GSTM1-transfected human CAL1 melanoma cells from toxic effects of vincristine (VCR). Herein, we investigated the role of these proteins in the acquired resistance of CAL1 cells to vinca alkaloids (VAs). Resistant lines were established by continuous exposure (>1 year) of parental CAL1-wt cells to VCR, vindesine (VDS), or vinorelbine (VRB): CAL1R-VCR, CAL1R-VDS, CAL1R-VRB, respectively. All resistant lines displayed more than 10-fold increase in resistance to their selection VA, and specifically expressed GSTM1. Suggesting a direct interaction between this protein and VAs, each VA specifically decreased the GSTM1-mediated glutathione conjugation activity in cell lysates. Curcumin (GSTM1 inhibitor), BSO (glutathione synthesis inhibitor), and MK571 (MRP1 inhibitor) considerably reversed the acquired resistance to VCR and VDS, but not to VRB. Microarray data analysis revealed similar gene expression patterns of CAL1R-VCR and CAL1R-VDS, and a distinct one for CAL1R-VRB. These data suggest a differential involvement of GSTM1 and MRP1 in acquired resistance to VAs. A coordinated expression and activity of GSTM1 and MRP1 is required to protect CAL1 cells from VCR and VDS, while the simple expression of GSTM1 is sufficient, possibly by a direct drug/protein interaction, to confer resistance against VRB. PMID:25283245

  16. EGFR-Mediated Reactivation of MAPK Signaling Induces Acquired Resistance to GSK2118436 in BRAF V600E-Mutant NSCLC Cell Lines.

    PubMed

    Kim, Sung-Moo; Kim, Hwan; Jang, Kang Won; Kim, Min Hwan; Sohn, Jinyoung; Yun, Mi Ran; Kang, Han Na; Kang, Chan Woo; Kim, Hye Ryun; Lim, Sun Min; Moon, Yong Wha; Kim, Joo Hang; Paik, Soonmyung; Cho, Byoung Chul

    2016-07-01

    Although treatment of BRAF V600E-mutant non-small cell lung cancer (NSCLC(V600E)) with GSK2118436 has shown an encouraging efficacy, most patients develop resistance. To investigate the mechanisms of acquired resistance to GSK2118436 in NSCLC(V600E), we established GSK2118436-resistant (GSR) cells by exposing MV522 NSCLC(V600E) to increasing GSK2118436 concentrations. GSR cells displayed activated EGFR-RAS-CRAF signaling with upregulated EGFR ligands and sustained activation of ERK1/2, but not MEK1/2, in the presence of GSK2118436. Treatment of GSR cells with GSK2118436 enhanced EGFR-mediated RAS activity, leading to the formation of BRAF-CRAF dimers and transactivation of CRAF. Interestingly, sustained activation of ERK1/2 was partly dependent on receptor-interacting protein kinase-2 (RIP2) activity, but not on MEK1/2 activity. Combined BRAF and EGFR inhibition blocked reactivation of ERK signaling and improved efficacy in vitro and in vivo Our findings support the evaluation of combined BRAF and EGFR inhibition in NSCLC(V600E) with acquired resistance to BRAF inhibitors. Mol Cancer Ther; 15(7); 1627-36. ©2016 AACR. PMID:27196768

  17. Low Prevalence of Carbapenem-Resistant Bacteria in River Water: Resistance Is Mostly Related to Intrinsic Mechanisms.

    PubMed

    Tacão, Marta; Correia, António; Henriques, Isabel S

    2015-10-01

    Carbapenems are last-resort antibiotics to handle serious infections caused by multiresistant bacteria. The incidence of resistance to these antibiotics has been increasing and new resistance mechanisms have emerged. The dissemination of carbapenem resistance in the environment has been overlooked. The main goal of this research was to assess the prevalence and diversity of carbapenem-resistant bacteria in riverine ecosystems. The presence of frequently reported carbapenemase-encoding genes was inspected. The proportion of imipenem-resistant bacteria was on average 2.24 CFU/ml. Imipenem-resistant strains (n=110) were identified as Pseudomonas spp., Stenotrophomonas maltophilia, Aeromonas spp., Chromobacterium haemolyticum, Shewanella xiamenensis, and members of Enterobacteriaceae. Carbapenem-resistant bacteria were highly resistant to other beta-lactams such as quinolones, aminoglycosides, chloramphenicol, tetracyclines, and sulfamethoxazole/trimethoprim. Carbapenem resistance was mostly associated with intrinsically resistant bacteria. As intrinsic resistance mechanisms, we have identified the blaCphA gene in 77.3% of Aeromonas spp., blaL1 in all S. maltophilia, and blaOXA-48-like in all S. xiamenensis. As acquired resistance mechanisms, we have detected the blaVIM-2 gene in six Pseudomonas spp. (5.45%). Integrons with gene cassettes encoding resistance to aminoglycosides (aacA and aacC genes), trimethoprim (dfrB1b), and carbapenems (blaVIM-2) were found in Pseudomonas spp. Results suggest that carbapenem resistance dissemination in riverine ecosystems is still at an early stage. Nevertheless, monitoring these aquatic compartments for the presence of resistance genes and its host organisms is essential to outline strategies to minimize resistance dissemination. PMID:26430939

  18. Nasopharyngeal carriage of community-acquired, antibiotic-resistant Streptococcus pneumoniae in a Zambian paediatric population.

    PubMed Central

    Woolfson, A.; Huebner, R.; Wasas, A.; Chola, S.; Godfrey-Faussett, P.; Klugman, K.

    1997-01-01

    The emergence of antibiotic-resistant Streptococcus pneumoniae is an international health problem. Apart from South Africa few data on pneumococcal resistance are available for sub-Saharan Africa. This study examines the nasopharyngeal carriage and prevalence of antibiotic resistance in pneumococci isolated from 260 Zambian children aged < 6 years. Pneumococci were isolated from 71.9% of the children; the odds of carrying organisms were twice as high among children < 2 years of age compared with older children. Antibacterial resistance was found in 34.1% of the isolates; resistance to tetracycline, penicillin, sulfamethoxazole + trimethoprim, and chloramphenicol occurred in 23.0%, 14.3%, 12.7%, and 3.9% of the isolates, respectively. Only 4% of the isolates were resistant to three drugs. High-level resistance was found in all isolates resistant to tetracycline; but only intermediate level penicillin resistance was found. A total of 11.1% of the isolates demonstrated intermediate resistance to sulfamethoxazole + trimethoprim. Children aged < 6 months were less likely to carry antibiotic-resistant organisms. Antibiotic resistance in S. pneumoniae appears to be an emerging public health problem in Zambia, and the national policy for the empirical treatment of pneumococcal meningitis and acute respiratory tract infections may need to be re-evaluated. The establishment of ongoing surveillance to monitor trends in pneumococcal resistance should be considered. PMID:9447779

  19. Hitting a Moving Target: Basic Mechanisms of Recovery from Acquired Developmental Brain Injury

    PubMed Central

    Giza, Christopher C.; Kolb, Bryan; Harris, Neil G.; Asarnow, Robert F.; Prins, Mayumi L.

    2009-01-01

    Acquired brain injuries represent a major cause of disability in the pediatric population. Understanding responses to developmental acquired brain injuries requires knowledge of the neurobiology of normal development, age-at-injury effects and experience-dependent neuroplasticity. In the developing brain, full recovery cannot be considered as a return to the premorbid baseline, since ongoing maturation means that cerebral functioning in normal individuals will continue to advance. Thus, the recovering immature brain has to ‘hit a moving target’ to achieve full functional recovery, defined as parity with age-matched uninjured peers. This review will discuss the consequences of developmental injuries such as focal lesions, diffuse hypoxia and traumatic brain injury (TBI). Underlying cellular and physiological mechanisms relevant to age-at-injury effects will be described in considerable detail, including but not limited to alterations in neurotransmission, connectivity/network functioning, the extracellular matrix, response to oxidative stress and changes in cerebral metabolism. Finally, mechanisms of experience-dependent plasticity will be reviewed in conjunction with their effects on neural repair and recovery. PMID:19956795

  20. Molecular Characterization of Acquired Enrofloxacin Resistance in Mycoplasma synoviae Field Isolates

    PubMed Central

    Gerchman, I.; Mikula, I.; Gobbo, F.; Catania, S.; Levisohn, S.

    2013-01-01

    The in vitro activity of enrofloxacin against 73 Mycoplasma synoviae field strains isolated in Israel and Europe was determined by broth microdilution. Decreased susceptibility to enrofloxacin was identified in 59% of strains, with the MICs ranging from 1 to >16 μg/ml. The estimated MIC50 and MIC90 values for enrofloxacin were 2 and 8 μg/ml, respectively. Moreover, this study showed that 92% of recent Israeli field isolates (2009 to 2011) of M. synoviae have MICs of ≥2 μg/ml to enrofloxacin. Comparison of the quinolone resistance-determining regions (QRDRs) in M. synoviae isolates revealed a clear correlation between the presence of one of the amino acid substitutions Asp79-Asn, Thr80-Ala/Ile, Ser81-Pro, and Asp84-Asn/Tyr/His of the ParC QRDR and decreased susceptibility to enrofloxacin (MIC, ≥1 μg/ml). Amino acid substitutions at positions GyrA 87, GyrB 401/402, and ParE 420/454 were also identified, but there was no clear-cut correlation with susceptibility to enrofloxacin. Comparison of vlhA molecular profiles revealed the presence of 9 different genotypes in the Israeli M. synoviae field isolates and 10 genotypes in the European isolates; only one vlhA genotype (type 4) was identified in both cohorts. Based on results of vlhA molecular typing, several mechanisms for emergence and dissemination of Israeli enrofloxacin-resistant M. synoviae isolates are suggested. PMID:23612192

  1. Community-Acquired Methicillin-Resistant Staphylococcus aureus: Prevalence and Risk Factors

    PubMed Central

    Beam, Joel W; Buckley, Bernadette

    2006-01-01

    Reference/Citation: Salgado CD, Farr BM, Calfee DP. Community-acquired methicillin-resistant Staphylococcus aureus: a meta-analysis of prevalence and risk factors. Clin Infect Dis.20033613113912522744. Clinical Question: What are the prevalence rates and risk factors associated with community-acquired methicillin-resistant Staphylococcus aureus (MRSA)? Data Sources: Studies were identified by searching MEDLINE (January 1966–February 2002) and abstracts from scientific meetings (1996–2001). Reviews of citations and reference lists were performed to identify additional eligible studies. The search terms included Staphylococcus aureus , infection, colonization, methicillin resistance, community-acquired, community-onset, prevalence, frequency, and risk factors. Study Selection: The search was limited to English-language investigations identified from the electronic and manual searches. Studies were divided into 2 groups, as follows: group 1, retrospective or prospective studies that reported the prevalence of community-acquired MRSA (CA-MRSA) among hospital patients who were colonized (presence of bacteria without infection) or infected with MRSA; and group 2, studies that reported the prevalence of MRSA colonization in the community. The studies were evaluated independently by 2 authors, and case reports were excluded. Data Extraction: Data extraction and study quality assessment procedures were not fully explained. The outcome measures for hospital patients were definitions of CA-MRSA used in the study, prevalence of CA-MRSA, sample size, number and type of risk factors assessed, and number of patients with ≥1 health care–associated risk factor. The studies were grouped based on type, retrospective or prospective. The pooled prevalence of CA-MRSA was calculated for each group (retrospective or prospective) and was limited to the prevalence among patients with MRSA. The proportion of patients who reported ≥1 health care–associated risk factor was also

  2. Spread of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) in hospitals in Taipei, Taiwan in 2005, and comparison of its drug resistance with previous hospital-acquired MRSA.

    PubMed

    Takano, Tomomi; Saito, Kohei; Teng, Lee-Jene; Yamamoto, Tatsuo

    2007-01-01

    Panton-Valentine leucocidin (PVL)-positive methicillin-resistant Staphylococcus aureus (PVL+ MRSA) is an emerging pathogen in the community worldwide. The incidence of PVL+ MRSA in Taipei, Taiwan was 23.3% for hospital MRSA. PVL+ MRSA was isolated from both outpatients and inpatients. Some PVL+ (mecA+) strains (36.8%) showed low MIC values (resistance pattern was oxacillin and clindamycin resistance (81%). There was no multidrug resistance over three drugs, in contrast to patient PVL- MRSA with resistance to five drugs as a major resistance pattern. The majority of PVL+ MRSA belonged to multilocus sequence (ST) type 59, while PVL+ MRSA belonged to ST239, ST59 and ST5. The data suggests that although PVL+ CA-MRSA is isolated at a high incidence from hospitals in Taipei, the drug resistance is mostly selected in the community and less prominent compared with previous PVL- hospital-acquired MRSA. PMID:17579274

  3. Drug resistance in castration resistant prostate cancer: resistance mechanisms and emerging treatment strategies

    PubMed Central

    Armstrong, Cameron M; Gao, Allen C

    2015-01-01

    Several mechanisms facilitate the progression of hormone-sensitive prostate cancer to castration-resistant prostate cancer (CRPC). At present, the approved chemotherapies for CRPC include systemic drugs (docetaxel and cabazitaxel) and agents that target androgen signaling, including enzalutamide and abiraterone. While up to 30% of patients have primary resistance to these treatments, each of these drugs confers a significant survival benefit for many. Over time, however, all patients inevitably develop resistance to treatment and their disease will continue to progress. Several key mechanisms have been identified that give rise to drug resistance. Expression of constitutively active variants of the androgen receptor, such as AR-V7, intracrine androgens and overexpression of androgen synthesis enzymes like AKR1C3, and increased drug efflux through ABCB1 are just some of the many discovered mechanisms of drug resistance. Treatment strategies are being developed to target these pathways and reintroduce drug sensitivity. Niclosamide has been discovered to reduce AR-V7 activity and synergized to enzalutamide. Indomethacin has been explored to inhibit AKR1C3 activity and showed to be able to reverse resistance to enzalutamide. ABCB1 transport activity can be mitigated by the phytochemical apigenin and by antiandrogens such as bicalutamide, with each improving cellular response to chemotherapeutics. By better understanding the mechanisms by which drug resistance develops improved treatment strategies will be made possible. Herein, we review the existing knowledge of CRPC therapies and resistance mechanisms as well as methods that have been identified which may improve drug sensitivity. PMID:26309896

  4. Systemic acquired resistance in Cavendish banana induced by infection with an incompatible strain of Fusarium oxysporum f. sp. cubense.

    PubMed

    Wu, Yuanli; Yi, Ganjun; Peng, Xinxiang; Huang, Bingzhi; Liu, Ee; Zhang, Jianjun

    2013-07-15

    Fusarium wilt of banana is caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc). The fact that there are no economically viable biological, chemical, or cultural measures of controlling the disease in an infected field leads to search for alternative strategies involving activation of the plant's innate defense system. The mechanisms underlying systemic acquired resistance (SAR) are much less understood in monocots than in dicots. Since systemic protection of plants by attenuated or avirulent pathogens is a typical SAR response, the establishment of a biologically induced SAR model in banana is helpful to investigate the mechanism of SAR to Fusarium wilt. This paper described one such model using incompatible Foc race 1 to induce resistance against Foc tropical race 4 in an in vitro pathosystem. Consistent with the observation that the SAR provided the highest level of protection when the time interval between primary infection and challenge inoculation was 10d, the activities of defense-related enzymes such as phenylalanine ammonia lyase (PAL, EC 4.3.1.5), peroxidase (POD, EC 1.11.1.7), polyphenol oxidase (PPO, EC 1.14.18.1), and superoxide dismutase (SOD, EC 1.15.1.1) in systemic tissues also reached the maximum level and were 2.00-2.43 times higher than that of the corresponding controls on the tenth day. The total salicylic acid (SA) content in roots of banana plantlets increased from about 1 to more than 5 μg g⁻¹ FW after the second leaf being inoculated with Foc race 1. The systemic up-regulation of MaNPR1A and MaNPR1B was followed by the second up-regulation of PR-1 and PR-3. Although SA and jasmonic acid (JA)/ethylene (ET) signaling are mostly antagonistic, systemic expression of PR genes regulated by different signaling pathways were simultaneously up-regulated after primary infection, indicating that both pathways are involved in the activation of the SAR. PMID:23702248

  5. Antifungals: Mechanism of Action and Drug Resistance.

    PubMed

    Prasad, Rajendra; Shah, Abdul Haseeb; Rawal, Manpreet Kaur

    2016-01-01

    There are currently few antifungals in use which show efficacy against fungal diseases. These antifungals mostly target specific components of fungal plasma membrane or its biosynthetic pathways. However, more recent class of antifungals in use is echinocandins which target the fungal cell wall components. The availability of mostly fungistatic antifungals in clinical use, often led to the development of tolerance to these very drugs by the pathogenic fungal species. Thus, the development of clinical multidrug resistance (MDR) leads to higher tolerance to drugs and its emergence is helped by multiple mechanisms. MDR is indeed a multifactorial phenomenon wherein a resistant organism possesses several mechanisms which contribute to display reduced susceptibility to not only single drug in use but also show collateral resistance to several drugs. Considering the limited availability of antifungals in use and the emergence of MDR in fungal infections, there is a continuous need for the development of novel broad spectrum antifungal drugs with better efficacy. Here, we briefly present an overview of the current understanding of the antifungal drugs in use, their mechanism of action and the emerging possible novel antifungal drugs with great promise. PMID:26721281

  6. Origin and Evolution of Antibiotic Resistance: The Common Mechanisms of Emergence and Spread in Water Bodies

    PubMed Central

    Lupo, Agnese; Coyne, Sébastien; Berendonk, Thomas Ulrich

    2011-01-01

    The environment, and especially freshwater, constitutes a reactor where the evolution and the rise of new resistances occur. In water bodies such as waste water effluents, lakes, and rivers or streams, bacteria from different sources, e.g., urban, industrial, and agricultural waste, probably selected by intensive antibiotic usage, are collected and mixed with environmental species. This may cause two effects on the development of antibiotic resistances: first, the contamination of water by antibiotics or other pollutants lead to the rise of resistances due to selection processes, for instance, of strains over-expressing broad range defensive mechanisms, such as efflux pumps. Second, since environmental species are provided with intrinsic antibiotic resistance mechanisms, the mixture with allochthonous species is likely to cause genetic exchange. In this context, the role of phages and integrons for the spread of resistance mechanisms appears significant. Allochthonous species could acquire new resistances from environmental donors and introduce the newly acquired resistance mechanisms into the clinics. This is illustrated by clinically relevant resistance mechanisms, such as the fluoroquinolones resistance genes qnr. Freshwater appears to play an important role in the emergence and in the spread of antibiotic resistances, highlighting the necessity for strategies of water quality improvement. We assume that further knowledge is needed to better understand the role of the environment as reservoir of antibiotic resistances and to elucidate the link between environmental pollution by anthropogenic pressures and emergence of antibiotic resistances. Only an integrated vision of these two aspects can provide elements to assess the risk of spread of antibiotic resistances via water bodies and suggest, in this context, solutions for this urgent health issue. PMID:22303296

  7. The Viriato study: update on antimicrobial resistance of microbial pathogens responsible for community-acquired respiratory tract infections in Portugal.

    PubMed

    Melo-Cristino, José; Santos, Letícia; Silva-Costa, Catarina; Friães, Ana; Pinho, Marcos D; Ramirez, Mário

    2010-06-29

    The Viriato study is a prospective, multicentre laboratory-based surveillance study of antimicrobial susceptibility in which 30 microbiology laboratories throughout Portugal are asked to isolate, identify and submit to a central laboratory for testing Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis responsible for community-acquired lower respiratory tract infections and Streptococcus pyogenes from tonsillitis. To monitor changes in antimicrobial resistance patterns of these frequent respiratory pathogens. Susceptibility was determined by disk diffusion (Kirby-Bauer) or using Etest strips following the Clinical and Laboratory Standards Institute guidelines. From 1999 to 2007 over 13 900 isolates were analysed. Among S. pneumoniae penicillin non-susceptibility decreased from 25% in 1999 to 18% in 2007 (p = 0.002) but resistance to macrolides showed a steady increase, reaching 20% in the last 6 years. Resistance to amoxicillin and the quinolones remained stable and very low (1-2%) throughout the study period. Antimicrobial resistance among H. influenzae and M. catarrhalis remained stable. The most significant resistance was to ampicillin, of 10-12% and greater than 80%, respectively, as a result of the production of beta-lactamases. Macrolide resistance among S. pyogenes was stable during 1999-2003 (20-23%) but after 2003 there was a steady decline in resistance, which in 2007 reached 10%. The Viriato surveillance study showed that penicillin remains the most active antimicrobial agent against S. pyogenes causing tonsillitis, and amoxicillin-clavulanate and the quinolones are the most active in vitro simultaneously against S. pneumoniae, H. influenzae and M. catarrhalis responsible for community-acquired lower respiratory tract infections in Portugal. PMID:20590169

  8. Apparent Acquired Resistance by a Weevil to Its Parasitoid Is Influenced by Host Plant.

    PubMed

    Goldson, Stephen L; Tomasetto, Federico

    2016-01-01

    parasitism rates under any treatment conditions suggesting that plant architecture may not be contributing to the underlying mechanism resulting in different rates of parasitism. The evolutionary implications of what appears to be plant-mediated resistance of L. bonariensis to parasitism by M. hyperodae are discussed. PMID:27602040

  9. Apparent Acquired Resistance by a Weevil to Its Parasitoid Is Influenced by Host Plant

    PubMed Central

    Goldson, Stephen L.; Tomasetto, Federico

    2016-01-01

    on parasitism rates under any treatment conditions suggesting that plant architecture may not be contributing to the underlying mechanism resulting in different rates of parasitism. The evolutionary implications of what appears to be plant-mediated resistance of L. bonariensis to parasitism by M. hyperodae are discussed. PMID:27602040

  10. Acquired multi-azole resistance in Candida tropicalis during persistent urinary tract infection in a dog

    PubMed Central

    Álvarez-Pérez, Sergio; García, Marta E.; Cutuli, María Teresa; Fermín, María Luisa; Daza, María Ángeles; Peláez, Teresa; Blanco, José L.

    2016-01-01

    Multi-azole resistance acquisition by Candida tropicalis after prolonged antifungal therapy in a dog with urinary candidiasis is reported. Pre- and post-azole treatment isolates were clonally related and had identical silent mutations in the ERG11 gene, but the latter displayed increased azole minimum inhibitory concentrations. A novel frameshift mutation in ERG3 was found in some isolates recovered after resistance development, so it appears unlikely that this mutation is responsible for multi-azole resistance. PMID:26949597

  11. Acquired multi-azole resistance in Candida tropicalis during persistent urinary tract infection in a dog.

    PubMed

    Álvarez-Pérez, Sergio; García, Marta E; Cutuli, María Teresa; Fermín, María Luisa; Daza, María Ángeles; Peláez, Teresa; Blanco, José L

    2016-03-01

    Multi-azole resistance acquisition by Candida tropicalis after prolonged antifungal therapy in a dog with urinary candidiasis is reported. Pre- and post-azole treatment isolates were clonally related and had identical silent mutations in the ERG11 gene, but the latter displayed increased azole minimum inhibitory concentrations. A novel frameshift mutation in ERG3 was found in some isolates recovered after resistance development, so it appears unlikely that this mutation is responsible for multi-azole resistance. PMID:26949597

  12. Ligand associated ERBB2/3 activation confers acquired resistance to FGFR inhibition in FGFR3 dependent cancer cells

    PubMed Central

    Wang, Jun; Mikse, Oliver; Liao, Rachel G.; Li, Yvonne; Tan, Li; Janne, Pasi A.; Gray, Nathanael S.; Wong, Kwok-kin; Hammerman, Peter S.

    2014-01-01

    Somatic alterations of Fibroblast Growth Factor Receptors (FGFRs) have been described in a wide range of malignancies. A number of anti-FGFR therapies are currently under investigation in clinical trials for subjects with FGFR gene amplifications, mutations and translocations. Here, we develop cell line models of acquired resistance to FGFR inhibition by exposure of cell lines harboring FGFR3 gene amplification and translocation to the selective FGFR inhibitor BGJ398 and multi-targeted FGFR inhibitor ponatinib. We show that the acquisition of resistance is rapid, reversible and characterized by an epithelial to mesenchymal transition (EMT) and a switch from dependency on FGFR3 to ERBB family members. Acquired resistance was associated with demonstrable changes in gene expression including increased production of ERBB2/3 ligands which were sufficient to drive resistance in the setting of FGFR3 dependency but not dependency on other FGFR family members. These data support the concept that activation of ERBB family members is sufficient to bypass dependency on FGFR3 and suggest that concurrent inhibition of these two pathways may be desirable when targeting FGFR3 dependent cancers. PMID:24909170

  13. Ligand-associated ERBB2/3 activation confers acquired resistance to FGFR inhibition in FGFR3-dependent cancer cells.

    PubMed

    Wang, J; Mikse, O; Liao, R G; Li, Y; Tan, L; Janne, P A; Gray, N S; Wong, K-k; Hammerman, P S

    2015-04-23

    Somatic alterations of fibroblast growth factor receptors (FGFRs) have been described in a wide range of malignancies. A number of anti-FGFR therapies are currently under investigation in clinical trials for subjects with FGFR gene amplifications, mutations and translocations. Here, we develop cell line models of acquired resistance to FGFR inhibition by exposure of cell lines harboring FGFR3 gene amplification and translocation to the selective FGFR inhibitor BGJ398 and multitargeted FGFR inhibitor ponatinib. We show that the acquisition of resistance is rapid, reversible and characterized by an epithelial to mesenchymal transition and a switch from dependency on FGFR3 to ERBB family members. Acquired resistance was associated with demonstrable changes in gene expression including increased production of ERBB2/3 ligands, which were sufficient to drive resistance in the setting of FGFR3 dependency but not dependency on other FGFR family members. These data support the concept that activation of ERBB family members is sufficient to bypass dependency on FGFR3 and suggest that concurrent inhibition of these two pathways may be desirable when targeting FGFR3-dependent cancers. PMID:24909170

  14. Proteomic Signatures of Acquired Letrozole Resistance in Breast Cancer: Suppressed Estrogen Signaling and Increased Cell Motility and Invasiveness*

    PubMed Central

    Tilghman, Syreeta L.; Townley, Ian; Zhong, Qiu; Carriere, Patrick P.; Zou, Jin; Llopis, Shawn D.; Preyan, Lynez C.; Williams, Christopher C.; Skripnikova, Elena; Bratton, Melyssa R.; Zhang, Qiang; Wang, Guangdi

    2013-01-01

    Aromatase inhibitors, such as letrozole, have become the first-line treatment for postmenopausal women with estrogen-dependent breast cancer. However, acquired resistance remains a major clinical obstacle. Previous studies demonstrated constitutive activation of the MAPK signaling, overexpression of HER2, and down-regulation of aromatase and ERα in letrozole-resistant breast cancer cells. Given the complex signaling network involved in letrozole-refractory breast cancer and the lack of effective treatment for hormone resistance, further investigation of aromatase inhibitor resistance by a novel systems biology approach may reveal previously unconsidered molecular changes that could be utilized as therapeutic targets. This study was undertaken to characterize for the first time global proteomic alterations occurring in a letrozole-resistant cell line. A quantitative proteomic analysis of the whole cell lysates of LTLT-Ca (resistant) versus AC-1 cells (sensitive) was performed to identify significant protein expression changes. A total of 1743 proteins were identified and quantified, of which 411 were significantly up-regulated and 452 significantly down-regulated (p < 0.05, fold change > 1.20). Bioinformatics analysis revealed that acquired letrozole resistance is associated with a hormone-independent, more aggressive phenotype. LTLT-Ca cells exhibited 84% and 138% increase in migration and invasion compared with the control cells. The ROCK inhibitor partially abrogated the enhanced migration and invasion of the letrozole-resistant cells. Flow cytometric analyses also demonstrated an increase in vimentin and twist expression in letrozole-resistance cells, suggesting an onset of epithelial to mesenchymal transition (EMT). Moreover, targeted gene expression arrays confirmed a 28-fold and sixfold up-regulation of EGFR and HER2, respectively, whereas ERα and pS2 were dramatically reduced by 28-fold and 1100-fold, respectively. Taken together, our study revealed global

  15. Role of OXA-23 and AdeABC efflux pump for acquiring carbapenem resistance in an Acinetobacter baumannii strain carrying the blaOXA-66 gene.

    PubMed

    Lee, Yangsoon; Yum, Jong Hwa; Kim, Chang-Ki; Yong, Dongeun; Jeon, Eun Hee; Jeong, Seok Hoon; Ahn, Jee Young; Lee, Kyungwon

    2010-01-01

    This study was performed to determine the mechanisms for acquiring carbapenem resistance in six clinical isolates of Acinetobacter baumannii. All isolates showed similar SmaI-macrorestriction patterns with less than 3 band differences by PFGE. The isolates showed a high level resistance (>32 mg/L) to both imipenem and meropenem by Etest. Phe-Arg-beta-naphthylamide lowered the MICs of carbapenems. Real-time PCR experiments showed that expression levels of the adeB gene in the six A. baumannii isolates were 10- to 40-times higher than those of imipenem-susceptible strains. Direct sequencing of PCR products showed that all isolates carried the bla(OXA-23) gene, which was preceded by ISAba1. The bla(OXA-23) probe hybridized with approximately 500-kb I-CeuI chromosomal fragments, but not with a plasmid. These findings suggest that overexpression of the AdeABC efflux pump as well as chromosome-borne OXA-23 may play a role in acquiring carbapenem resistance in our A. baumannii isolates. PMID:20124329

  16. Multiple transport systems mediate virus-induced acquired resistance to oxidative stress

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this paper, we report the phenomenon of acquired cross-tolerance to oxidative (UV-C and H2O2) stress in Nicotiana benthamiana plants infected with Potato virus X (PVX) and investigate the functional expression of transport systems in mediating this phenomenon. By combining multiple approaches, we...

  17. Community-acquired pneumonia caused by carbapenem-resistant Streptococcus pneumoniae: re-examining its prevention and treatment

    PubMed Central

    Doi, Asako; Iwata, Kentaro; Takegawa, Hiroshi; Miki, Kanji; Sono, Yumi; Nishioka, Hiroaki; Takeshita, Jumpei; Tomii, Keisuke; Haruta, Tsunekazu

    2014-01-01

    A 73-year-old man with no significant past medical history or any history of health care visits was hospitalized for pneumonia. Sputum culture revealed multidrug-resistant Streptococcus pneumoniae, even to carbapenems. The patient was later treated successfully with levofloxacin. Throat cultures from his two grandchildren revealed S. pneumoniae with the same susceptibility pattern. Analysis for resistant genes revealed gPRSP (pbp1a + pbp2x + pbp2b gene variants) in both the patient and his grandchildren, none of whom had received pneumococcal vaccines of any kind. This case illustrates the importance of the emergence of carbapenem-resistant S. pneumoniae. Non-rational use of carbapenems for community-acquired infections may be counterproductive. This case also highlights the importance of pneumococcal vaccinations in children and the elderly. PMID:24899822

  18. [3rd generation's TKI in lung cancer non-small cell EGFR-mutated having acquired a secondary T790M resistance].

    PubMed

    Brosseau, Solenn; Viala, Marie; Varga, Andréa; Planchard, David; Besse, Benjamin; Soria, Jean-Charles

    2015-09-01

    Activating EGFR mutations discovery and efficacy of 1st generation tyrosine kinase inhibitors (TKI), such as erlotinib or gefitinib, inaugurated the beginning of personalized medicine in the treatment of EGFR-mutated non-small cell lung cancer (NSCLC). However, all patients showed a tumor progression of 10 to 16 months after the onset of TKI therapy related to molecular resistance mechanisms as T790M mutation. Till now, patients suffering from EGFR-mutated NSCLC with acquired resistance have conventional treatment options. Two new 3rd generations' TKI, AZD9291 and rociletinib, are currently being studied in phases 1-3 studies. Preliminary results show relevant therapeutic properties in patients with T790M mutated-EGFR NSCLC. This review aims to highlight these new molecules, their effectiveness and their clinical toxicities in the treatment of advanced stages of NSCLC expressing the T790M mutation. PMID:26235419

  19. Reciprocal positive regulation between Cx26 and PI3K/Akt pathway confers acquired gefitinib resistance in NSCLC cells via GJIC-independent induction of EMT

    PubMed Central

    Yang, J; Qin, G; Luo, M; Chen, J; Zhang, Q; Li, L; Pan, L; Qin, S

    2015-01-01

    Gefitinib efficiency in non-small-cell lung cancer (NSCLC) therapy is limited due to development of drug resistance. The molecular mechanisms of gefitinib resistance remain still unclear. In this study, we first found that connexin 26 (Cx26) is the predominant Cx isoform expressed in various NSCLC cell lines. Then, two gefitinib-resistant (GR) NSCLC cell lines, HCC827 GR and PC9 GR, from their parental cells were established. In these GR cells, the results showed that gefitinib resistance correlated with changes in cellular EMT phenotypes and upregulation of Cx26. Cx26 was detected to be accumulated in the cytoplasm and failed to establish functional gap-junctional intercellular communication (GJIC) either in GR cells or their parental cells. Ectopic expression of GJIC-deficient chimeric Cx26 was sufficient to induce EMT and gefitinib insensitivity in HCC827 and PC9 cells, while knockdown of Cx26 reversed EMT and gefitinib resistance in their GR cells both in vitro and in vivo. Furthermore, Cx26 overexpression could activate PI3K/Akt signaling in these cells. Cx26-mediated EMT and gefitinib resistance were significantly blocked by inhibition of PI3K/Akt pathway. Specifically, inhibition of the constitutive activation of PI3K/Akt pathway substantially suppressed Cx26 expression, and Cx26 was confirmed to functionally interplay with PI3K/Akt signaling to promote EMT and gefitinib resistance in NSCLC cells. In conclusion, the reciprocal positive regulation between Cx26 and PI3K/Akt signaling contributes to acquired gefitinib resistance in NSCLC cells by promoting EMT via a GJIC-independent manner. PMID:26203858

  20. Influence of Infection of Cotton by Rotylenchulus Reniformis and Meloidogyne Incognita on the Production of Enzymes Involved in Systemic Acquired Resistance

    PubMed Central

    Aryal, Sudarshan K.; Davis, Richard F.; Stevenson, Katherine L.; Timper, Patricia; Ji, Pingsheng

    2011-01-01

    Systemic acquired resistance (SAR), which results in enhanced defense mechanisms in plants, can be elicited by virulent and avirulent strains of pathogens including nematodes. Recent studies of nematode reproduction strongly suggest that Meloidogyne incognita and Rotylenchulus reniformis induce SAR in cotton, but biochemical evidence of SAR was lacking. Our objective was to determine whether infection of cotton by M. incognita and R. reniformis increases the levels of P-peroxidase, G-peroxidase, and catalase enzymes which are involved in induced resistance. A series of greenhouse trials was conducted; each trial included six replications of four treatments applied to one of three cotton genotypes in a randomized complete block design. The four treatments were cotton plants inoculated with i) R. reniformis, ii) M. incognita, iii) BTH (Actigard), and iv) a nontreated control. Experiments were conducted on cotton genotypes DP 0935 B2RF (susceptible to both nematodes), LONREN-1 (resistant to R. reniformis), and M-120 RNR (resistant to M. incognita), and the level of P-peroxidase, G-peroxidase, and catalase activity was measured before and 2, 4, 6, 10, and 14 d after treatment application. In all cotton genotypes, activities of all three enzymes were higher (P ≤ 0.05) in leaves of plants infected with M. incognita and R. reniformis than in the leaves of control plants, except that M. incognita did not increase catalase activity on LONREN-1. Increased enzyme activity was usually apparent 6 d after treatment. This study documents that infection of cotton by M. incognita or R. reniformis increases the activity of the enzymes involved in systemic acquired resistance; thereby providing biochemical evidence to substantiate previous reports of nematode-induced SAR in cotton. PMID:23431029

  1. The Systemic Acquired Resistance Regulator OsNPR1 Attenuates Growth by Repressing Auxin Signaling through Promoting IAA-Amido Synthase Expression.

    PubMed

    Li, Xiaozun; Yang, Dong-Lei; Sun, Li; Li, Qun; Mao, Bizeng; He, Zuhua

    2016-09-01

    Systemic acquired resistance is a long-lasting and broad-spectrum disease resistance to pathogens. Our previous study demonstrated that overexpression of NONEXPRESSOR OF PATHOGENESIS-RELATED GENES1 (OsNPR1), a master gene for systemic acquired resistance in rice (Oryza sativa), greatly enhanced resistance to bacterial blight caused by Xanthomonas oryzae pv oryzae However, the growth and development of the OsNPR1 overexpression (OsNPR1-OX) plants were restrained, and the mechanism remained elusive. In this study, we dissected the OsNPR1-induced growth inhibition. We found that the OsNPR1-OX lines displayed phenotypes mimicking auxin-defective mutants, with decreases in root system, seed number and weight, internode elongation, and tiller number. Whole-genome expression analysis revealed that genes related to the auxin metabolism and signaling pathway were differentially expressed between the OsNPR1-OX and wild-type plants. Consistently, the indole-3-acetic acid (IAA) content was decreased and the auxin distribution pattern was altered in OsNPR1-OX plants. Importantly, we found that some GH3 family members, in particular OsGH3.8 coding IAA-amido synthetase, were constitutively up-regulated in OsNPR1-OX plants. Decreased OsGH3.8 expression by RNA interference could partially restore IAA level and largely rescue the restrained growth and development phenotypes but did not affect the disease resistance of OsNPR1-OX plants. Taken together, we revealed that OsNPR1 affects rice growth and development by disrupting the auxin pathway at least partially through indirectly up-regulating OsGH3.8 expression. PMID:27378815

  2. Recall of acquired cellular resistance in mice by antigens from killed Brucella.

    PubMed

    Halliburton, B L; Hinsdill, R D

    1972-01-01

    Mice infected with Brucella abortus 19 were challenged intravenously with Listeria monocytogenes. Spleen assays to determine the number of viable Listeria cells present revealed that these mice were highly resistant to Listeria when challenged on day 17 of the Brucella infection. Resistance was absent in mice challenged on the 5th day and was declining in mice challenged on the 33rd day. Resistance could not be detected by day 49 of the Brucella infection but could be recalled by the injection of antigens from smooth B. abortus 2308. Thus, extracted antigens appeared to be as effective in recall as the live cells used in earlier studies. Similar injections of extracts from rough B. abortus 45/20, or from B. ovis REO 198, were also effective in recalling resistance; this suggests that the smooth surface agglutinogen may be relatively unimportant in recall. PMID:4632467

  3. Interplay between intrinsic and acquired resistance to quinolones in Stenotrophomonas maltophilia.

    PubMed

    García-León, Guillermo; Salgado, Fabiola; Oliveros, Juan Carlos; Sánchez, María Blanca; Martínez, José Luis

    2014-05-01

    To analyse whether the mutation-driven resistance-acquisition potential of a given bacterium might be a function of its intrinsic resistome, quinolones were used as selective agents and Stenotrophomonas maltophilia was chosen as a bacterial model. S. maltophilia has two elements - SmQnr and SmeDEF - that are important in intrinsic resistance to quinolones. Using a battery of mutants in which either or both of these elements had been removed, the apparent mutation frequency for quinolone resistance and the phenotype of the selected mutants were found to be related to the intrinsic resistome and also depended on the concentration of the selector. Most mutants had phenotypes compatible with the overexpression of multidrug efflux pump(s); SmeDEF overexpression was the most common cause of quinolone resistance. Whole genome sequencing showed that mutations of the SmeRv regulator, which result in the overexpression of the efflux pump SmeVWX, are the cause of quinolone resistance in mutants not overexpressing SmeDEF. These results indicate that the development of mutation-driven antibiotic resistance is highly dependent on the intrinsic resistome, which, at least for synthetic antibiotics such as quinolones, did not develop as a response to the presence of antibiotics in the natural ecosystems in which S. maltophilia evolved. PMID:24447641

  4. RACK1 overexpression is linked to acquired imatinib resistance in gastrointestinal stromal tumor

    PubMed Central

    Gao, Xiaodong; Xue, Anwei; Fang, Yong; Shu, Ping; Ling, Jiaqian; Hou, Yingyong; Shen, Kuntang; Qin, Jing; Sun, Yihong; Qin, Xinyu

    2016-01-01

    Although treatment with imatinib, which inhibits KIT and PDGFR, controls advanced disease in about 80% of gastrointestinal stromal tumor (GIST) patients, resistance to imatinib often develops. RACK1 (Receptor for Activated C Kinase 1) is a ribosomal protein that contributes to tumor progression by affecting proliferation, apoptosis, angiogenesis, and migration. Here, we found that c-KIT binds to RACK1 and increases proteasome-mediated RACK1 degradation. Imatinib treatment inhibits c-KIT activity and prevents RACK1 degradation, and RACK1 is upregulated in imatinib-resistant GIST cells compared to non-resistant parental cells. Moreover, Erk and Akt signaling were reactivated by imatinib in resistant GIST cells. RACK1 functioned as a scaffold protein and mediated Erk and Akt reactivation after imatinib treatment, thereby promoting GIST cell survival even in the presence of imatinib. Combined inhibition of KIT and RACK1 inhibited growth in imatinib-resistant GIST cell lines and reduced tumor relapse in GIST xenografts. These findings provide new insight into the role of RACK1 in imatinib resistance in GIST. PMID:26893362

  5. Combine therapy of gefitinib and fulvestrant enhances antitumor effects on NSCLC cell lines with acquired resistance to gefitinib.

    PubMed

    Xu, Ruitong; Shen, Hua; Guo, Renhua; Sun, Jing; Gao, Wen; Shu, Yongqian

    2012-07-01

    Gefitinib, an EGFR receptor tyrosine kinase inhibitor, is approved for clinical use in the treatment of non-small cell lung cancer (NSCLC), but the emergence of mutations resistant to these inhibitors, such as T790M, has become a clinical problem. According to statistics, female patients, the presence of adenocarcinoma or non-smokers experienced a higher response rate. This may be involved in interaction between the estrogen receptor (ER) and the epidermal growth factor receptor (EGFR). To test whether inhibition of the ER signaling pathway affects the antitumor effect of gefitinib, gefitinib and an ER antagonist, fulvestrant, were administered to NSCLC cell lines with acquired resistance to gefitinib. Compared with treatment of either fulvestrant or gefitinib alone, drug combination obviously decreased proliferation of H1976, H1650 and PC-9 cells coming from adenocarcinoma. Rapid activations of EGFR pathway by E2β were observed in H1975 cells with T790M mutation. Additionally, EGFR and ERs expression were down-regulated respectively in response to estrogen and EGF but up-regulated in response to fulvestrant and gefitinib in vitro. These results suggest that there is a functional cross-signaling between the EGFR/ER pathways in NSCLC with acquired resistance to gefitinib, possibly providing rationale for combining gefitinib with anti-estrogen therapy for advanced NSCLC treatment. PMID:22560634

  6. Candidate DNA methylation drivers of acquired cisplatin resistance in ovarian cancer identified by methylome and expression profiling.

    PubMed

    Zeller, C; Dai, W; Steele, N L; Siddiq, A; Walley, A J; Wilhelm-Benartzi, C S M; Rizzo, S; van der Zee, A; Plumb, J A; Brown, R

    2012-10-18

    Multiple DNA methylation changes in the cancer methylome are associated with the acquisition of drug resistance; however it remains uncertain how many represent critical DNA methylation drivers of chemoresistance. Using isogenic, cisplatin-sensitive/resistant ovarian cancer cell lines and inducing resensitizaton with demethylating agents, we aimed to identify consistent methylation and expression changes associated with chemoresistance. Using genome-wide DNA methylation profiling across 27 578 CpG sites, we identified loci at 4092 genes becoming hypermethylated in chemoresistant A2780/cp70 compared with the parental-sensitive A2780 cell line. Hypermethylation at gene promoter regions is often associated with transcriptional silencing; however, expression of only 245 of these hypermethylated genes becomes downregulated in A2780/cp70 as measured by microarray expression profiling. Treatment of A2780/cp70 with the demethylating agent 2-deoxy-5'-azacytidine induces resensitization to cisplatin and re-expression of 41 of the downregulated genes. A total of 13/41 genes were consistently hypermethylated in further independent cisplatin-resistant A2780 cell derivatives. CpG sites at 9 of the 13 genes (ARHGDIB, ARMCX2, COL1A, FLNA, FLNC, MEST, MLH1, NTS and PSMB9) acquired methylation in ovarian tumours at relapse following chemotherapy or chemoresistant cell lines derived at the time of patient relapse. Furthermore, 5/13 genes (ARMCX2, COL1A1, MDK, MEST and MLH1) acquired methylation in drug-resistant ovarian cancer-sustaining (side population) cells. MLH1 has a direct role in conferring cisplatin sensitivity when reintroduced into cells in vitro. This combined genomics approach has identified further potential key drivers of chemoresistance whose expression is silenced by DNA methylation that should be further evaluated as clinical biomarkers of drug resistance. PMID:22249249

  7. Emergence of Multidrug-Resistant Campylobacter Species Isolates with a Horizontally Acquired rRNA Methylase

    PubMed Central

    Wang, Yang; Zhang, Maojun; Deng, Fengru; Shen, Zhangqi; Wu, Congming; Zhang, Jianzhong

    2014-01-01

    Antibiotic-resistant Campylobacter constitutes a serious threat to public health, and resistance to macrolides is of particular concern, as this class of antibiotics is the drug of choice for clinical therapy of campylobacteriosis. Very recently, a horizontally transferrable macrolide resistance mediated by the rRNA methylase gene erm(B) was reported in a Campylobacter coli isolate, but little is known about the dissemination of erm(B) among Campylobacter isolates and the association of erm(B)-carrying isolates with clinical disease. To address this question and facilitate the control of antibiotic-resistant Campylobacter, we determined the distribution of erm(B) in 1,554 C. coli and Campylobacter jejuni isolates derived from food-producing animals and clinically confirmed human diarrheal cases. The results revealed that 58 of the examined isolates harbored erm(B) and exhibited high-level resistance to macrolides, and most were recent isolates, derived in 2011-2012. In addition, the erm(B)-positive isolates were all resistant to fluoroquinolones, another clinically important antibiotic used for treating campylobacteriosis. The erm(B) gene is found to be associated with chromosomal multidrug resistance genomic islands (MDRGIs) of Gram-positive origin or with plasmids of various sizes. All MDRGIs were transferrable to macrolide-susceptible C. jejuni by natural transformation under laboratory conditions. Molecular typing of the erm(B)-carrying isolates by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) identified diverse genotypes and outbreak-associated diarrheal isolates. Molecular typing also suggested zoonotic transmission of erm(B)-positive Campylobacter. These findings reveal an emerging and alarming trend of dissemination of erm(B) and MDRGIs in Campylobacter and underscore the need for heightened efforts to control their further spread. PMID:24982085

  8. Quinolone resistant Aeromonas spp. as carriers and potential tracers of acquired antibiotic resistance in hospital and municipal wastewater.

    PubMed

    Varela, Ana Rita; Nunes, Olga C; Manaia, Célia M

    2016-01-15

    Members of the genus Aeromonas are recognized carriers of antibiotic resistance in aquatic environments. However, their importance on the spread of resistance from hospital effluents to the environment is poorly understood. Quinolone resistant Aeromonas spp. (n = 112) isolated from hospital effluent (HE) and from raw (RWW) and treated wastewater (TWW) of the receiving urban wastewater treatment plant (UWTP) were characterized. Species identification and genetic intraspecies diversity were assessed based on the 16S rRNA, cpn60 and gyrB genes sequence analysis. The antibiotic resistance phenotypes and genotypes (qnrA, qnrB, qnrC, qnrD, qnrS, qnrVC; qepA; oqxAB; aac(6′)-Ib-cr; blaOXA; incU) were analyzed in function of the origin and taxonomic group. Most isolates belonged to the species Aeromonas caviae and Aeromonas hydrophila (50% and 41%, respectively). The quinolone and the beta-lactamase resistance genes aac(6′)-Ib-cr and blaOXA, including gene blaOXA-101, identified for the first time in Aeromonas spp., were detected in 58% and 56% of the isolates, respectively, with identical prevalence in HE and UWTP wastewater. In contrast, the gene qnrS2 was observed mainly in isolates from the UWTP (51%) and rarely in HE isolates (3%), suggesting that its origin is not the clinical setting. Bacterial groups and genes that allow the identification of major routes of antibiotic resistance dissemination are valuable tools to control this problem. In this study, it was concluded that members of the genus Aeromonas harboring the genes aac(6′)-Ib-cr and blaOXA are relevant tracers of antibiotic resistance dissemination in wastewater habitats, while those yielding the gene qnrS2 allow the traceability from non-clinical sources. PMID:26546762

  9. Continuous administration of bevacizumab plus capecitabine, even after acquired resistance to bevacizumab, restored anti-angiogenic and antitumor effect in a human colorectal cancer xenograft model.

    PubMed

    Iwai, Toshiki; Sugimoto, MasamichI; Harada, Suguru; Yorozu, Keigo; Kurasawa, Mitsue; Yamamoto, Kaname

    2016-08-01

    Vascular endothelial growth factor (VEGF)-neutralizing therapy with bevacizumab has become increasingly important for treating colorectal cancer. It was demonstrated that second-line chemotherapy together with bevacizumab after disease progression (PD) on first-line therapy including bevacizumab showed clinical benefits in metastatic colorectal and breast cancers (ML18147 trial, TANIA trial). One of the rationales for these trials was that the refractoriness to first-line therapy is caused by resistance to not so much bevacizumab as to the chemotherapeutic agents. Nevertheless, resistance to bevacizumab cannot be ruled out because VEGF-independent angiogenesis has been reported to be a mechanism of resistance to anti-VEGF therapy. In this study, we used a xenograft model with the human colon cancer HT-29 cells to investigate the mechanisms underlying the effect of continued administration of bevacizumab plus capecitabine even after resistance to bevacizumab was acquired. The combination of capecitabine plus bevacizumab exhibited significantly stronger antitumor and anti-angiogenic activities than did monotherapy with either agent. Capecitabine treatment significantly increased the intratumoral VEGF level compared with the control group; however, the combination with bevacizumab neutralized the VEGF. Among angiogenic factors other than VEGF, intratumoral galectin-3, which reportedly promotes angiogenesis both dependent on, and independently of VEGF, was significantly decreased in the capecitabine group and the combination group compared with the control group. In an in vitro experiment, 5-fluorouracil (5-FU), an active metabolite of capecitabine, inhibited galectin-3 production by HT-29 cells. These results suggested that capecitabine has a dual mode of action: namely, inhibition of tumor cell growth and inhibition of galectin-3 production by tumor cells. Thus, capecitabine and bevacizumab may work in a mutually complementary manner in tumor angiogenesis inhibition

  10. Continuous administration of bevacizumab plus capecitabine, even after acquired resistance to bevacizumab, restored anti-angiogenic and antitumor effect in a human colorectal cancer xenograft model

    PubMed Central

    Iwai, Toshiki; Sugimoto, Masamichi; Harada, Suguru; Yorozu, Keigo; Kurasawa, Mitsue; Yamamoto, Kaname

    2016-01-01

    Vascular endothelial growth factor (VEGF)-neutralizing therapy with bevacizumab has become increasingly important for treating colorectal cancer. It was demonstrated that second-line chemotherapy together with bevacizumab after disease progression (PD) on first-line therapy including bevacizumab showed clinical benefits in metastatic colorectal and breast cancers (ML18147 trial, TANIA trial). One of the rationales for these trials was that the refractoriness to first-line therapy is caused by resistance to not so much bevacizumab as to the chemotherapeutic agents. Nevertheless, resistance to bevacizumab cannot be ruled out because VEGF-independent angiogenesis has been reported to be a mechanism of resistance to anti-VEGF therapy. In this study, we used a xenograft model with the human colon cancer HT-29 cells to investigate the mechanisms underlying the effect of continued administration of bevacizumab plus capecitabine even after resistance to bevacizumab was acquired. The combination of capecitabine plus bevacizumab exhibited significantly stronger antitumor and anti-angiogenic activities than did monotherapy with either agent. Capecitabine treatment significantly increased the intratumoral VEGF level compared with the control group; however, the combination with bevacizumab neutralized the VEGF. Among angiogenic factors other than VEGF, intratumoral galectin-3, which reportedly promotes angiogenesis both dependent on, and independently of VEGF, was significantly decreased in the capecitabine group and the combination group compared with the control group. In an in vitro experiment, 5-fluorouracil (5-FU), an active metabolite of capecitabine, inhibited galectin-3 production by HT-29 cells. These results suggested that capecitabine has a dual mode of action: namely, inhibition of tumor cell growth and inhibition of galectin-3 production by tumor cells. Thus, capecitabine and bevacizumab may work in a mutually complementary manner in tumor angiogenesis inhibition

  11. The tumor microenvironment underlies acquired resistance to CSF-1R inhibition in gliomas.

    PubMed

    Quail, Daniela F; Bowman, Robert L; Akkari, Leila; Quick, Marsha L; Schuhmacher, Alberto J; Huse, Jason T; Holland, Eric C; Sutton, James C; Joyce, Johanna A

    2016-05-20

    Macrophages accumulate with glioblastoma multiforme (GBM) progression and can be targeted via inhibition of colony-stimulating factor-1 receptor (CSF-1R) to regress high-grade tumors in animal models of this cancer. However, whether and how resistance emerges in response to sustained CSF-1R blockade is unknown. We show that although overall survival is significantly prolonged, tumors recur in >50% of mice. Gliomas reestablish sensitivity to CSF-1R inhibition upon transplantation, indicating that resistance is tumor microenvironment-driven. Phosphatidylinositol 3-kinase (PI3K) pathway activity was elevated in recurrent GBM, driven by macrophage-derived insulin-like growth factor-1 (IGF-1) and tumor cell IGF-1 receptor (IGF-1R). Combining IGF-1R or PI3K blockade with CSF-1R inhibition in recurrent tumors significantly prolonged overall survival. Our findings thus reveal a potential therapeutic approach for treating resistance to CSF-1R inhibitors. PMID:27199435

  12. Distinct mechanisms account for acquired von Willebrand syndrome in plasma cell dyscrasias.

    PubMed

    Dicke, Christina; Schneppenheim, Sonja; Holstein, Katharina; Spath, Brigitte; Bokemeyer, Carsten; Dittmer, Rita; Budde, Ulrich; Langer, Florian

    2016-05-01

    Acquired von Willebrand syndrome (AVWS) is a rare bleeding disorder that may cause life-threatening hemorrhages in patients with plasma cell dyscrasias (PCDs). Early diagnosis and treatment require a thorough understanding of its underlying pathophysiology. Two patients with IgG MGUS presented with dramatically decreased plasma von Willebrand factor (VWF) and a severe type-1 pattern on multimer analysis. A prompt response to intravenous immunoglobulins (IVIG), but not to VWF/FVIII, was consistent with accelerated immunologic clearance of plasma VWF. Another IgG MGUS patient showed a type-2 pattern and a less pronounced response to IVIG, suggesting that additional mechanism(s) contributed to AVWS evolution. In a patient with Waldenström's macroglobulinemia and severe depletion of plasma VWF, multimer analysis indicated association of the IgM paraprotein with VWF before, but not after plasmapheresis, resulting in destruction of the agarose gel and a characteristically distorted band structure of VWF multimers. A type-2 pattern with highly abnormal VWF triplets and laboratory evidence of excessive fibrinolytic activity suggested that plasmin-mediated VWF degradation contributed to AVWS in a patient with multiple myeloma (MM) and AL amyloidosis. Finally, in a patient with IgG MM, maximally prolonged PFA-100® closure times and a specific defect in ristocetin-induced platelet agglutination, both of which resolved after remission induction, indicated interference of the paraprotein with VWF binding to platelet GPIb. Importantly, in none of the six patients, circulating autoantibodies to VWF were detected by a specific in-house ELISA. In summary, when evaluating PCD patients with severe bleeding symptoms, AVWS due to various pathogenic mechanisms should be considered. PMID:27040683

  13. Analysis and modeling of resistive switching mechanisms oriented to resistive random-access memory

    NASA Astrophysics Data System (ADS)

    Huang, Da; Wu, Jun-Jie; Tang, Yu-Hua

    2013-03-01

    With the progress of the semiconductor industry, the resistive random-access memory (RAM) has drawn increasing attention. The discovery of the memristor has brought much attention to this study. Research has focused on the resistive switching characteristics of different materials and the analysis of resistive switching mechanisms. We discuss the resistive switching mechanisms of different materials in this paper and analyze the differences of those mechanisms from the view point of circuitry to establish their respective circuit models. Finally, simulations are presented. We give the prospect of using different materials in resistive RAM on account of their resistive switching mechanisms, which are applied to explain their resistive switchings.

  14. Defense Responses in Infected and Elicited Cucumber (Cucumis sativus L.) Hypocotyl Segments Exhibiting Acquired Resistance.

    PubMed Central

    Siegrist, J.; Jeblick, W.; Kauss, H.

    1994-01-01

    Segments from dark-grown cucumber (Cucumis sativus L.) hypocotyls were used to study defense reactions occurring upon fungal infection and induced by elicitors in the same tissue. The segments were rendered resistant to infection by Colletotrichum lagenarium either by growing the seedlings in the presence of dichloroisonicotinic acid (DCIA) or by preincubation of the cut segments with DCIA, salicylic acid (SA), or 5-chlorosalicylic acid (5CSA). This resistance appears to be due mainly to inhibition of fungal penetration into epidermal cells. In the resistant hypocotyl segments, the fungus induced, at the time of attempted penetration, an increased deposition of phenolics, which were visualized by autofluorescence. These phenolics were located mainly in the epidermal cell wall around and in the emerging papillae below appressoria and were quantified either as lignin-like polymers by the thioglycolic acid method or as 4-OH-benzaldehyde, 4-OH-benzoic, or 4-coumaric acid liberated upon treatment with alkali at room temperature. Pretreatment with DCIA, SA, and 5CSA induced little chitinase activity, but this activity greatly increased in resistant tissues upon subsequent infection. These observations indicate that resistance is associated with an improved perception of the pathogen stimulus resulting in the enhanced induction of diverse defense reactions. When the cut segments were pretreated with DCIA, SA, or 5CSA and then split and incubated with chitosan fragments, the deposition of cell wall phenolics was also enhanced. These pretreated and split segments also exhibited an increase in the rapid production of activated oxygen species induced by an elicitor preparation from Phytophthora megasperma f. sp. Glya. Pretreatment of the segments with methyl jasmonate neither induced resistance nor enhanced induction of cell wall phenolics upon fungal infection, although we observed in the corresponding split segments some increase in chitosan-induced cell wall phenolics and

  15. Defense Responses in Infected and Elicited Cucumber (Cucumis sativus L.) Hypocotyl Segments Exhibiting Acquired Resistance.

    PubMed

    Siegrist, J.; Jeblick, W.; Kauss, H.

    1994-08-01

    Segments from dark-grown cucumber (Cucumis sativus L.) hypocotyls were used to study defense reactions occurring upon fungal infection and induced by elicitors in the same tissue. The segments were rendered resistant to infection by Colletotrichum lagenarium either by growing the seedlings in the presence of dichloroisonicotinic acid (DCIA) or by preincubation of the cut segments with DCIA, salicylic acid (SA), or 5-chlorosalicylic acid (5CSA). This resistance appears to be due mainly to inhibition of fungal penetration into epidermal cells. In the resistant hypocotyl segments, the fungus induced, at the time of attempted penetration, an increased deposition of phenolics, which were visualized by autofluorescence. These phenolics were located mainly in the epidermal cell wall around and in the emerging papillae below appressoria and were quantified either as lignin-like polymers by the thioglycolic acid method or as 4-OH-benzaldehyde, 4-OH-benzoic, or 4-coumaric acid liberated upon treatment with alkali at room temperature. Pretreatment with DCIA, SA, and 5CSA induced little chitinase activity, but this activity greatly increased in resistant tissues upon subsequent infection. These observations indicate that resistance is associated with an improved perception of the pathogen stimulus resulting in the enhanced induction of diverse defense reactions. When the cut segments were pretreated with DCIA, SA, or 5CSA and then split and incubated with chitosan fragments, the deposition of cell wall phenolics was also enhanced. These pretreated and split segments also exhibited an increase in the rapid production of activated oxygen species induced by an elicitor preparation from Phytophthora megasperma f. sp. Glya. Pretreatment of the segments with methyl jasmonate neither induced resistance nor enhanced induction of cell wall phenolics upon fungal infection, although we observed in the corresponding split segments some increase in chitosan-induced cell wall phenolics and

  16. The multixenobiotic resistance mechanism in aquatic organisms

    SciTech Connect

    Kurelec, B. )

    1992-01-01

    Many aquatic organisms thrive and reproduce in polluted waters. This fact indicates that they are well equipped with a defense system(s) against several toxic xenobiotics simultaneously because water pollution is typically caused by a mixture of a number of pollutants. We have found that the biochemical mechanism underlying such multixenobiotic' resistance in freshwater and marine mussel, in several marine sponges, and in freshwater fish is similar to the mechanism of multidrug resistance (MDR) found in tumor cells that became refractory to treatment with a variety of chemotherapeutic agents. All these organisms possess a verapamil-sensitive potential to bind 2-acetylaminofluorene and vincristine onto membrane vesicles. They all express mRNA for mdr1 gene, and mdr1 protein product, the glycoprotein P170. Finally, in in vivo experiments, the accumulation of xenobiotics is enhanced in all investigated organisms in the presence of verapamil, the inhibitor of the P170 extrusion pump. The knowledge that the presence of one xenobiotic may block the pumping out, and hence accelerating accumulation, of others, may help us to understand and interpret our present and past data on different environmental parameters obtained using indicator organisms.99 references.

  17. Antimicrobial activity of tigecycline against community-acquired methicillin-resistant Staphylococcus aureus isolates recovered from North American medical centers.

    PubMed

    Mendes, Rodrigo E; Sader, Helio S; Deshpande, Lalitagauri; Jones, Ronald N

    2008-04-01

    A total of 1989 community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) were susceptibility tested by broth microdilution. Pulsed-field gel electrophoresis, SCCmec type, and polymerase chain reaction for Panton-Valentine leukocidin (PVL) genes were also performed. The overall tigecycline susceptibility rate was 98.2%. Glycopeptides, quinupristin/dalfopristin, linezolid, and chloramphenicol were also active against this collection (< or =0.7% resistant). The vast majority (70.8%) of the CA-MRSA was SCCmec type IV, from which 88.4% belonged to the USA300-0114 clone and 94.7% were PVL positive. Tigecycline showed in vitro activity comparable with other highly active parenteral agents and represents an option for treating complicated infections caused by CA-MRSA. PMID:18068326

  18. Preclinical evidence of multiple mechanisms underlying trastuzumab resistance in gastric cancer

    PubMed Central

    Arienti, Chiara; Zanoni, Michele; Pignatta, Sara; Del Rio, Alberto; Carloni, Silvia; Tebaldi, Michela; Tedaldi, Gianluca; Tesei, Anna

    2016-01-01

    HER2-positive advanced gastric cancer patients frequently develop resistance to trastuzumab through mechanisms still poorly understood. In breast cancer, other members of the HER-family are known to be involved in trastuzumab-resistance, as is overexpression of the scaffold protein IQGAP1. In the present work, we investigated acquired resistance to trastuzumab in gastric cancer experimental models. Trastuzumab-resistant (HR) subclones derived from 3 HER2-overexpressing gastric cancer cells were generated and characterized for alterations in HER2-signaling mechanisms by next-generation sequencing, immunohistochemical, western blot and qRT-PCR techniques, and molecular modeling analysis. All subclones showed a reduced growth rate with respect to parental cell lines but each had a different resistance mechanism. In NCI N87 HR cells, characterized by a marked increase in HER2-signaling pathways with respect to the parental cell line, trastuzumab sensitivity was restored when IQGAP1 expression was silenced. AKG HR subclone showed higher HER3 protein expression than the parental line. High nuclear HER4 levels were observed in KKP HR cells. In conclusion, our study revealed that high IQGAP1 expression leads to resistance to trastuzumab in gastric cancer. Furthermore, 2 new mutations of the HER2 gene that may be involved in acquired resistance were identified in AKG HR and KKP HR subclones. PMID:26919099

  19. Preclinical evidence of multiple mechanisms underlying trastuzumab resistance in gastric cancer.

    PubMed

    Arienti, Chiara; Zanoni, Michele; Pignatta, Sara; Del Rio, Alberto; Carloni, Silvia; Tebaldi, Michela; Tedaldi, Gianluca; Tesei, Anna

    2016-04-01

    HER2-positive advanced gastric cancer patients frequently develop resistance to trastuzumab through mechanisms still poorly understood. In breast cancer, other members of the HER-family are known to be involved in trastuzumab-resistance, as is overexpression of the scaffold protein IQGAP1. In the present work, we investigated acquired resistance to trastuzumab in gastric cancer experimental models. Trastuzumab-resistant (HR) subclones derived from 3 HER2-overexpressing gastric cancer cells were generated and characterized for alterations in HER2-signaling mechanisms by next-generation sequencing, immunohistochemical, western blot and qRT-PCR techniques, and molecular modeling analysis. All subclones showed a reduced growth rate with respect to parental cell lines but each had a different resistance mechanism. In NCI N87 HR cells, characterized by a marked increase in HER2-signaling pathways with respect to the parental cell line, trastuzumab sensitivity was restored when IQGAP1 expression was silenced. AKG HR subclone showed higher HER3 protein expression than the parental line. High nuclear HER4 levels were observed in KKP HR cells. In conclusion, our study revealed that high IQGAP1 expression leads to resistance to trastuzumab in gastric cancer. Furthermore, 2 new mutations of the HER2 gene that may be involved in acquired resistance were identified in AKG HR and KKP HR subclones. PMID:26919099

  20. Novel characteristics of community-acquired methicillin-resistant Staphylococcus aureus strains belonging to multilocus sequence type 59 in Taiwan.

    PubMed

    Takano, Tomomi; Higuchi, Wataru; Zaraket, Hassan; Otsuka, Taketo; Baranovich, Tatiana; Enany, Shymaa; Saito, Kohei; Isobe, Hirokazu; Dohmae, Soshi; Ozaki, Kyoko; Takano, Misao; Iwao, Yasuhisa; Shibuya, Michiko; Okubo, Takeshi; Yabe, Shizuka; Shi, Da; Reva, Ivan; Teng, Lee-Jene; Yamamoto, Tatsuo

    2008-03-01

    Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strains, which often produce Panton-Valentine leucocidin (PVL), are increasingly noted worldwide. In this study, we examined 42 MRSA strains (25 PVL-positive [PVL+] strains and 17 PVL-negative [PVL(-)] strains) isolated in Taiwan for their molecular characteristics. The PVL+ MRSA strains included CA-MRSA strains with multilocus sequence type (ST) 59 (major PVL+ MRSA in Taiwan), its variants, and worldwide CA-MRSA ST30 strains. The PVL(-) MRSA strains included the pandemic Hungarian MRSA ST239 strain, the Hungarian MRSA ST239 variant, MRSA ST59 (largely hospital-acquired MRSA strains) and its variants, the pandemic New York/Japan MRSA ST5 strain (Japanese type), and the MRSA ST8 strain. The major PVL+ CA-MRSA ST59 strain possessed a tetracycline resistance-conferring (tetK positive) penicillinase plasmid and a drug resistance gene cluster (a possible composite transposon) for multidrug resistance. Moreover, it carried a novel staphylococcal cassette chromosome mec (SCCmec) with two distinct ccrC genes (ccrC2-C8). This SCCmec (previously named SCCmec type V(T)) was tentatively designated SCCmec type VII. Sequencing of the PVL genes revealed the polymorphisms, and the PVL+ CA-MRSA ST59 strain possessed the ST59-specific PVL gene sequence. The data suggest that a significant amount of clonal spread is occurring in Taiwan and that the major PVL+ CA-MRSA ST59 Taiwan strain exhibits unique genetic characteristics, such as a novel SCCmec type and an ST59-specific PVL gene sequence. PMID:18086843

  1. Acquired resistance to anti-EGFR mAb ICR62 in cancer cells is accompanied by an increased EGFR expression, HER-2/HER-3 signalling and sensitivity to pan HER blockers

    PubMed Central

    Khelwatty, Said A; Essapen, Sharadah; Seddon, Alan M; Fan, Zhen; Modjtahedi, Helmout

    2015-01-01

    Background: The human epidermal growth factor receptor (EGFR) is an important target for cancer treatment. Currently, only the EGFR antibodies cetuximab and panitumumab are approved for the treatment of patients with colorectal cancer. However, a major clinical challenge is a short-term response owing to development of acquired resistance during the course of the treatment. Methods: In this study, we investigated the molecular mechanisms underlying development of acquired resistance in DiFi colorectal cancer cells to the anti-EGFR mAb ICR62 (termed DiFi62) and to the small molecule tyrosine kinase inhibitor (TKI) gefitinib (termed DiFiG) using a range of techniques. Results: Compared with the findings from parental DiFi and DiFiG cells, development of acquired resistance to anti-EGFR mAb ICR62 in DiFi62 cells was accompanied by an increase in cell surface EGFR and increased phosphorylation of HER-2 and HER-3. Interestingly, DiFi62 cells also acquired resistance to treatment with anti-EGFR mAbs cetuximab and ICR61, which bind to other distinct epitopes on the extracellular domain of EGFR, but these cells remained equally sensitive as the parental cells to treatment with pan-HER inhibitors such as afatinib. Conclusions: Our results provide a novel mechanistic insight into the development of acquired resistance to EGFR antibody-based therapy in colorectal cancer cells and justify further investigations on the therapeutic benefits of pan-HER family inhibitors in the treatment of colorectal cancer patients once acquired resistance to EGFR antibody-based therapy is developed. PMID:26372697

  2. Acquired Activated Protein C Resistance, Thrombophilia and Adverse Pregnancy Outcomes: A Study Performed in an Irish Cohort of Pregnant Women

    PubMed Central

    Sedano-Balbás, Sara; Lyons, Mark; Cleary, Brendan; Murray, Margaret; Gaffney, Geraldine; Maher, Majella

    2011-01-01

    The combination of thrombophilia and pregnancy increases the risk of thrombosis and the potential for adverse outcomes during pregnancy. The most significant common inherited risk factor for thrombophilia is activated protein C resistance (APCR), a poor anticoagulant response of APC in haemostasis, which is mainly caused by an inherited single-nucleotide polymorphism (SNP), factor V G1691A (FV Leiden) (FVL), referred as inherited APCR. Changes in the levels of coagulation factors: FV, FVIII, and FIX, and anticoagulant factors: protein S (PS) and protein C (PC) can alter APC function causing acquired APCR. Prothrombin G20210A and methylenetetrahydrofolate reductase (MTHFR) C677T are prothrombotic SNPs which in association with APCR can also increase the risk of thrombosis amongst Caucasians. In this study, a correlation between an acquired APCR phenotype and increased levels of factors V, VIII, and IX was demonstrated. Thrombophilic mutations amongst our acquired APCR pregnant women cohort are relatively common but do not appear to exert a severe undue adverse effect on pregnancy. PMID:21869933

  3. Community-acquired multidrug-resistant Gram-negative bacterial infective endocarditis

    PubMed Central

    Naha, Sowjanya; Naha, Kushal; Acharya, Vasudev; Hande, H Manjunath; Vivek, G

    2014-01-01

    We describe two cases of bacterial endocarditis secondary to multidrug-resistant Gram-negative organisms. In both cases, the diagnosis was made in accordance with the modified Duke's criteria and confirmed by histopathological analysis. Furthermore, in both instances there were no identifiable sources of bacteraemia and no history of contact with hospital or other medical services prior to the onset of symptoms. The patients were managed in similar fashion with prolonged broad-spectrum antibiotic therapy and surgical intervention and made complete recoveries. These cases highlight Gram-negative organisms as potential agents for endocarditis, as well as expose the dissemination of such multidrug-resistant bacteria into the community. The application of an integrated medical and surgical approach and therapeutic dilemmas encountered in managing these cases are described. PMID:25096655

  4. Mechanisms of action of systemic antibiotics used in periodontal treatment and mechanisms of bacterial resistance to these drugs

    PubMed Central

    SOARES, Geisla Mary Silva; FIGUEIREDO, Luciene Cristina; FAVERI, Marcelo; CORTELLI, Sheila Cavalca; DUARTE, Poliana Mendes; FERES, Magda

    2012-01-01

    Antibiotics are important adjuncts in the treatment of infectious diseases, including periodontitis. The most severe criticisms to the indiscriminate use of these drugs are their side effects and, especially, the development of bacterial resistance. The knowledge of the biological mechanisms involved with the antibiotic usage would help the medical and dental communities to overcome these two problems. Therefore, the aim of this manuscript was to review the mechanisms of action of the antibiotics most commonly used in the periodontal treatment (i.e. penicillin, tetracycline, macrolide and metronidazole) and the main mechanisms of bacterial resistance to these drugs. Antimicrobial resistance can be classified into three groups: intrinsic, mutational and acquired. Penicillin, tetracycline and erythromycin are broad-spectrum drugs, effective against gram-positive and gram-negative microorganisms. Bacterial resistance to penicillin may occur due to diminished permeability of the bacterial cell to the antibiotic; alteration of the penicillin-binding proteins, or production of β-lactamases. However, a very small proportion of the subgingival microbiota is resistant to penicillins. Bacteria become resistant to tetracyclines or macrolides by limiting their access to the cell, by altering the ribosome in order to prevent effective binding of the drug, or by producing tetracycline/macrolide-inactivating enzymes. Periodontal pathogens may become resistant to these drugs. Finally, metronidazole can be considered a prodrug in the sense that it requires metabolic activation by strict anaerobe microorganisms. Acquired resistance to this drug has rarely been reported. Due to these low rates of resistance and to its high activity against the gram-negative anaerobic bacterial species, metronidazole is a promising drug for treating periodontal infections. PMID:22858695

  5. Acquired color vision loss and a possible mechanism of ganglion cell death in glaucoma.

    PubMed Central

    Nork, T M

    2000-01-01

    PURPOSE: First, to study the cellular mechanisms of acquired color vision loss in retinal detachment and diabetic retinopathy. Second, to learn why, in glaucoma, the type of color vision deficit that is observed is more characteristic of a retinal injury than it is of an optic neuropathy. Third, to test a hypothesis of photoreceptor-induced, ganglion cell death in glaucoma. METHODS: Various histologic techniques were employed to distinguish the L/M-cones (long/medium wavelength-sensitive cones, or red/green sensitive cones) from the S-cones (short wavelength-sensitive cones, or blue sensitive cones) in humans and monkeys with retinal detachment, humans with diabetic retinopathy, and both humans and monkeys with glaucoma. To test if the photoreceptors were contributing to ganglion cell death, laser photocoagulation was used in a experimental model of glaucoma to focally eliminate the photoreceptors. As a control, optic nerve transection was done following retinal laser photocoagulation in one animal. RESULTS: Selective and widespread loss of the S-cones was found in retinal detachment as well as diabetic retinopathy. By contrast, in human as well as experimental glaucoma, marked swelling of the L/M-cones was the predominant histopathologic feature. Retinal laser photocoagulation followed by experimental glaucoma resulted in selective protection of ganglion cells overlying the laser spots. This was not seen with retinal laser photocoagulation by optic nerve transection. CONCLUSIONS: In retinal detachment and diabetic retinopathy, acquired tritan-like color vision loss could be caused, or contributed to, by selective loss of the S-cones. Both L- and M-cones are affected in glaucoma, which is also consistent with a tritan-like deficit. Although not a therapeutic option, protection of ganglion cells by retinal laser in experimental glaucoma is consistent with an hypothesis of anterograde, photoreceptor-induced, ganglion cell death. Images FIGURE 1 FIGURE 2 FIGURE 3

  6. MM-151 overcomes acquired resistance to cetuximab and panitumumab in colorectal cancers harboring EGFR extracellular domain mutations.

    PubMed

    Arena, Sabrina; Siravegna, Giulia; Mussolin, Benedetta; Kearns, Jeffrey D; Wolf, Beni B; Misale, Sandra; Lazzari, Luca; Bertotti, Andrea; Trusolino, Livio; Adjei, Alex A; Montagut, Clara; Di Nicolantonio, Federica; Nering, Rachel; Bardelli, Alberto

    2016-02-01

    The anti-epidermal growth factor receptor (EGFR) antibodies cetuximab and panitumumab are used to treat RAS wild-type colorectal cancers (CRCs), but their efficacy is limited by the emergence of acquired drug resistance. After EGFR blockade, about 20% of CRCs develop mutations in the EGFR extracellular domain (ECD) that impair antibody binding and are associated with clinical relapse. We hypothesized that EGFR ECD-resistant variants could be targeted by the recently developed oligoclonal antibody MM-151 that binds multiple regions of the EGFR ECD. MM-151 inhibits EGFR signaling and cell growth in preclinical models, including patient-derived cells carrying mutant EGFR. Upon MM-151 treatment, EGFR ECD mutations decline in circulating cell-free tumor DNA (ctDNA) of CRC patients who previously developed resistance to EGFR blockade. These data provide molecular rationale for the clinical use of MM-151 in patients who become resistant to cetuximab or panitumumab as a result of EGFR ECD mutations. PMID:26843189

  7. Let-7 modulates acquired resistance of ovarian cancer to Taxanes via IMP-1-mediated stabilization of MDR1

    PubMed Central

    Boyerinas, Benjamin; Park, Sun-Mi; Murmann, Andrea E.; Gwin, Katja; Montag, Anton G.; Zillardt, Marion R.; Hua, You-Jia; Lengyel, Ernst; Peter, Marcus E.

    2011-01-01

    Summary Ovarian cancer patients frequently develop resistance to chemotherapy regiments utilizing Taxol and carboplatin. One of the resistance factors that protects cancer cells from Taxol-based therapy is multi-drug resistance 1 (MDR1). micro(mi)RNAs are small noncoding RNAs that negatively regulate protein expression. Members of the let-7 family of miRNAs are downregulated in many human cancers, and low let-7 expression has been correlated with resistance to microtubule targeting drugs (Taxanes), although little is known that would explain this activity. We now provide evidence that, while let-7 is not a universal sensitizer of cancer cells to Taxanes, it affects acquired resistance of cells to this class of drugs by targeting IMP-1, resulting in de-stabilization of the mRNA of MDR1. Introducing let-7g into ADR-RES cells expressing both IMP-1 and MDR1 reduced expression of both proteins rendering the cells more sensitive to treatment with either Taxol or vinblastine without affecting the sensitivity of the cells to carboplatin, a non-MDR1 substrate. This effect could be reversed by reintroducing IMP-1 into let-7g high/MDR1 low cells causing MDR1 to again become stabilized. Consistently, many relapsed ovarian cancer patients tested before and after chemotherapy were found to downregulate let-7 and to co-upregulate IMP-1 and MDR1, and the increase in the expression levels of both proteins after chemotherapy negatively correlated with disease-free time before recurrence. Our data point at IMP-1 and MDR1 as indicators for response to therapy, and at IMP-1 as a novel therapeutic target for overcoming multidrug resistance of ovarian cancer. PMID:21618519

  8. Cisplatin Resistant Spheroids Model Clinically Relevant Survival Mechanisms in Ovarian Tumors.

    PubMed

    Chowanadisai, Winyoo; Messerli, Shanta M; Miller, Daniel H; Medina, Jamie E; Hamilton, Joshua W; Messerli, Mark A; Brodsky, Alexander S

    2016-01-01

    The majority of ovarian tumors eventually recur in a drug resistant form. Using cisplatin sensitive and resistant cell lines assembled into 3D spheroids we profiled gene expression and identified candidate mechanisms and biological pathways associated with cisplatin resistance. OVCAR-8 human ovarian carcinoma cells were exposed to sub-lethal concentrations of cisplatin to create a matched cisplatin-resistant cell line, OVCAR-8R. Genome-wide gene expression profiling of sensitive and resistant ovarian cancer spheroids identified 3,331 significantly differentially expressed probesets coding for 3,139 distinct protein-coding genes (Fc >2, FDR < 0.05) (S2 Table). Despite significant expression changes in some transporters including MDR1, cisplatin resistance was not associated with differences in intracellular cisplatin concentration. Cisplatin resistant cells were significantly enriched for a mesenchymal gene expression signature. OVCAR-8R resistance derived gene sets were significantly more biased to patients with shorter survival. From the most differentially expressed genes, we derived a 17-gene expression signature that identifies ovarian cancer patients with shorter overall survival in three independent datasets. We propose that the use of cisplatin resistant cell lines in 3D spheroid models is a viable approach to gain insight into resistance mechanisms relevant to ovarian tumors in patients. Our data support the emerging concept that ovarian cancers can acquire drug resistance through an epithelial-to-mesenchymal transition. PMID:26986722

  9. Cisplatin Resistant Spheroids Model Clinically Relevant Survival Mechanisms in Ovarian Tumors

    PubMed Central

    Miller, Daniel H.; Medina, Jamie E.; Hamilton, Joshua W.; Messerli, Mark A.; Brodsky, Alexander S.

    2016-01-01

    The majority of ovarian tumors eventually recur in a drug resistant form. Using cisplatin sensitive and resistant cell lines assembled into 3D spheroids we profiled gene expression and identified candidate mechanisms and biological pathways associated with cisplatin resistance. OVCAR-8 human ovarian carcinoma cells were exposed to sub-lethal concentrations of cisplatin to create a matched cisplatin-resistant cell line, OVCAR-8R. Genome-wide gene expression profiling of sensitive and resistant ovarian cancer spheroids identified 3,331 significantly differentially expressed probesets coding for 3,139 distinct protein-coding genes (Fc >2, FDR < 0.05) (S2 Table). Despite significant expression changes in some transporters including MDR1, cisplatin resistance was not associated with differences in intracellular cisplatin concentration. Cisplatin resistant cells were significantly enriched for a mesenchymal gene expression signature. OVCAR-8R resistance derived gene sets were significantly more biased to patients with shorter survival. From the most differentially expressed genes, we derived a 17-gene expression signature that identifies ovarian cancer patients with shorter overall survival in three independent datasets. We propose that the use of cisplatin resistant cell lines in 3D spheroid models is a viable approach to gain insight into resistance mechanisms relevant to ovarian tumors in patients. Our data support the emerging concept that ovarian cancers can acquire drug resistance through an epithelial-to-mesenchymal transition. PMID:26986722

  10. The novel ATP-competitive MEK/Aurora kinase inhibitor BI-847325 overcomes acquired BRAF inhibitor resistance through suppression of Mcl-1 and MEK expression

    PubMed Central

    Phadke, Manali S.; Sini, Patrizia; Smalley, Keiran S. M.

    2015-01-01

    Resistance to BRAF inhibitors is a major clinical problem. Here we evaluate BI-847325, an ATP-competitive inhibitor of MEK and Aurora kinases, in treatment-naïve and drug-resistant BRAF-mutant melanoma models. BI-847325 potently inhibited growth and survival of melanoma cell lines that were both BRAF inhibitor naïve and resistant in 2D culture, 3D cell culture conditions and in colony formation assays. Western blot studies showed BI-847325 to reduce expression of phospho-ERK and phospho-histone 3 in multiple models of vemurafenib resistance. Mechanistically, BI-847325 decreased the expression of MEK and Mcl-1 while increasing the expression of the pro-apoptotic protein BIM. Strong suppression of MEK expression was observed after 48 h of treatment, with no recovery following >72 h of washout. siRNA mediated knockdown of Mcl-1 enhanced the effects of BI-847325, whereas Mcl-1 overexpression reversed this in both 2D cell culture and 3D spheroid melanoma models. In vivo, once weekly BI-847325 (70 mg/kg) led to durable regression of BRAF-inhibitor naive xenografts with no regrowth seen (>65 days of treatment). In contrast, treatment with the vemurafenib analog PLX4720 was associated with tumor relapse at >30 days. BI-847325 also suppressed the long-term growth of xenografts with acquired PLX4720 resistance. Analysis of tumor samples revealed BI-847325 to induce apoptosis associated with suppression of phospho-ERK, total MEK, phospho-Histone3 and Mcl-1 expression. Our studies indicate that BI-847325 is effective in overcoming BRAF inhibitor resistance and has long-term inhibitory effects upon BRAF-mutant melanoma in vivo, through a mechanism associated with the decreased expression of both MEK and Mcl-1. PMID:25873592

  11. The Novel ATP-Competitive MEK/Aurora Kinase Inhibitor BI-847325 Overcomes Acquired BRAF Inhibitor Resistance through Suppression of Mcl-1 and MEK Expression.

    PubMed

    Phadke, Manali S; Sini, Patrizia; Smalley, Keiran S M

    2015-06-01

    Resistance to BRAF inhibitors is a major clinical problem. Here, we evaluate BI-847325, an ATP-competitive inhibitor of MEK and Aurora kinases, in treatment-naïve and drug-resistant BRAF-mutant melanoma models. BI-847325 potently inhibited growth and survival of melanoma cell lines that were both BRAF inhibitor naïve and resistant in 2D culture, 3D cell culture conditions, and in colony formation assays. Western blot studies showed BI-847325 to reduce expression of phospho-ERK and phospho-histone 3 in multiple models of vemurafenib resistance. Mechanistically, BI-847325 decreased the expression of MEK and Mcl-1 while increasing the expression of the proapoptotic protein BIM. Strong suppression of MEK expression was observed after 48 hours of treatment, with no recovery following >72 hours of washout. siRNA-mediated knockdown of Mcl-1 enhanced the effects of BI-847325, whereas Mcl-1 overexpression reversed this in both 2D cell culture and 3D spheroid melanoma models. In vivo, once weekly BI-847325 (70 mg/kg) led to durable regression of BRAF-inhibitor naïve xenografts with no regrowth seen (>65 days of treatment). In contrast, treatment with the vemurafenib analog PLX4720 was associated with tumor relapse at >30 days. BI-847325 also suppressed the long-term growth of xenografts with acquired PLX4720 resistance. Analysis of tumor samples revealed BI-847325 to induce apoptosis associated with suppression of phospho-ERK, total MEK, phospho-Histone3, and Mcl-1 expression. Our studies indicate that BI-847325 is effective in overcoming BRAF inhibitor resistance and has long-term inhibitory effects upon BRAF-mutant melanoma in vivo, through a mechanism associated with the decreased expression of both MEK and Mcl-1. PMID:25873592

  12. Bile resistance mechanisms in Lactobacillus and Bifidobacterium

    PubMed Central

    Ruiz, Lorena; Margolles, Abelardo; Sánchez, Borja

    2013-01-01

    Probiotics are live microorganisms which when administered in adequate amounts confer a health benefit on the host. Most of the probiotic bacteria currently available in the market belong to the genera Lactobacillus and Bifidobacterium, and specific health-promoting activities, such as treatment of diarrhea or amelioration of gastrointestinal discomfort, have been attributed to them. In order to be able to survive the gastrointestinal transit and transiently colonize our gut, these bacteria must be able to counteract the deleterious action of bile salts, which are the main components of bile. Bile salts are detergent-like biological substances synthesized in the liver from cholesterol. Host enzymes conjugate the newly synthesized free bile acids in the liver with the amino acids glycine or taurine, generating conjugated bile salts. These compounds are stored in the gall bladder and they are released into the duodenum during digestion to perform their physiological function, which is the solubilization of fat coming from diet. These bile salts possess strong antimicrobial activity, since they are able to disorganize the structure of the cell membrane, as well as trigger DNA damage. This means that bacteria inhabiting our intestinal tract must have intrinsic resistance mechanisms to cope with bile salts. To do that, Lactobacillus and Bifidobacterium display a variety of proteins devoted to the efflux of bile salts or protons, to modify sugar metabolism or to prevent protein misfolding. In this manuscript, we review and discuss specific bile resistance mechanisms, as well as the processes responsible for the adaptation of bifidobacteria and lactobacilli to bile. PMID:24399996

  13. Bile resistance mechanisms in Lactobacillus and Bifidobacterium.

    PubMed

    Ruiz, Lorena; Margolles, Abelardo; Sánchez, Borja

    2013-01-01

    Probiotics are live microorganisms which when administered in adequate amounts confer a health benefit on the host. Most of the probiotic bacteria currently available in the market belong to the genera Lactobacillus and Bifidobacterium, and specific health-promoting activities, such as treatment of diarrhea or amelioration of gastrointestinal discomfort, have been attributed to them. In order to be able to survive the gastrointestinal transit and transiently colonize our gut, these bacteria must be able to counteract the deleterious action of bile salts, which are the main components of bile. Bile salts are detergent-like biological substances synthesized in the liver from cholesterol. Host enzymes conjugate the newly synthesized free bile acids in the liver with the amino acids glycine or taurine, generating conjugated bile salts. These compounds are stored in the gall bladder and they are released into the duodenum during digestion to perform their physiological function, which is the solubilization of fat coming from diet. These bile salts possess strong antimicrobial activity, since they are able to disorganize the structure of the cell membrane, as well as trigger DNA damage. This means that bacteria inhabiting our intestinal tract must have intrinsic resistance mechanisms to cope with bile salts. To do that, Lactobacillus and Bifidobacterium display a variety of proteins devoted to the efflux of bile salts or protons, to modify sugar metabolism or to prevent protein misfolding. In this manuscript, we review and discuss specific bile resistance mechanisms, as well as the processes responsible for the adaptation of bifidobacteria and lactobacilli to bile. PMID:24399996

  14. Estimating Trends in the Proportion of Transmitted and Acquired HIV Drug Resistance in a Long Term Observational Cohort in Germany

    PubMed Central

    Schmidt, Daniel; Kollan, Christian; Fätkenheuer, Gerd; Schülter, Eugen; Stellbrink, Hans-Jürgen; Noah, Christian; Jensen, Björn-Erik Ole; Stoll, Matthias; Bogner, Johannes R.; Eberle, Josef; Meixenberger, Karolin; Kücherer, Claudia; Hamouda, Osamah; Bartmeyer, Barbara

    2014-01-01

    Objective We assessed trends in the proportion of transmitted (TDR) and acquired (ADR) HIV drug resistance and associated mutations between 2001 and 2011 in the German ClinSurv-HIV Drug Resistance Study. Method The German ClinSurv-HIV Drug Resistance Study is a subset of the German ClinSurv-HIV Cohort. For the ClinSurv-HIV Drug Resistance Study all available sequences isolated from patients in five study centres of the long term observational ClinSurv-HIV Cohort were included. TDR was estimated using the first viral sequence of antiretroviral treatment (ART) naïve patients. One HIV sequence/patient/year of ART experienced patients was considered to estimate the proportion of ADR. Trends in the proportion of HIV drug resistance were calculated by logistic regression. Results 9,528 patients were included into the analysis. HIV-sequences of antiretroviral naïve and treatment experienced patients were available from 34% (3,267/9,528) of patients. The proportion of TDR over time was stable at 10.4% (95% CI 9.1–11.8; p for trend = 0.6; 2001–2011). The proportion of ADR among all treated patients was 16%, whereas it was high among those with available HIV genotypic resistance test (64%; 1,310/2,049 sequences; 95% CI 62–66) but declined significantly over time (OR 0.8; 95% CI 0.77–0.83; p for trend<0.001; 2001–2011). Viral load monitoring subsequent to resistance testing was performed in the majority of treated patients (96%) and most of them (67%) were treated successfully. Conclusions The proportion of TDR was stable in this study population. ADR declined significantly over time. This decline might have been influenced by broader resistance testing, resistance test guided therapy and the availability of more therapeutic options and not by a decline in the proportion of TDR within the study population. PMID:25148412

  15. Role of major histocompatibility complex class II in resistance of mice to naturally acquired infection with Syphacia obvelata

    NASA Technical Reports Server (NTRS)

    Stewart, Patricia W.; Chapes, Stephen K.

    2003-01-01

    Genetics plays a substantial role in host resistance in many host-parasite interactions. We examined the prevalence of naturally acquired infection with Syphacia obvelata in a number of mouse strains housed in a non-barrier facility. These mice, which included cross-bred and congenic, inbred strains on various genetic backgrounds, differ in the loci for the immune function genes--major histocompatibility complex class II (MHCII), toll-like receptor 4 (Tlr4), and solute carrier family 11, member 1 (Slc11a1)--which allowed comparisons of the impact of these genes on resistance to pinworm infection. Male and female mice of various ages were sampled over an 18-month period; infection was determined by use of the cellophane tape test. Results indicated that mice that were MHCII+/+ had a significantly lower prevalence of infection than did mice that were MHCII-/-. Differences were not seen between male and female mice. Although MHCII+/+ mice had an age-associated decrease in infection prevalence, such decrease was not seen in MHCII-/- mice. In contrast, infection prevalence in mice with the normal Tlr4 gene (Tlr4(LPS-n/LPS-n)) gene did not differ significantly compared with that in mice that were homozygous for either the point mutation (Tlr4(LPS-d/LPS-d)) or deletion (Tlr4(LPS-del/LPS-del)) of that gene. Likewise, the presence (Sle11a1r/r) or absence (Slc11a1s/s) of functional alleles for Slc11a1 had no effect on the prevalence of infection with S. obvelata. In conclusion, presence of MHCII, but not Tlr4 or Slc11a1 significantly influences prevalence of naturally acquired infection with S. obvelata. These data justify further comprehensive analyses of the immune components that are involved in pinworm resistance.

  16. Circulating tumor DNA to monitor treatment response and detect acquired resistance in patients with metastatic melanoma.

    PubMed

    Gray, Elin S; Rizos, Helen; Reid, Anna L; Boyd, Suzanah C; Pereira, Michelle R; Lo, Johnny; Tembe, Varsha; Freeman, James; Lee, Jenny H J; Scolyer, Richard A; Siew, Kelvin; Lomma, Chris; Cooper, Adam; Khattak, Muhammad A; Meniawy, Tarek M; Long, Georgina V; Carlino, Matteo S; Millward, Michael; Ziman, Melanie

    2015-12-01

    Repeat tumor biopsies to study genomic changes during therapy are difficult, invasive and data are confounded by tumoral heterogeneity. The analysis of circulating tumor DNA (ctDNA) can provide a non-invasive approach to assess prognosis and the genetic evolution of tumors in response to therapy. Mutation-specific droplet digital PCR was used to measure plasma concentrations of oncogenic BRAF and NRAS variants in 48 patients with advanced metastatic melanoma prior to treatment with targeted therapies (vemurafenib, dabrafenib or dabrafenib/trametinib combination) or immunotherapies (ipilimumab, nivolumab or pembrolizumab). Baseline ctDNA levels were evaluated relative to treatment response and progression-free survival (PFS). Tumor-associated ctDNA was detected in the plasma of 35/48 (73%) patients prior to treatment and lower ctDNA levels at this time point were significantly associated with response to treatment and prolonged PFS, irrespective of therapy type. Levels of ctDNA decreased significantly in patients treated with MAPK inhibitors (p < 0.001) in accordance with response to therapy, but this was not apparent in patients receiving immunotherapies. We show that circulating NRAS mutations, known to confer resistance to BRAF inhibitors, were detected in 3 of 7 (43%) patients progressing on kinase inhibitor therapy. Significantly, ctDNA rebound and circulating mutant NRAS preceded radiological detection of progressive disease. Our data demonstrate that ctDNA is a useful biomarker of response to kinase inhibitor therapy and can be used to monitor tumor evolution and detect the early appearance of resistance effectors. PMID:26524482

  17. Circulating tumor DNA to monitor treatment response and detect acquired resistance in patients with metastatic melanoma

    PubMed Central

    Gray, Elin S.; Rizos, Helen; Reid, Anna L.; Boyd, Suzanah C.; Pereira, Michelle R.; Lo, Johnny; Tembe, Varsha; Freeman, James; Lee, Jenny H.J.; Scolyer, Richard A.; Siew, Kelvin; Lomma, Chris; Cooper, Adam; Khattak, Muhammad A.; Meniawy, Tarek M.; Long, Georgina V.; Carlino, Matteo S.; Millward, Michael; Ziman, Melanie

    2015-01-01

    Repeat tumor biopsies to study genomic changes during therapy are difficult, invasive and data are confounded by tumoral heterogeneity. The analysis of circulating tumor DNA (ctDNA) can provide a non-invasive approach to assess prognosis and the genetic evolution of tumors in response to therapy. Mutation-specific droplet digital PCR was used to measure plasma concentrations of oncogenic BRAF and NRAS variants in 48 patients with advanced metastatic melanoma prior to treatment with targeted therapies (vemurafenib, dabrafenib or dabrafenib/trametinib combination) or immunotherapies (ipilimumab, nivolumab or pembrolizumab). Baseline ctDNA levels were evaluated relative to treatment response and progression-free survival (PFS). Tumor-associated ctDNA was detected in the plasma of 35/48 (73%) patients prior to treatment and lower ctDNA levels at this time point were significantly associated with response to treatment and prolonged PFS, irrespective of therapy type. Levels of ctDNA decreased significantly in patients treated with MAPK inhibitors (p < 0.001) in accordance with response to therapy, but this was not apparent in patients receiving immunotherapies. We show that circulating NRAS mutations, known to confer resistance to BRAF inhibitors, were detected in 3 of 7 (43%) patients progressing on kinase inhibitor therapy. Significantly, ctDNA rebound and circulating mutant NRAS preceded radiological detection of progressive disease. Our data demonstrate that ctDNA is a useful biomarker of response to kinase inhibitor therapy and can be used to monitor tumor evolution and detect the early appearance of resistance effectors. PMID:26524482

  18. Benzoylsalicylic acid isolated from seed coats of Givotia rottleriformis induces systemic acquired resistance in tobacco and Arabidopsis.

    PubMed

    Kamatham, Samuel; Neela, Kishore Babu; Pasupulati, Anil Kumar; Pallu, Reddanna; Singh, Surya Satyanarayana; Gudipalli, Padmaja

    2016-06-01

    Systemic acquired resistance (SAR), a whole plant defense response to a broad spectrum of pathogens, is characterized by a coordinated expression of a large number of defense genes. Plants synthesize a variety of secondary metabolites to protect themselves from the invading microbial pathogens. Several studies have shown that salicylic acid (SA) is a key endogenous component of local and systemic disease resistance in plants. Although SA is a critical signal for SAR, accumulation of endogenous SA levels alone is insufficient to establish SAR. Here, we have identified a new acyl derivative of SA, the benzoylsalicylic acid (BzSA) also known as 2-(benzoyloxy) benzoic acid from the seed coats of Givotia rottleriformis and investigated its role in inducing SAR in tobacco and Arabidopsis. Interestingly, exogenous BzSA treatment induced the expression of NPR1 (Non-expressor of pathogenesis-related gene-1) and pathogenesis related (PR) genes. BzSA enhanced the expression of hypersensitivity related (HSR), mitogen activated protein kinase (MAPK) and WRKY genes in tobacco. Moreover, Arabidopsis NahG plants that were treated with BzSA showed enhanced resistance to tobacco mosaic virus (TMV) as evidenced by reduced leaf necrosis and TMV-coat protein levels in systemic leaves. We, therefore, conclude that BzSA, hitherto unknown natural plant product, is a new SAR inducer in plants. PMID:26988727

  19. Plasmodesmata-located protein overexpression negatively impacts the manifestation of systemic acquired resistance and the long-distance movement of Defective in Induced Resistance1 in Arabidopsis.

    PubMed

    Carella, P; Isaacs, M; Cameron, R K

    2015-03-01

    Systemic acquired resistance (SAR) is a plant defence response that provides immunity to distant uninfected leaves after an initial localised infection. The lipid transfer protein (LTP) Defective in Induced Resistance1 (DIR1) is an essential component of SAR that moves from induced to distant leaves following a SAR-inducing local infection. To understand how DIR1 is transported to distant leaves during SAR, we analysed DIR1 movement in transgenic Arabidopsis lines with reduced cell-to-cell movement caused by the overexpression of Plasmodesmata-Located Proteins PDLP1 and PDLP5. These PDLP-overexpressing lines were defective for SAR, and DIR1 antibody signals were not observed in phloem sap-enriched petiole exudates collected from distant leaves. Our data support the idea that cell-to-cell movement of DIR1 through plasmodesmata is important during long-distance SAR signalling in Arabidopsis. PMID:25296648

  20. l-carnosine dipeptide overcomes acquired resistance to 5-fluorouracil in HT29 human colon cancer cells via downregulation of HIF1-alpha and induction of apoptosis.

    PubMed

    Iovine, Barbara; Guardia, Francesca; Irace, Carlo; Bevilacqua, Maria Assunta

    2016-08-01

    Hypoxia-inducible factor (HIF-1α) protein is over-expressed in many human cancers and is a major cause of resistance to drugs. HIF-1α up-regulation decreases the effectiveness of several anticancer agents, including 5-fluorouracil (5-FU), because it induces the expression of drug efflux transporters, alters DNA repair mechanisms and modifies the balance between pro- and antiapoptotic factors. These findings suggest that inhibition of HIF-1α activity may sensitize cancer cells to cytotoxic drugs. We previously reported that l-carnosine reduces HIF-1α expression by inhibiting the proliferation of colon cancer cells. In the present study we investigated the effect of l-carnosine on HT29 colon cancer cells with acquired resistance to 5-FU. We found that l-carnosine reduces colon cancer cell viability, decreases HIF-1α and multi-drug resistant protein MDR1-pg expression, and induces apoptosis. Moreover, the l-carnosine/5-FU combination lowers the expression of some chemoresistance markers. The combination index evaluated in vitro on the HT29-5FU cell line by median drug effect analysis reveals a significant synergistic effect. PMID:27234614

  1. Diverse drug-resistance mechanisms can emerge from drug-tolerant cancer persister cells

    PubMed Central

    Ramirez, Michael; Rajaram, Satwik; Steininger, Robert J.; Osipchuk, Daria; Roth, Maike A.; Morinishi, Leanna S.; Evans, Louise; Ji, Weiyue; Hsu, Chien-Hsiang; Thurley, Kevin; Wei, Shuguang; Zhou, Anwu; Koduru, Prasad R.; Posner, Bruce A.; Wu, Lani F.; Altschuler, Steven J.

    2016-01-01

    Cancer therapy has traditionally focused on eliminating fast-growing populations of cells. Yet, an increasing body of evidence suggests that small subpopulations of cancer cells can evade strong selective drug pressure by entering a ‘persister' state of negligible growth. This drug-tolerant state has been hypothesized to be part of an initial strategy towards eventual acquisition of bona fide drug-resistance mechanisms. However, the diversity of drug-resistance mechanisms that can expand from a persister bottleneck is unknown. Here we compare persister-derived, erlotinib-resistant colonies that arose from a single, EGFR-addicted lung cancer cell. We find, using a combination of large-scale drug screening and whole-exome sequencing, that our erlotinib-resistant colonies acquired diverse resistance mechanisms, including the most commonly observed clinical resistance mechanisms. Thus, the drug-tolerant persister state does not limit—and may even provide a latent reservoir of cells for—the emergence of heterogeneous drug-resistance mechanisms. PMID:26891683

  2. Activation of the IGF1R pathway potentially mediates acquired resistance to mutant-selective 3rd-generation EGF receptor tyrosine kinase inhibitors in advanced non-small cell lung cancer.

    PubMed

    Park, Ji Hyun; Choi, Yun Jung; Kim, Seon Ye; Lee, Jung-Eun; Sung, Ki Jung; Park, Sojung; Kim, Woo Sung; Song, Joon Seon; Choi, Chang-Min; Sung, Young Hoon; Rho, Jin Kyung; Lee, Jae Cheol

    2016-04-19

    Mutant-selective, 3rd-generation EGFR-TKIs were recently developed to control lung cancer cells harboring T790M-mediated resistance. However, the development of resistance to these novel drugs seems inevitable. Thus, we investigated the mechanism of acquired resistance to the mutant-selective EGFR-TKI WZ4002. We established five WZ4002-resistant cells, derived from cells harboring both EGFR and T790M mutations by long-term exposure to increasing doses of WZ4002. Compared with the parental cells, all resistant cells showed 10-100-folds higher resistance to WZ4002, as well as cross-resistance to other mutant-selective inhibitors. Among them, three resistant cells (HCC827/WR, PC-9/WR and H1975/WR) showed dependency on EGFR signaling, but two other cells (PC-9/GR/WR and PC-9/ER/WR) were not. Notably, insulin-like growth factor-1 receptor (IGF1R) was aberrantly activated in PC-9/GR/WR cells in phospho-receptor tyrosine kinase array, consistently accompanied by loss of IGF binding protein-3 (IGFBP3). Down-regulation of IGF1R by shRNA, as well as inhibition of IGF1R activity either by AG-1024 (a small molecule IGF1R inhibitor) or BI 836845 (a monoclonal anti-IGF1/2 blocking antibody), restored the sensitivity to WZ4002 both in vitro and xenograft. Taken together, these results suggest that activation of the IGF1R pathway associated with IGFBP3 loss can induce an acquired resistance to the mutant-selective EGFR-TKI, WZ4002. Therefore, a combined therapy of IGF1R inhibitors and mutant-selective EGFR-TKIs might be a viable treatment strategy for overcoming acquired resistance. PMID:26980747

  3. Activation of the IGF1R pathway potentially mediates acquired resistance to mutant-selective 3rd-generation EGF receptor tyrosine kinase inhibitors in advanced non-small cell lung cancer

    PubMed Central

    Park, Ji Hyun; Choi, Yun Jung; Kim, Seon Ye; Lee, Jung-Eun; Sung, Ki Jung; Park, Sojung; Kim, Woo Sung; Song, Joon Seon; Choi, Chang-Min; Sung, Young Hoon; Rho, Jin Kyung; Lee, Jae Cheol

    2016-01-01

    Mutant-selective, 3rd-generation EGFR-TKIs were recently developed to control lung cancer cells harboring T790M-mediated resistance. However, the development of resistance to these novel drugs seems inevitable. Thus, we investigated the mechanism of acquired resistance to the mutant-selective EGFR-TKI WZ4002. We established five WZ4002-resistant cells, derived from cells harboring both EGFR and T790M mutations by long-term exposure to increasing doses of WZ4002. Compared with the parental cells, all resistant cells showed 10–100-folds higher resistance to WZ4002, as well as cross-resistance to other mutant-selective inhibitors. Among them, three resistant cells (HCC827/WR, PC-9/WR and H1975/WR) showed dependency on EGFR signaling, but two other cells (PC-9/GR/WR and PC-9/ER/WR) were not. Notably, insulin-like growth factor-1 receptor (IGF1R) was aberrantly activated in PC-9/GR/WR cells in phospho-receptor tyrosine kinase array, consistently accompanied by loss of IGF binding protein-3 (IGFBP3). Down-regulation of IGF1R by shRNA, as well as inhibition of IGF1R activity either by AG-1024 (a small molecule IGF1R inhibitor) or BI 836845 (a monoclonal anti-IGF1/2 blocking antibody), restored the sensitivity to WZ4002 both in vitro and xenograft. Taken together, these results suggest that activation of the IGF1R pathway associated with IGFBP3 loss can induce an acquired resistance to the mutant-selective EGFR-TKI, WZ4002. Therefore, a combined therapy of IGF1R inhibitors and mutant-selective EGFR-TKIs might be a viable treatment strategy for overcoming acquired resistance. PMID:26980747

  4. Inhibition of Casein Kinase 1 Alpha Prevents Acquired Drug Resistance to Erlotinib in EGFR-Mutant Non-Small Cell Lung Cancer.

    PubMed

    Lantermann, Alexandra B; Chen, Dongshu; McCutcheon, Kaitlin; Hoffman, Greg; Frias, Elizabeth; Ruddy, David; Rakiec, Daniel; Korn, Joshua; McAllister, Gregory; Stegmeier, Frank; Meyer, Matthew J; Sharma, Sreenath V

    2015-11-15

    Patients with lung tumors harboring activating mutations in the EGF receptor (EGFR) show good initial treatment responses to the EGFR tyrosine kinase inhibitors (TKI) erlotinib or gefitinib. However, acquired resistance invariably develops. Applying a focused shRNA screening approach to identify genes whose knockdown can prevent and/or overcome acquired resistance to erlotinib in several EGFR-mutant non-small cell lung cancer (NSCLC) cell lines, we identified casein kinase 1 α (CSNK1A1, CK1α). We found that CK1α suppression inhibits the NF-κB prosurvival signaling pathway. Furthermore, downregulation of NF-κB signaling by approaches independent of CK1α knockdown can also attenuate acquired erlotinib resistance, supporting a role for activated NF-κB signaling in conferring acquired drug resistance. Importantly, CK1α suppression prevented erlotinib resistance in an HCC827 xenograft model in vivo. Our findings suggest that patients with EGFR-mutant NSCLC might benefit from a combination of EGFR TKIs and CK1α inhibition to prevent acquired drug resistance and to prolong disease-free survival. PMID:26490646

  5. Mechanisms of Resistance to Grapevine Powdery Mildew

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although all high quality Vitis vinifera cultivars are highly susceptible to powdery mildew, current efforts show promise for the identification or modulation of resistance within the species and for continued introgression of resistance from resistant accessions of wild Vitis spp. Examination of t...

  6. A novel elicitor protein from Phytophthora parasitica induces plant basal immunity and systemic acquired resistance.

    PubMed

    Chang, Yi-Hsuan; Yan, Hao-Zhi; Liou, Ruey-Fen

    2015-02-01

    The interaction between Phytophthora pathogens and host plants involves the exchange of complex molecular signals from both sides. Recent studies of Phytophthora have led to the identification of various apoplastic elicitors known to trigger plant immunity. Here, we provide evidence that the protein encoded by OPEL of Phytophthora parasitica is a novel elicitor. Homologues of OPEL were identified only in oomycetes, but not in fungi and other organisms. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) revealed that OPEL is expressed throughout the development of P. parasitica and is especially highly induced after plant infection. Infiltration of OPEL recombinant protein from Escherichia coli into leaves of Nicotiana tabacum (cv. Samsun NN) resulted in cell death, callose deposition, the production of reactive oxygen species and induced expression of pathogen-associated molecular pattern (PAMP)-triggered immunity markers and salicylic acid-responsive defence genes. Moreover, the infiltration conferred systemic resistance against a broad spectrum of pathogens, including Tobacco mosaic virus, the bacteria wilt pathogen Ralstonia solanacearum and P. parasitica. In addition to the signal peptide, OPEL contains three conserved domains: a thaumatin-like domain, a glycine-rich protein domain and a glycosyl hydrolase (GH) domain. Intriguingly, mutation of a putative laminarinase active site motif in the predicted GH domain abolished its elicitor activity, which suggests enzymatic activity of OPEL in triggering the defence response. PMID:24965864

  7. A Case of Acute Pyogenic Sacroiliitis and Bacteremia Caused by Community-Acquired Methicillin-Resistant Staphylococcus aureus

    PubMed Central

    Kim, Suyoung; Lee, Kang Lock; Baek, Hae Lim; Jang, Seung Jun; Moon, Song Mi

    2013-01-01

    Pyogenic sacroiliitis is a rare osteoarticular infection, occurring most frequently in children and young adults. Diagnosis of the disease is challenging because of a general lack of awareness of the disease and its nonspecific signs and symptoms. Staphylococcus aureus is the most common causative bacteria in pyogenic sacroiliitis. Methicillin-resistant S. aureus (MRSA) has typically been considered a hospital-associated pathogen; however, community-acquired (CA)-MRSA infections are becoming increasingly common in Korea. We report the first domestic case of acute pyogenic sacroiliitis with abscess and bacteremia caused by CA-MRSA. The pathogen carried the type IV-A staphylococcal cassette chromosome mec (SCCmec) without the Panton-Valentine leukocidin (PVL) gene, and was identified as sequence type (ST) 72 by multilocus sequence typing. PMID:24475359

  8. Lemierre Syndrome Secondary to Community-Acquired Methicillin-Resistant Staphylococcus Aureus Infection Associated with Cavernous Sinus Thromboses

    PubMed Central

    Stauffer, Craig; Josiah, Anne F.; Fortes, Manuel; Menaker, Jay; Cole, John W.

    2012-01-01

    Background Lemierre’s Syndrome (LS) is a highly aggressive rare disease process with a predilection for young, healthy adolescents. Often beginning with a primary cervicofacial infection, LS rapidly progresses to thrombophlebitis of the cerebral vasculature, metastatic infection, and septicemia. Untreated LS can be rapidly fatal. Thrombus within the cerebral vasculature can have devastating neurological effects. Advances in antibacterial therapy have resulted in a global decline in the incidence of LS, and clinicians may not consider LS early in the disease process. While the mortality of LS has declined, the morbidity associated with the disease has increased, particularly the neurological sequelae. Objectives This report will provide readers with a better understanding of the etiology, clinical presentation, evaluation methods, and appropriate treatment of LS. Case Report We present an atypical case of LS secondary to community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infection progressing to bilateral cavernous sinus and ophthalmic vein thromboses with resultant binocular vision loss secondary to optic nerve and retinal ischemia. Conclusion This case highlights the importance of early recognition of LS in the setting of a community-acquired MRSA infection as the unifying condition in a young patient with multiple acute neurologic impairments. PMID:22989693

  9. Differential Distribution and Expression of Panton-Valentine Leucocidin among Community-Acquired Methicillin-Resistant Staphylococcus aureus Strains

    PubMed Central

    Saïd-Salim, Battouli; Mathema, Barun; Braughton, Kevin; Davis, Stacy; Sinsimer, Daniel; Eisner, William; Likhoshvay, Yekaterina; DeLeo, Frank R.; Kreiswirth, Barry N.

    2005-01-01

    Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is an emerging threat worldwide. CA-MRSA strains differ from hospital-acquired MRSA strains in their antibiotic susceptibilities and genetic backgrounds. Using several genotyping methods, we clearly define CA-MRSA at the genetic level and demonstrate that the prototypic CA-MRSA strain, MW2, has spread as a homogeneous clonal strain family that is distinct from other CA-MRSA strains. The Panton-Valentine leucocidin (PVL)-encoding genes, lukF and lukS, are prevalent among CA-MRSA strains and have previously been associated with CA-MRSA infections. To better elucidate the role of PVL in the pathogenesis of CA-MRSA, we first analyzed the distribution and expression of PVL among different CA-MRSA strains. Our data demonstrate that PVL genes are differentially distributed among CA-MRSA strains and, when they are present, are always transcribed, albeit with strain-to-strain variability of transcript levels. To directly test whether PVL is critical for the pathogenesis of CA-MRSA, we evaluated the lysis of human polymorphonuclear leukocytes (PMNs) during phagocytic interaction with PVL-positive and PVL-negative CA-MRSA strains. Unexpectedly, there was no correlation between PVL expression and PMN lysis, suggesting that additional virulence factors underlie leukotoxicity and, thus, the pathogenesis of CA-MRSA. PMID:16000462

  10. GLP-1 responses are heritable and blunted in acquired obesity with high liver fat and insulin resistance.

    PubMed

    Matikainen, Niina; Bogl, Leonie H; Hakkarainen, Antti; Lundbom, Jesper; Lundbom, Nina; Kaprio, Jaakko; Rissanen, Aila; Holst, Jens J; Pietiläinen, Kirsi H

    2014-01-01

    OBJECTIVE Impaired incretin response represents an early and uniform defect in type 2 diabetes, but the contributions of genes and the environment are poorly characterized. RESEARCH DESIGN AND METHODS We studied 35 monozygotic (MZ) and 75 dizygotic (DZ) twin pairs (discordant and concordant for obesity) to determine the heritability of glucagon-like peptide 1 (GLP-1) responses to an oral glucose tolerance test (OGTT) and the influence of acquired obesity to GLP-1, glucose-dependent insulinotropic peptide (GIP), and peptide YY (PYY) during OGTT or meal test. RESULTS The heritability of GLP-1 area under the curve was 67% (95% CI 45-80). Cotwins from weight-concordant MZ and DZ pairs and weight-discordant MZ pairs but concordant for liver fat content demonstrated similar glucose, insulin, and incretin profiles after the OGTT and meal tests. In contrast, higher insulin responses and blunted 60-min GLP-1 responses during the OGTT were observed in the heavier as compared with leaner MZ cotwins discordant for BMI, liver fat, and insulin sensitivity. Blunted GLP-1 response to OGTT was observed in heavier as compared with leaner DZ cotwins discordant for obesity and insulin sensitivity. CONCLUSIONS Whereas the GLP-1 response to the OGTT is heritable, an acquired unhealthy pattern of obesity characterized by liver fat accumulation and insulin resistance is closely related to impaired GLP-1 response in young adults. PMID:23990519

  11. Induction of acquired resistance to anti estrogen by reversible mitochondrial DNA depletion in breast cancer cell line

    PubMed Central

    Naito, Akihiro; Carcel-Trullols, Jaime; Xie, Cheng-hui; Evans, Teresa T; Mizumachi, Takatsugu; Higuchi, Masahiro

    2008-01-01

    Although the net benefits of tamoxifen in adjuvant breast cancer therapy have been proven, the recurrence of the cancer in an aggressive and hormone independent form has been highly problematic. We previously demonstrated the important role mitochondrial DNA (mtDNA) plays in hormone-independence in prostate cancer. Here, the role of mtDNA in breast cancer progression was investigated. We established hydroxytamoxifen (4-OHT) resistant HTRMCF by growing MCF-7, a human breast adenocarcinoma cells, in the presence of 4-OHT. HTRMCF was cross-resistant to 4-OHT and ICI182,780 concurrent with the depletion of mtDNA. To further investigate the role of mtDNA depletion, MCF-7 was depleted of mtDNA by treatment with ethidium bromide. MCFρ0 was resistant to both 4-OHT and ICI182,780. Furthermore, cybrid (MCFcyb) prepared by fusion MCFρ0 with platelet to transfer mtDNA showed susceptibility to anti-estrogen. Surprisingly, after withdrawal of 4-OHT for 8 weeks, HTRMCF and their clones became susceptible to both drugs concurrent with a recovery of mtDNA. Herein, our results substantiated the first evidence that the depletion of mtDNA induced by hormone therapy triggers a shift to acquired resistance to hormone therapy in breast cancer. In addition, we showed that mtDNA depletion can be reversed, rendering the cancer cells susceptible to anti-estrogen. The hormone independent phenotype can be reversed should be a step toward more effective treatments for estrogen-responsive breast cancer. PMID:17990320

  12. Low inducible expression of p21Cip1 confers resistance to paclitaxel in BRAF mutant melanoma cells with acquired resistance to BRAF inhibitor.

    PubMed

    Jang, Gun-Hee; Kim, Na-Yeon; Lee, Michael

    2015-08-01

    The therapeutic efficacy of oncogenic BRAF inhibitor is limited by the onset of acquired resistance. In this study, we investigated the potential therapeutic effects of the mitotic inhibitor paclitaxel on three melanoma cell lines with differing sensitivity to the BRAF inhibitor. Of the two BRAF inhibitor-resistant cell lines, A375P/Mdr cells harboring the BRAF V600E mutant were resistant and the wild-type BRAF SK-MEL-2 cells were sensitive to paclitaxel. In particular, paclitaxel caused the growth inhibition of SK-MEL-2 cells to a much greater extent than it caused growth inhibition of A375P cells. Paclitaxel exhibited no significant effect on the phosphorylation of MEK-ERK in any cell lines tested, regardless of both the BRAF mutation and the drug resistance, implying that paclitaxel activity is independent of MEK-ERK inhibition. In A375P cells, paclitaxel treatment resulted in a marked emergence of apoptotic cells after mitotic arrest, concomitant with a remarkable induction of p21(Cip1). However, paclitaxel only moderately increased the levels of p21(Cip1) in A375P/Mdr cells, which exhibited a strong resistance to paclitaxel. The p21(Cip1) overexpression partially conferred paclitaxel sensitivity to A375P/Mdr cells. Interestingly, we found an extremely low background expression level of p21(Cip1) in SK-MEL-2 cells lacking normal p53 function, which caused much greater G2/M arrest than that seen in A375P cells. Taken together, these results suggest that paclitaxel may be an effective anticancer agent through regulating the expression of p21(Cip1) for the treatment of BRAF mutant melanoma cells resistant to BRAF inhibitors. PMID:25912549

  13. Metabolomic analysis reveals the relationship between AZI1 and sugar signaling in systemic acquired resistance of Arabidopsis.

    PubMed

    Wang, Xiao-Yan; Li, Dian-Zhen; Li, Qi; Ma, Yan-Qin; Yao, Jing-Wen; Huang, Xuan; Xu, Zi-Qin

    2016-10-01

    The function of AZI1 in systemic acquired resistance of Arabidopsis was confirmed by investigation of the phenotypic features of wild-type Col-0, AZI1 T-DNA knockout and AZI1 overexpressing plants after infection with virulent and avirulent Pseudomonas syringae. Real-time quantitative PCR and Northern blotting analyses showed that the transcript abundances of PR genes increased significantly in local and systemic leaves of wild-type Col-0 and AZI1 overexpressing plants challenged with avirulent P. syringae, whereas the mRNA accumulation of PR genes was obviously attenuated in local and systemic leaves of AZI1 T-DNA knockout plants after localized infiltration with avirulent Psm avrRpm1. The changes of metabolomic profiles in distal leaves of three types of materials infected with avirulent P. syringae were determined by (1)H NMR spectrometry and data mining showed that the soluble carbonhydrates might function as signal substances in the systemic immunity of Arabidopsis. At the same time, the expression of the sugar signaling genes in local and distal leaves after infection of avirulent P. syringae was compared. As a result, it was found that the transcript abundances of sugar signaling genes, including SUS1, SUS2, SUS3, SUS6, SUT1, HXK1, HXK2, SNRK1.2, ERD6, TPS1, TOR, SNRK1.1, SNRK1.3 and bZIP11, were obviously changed in distal leaves of different materials with the modulated AZI1 activities, indicating sugar-related genes are involved in regulation of the systemic immunity mediated by AZI1. These results also illustrated that the immune system associated with sugar molecules probably was an important part of the systemic acquired resistance in Arabidopsis. PMID:27337039

  14. Acute haematogenous community-acquired methicillin-resistant Staphylococcus aureus osteomyelitis in an adult: Case report and review of literature

    PubMed Central

    2012-01-01

    Background Methicillin-resistant Staphylococcus aureus (MRSA) has of late emerged as a cause of community-acquired infections among immunocompetent adults without risk factors. Skin and soft tissue infections represent the majority of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) clinical presentations, whilst invasive and life-threatening illness like necrotizing pneumonia, necrotizing fasciitis, pyomyositis, osteomyelitis and sepsis syndrome are less common. Although more widely described in the pediatric age group, the occurrence of CA-MRSA osteomyelitis in adults is an uncommonly reported entity. Case presentation We describe an invasive CA-MRSA infection in a 28 year-old previously healthy male, manifesting with bacteraemia, osteomyelitis of femur, pyomyositis and septic arthritis of the knee. Initially a preliminary diagnosis of osteosarcoma was suggested by imaging studies and patient underwent a bone biopsy. MRSA was subsequently isolated from blood cultures taken on day of admission, bone, tissue and pus cultures. Incision and drainage of abscess was performed and patient was treated with vancomycin, with fusidic acid added later. It took 6 months for the inflammatory markers to normalize, warranting 6-months of anti-MRSA therapy. Patient was a fervent deer hunter and we speculate that he acquired this infection from extensive direct contact with deer. Molecular characterization of this isolate showed that it belonged to multilocus sequence type (MLST) ST30 and exhibited the staphylococcal chromosome cassette mec (SCCmec) type IV, staphylococcus protein A (spa) type t019, accessory gene regulator (agr) type III and dru type dt10m. This strain harbored Panton-Valentine leukocidin (pvl) genes together with 3 other virulent genes; sei (enterotoxin), hlg (hemolysin) and fnbA (fibronectin binding protein). Conclusion This case study alerts physicians that beyond the most commonly encountered skin and soft tissue infections, pvl

  15. CXCR4-targeted lipid-coated PLGA nanoparticles deliver sorafenib and overcome acquired drug resistance in liver cancer.

    PubMed

    Gao, Dong-Yu; Lin, Ts-Ting; Sung, Yun-Chieh; Liu, Ya Chi; Chiang, Wen-Hsuan; Chang, Chih-Chun; Liu, Jia-Yu; Chen, Yunching

    2015-10-01

    Sorafenib, a multikinase inhibitor, has been used as an anti-angiogenic agent against highly vascular hepatocellular carcinoma (HCC) - yet associated with only moderate therapeutic effect and the high incidence of HCC recurrence. We have shown intratumoral hypoxia induced by sorafenib activated C-X-C receptor type 4 (CXCR4)/stromal-derived factor 1α (SDF1α) axis, resulting in polarization toward a tumor-promoting microenvironment and resistance to anti-angiogenic therapy in HCC. Herein, we formulated sorafenib in CXCR4-targeted lipid-coated poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) modified with a CXCR4 antagonist, AMD3100 to systemically deliver sorafenib into HCC and sensitize HCC to sorafenib treatment. We demonstrated that CXCR4-targeted NPs efficiently delivered sorafenib into HCCs and human umbilical vein endothelial cells (HUVECs) to achieve cytotoxicity and anti-angiogenic effect in vitro and in vivo. Despite the increased expression of SDF1α upon the persistent hypoxia induced by sorafenib-loaded CXCR4-targeted NPs, AMD3100 attached to the NPs can block CXCR4/SDF1α, leading to the reduced infiltration of tumor-associated macrophages, enhanced anti-angiogenic effect, a delay in tumor progression and increased overall survival in the orthotopic HCC model compared with other control groups. In conclusion, our results highlight the clinical potential of CXCR4-targeted NPs for delivering sorafenib and overcoming acquired drug resistance in liver cancer. PMID:26218745

  16. Potential therapeutic drug target identification in Community Acquired-Methicillin Resistant Staphylococcus aureus (CA-MRSA) using computational analysis

    PubMed Central

    Yadav, Pramod Kumar; Singh, Gurmit; Singh, Satendra; Gautam, Budhayash; Saad, Esmaiel IF

    2012-01-01

    The emergence of multidrug-resistant strain of community-acquired methicillin resistant Staphylococcus aureus (CA-MRSA) strain has highlighted the urgent need for the alternative and effective therapeutic approach to combat the menace of this nosocomial pathogen. In the present work novel potential therapeutic drug targets have been identified through the metabolic pathways analysis. All the gene products involved in different metabolic pathways of CA-MRSA in KEGG database were searched against the proteome of Homo sapiens using the BLASTp program and the threshold of E-value was set to as 0.001. After database searching, 152 putative targets were identified. Among all 152 putative targets, 39 genes encoding for putative targets were identified as the essential genes from the DEG database which are indispensable for the survival of CA-MRSA. After extensive literature review, 7 targets were identified as potential therapeutic drug target. These targets are Fructose-bisphosphate aldolase, Phosphoglyceromutase, Purine nucleoside phosphorylase, Uridylate kinase, Tryptophan synthase subunit beta, Acetate kinase and UDP-N-acetylglucosamine 1-carboxyvinyltransferase. Except Uridylate kinase all the identified targets were involved in more than one metabolic pathways of CA-MRSA which underlines the importance of drug targets. These potential therapeutic drug targets can be exploited for the discovery of novel inhibitors for CA-MRSA using the structure based drug design (SBDD) strategy. PMID:23055607

  17. Shigella Antimicrobial Drug Resistance Mechanisms, 2004-2014.

    PubMed

    Nüesch-Inderbinen, Magdalena; Heini, Nicole; Zurfluh, Katrin; Althaus, Denise; Hächler, Herbert; Stephan, Roger

    2016-06-01

    To determine antimicrobial drug resistance mechanisms of Shigella spp., we analyzed 344 isolates collected in Switzerland during 2004-2014. Overall, 78.5% of isolates were multidrug resistant; 10.5% were ciprofloxacin resistant; and 2% harbored mph(A), a plasmid-mediated gene that confers reduced susceptibility to azithromycin, a last-resort antimicrobial agent for shigellosis. PMID:27191035

  18. Shigella Antimicrobial Drug Resistance Mechanisms, 2004–2014

    PubMed Central

    Nüesch-Inderbinen, Magdalena; Heini, Nicole; Zurfluh, Katrin; Althaus, Denise; Hächler, Herbert

    2016-01-01

    To determine antimicrobial drug resistance mechanisms of Shigella spp., we analyzed 344 isolates collected in Switzerland during 2004–2014. Overall, 78.5% of isolates were multidrug resistant; 10.5% were ciprofloxacin resistant; and 2% harbored mph(A), a plasmid-mediated gene that confers reduced susceptibility to azithromycin, a last-resort antimicrobial agent for shigellosis. PMID:27191035

  19. Arabidopsis ENHANCED DISEASE SUSCEPTIBILITY1 promotes systemic acquired resistance via azelaic acid and its precursor 9-oxo nonanoic acid.

    PubMed

    Wittek, Finni; Hoffmann, Thomas; Kanawati, Basem; Bichlmeier, Marlies; Knappe, Claudia; Wenig, Marion; Schmitt-Kopplin, Philippe; Parker, Jane E; Schwab, Wilfried; Vlot, A Corina

    2014-11-01

    Systemic acquired resistance (SAR) is a form of inducible disease resistance that depends on salicylic acid and its upstream regulator ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1). Although local Arabidopsis thaliana defence responses activated by the Pseudomonas syringae effector protein AvrRpm1 are intact in eds1 mutant plants, SAR signal generation is abolished. Here, the SAR-specific phenotype of the eds1 mutant is utilized to identify metabolites that contribute to SAR. To this end, SAR bioassay-assisted fractionation of extracts from the wild type compared with eds1 mutant plants that conditionally express AvrRpm1 was performed. Using high-performance liquid chromatography followed by mass spectrometry, systemic immunity was associated with the accumulation of 60 metabolites, including the putative SAR signal azelaic acid (AzA) and its precursors 9-hydroperoxy octadecadienoic acid (9-HPOD) and 9-oxo nonanoic acid (ONA). Exogenous ONA induced SAR in systemic untreated leaves when applied at a 4-fold lower concentration than AzA. The data suggest that in planta oxidation of ONA to AzA might be partially responsible for this response and provide further evidence that AzA mobilizes Arabidopsis immunity in a concentration-dependent manner. The AzA fragmentation product pimelic acid did not induce SAR. The results link the C9 lipid peroxidation products ONA and AzA with systemic rather than local resistance and suggest that EDS1 directly or indirectly promotes the accumulation of ONA, AzA, or one or more of their common precursors possibly by activating one or more pathways that either result in the release of these compounds from galactolipids or promote lipid peroxidation. PMID:25114016

  20. Arabidopsis ENHANCED DISEASE SUSCEPTIBILITY1 promotes systemic acquired resistance via azelaic acid and its precursor 9-oxo nonanoic acid

    PubMed Central

    Wittek, Finni; Hoffmann, Thomas; Kanawati, Basem; Bichlmeier, Marlies; Knappe, Claudia; Wenig, Marion; Schmitt-Kopplin, Philippe; Parker, Jane E.; Schwab, Wilfried; Vlot, A. Corina

    2014-01-01

    Systemic acquired resistance (SAR) is a form of inducible disease resistance that depends on salicylic acid and its upstream regulator ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1). Although local Arabidopsis thaliana defence responses activated by the Pseudomonas syringae effector protein AvrRpm1 are intact in eds1 mutant plants, SAR signal generation is abolished. Here, the SAR-specific phenotype of the eds1 mutant is utilized to identify metabolites that contribute to SAR. To this end, SAR bioassay-assisted fractionation of extracts from the wild type compared with eds1 mutant plants that conditionally express AvrRpm1 was performed. Using high-performance liquid chromatography followed by mass spectrometry, systemic immunity was associated with the accumulation of 60 metabolites, including the putative SAR signal azelaic acid (AzA) and its precursors 9-hydroperoxy octadecadienoic acid (9-HPOD) and 9-oxo nonanoic acid (ONA). Exogenous ONA induced SAR in systemic untreated leaves when applied at a 4-fold lower concentration than AzA. The data suggest that in planta oxidation of ONA to AzA might be partially responsible for this response and provide further evidence that AzA mobilizes Arabidopsis immunity in a concentration-dependent manner. The AzA fragmentation product pimelic acid did not induce SAR. The results link the C9 lipid peroxidation products ONA and AzA with systemic rather than local resistance and suggest that EDS1 directly or indirectly promotes the accumulation of ONA, AzA, or one or more of their common precursors possibly by activating one or more pathways that either result in the release of these compounds from galactolipids or promote lipid peroxidation. PMID:25114016

  1. Hospital Acquired Pneumonia Due to Achromobacter spp. in a Geriatric Ward in China: Clinical Characteristic, Genome Variability, Biofilm Production, Antibiotic Resistance and Integron in Isolated Strains

    PubMed Central

    Liu, Chao; Pan, Fei; Guo, Jun; Yan, Weifeng; Jin, Yi; Liu, Changting; Qin, Long; Fang, Xiangqun

    2016-01-01

    Background: Hospital-acquired pneumonia (HAP) due to Achromobacter has become a substantial concern in recent years. However, HAP due to Achromobacter in the elderly is rare. Methods: A retrospective analysis was performed on 15 elderly patients with HAP due to Achromobacter spp., in which the sequence types (STs), integrons, biofilm production and antibiotic resistance of the Achromobacter spp. were examined. Results: The mean age of the 15 elderly patients was 88.8 ± 5.4 years. All patients had at least three underlying diseases and catheters. Clinical outcomes improved in 10 of the 15 patients after antibiotic and/or mechanical ventilation treatment, but three patients had chronic infections lasting more than 1 year. The mortality rate was 33.3% (5/15). All strains were resistant to aminoglycosides, aztreonam, nitrofurantoin, and third- and fourth-generation cephalosporins (except ceftazidime and cefoperazone). Six new STs were detected. The most frequent ST was ST306. ST5 was identified in two separate buildings of the hospital. ST313 showed higher MIC in cephalosporins, quinolones and carbapenems, which should be more closely considered in clinical practice. All strains produced biofilm and had integron I and blaOXA-114-like. The main type was blaOXA-114q. The variable region of integron I was different among strains, and the resistance gene of the aminoglycosides was most commonly inserted in integron I. Additionally, blaPSE-1 was first reported in this isolate. Conclusion: Achromobacter spp. infection often occurs in severely ill elders with underlying diseases. The variable region of integrons differs, suggesting that Achromobacter spp. is a reservoir of various resistance genes. PMID:27242678

  2. Defense mechanisms in congenital and acquired facial disfigurement: a clinical-empirical study.

    PubMed

    van den Elzen, Marijke E P; Versnel, Sarah L; Perry, J Christopher; Mathijssen, Irene M J; Duivenvoorden, Hugo J

    2012-04-01

    It is of clinical interest to investigate the degree to which patients with facial disfigurement use defense styles. Therefore, 59 adults born with rare facial clefts, 59 patients with facial deformities acquired at an adult age, and a reference group of 141 adults without facial disfigurements completed standardized questionnaires. There was a significant difference between the group with and the group without disfigurements on immature defense styles, with the disfigured group using the immature style more frequently. There was a trend for the nondisfigured group to use more mature defense styles. No difference between congenital and acquired groups was seen on individual types of defense style. Self-esteem had the strength to differentiate mature and immature defense styles within our disfigured groups. The association of low self-esteem and the utilization of immature defense styles suggests that professional help may tailor treatment on discussing immature defense style and problems triggering or maintaining this style. PMID:22456586

  3. Significant Differences in the Development of Acquired Resistance to the MDM2 Inhibitor SAR405838 between In Vitro and In Vivo Drug Treatment

    PubMed Central

    Hoffman-Luca, C. Gianna; Yang, Chao-Yie; Lu, Jianfeng; Ziazadeh, Daniel; McEachern, Donna; Debussche, Laurent; Wang, Shaomeng

    2015-01-01

    SAR405838 is a potent and specific MDM2 inhibitor currently being evaluated in Phase I clinical trials for the treatment of human cancer. Using the SJSA-1 osteosarcoma cell line which harbors an amplified MDM2 gene and wild-type p53, we have investigated the acquired resistance mechanisms both in vitro and in vivo to SAR405838. Treatment of SJSA-1 cells with SAR405838 in vitro leads to dose-dependent cell growth inhibition, cell cycle arrest and robust apoptosis. However, prolonged treatment of SJSA-1 cells in vitro with SAR405838 results in profound acquired resistance to the drug. Analysis of in vitro-derived resistant cell lines showed that p53 is mutated in the DNA binding domain and can no longer be activated by SAR405838. Treatment of the parental SJSA-1 xenograft tumors with SAR405838 in mice yields rapid tumor regression but the tumors eventually regrow. Culturing the regrown tumors established a number of sublines, which showed only modest (3–5 times) loss of sensitivity to SAR405838 in vitro. Sequencing of the p53 showed that it retains its wild-type status in these in vivo sublines, with the exception of one subline, which harbors a single heterozygous C176F p53 mutation. Using xenograft models of two in vivo derived sublines, which has either wild-type p53 or p53 containing a single heterozygous C176F mutation, we showed that while SAR405838 effectively achieves partial tumor regression in these models, it no longer induces complete tumor regression and tumors resume growth once the treatment is stopped. Harvesting and culturing tumors obtained from a prolonged treatment with SAR405838 in mice established additional in vivo sublines, which all contain a single heterozygous C176F mutation with no additional p53 mutation detected. Interestingly, SAR405838 can still effectively activate p53 in all sublines containing a single heterozygous C176F mutation, with a moderately reduced potency as compared to that in the parental cell line. Consistently, SAR

  4. Targeting glucosylceramide synthase induction of cell surface globotriaosylceramide (Gb3) in acquired cisplatin-resistance of lung cancer and malignant pleural mesothelioma cells

    SciTech Connect

    Tyler, Andreas; Johansson, Anders; Karlsson, Terese; Gudey, Shyam Kumar; Brännström, Thomas; Grankvist, Kjell; Behnam-Motlagh, Parviz

    2015-08-01

    Background: Acquired resistance to cisplatin treatment is a caveat when treating patients with non-small cell lung cancer (NSCLC) and malignant pleural mesothelioma (MPM). Ceramide increases in response to chemotherapy, leading to proliferation arrest and apoptosis. However, a tumour stress activation of glucosylceramide synthase (GCS) follows to eliminate ceramide by formation of glycosphingolipids (GSLs) such as globotriaosylceramide (Gb3), the functional receptor of verotoxin-1. Ceramide elimination enhances cell proliferation and apoptosis blockade, thus stimulating tumor progression. GSLs transactivate multidrug resistance 1/P-glycoprotein (MDR1) and multidrug resistance-associated protein 1 (MRP1) expression which further prevents ceramide accumulation and stimulates drug efflux. We investigated the expression of Gb3, MDR1 and MRP1 in NSCLC and MPM cells with acquired cisplatin resistance, and if GCS activity or MDR1 pump inhibitors would reduce their expression and reverse cisplatin-resistance. Methods: Cell surface expression of Gb3, MDR1 and MRP1 and intracellular expression of MDR1 and MRP1 was analyzed by flow cytometry and confocal microscopy on P31 MPM and H1299 NSCLC cells and subline cells with acquired cisplatin resistance. The effect of GCS inhibitor PPMP and MDR1 pump inhibitor cyclosporin A for 72 h on expression and cisplatin cytotoxicity was tested. Results: The cisplatin-resistant cells expressed increased cell surface Gb3. Cell surface Gb3 expression of resistant cells was annihilated by PPMP whereas cyclosporin A decreased Gb3 and MDR1 expression in H1299 cells. No decrease of MDR1 by PPMP was noted in using flow cytometry, whereas a decrease of MDR1 in H1299 and H1299res was indicated with confocal microscopy. No certain co-localization of Gb3 and MDR1 was noted. PPMP, but not cyclosporin A, potentiated cisplatin cytotoxicity in all cells. Conclusions: Cell surface Gb3 expression is a likely tumour biomarker for acquired cisplatin

  5. Humoral immunity in experimental syphilis. II. The relationship of neutralizing factors in immune serum to acquired resistance.

    PubMed

    Bishop, N H; Miller, J N

    1976-07-01

    Evidence for a humoral mechanism in immunity to experimental syphilis was provided by the demonstration of immune rabbit serum factor(s) capable of inactivating virulent Treponema pallidum, Nichols strain, in an in vitro-in vivo neutralization test. After intratesticular infection, rabbits were bled periodically and their resistance to reinfection was determined by challenge with T. pallidum. The results of challenge showed that resistance to reinfection begins to develop by 11 days after infection, becomes complete by 3 months, and persists for at least 2 years. In the neutralization test, a mixture of treponemal suspension and serum from the infected animals was incubated anaerobically at 34 degrees C and the virulence of the treponemes was determined by intradermal inoculation into normal rabbits. Complete inactivation of treponemes by immune serum required heat-stable and heat-labile (56 degrees C, 30 min) serum components and 16 hr of incubation, and was accelerated by pre-incubation of the treponemes for 4 hr with nonimmune serum but not by 100 mug/ml of added lysozyme. Serum-neutralizing activity, first demonstrable 1 month postinfection, was quantitated by a neutralizing endpoint (NEP). A relatively close quantitative correlation was shown between the development of resistance to symptomatic reinfection and the appearance and persistence of both TPI antibody and neutralizing serum factor(s). The nature of the serum factor(s), the mechanism of treponemal inactivation, and the application of the test in assessing the immune status are discussed. PMID:778262

  6. Community-acquired necrotizing pneumonia caused by methicillin-resistant Staphylococcus aureus ST30-SCCmecIVc-spat019-PVL positive in San Antonio de Areco, Argentina.

    PubMed

    Fernandez, Silvina; Murzicato, Sofía; Sandoval, Orlando; Fernández-Canigia, Liliana; Mollerach, Marta

    2015-01-01

    Community-acquired methicillin-resistant Staphylococcus aureus is the first cause of skin and soft tissue infections, but can also produce severe diseases such as bacteremia, osteomyelitis and necrotizing pneumonia. Some S. aureus lineages have been described in cases of necrotizing pneumonia worldwide, usually in young, previously healthy patients. In this work, we describe a fatal case of necrotizing pneumonia due to community-acquired methicillin-resistant S. aureus clone ST30-SCCmecIVc-spat019-PVL positive in an immunocompetent adult patient. PMID:25681265

  7. Acquired hyperpigmentations*

    PubMed Central

    Cestari, Tania Ferreira; Dantas, Lia Pinheiro; Boza, Juliana Catucci

    2014-01-01

    Cutaneous hyperpigmentations are frequent complaints, motivating around 8.5% of all dermatological consultations in our country. They can be congenital, with different patterns of inheritance, or acquired in consequence of skin problems, systemic diseases or secondary to environmental factors. The vast majority of them are linked to alterations on the pigment melanin, induced by different mechanisms. This review will focus on the major acquired hyperpigmentations associated with increased melanin, reviewing their mechanisms of action and possible preventive measures. Particularly prominent aspects of diagnosis and therapy will be emphasized, with focus on melasma, post-inflammatory hyperpigmentation, periorbital pigmentation, dermatosis papulosa nigra, phytophotodermatoses, flagellate dermatosis, erythema dyschromicum perstans, cervical poikiloderma (Poikiloderma of Civatte), acanthosis nigricans, cutaneous amyloidosis and reticulated confluent dermatitis PMID:24626644

  8. Tracking Cefoperazone/Sulbactam Resistance Development In vivo in A. baumannii Isolated from a Patient with Hospital-Acquired Pneumonia by Whole-Genome Sequencing.

    PubMed

    Liu, Xiaofen; Zheng, Huajun; Zhang, Weipeng; Shen, Zhen; Zhao, Miao; Chen, Yuancheng; Sun, Li; Shi, Jun; Zhang, Jing

    2016-01-01

    Cefoperazone/sulbactam has been shown to be efficacious for the treatment of infections caused by Acinetobacter baumannii; however, the mechanism underlying resistance to this synergistic combination is not well understood. In the present study, two A. baumannii isolates, AB1845 and AB2092, were isolated from a patient with hospital-acquired pneumonia before and after 20 days of cefoperazone/sulbactam therapy (2:1, 3 g every 8 h with a 1-h infusion). The minimum inhibitory concentration (MIC) of cefoperazone/sulbactam for AB1845 and AB2092 was 16/8 and 128/64 mg/L, respectively. Blood samples were collected on day 4 of the treatment to determine the concentration of cefoperazone and sulbactam. The pharmacokinetic/pharmacodynamic (PK/PD) indices (%T>MIC) were calculated to evaluate the dosage regimen and resistance development. The results showed that %T>MIC of cefoperazone and sulbactam was 100% and 34.5% for AB1845, and 0% and 0% for AB2092, respectively. Although there was no available PK/PD target for sulbactam, it was proposed that sulbactam should be administered at higher doses or for prolonged infusion times to achieve better efficacy. To investigate the mechanism of A. baumannii resistance to the cefoperazone/sulbactam combination in vivo, whole-genome sequencing of these two isolates was further performed. The sequencing results showed that 97.6% of the genome sequences were identical and 33 non-synonymous mutations were detected between AB1845 and AB2092. The only difference of these two isolates was showed in sequencing coverage comparison. There was a 6-kb amplified DNA fragment which was three times higher in AB2092, compared with AB1845. The amplified DNA fragment containing the bla OXA-23 gene on transposon Tn2009. Further quantitative real-time PCR results demonstrated that gene expression at the mRNA level of bla OXA-23 was >5 times higher in AB2092 than in AB1845. These results suggested that the bla OXA-23 gene had higher expression level in AB

  9. Tracking Cefoperazone/Sulbactam Resistance Development In vivo in A. baumannii Isolated from a Patient with Hospital-Acquired Pneumonia by Whole-Genome Sequencing

    PubMed Central

    Liu, Xiaofen; Zheng, Huajun; Zhang, Weipeng; Shen, Zhen; Zhao, Miao; Chen, Yuancheng; Sun, Li; Shi, Jun; Zhang, Jing

    2016-01-01

    Cefoperazone/sulbactam has been shown to be efficacious for the treatment of infections caused by Acinetobacter baumannii; however, the mechanism underlying resistance to this synergistic combination is not well understood. In the present study, two A. baumannii isolates, AB1845 and AB2092, were isolated from a patient with hospital-acquired pneumonia before and after 20 days of cefoperazone/sulbactam therapy (2:1, 3 g every 8 h with a 1-h infusion). The minimum inhibitory concentration (MIC) of cefoperazone/sulbactam for AB1845 and AB2092 was 16/8 and 128/64 mg/L, respectively. Blood samples were collected on day 4 of the treatment to determine the concentration of cefoperazone and sulbactam. The pharmacokinetic/pharmacodynamic (PK/PD) indices (%T>MIC) were calculated to evaluate the dosage regimen and resistance development. The results showed that %T>MIC of cefoperazone and sulbactam was 100% and 34.5% for AB1845, and 0% and 0% for AB2092, respectively. Although there was no available PK/PD target for sulbactam, it was proposed that sulbactam should be administered at higher doses or for prolonged infusion times to achieve better efficacy. To investigate the mechanism of A. baumannii resistance to the cefoperazone/sulbactam combination in vivo, whole-genome sequencing of these two isolates was further performed. The sequencing results showed that 97.6% of the genome sequences were identical and 33 non-synonymous mutations were detected between AB1845 and AB2092. The only difference of these two isolates was showed in sequencing coverage comparison. There was a 6-kb amplified DNA fragment which was three times higher in AB2092, compared with AB1845. The amplified DNA fragment containing the blaOXA-23 gene on transposon Tn2009. Further quantitative real-time PCR results demonstrated that gene expression at the mRNA level of blaOXA-23 was >5 times higher in AB2092 than in AB1845. These results suggested that the blaOXA-23 gene had higher expression level in AB2092

  10. A platinum-based hybrid drug design approach to circumvent acquired resistance to molecular targeted tyrosine kinase inhibitors

    NASA Astrophysics Data System (ADS)

    Wei, Yuming; Poon, Daniel C.; Fei, Rong; Lam, Amy S. M.; Au-Yeung, Steve C. F.; To, Kenneth K. W.

    2016-05-01

    Three molecular targeted tyrosine kinase inhibitors (TKI) were conjugated to classical platinum-based drugs with an aim to circumvent TKI resistance, predominately mediated by the emergence of secondary mutations on oncogenic kinases. The hybrids were found to maintain specificity towards the same oncogenic kinases as the original TKI. Importantly, they are remarkably less affected by TKI resistance, presumably due to their unique structure and the observed dual mechanism of anticancer activity (kinase inhibition and DNA damage). The study is also the first to report the application of a hybrid drug approach to switch TKIs from being efflux transporter substrates into non-substrates. TKIs cannot penetrate into the brain for treating metastases because of efflux transporters at the blood brain barrier. The hybrids were found to escape drug efflux and they accumulate more than the original TKI in the brain in BALB/c mice. Further development of the hybrid compounds is warranted.

  11. A platinum-based hybrid drug design approach to circumvent acquired resistance to molecular targeted tyrosine kinase inhibitors

    PubMed Central

    Wei, Yuming; Poon, Daniel C.; Fei, Rong; Lam, Amy S. M.; Au-Yeung, Steve C. F.; To, Kenneth K. W.

    2016-01-01

    Three molecular targeted tyrosine kinase inhibitors (TKI) were conjugated to classical platinum-based drugs with an aim to circumvent TKI resistance, predominately mediated by the emergence of secondary mutations on oncogenic kinases. The hybrids were found to maintain specificity towards the same oncogenic kinases as the original TKI. Importantly, they are remarkably less affected by TKI resistance, presumably due to their unique structure and the observed dual mechanism of anticancer activity (kinase inhibition and DNA damage). The study is also the first to report the application of a hybrid drug approach to switch TKIs from being efflux transporter substrates into non-substrates. TKIs cannot penetrate into the brain for treating metastases because of efflux transporters at the blood brain barrier. The hybrids were found to escape drug efflux and they accumulate more than the original TKI in the brain in BALB/c mice. Further development of the hybrid compounds is warranted. PMID:27150583

  12. Understanding the mechanisms and drivers of antimicrobial resistance.

    PubMed

    Holmes, Alison H; Moore, Luke S P; Sundsfjord, Arnfinn; Steinbakk, Martin; Regmi, Sadie; Karkey, Abhilasha; Guerin, Philippe J; Piddock, Laura J V

    2016-01-01

    To combat the threat to human health and biosecurity from antimicrobial resistance, an understanding of its mechanisms and drivers is needed. Emergence of antimicrobial resistance in microorganisms is a natural phenomenon, yet antimicrobial resistance selection has been driven by antimicrobial exposure in health care, agriculture, and the environment. Onward transmission is affected by standards of infection control, sanitation, access to clean water, access to assured quality antimicrobials and diagnostics, travel, and migration. Strategies to reduce antimicrobial resistance by removing antimicrobial selective pressure alone rely upon resistance imparting a fitness cost, an effect not always apparent. Minimising resistance should therefore be considered comprehensively, by resistance mechanism, microorganism, antimicrobial drug, host, and context; parallel to new drug discovery, broad ranging, multidisciplinary research is needed across these five levels, interlinked across the health-care, agriculture, and environment sectors. Intelligent, integrated approaches, mindful of potential unintended results, are needed to ensure sustained, worldwide access to effective antimicrobials. PMID:26603922

  13. mTOR Inhibitors Control the Growth of EGFR Mutant Lung Cancer Even after Acquiring Resistance by HGF

    PubMed Central

    Ishikawa, Daisuke; Takeuchi, Shinji; Nakagawa, Takayuki; Sano, Takako; Nakade, Junya; Nanjo, Shigeki; Yamada, Tadaaki; Ebi, Hiromichi; Zhao, Lu; Yasumoto, Kazuo; Nakamura, Takahiro; Matsumoto, Kunio; Kagamu, Hiroshi; Yoshizawa, Hirohisa; Yano, Seiji

    2013-01-01

    Resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), gefitinib and erlotinib, is a critical problem in the treatment of EGFR mutant lung cancer. Several mechanisms, including bypass signaling by hepatocyte growth factor (HGF)-triggered Met activation, are implicated as mediators of resistance. The mammalian target of rapamycin (mTOR), is a downstream conduit of EGFR and MET signaling, and is thus considered a therapeutically attractive target in the treatment of various types of cancers. The purpose of this study was to examine whether 2 clinically approved mTOR inhibitors, temsirolimus and everolimus, overcome HGF-dependent resistance to EGFR-TKIs in EGFR mutant lung cancer cells. Both temsirolimus and everolimus inhibited the phosphorylation of p70S6K and 4E-BP1, which are downstream targets of the mTOR pathway, and reduced the viability of EGFR mutant lung cancer cells, PC-9, and HCC827, even in the presence of HGF in vitro. In a xenograft model, temsirolimus suppressed the growth of PC-9 cells overexpressing the HGF-gene; this was associated with suppression of the mTOR signaling pathway and tumor angiogenesis. In contrast, erlotinib did not suppress this signaling pathway or tumor growth. Multiple mechanisms, including the inhibition of vascular endothelial growth factor production by tumor cells and suppression of endothelial cell viability, contribute to the anti-angiogenic effect of temsirolimus. These findings indicate that mTOR inhibitors may be useful for controlling HGF-triggered EGFR-TKI resistance in EGFR mutant lung cancer, and they provide the rationale for clinical trials of mTOR inhibitors in patients stratified by EGFR mutation and HGF expression status. PMID:23690929

  14. Atypical Cell Populations Associated with Acquired Resistance to Cytostatics and Cancer Stem Cell Features: The Role of Mitochondria in Nuclear Encapsulation

    PubMed Central

    Gustmann, Sebastian; Jastrow, Holger; Acikelli, Ali Haydar; Dammann, Philip; Klein, Jacqueline; Dembinski, Ulrike; Bardenheuer, Walter; Malak, Sascha; Araúzo-Bravo, Marcos J.; Schultheis, Beate; Aldinger, Constanze; Strumberg, Dirk

    2014-01-01

    Until recently, acquired resistance to cytostatics had mostly been attributed to biochemical mechanisms such as decreased intake and/or increased efflux of therapeutics, enhanced DNA repair, and altered activity or deregulation of target proteins. Although these mechanisms have been widely investigated, little is known about membrane barriers responsible for the chemical imperviousness of cell compartments and cellular segregation in cytostatic-treated tumors. In highly heterogeneous cross-resistant and radiorefractory cell populations selected by exposure to anticancer agents, we found a number of atypical recurrent cell types in (1) tumor cell cultures of different embryonic origins, (2) mouse xenografts, and (3) paraffin sections from patient tumors. Alongside morphologic peculiarities, these populations presented cancer stem cell markers, aberrant signaling pathways, and a set of deregulated miRNAs known to confer both stem-cell phenotypes and highly aggressive tumor behavior. The first type, named spiral cells, is marked by a spiral arrangement of nuclei. The second type, monastery cells, is characterized by prominent walls inside which daughter cells can be seen maturing amid a rich mitochondrial environment. The third type, called pregnant cells, is a giant cell with a syncytium-like morphology, a main nucleus, and many endoreplicative functional progeny cells. A rare fourth cell type identified in leukemia was christened shepherd cells, as it was always associated with clusters of smaller cells. Furthermore, a portion of resistant tumor cells displayed nuclear encapsulation via mitochondrial aggregation in the nuclear perimeter in response to cytostatic insults, probably conferring imperviousness to drugs and long periods of dormancy until nuclear eclosion takes place. This phenomenon was correlated with an increase in both intracellular and intercellular mitochondrial traffic as well as with the uptake of free extracellular mitochondria. All these cellular

  15. Clinical features and molecular characteristics of invasive community-acquired methicillin-resistant Staphylococcus aureus infections in Taiwanese children.

    PubMed

    Chen, Chih-Jung; Su, Lin-Hui; Chiu, Cheng-Hsun; Lin, Tzou-Yien; Wong, Kin-Sun; Chen, Yi-Ywan M; Huang, Yhu-Chering

    2007-11-01

    Highly virulent community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has been associated with morbidity and mortality in various countries of the world. We characterized the clinical and molecular features of pediatric invasive CA-MRSA infections in Taiwan. Between July 2000 and June 2005, 31 previously healthy children with invasive CA-MRSA infections were identified from 423 children with community-onset methicillin-resistant S. aureus infections. The medical records were reviewed. The clinical isolates, if available, were collected for molecular characterization. Sixteen (51.6%) patients were male, and the mean age was 5.7 years. Adolescents accounted for 9 (29%) cases. Eighteen children had bone and/or joint infections, 14 had deep-seated soft tissue infections, 11 had pneumonia, and 2 had central nervous system infections. Multiorgan involvement was identified in 8 of 20 bacteremic cases. Twenty-two patients (71%) required surgical interventions. The mean hospital stay was 27.4 days. All of the 15 available isolates were classified as sequence type (ST) 59 or its single locus variant and belonged to 2 previously reported community-associated clones containing staphylococcal cassette chromosome mec (SCCmec) type IV or type V(T) in Taiwan. Most of the isolates were multiresistant to clindamycin (94%) and erythromycin (97%). Eleven (73.3%) isolates carried pvl genes, and the strains harboring pvl genes were significantly associated with lung involvement. In conclusion, invasive CA-MRSA infections in pediatric population were not limited to young children. Surgical interventions were often required, and a prolonged course of antibiotic therapy was needed. A multiresistant CA-MRSA clone characterized as ST59 was identified from these children in Taiwan. PMID:17662565

  16. Lack of acquired resistance in dogs to successive infestations of Rhipicephalus sanguineus ticks from Brazil and Argentina.

    PubMed

    Évora, Patricia Martinez; Sanches, Gustavo Seron; Jusi, Márcia Mariza Gomes; Alves, Lucas Bocchini Rodrigues; Machado, Rosangela Zacarias; Bechara, Gervásio Henrique

    2015-09-01

    Comparative studies between brown dog tick Rhipicephalus sanguineus populations from Brazil (Jaboticabal, São Paulo) and Argentina (Rafaela, Santa Fé) showed significant biological, morphological and genetic differences between them. This work aimed to study, in a comparative way, the acquisition of resistance in domestic dogs to R. sanguineus from Jaboticabal and Rafaela, after successive and controlled infestations. Ticks were kept in a BOD incubator under controlled conditions (27 °C, 80 % relative humidity, 12-h photoperiod). Ten dogs, Dachshund breed, males and females, 6 months old, short- or long-haired, without prior contact with ticks, were used as hosts. They were distributed into two experimental groups composed of five animals each: G1 infested with ten adult couples of R. sanguineus (Jaboticabal) per animal, and G2 infested with ten adult couples of R. sanguineus (Rafaela) per animal. Ticks' biological parameters and titration of antibodies from the dogs' sera by ELISA test were used for comparison between the strains. Results of the biological parameters showed that the dogs did not acquire immunity to either of the R. sanguineus strains after repeated infestations. The ELISA test showed low antibody titers in sera of dogs from G2, in successive infestations, and higher antibody responses post second and third infestations in G1. It also demonstrated cross-reactivity between sera of dogs infested with R. sanguineus (Jaboticabal) and antigens from R. sanguineus (Rafaela) and vice versa. We conclude that Dachshund dogs did not develop resistance against neither Jaboticabal nor Rafaela strains of R. sanguineus. PMID:26063405

  17. Demography and Intercontinental Spread of the USA300 Community-Acquired Methicillin-Resistant Staphylococcus aureus Lineage

    PubMed Central

    Glaser, Philippe; Martins-Simões, Patrícia; Villain, Adrien; Barbier, Maxime; Tristan, Anne; Bouchier, Christiane; Ma, Laurence; Bes, Michele; Laurent, Frederic; Guillemot, Didier; Wirth, Thierry

    2016-01-01

    ABSTRACT Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) was recognized worldwide during the 1990s; in less than a decade, several genetically distinct CA-MRSA lineages carrying Panton-Valentine leukocidin genes have emerged on every continent. Most notably, in the United States, the sequence type 18-IV (ST8-IV) clone known as USA300 has become highly prevalent, outcompeting methicillin-susceptible S. aureus (MSSA) and other MRSA strains in both community and hospital settings. CA-MRSA bacteria are much less prevalent in Europe, where the European ST80-IV European CA-MRSA clone, USA300 CA-MRSA strains, and other lineages, such as ST22-IV, coexist. The question that arises is whether the USA300 CA-MRSA present in Europe (i) was imported once or on very few occasions, followed by a broad geographic spread, anticipating an increased prevalence in the future, or (ii) derived from multiple importations with limited spreading success. In the present study, we applied whole-genome sequencing to a collection of French USA300 CA-MRSA strains responsible for sporadic cases and micro-outbreaks over the past decade and United States ST8 MSSA and MRSA isolates. Genome-wide phylogenetic analysis demonstrated that the population structure of the French isolates is the product of multiple introductions dating back to the onset of the USA300 CA-MRSA clone in North America. Coalescent-based demography of the USA300 lineage shows that a strong expansion occurred during the 1990s concomitant with the acquisition of the arginine catabolic mobile element and antibiotic resistance, followed by a sharp decline initiated around 2008, reminiscent of the rise-and-fall pattern previously observed in the ST80 lineage. A future expansion of the USA300 lineage in Europe is therefore very unlikely. PMID:26884428

  18. Emerging Mechanisms of Resistance to Androgen Receptor Inhibitors in Prostate Cancer

    PubMed Central

    Arora, Vivek K.

    2016-01-01

    Preface Over the past ten years, preclinical studies implicating sustained androgen receptor (AR) signaling as the primary driver of castration resistant prostate cancer (CRPC) led to the development of novel agents targeting the AR pathway that are now in widespread clinical use. These drugs prolong survival of patients with late stage prostate cancer but are not curative. In this review, we highlight emerging mechanisms of acquired resistance to these contemporary therapies, which fall into the three broad categories of restored AR signaling, AR bypass signaling and complete AR independence. This diverse spectrum of resistance mechanisms presents new challenges for long term disease control, which may be addressable through early use of combination therapies guided by recent insights from genomic landscape studies of CRPC. PMID:26563462

  19. Mechanisms of drug resistance in Mycobacterium tuberculosis: update 2015.

    PubMed

    Zhang, Y; Yew, W-W

    2015-11-01

    Drug-resistant tuberculosis (DR-TB), including multi- and extensively drug-resistant TB, is posing a significant challenge to effective treatment and TB control worldwide. New progress has been made in our understanding of the mechanisms of resistance to anti-tuberculosis drugs. This review provides an update on the major advances in drug resistance mechanisms since the previous publication in 2009, as well as added information on mechanisms of resistance to new drugs and repurposed agents. The recent application of whole genome sequencing technologies has provided new insight into the mechanisms and complexity of drug resistance. However, further research is needed to address the significance of newly discovered gene mutations in causing drug resistance. Improved knowledge of drug resistance mechanisms will help understand the mechanisms of action of the drugs, devise better molecular diagnostic tests for more effective DR-TB management (and for personalised treatment), and facilitate the development of new drugs to improve the treatment of this disease. PMID:26467578

  20. [Acquired drives. The cortical mechanism responsible to the emergence and development of social existence].

    PubMed

    József, Knoll

    2007-10-01

    This paper is a brief interpretation of the theory (J. Knoll: The Brain and Its Self, Springer, 2005) the main message of which is that the appearance of the mammalian brain with the ability to acquire drives ensured the development of social life, and eventually led to the evolution of the human society. In the mammalian brain capable to acquire drives, untrained cortical neurons (Group 1) possess the potentiality to change their functional state in response to practice, training, or experience in three consecutive stages, namely, by getting involved in (a) an extinguishable conditioned reflex (ECR) (Group 2), (b) an inextinguishable conditioned reflex (ICR) (Group 3), or (c)an acquired drive (Group 4). The activity of the cortical neurons belonging to Group 3 and 4 is inseparable from conscious perception. In any moment of life self is the sum of those cortical neurons that have already changed their functional significance and belong to Group 3 or 4. Metaphorically, every human being is born with a telencephalon that resembles a book with over 100 billion empty pages (untrained, naive cortical neurons, Group 1), and with the capacity to inscribe as much as possible in this book throughout life. Whenever a drive is acquired, chains of ICRs are fixed, neurons responsible for emotions are also coupled to the integral whole, thus cognitive/volitional consciousness is necessarily inseparable from an affective state of consciousness. Cortical neurons belonging to Group 3 or 4 continuously synthesize their specific enhancer substance within their capacity. This means that even in the vigilant resting state (leisure), in the absence of a dominant drive, as well as in the non-vigilant resting state (sleeping), the cortical neurons representing the totality of the already fixed ICRs and acquired drives are permanently under the influence of their specific enhancer substance. Although the level of this permanent, undulating activation remains low, it is unpredictable as to

  1. Acquired Color Vision Defects and Hexane Exposure: A Study of San Francisco Bay Area Automotive Mechanics.

    PubMed

    Beckman, Stella; Eisen, Ellen A; Bates, Michael N; Liu, Sa; Haegerstrom-Portnoy, Gunilla; Hammond, S Katharine

    2016-06-01

    Occupational exposure to solvents, including n-hexane, has been associated with acquired color vision defects. Blue-yellow defects are most common and may be due to neurotoxicity or retinal damage. Acetone may potentiate the neurotoxicity of n-hexane. We present results on nonhexane solvent and hexane exposure and color vision from a cross-sectional study of 835 automotive repair workers in the San Francisco Bay Area, California (2007-2013). Cumulative exposure was estimated from self-reported work history, and color vision was assessed using the Lanthony desaturated D-15 panel test. Log-binomial regression was used to estimate prevalence ratios for color vision defects. Acquired color vision defects were present in 29% of participants, of which 70% were blue-yellow. Elevated prevalence ratios were found for nonhexane solvent exposure, with a maximum of 1.31 (95% confidence interval (CI): 0.86, 2.00) for blue-yellow. Among participants aged ≤50 years, the prevalence ratio for blue-yellow defects was 2.17 (95% CI: 1.03, 4.56) in the highest quartile of nonhexane solvent exposure and 1.62 (95% CI: 0.97, 2.72) in the highest category of exposure to hexane with acetone coexposure. Cumulative exposures to hexane and nonhexane solvents in the highest exposure categories were associated with elevated prevalence ratios for color vision defects in younger participants. PMID:27188942

  2. Mechanisms Linking Inflammation to Insulin Resistance

    PubMed Central

    Chen, Li; Wang, Hua

    2015-01-01

    Obesity is now widespread around the world. Obesity-associated chronic low-grade inflammation is responsible for the decrease of insulin sensitivity, which makes obesity a major risk factor for insulin resistance and related diseases such as type 2 diabetes mellitus and metabolic syndromes. The state of low-grade inflammation is caused by overnutrition which leads to lipid accumulation in adipocytes. Obesity might increase the expression of some inflammatory cytokines and activate several signaling pathways, both of which are involved in the pathogenesis of insulin resistance by interfering with insulin signaling and action. It has been suggested that specific factors and signaling pathways are often correlated with each other; therefore, both of the fluctuation of cytokines and the status of relevant signaling pathways should be considered during studies analyzing inflammation-related insulin resistance. In this paper, we discuss how these factors and signaling pathways contribute to insulin resistance and the therapeutic promise targeting inflammation in insulin resistance based on the latest experimental studies. PMID:26136779

  3. Mechanisms Linking Inflammation to Insulin Resistance.

    PubMed

    Chen, Li; Chen, Rui; Wang, Hua; Liang, Fengxia

    2015-01-01

    Obesity is now widespread around the world. Obesity-associated chronic low-grade inflammation is responsible for the decrease of insulin sensitivity, which makes obesity a major risk factor for insulin resistance and related diseases such as type 2 diabetes mellitus and metabolic syndromes. The state of low-grade inflammation is caused by overnutrition which leads to lipid accumulation in adipocytes. Obesity might increase the expression of some inflammatory cytokines and activate several signaling pathways, both of which are involved in the pathogenesis of insulin resistance by interfering with insulin signaling and action. It has been suggested that specific factors and signaling pathways are often correlated with each other; therefore, both of the fluctuation of cytokines and the status of relevant signaling pathways should be considered during studies analyzing inflammation-related insulin resistance. In this paper, we discuss how these factors and signaling pathways contribute to insulin resistance and the therapeutic promise targeting inflammation in insulin resistance based on the latest experimental studies. PMID:26136779

  4. Acquired resistance to metformin in breast cancer cells triggers transcriptome reprogramming toward a degradome-related metastatic stem-like profile.

    PubMed

    Oliveras-Ferraros, Cristina; Vazquez-Martin, Alejandro; Cuyàs, Elisabet; Corominas-Faja, Bruna; Rodríguez-Gallego, Esther; Fernández-Arroyo, Salvador; Martin-Castillo, Begoña; Joven, Jorge; Menendez, Javier A

    2014-01-01

    , AURKB, BUB1, CENP-A, CENP-M) and pro-autophagic features (i.e., TRAIL upregulation and BCL-2 downregulation), it appears that the unique mechanism of acquired resistance to metformin has opposing roles in growth and metastatic dissemination. While refractoriness to metformin limits breast cancer cell growth, likely due to aberrant mitotic/cytokinetic machinery and accelerated autophagy, it notably increases the potential of metastatic dissemination by amplifying the number of pro-migratory and stemness inputs via the activation of a significant number of proteases and EMT regulators. Future studies should elucidate whether our findings using supra-physiological concentrations of metformin mechanistically mimic the ultimate processes that could paradoxically occur in a polyploid, senescent-autophagic scenario triggered by the chronic metabolic stresses that occur during cancer development and after treatment with cancer drugs. PMID:24553122

  5. Comparing the epidemiology of hospital-acquired methicillin-resistant Staphylococcus aureus clone groups in Alberta, Canada.

    PubMed

    Bruzzese, S; Bush, K; Leal, J; Kim, J; Vickers, D M; Rusk, A; Fathima, S; Li, V; Chui, L; Louie, M; Henderson, E

    2016-07-01

    Patients with methicillin-resistant Staphylococcus aureus (MRSA) clones, which were traditionally seen in the community setting (USA400/CMRSA7 and USA300/CMRSA10), are often identified as hospital-acquired (HA) infections using Infection Prevention and Control (IPC) surveillance definitions. This study examined the demographics and healthcare risk factors of patients with HA-MRSA to help understand if community MRSA clones are from a source internal or external to the hospital setting. Despite USA300/CMRSA10 being the predominant clone in Alberta, hospital clones (USA100/CMRSA2) still dominated in the acute care setting. In the Alberta hospitalized population, patients with USA400/CMRSA7 and USA300/CMRSA10 clones were significantly younger, had fewer comorbidities, and a greater proportion had none or ambulatory care-only healthcare exposure. These findings suggest that there are two distinct populations of HA-MRSA patients, and the patients with USA400/CMRSA7 and USA300/CMRSA10 clones identified in hospital more greatly resemble patients affected by those clones in the community. It is possible that epidemiological assessment overidentifies HA acquisition of MRSA in patients unscreened for MRSA on admission to acute care. PMID:26947456

  6. Antagonistic Interaction between Systemic Acquired Resistance and the Abscisic Acid–Mediated Abiotic Stress Response in Arabidopsis[W

    PubMed Central

    Yasuda, Michiko; Ishikawa, Atsushi; Jikumaru, Yusuke; Seki, Motoaki; Umezawa, Taishi; Asami, Tadao; Maruyama-Nakashita, Akiko; Kudo, Toshiaki; Shinozaki, Kazuo; Yoshida, Shigeo; Nakashita, Hideo

    2008-01-01

    Systemic acquired resistance (SAR) is a potent innate immunity system in plants that is effective against a broad range of pathogens. SAR development in dicotyledonous plants, such as tobacco (Nicotiana tabacum) and Arabidopsis thaliana, is mediated by salicylic acid (SA). Here, using two types of SAR-inducing chemicals, 1,2-benzisothiazol-3(2H)-one1,1-dioxide and benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester, which act upstream and downstream of SA in the SAR signaling pathway, respectively, we show that treatment with abscisic acid (ABA) suppresses the induction of SAR in Arabidopsis. In an analysis using several mutants in combination with these chemicals, treatment with ABA suppressed SAR induction by inhibiting the pathway both upstream and downstream of SA, independently of the jasmonic acid/ethylene-mediated signaling pathway. Suppression of SAR induction by the NaCl-activated environmental stress response proved to be ABA dependent. Conversely, the activation of SAR suppressed the expression of ABA biosynthesis–related and ABA-responsive genes, in which the NPR1 protein or signaling downstream of NPR1 appears to contribute. Therefore, our data have revealed that antagonistic crosstalk occurs at multiple steps between the SA-mediated signaling of SAR induction and the ABA-mediated signaling of environmental stress responses. PMID:18586869

  7. Systemic Induction of the Small Antibacterial Compound in the Leaf Exudate During Benzothiadiazole-elicited Systemic Acquired Resistance in Pepper.

    PubMed

    Lee, Boyoung; Park, Yong-Soon; Yi, Hwe-Su; Ryu, Choong-Min

    2013-09-01

    Plants protect themselves from diverse potential pathogens by induction of the immune systems such as systemic acquired resistance (SAR). Most bacterial plant pathogens thrive in the intercellular space (apoplast) of plant tissues and cause symptoms. The apoplastic leaf exudate (LE) is believed to contain nutrients to provide food resource for phytopathogenic bacteria to survive and to bring harmful phytocompounds to protect plants against bacterial pathogens. In this study, we employed the pepper-Xanthomonas axonopodis system to assess whether apoplastic fluid from LE in pepper affects the fitness of X. axonopodis during the induction of SAR. The LE was extracted from pepper leaves 7 days after soil drench-application of a chemical trigger, benzothiadiazole (BTH). Elicitation of plant immunity was confirmed by significant up-regulation of four genes, CaPR1, CaPR4, CaPR9, and CaCHI2, by BTH treatment. Bacterial fitness was evaluated by measuring growth rate during cultivation with LE from BTH- or water-treated leaves. LE from BTH-treatment significantly inhibited bacterial growth when compared to that from the water-treated control. The antibacterial activity of LE from BTH-treated samples was not affected by heating at 100°C for 30 min. Although the antibacterial molecules were not precisely identified, the data suggest that small (less than 5 kDa), heat-stable compound(s) that are present in BTH-induced LE directly attenuate bacterial growth during the elicitation of plant immunity. PMID:25288963

  8. A Case Series of Acquired Drug Resistance-Associated Mutations in Human Immunodeficiency Virus-Infected Children: An Emerging Public Health Concern in Rural Africa

    PubMed Central

    Gamell, Anna; Muri, Lukas; Ntamatungiro, Alex; Nyogea, Daniel; Luwanda, Lameck B.; Hatz, Christoph; Battegay, Manuel; Felger, Ingrid; Tanner, Marcel; Klimkait, Thomas; Letang, Emilio

    2016-01-01

    The acquisition of drug-resistance mutations among African children living with in human immunodeficiency virus on antiretroviral treatment has been scarcely reported. This threatens the overall success of antiretroviral programs and the clinical outcomes of children in care. We present a well characterized series of children from rural Tanzania with acquired drug-resistance mutations to contribute to the better understanding of this emerging public health concern. PMID:26807427

  9. Global Analysis of the Evolution and Mechanism of Echinocandin Resistance in Candida glabrata

    PubMed Central

    Singh-Babak, Sheena D.; Babak, Tomas; Diezmann, Stephanie; Hill, Jessica A.; Xie, Jinglin Lucy; Chen, Ying-Lien; Poutanen, Susan M.; Rennie, Robert P.; Heitman, Joseph; Cowen, Leah E.

    2012-01-01

    The evolution of drug resistance has a profound impact on human health. Candida glabrata is a leading human fungal pathogen that can rapidly evolve resistance to echinocandins, which target cell wall biosynthesis and are front-line therapeutics for Candida infections. Here, we provide the first global analysis of mutations accompanying the evolution of fungal drug resistance in a human host utilizing a series of C. glabrata isolates that evolved echinocandin resistance in a patient treated with the echinocandin caspofungin for recurring bloodstream candidemia. Whole genome sequencing identified a mutation in the drug target, FKS2, accompanying a major resistance increase, and 8 additional non-synonymous mutations. The FKS2-T1987C mutation was sufficient for echinocandin resistance, and associated with a fitness cost that was mitigated with further evolution, observed in vitro and in a murine model of systemic candidemia. A CDC6-A511G(K171E) mutation acquired before FKS2-T1987C(S663P), conferred a small resistance increase. Elevated dosage of CDC55, which acquired a C463T(P155S) mutation after FKS2-T1987C(S663P), ameliorated fitness. To discover strategies to abrogate echinocandin resistance, we focused on the molecular chaperone Hsp90 and downstream effector calcineurin. Genetic or pharmacological compromise of Hsp90 or calcineurin function reduced basal tolerance and resistance. Hsp90 and calcineurin were required for caspofungin-dependent FKS2 induction, providing a mechanism governing echinocandin resistance. A mitochondrial respiration-defective petite mutant in the series revealed that the petite phenotype does not confer echinocandin resistance, but renders strains refractory to synergy between echinocandins and Hsp90 or calcineurin inhibitors. The kidneys of mice infected with the petite mutant were sterile, while those infected with the HSP90-repressible strain had reduced fungal burden. We provide the first global view of mutations accompanying the

  10. Acquired resistance to HSP90 inhibitor 17-AAG and increased metastatic potential are associated with MUC1 expression in colon carcinoma cells.

    PubMed

    Liu, Xin; Ban, Li-Li; Luo, Gang; Li, Zhi-Yao; Li, Yun-Feng; Zhou, Yong-Chun; Wang, Xi-Cai; Jin, Cong-Guo; Ye, Jia-Gui; Ma, Ding-Ding; Xie, Qing; Huang, You-Guang

    2016-06-01

    Heat shock protein 90 (HSP90) is a molecular chaperone required for the stability and function of many proteins. The chaperoning of oncoproteins by HSP90 enhances the survival, growth, and invasive potential of cancer cells. HSP90 inhibitors are promising new anticancer agents, in which the benzoquinone ansamycin 17-allylamino-17-demethoxygeldanamycin (17-AAG) is currently in clinical evaluation. However, the implications of acquired resistance to this class of drug remain largely unexplored. In the present study, we have generated isogenic human colon cancer cell lines that are resistant to 17-AAG by continued culturing in the compound. Cross-resistance was found with another HSP90 inhibitor 17-dimethylaminoethylamino-17-demethoxygeldanamycin. The resistant cells showed obvious morphology changes with a metastatic phenotype and significant increases in migration and adhesion to collagens. Western blotting analysis of epithelial-mesenchymal transition molecular markers found that expression of E-cadherin downregulated, whereas expression of N-cadherin and β-catenin upregulated in the resistant cells. Mucin 1 (MUC1) has been reported to mediate metastasis as well as chemical resistance in many cancers. Here, we found that MUC1 expression was significantly elevated in the acquired drug resistance cells. 17-AAG treatment could decrease MUC1 more in parental cells than in acquired 17-AAG-resistant cells. Further study found that knockdown of MUC1 expression by small interfering RNA could obviously re-sensitize the resistant cells to 17-AAG treatment, and decrease the cell migration and adhesion. These were coupled with a downregulation in N-cadherin and β-catenin. The results indicate that HSP90 inhibitor therapies in colon carcinomas could generate resistance and increase metastatic potential that might mediated by upregulation of MUC1 expression. Findings from this study further our understanding of the potential clinical effects of HSP90-directed therapies in

  11. Mechanisms of antimicrobial resistance in Gram-negative bacilli.

    PubMed

    Ruppé, Étienne; Woerther, Paul-Louis; Barbier, François

    2015-12-01

    The burden of multidrug resistance in Gram-negative bacilli (GNB) now represents a daily issue for the management of antimicrobial therapy in intensive care unit (ICU) patients. In Enterobacteriaceae, the dramatic increase in the rates of resistance to third-generation cephalosporins mainly results from the spread of plasmid-borne extended-spectrum beta-lactamase (ESBL), especially those belonging to the CTX-M family. The efficacy of beta-lactam/beta-lactamase inhibitor associations for severe infections due to ESBL-producing Enterobacteriaceae has not been adequately evaluated in critically ill patients, and carbapenems still stands as the first-line choice in this situation. However, carbapenemase-producing strains have emerged worldwide over the past decade. VIM- and NDM-type metallo-beta-lactamases, OXA-48 and KPC appear as the most successful enzymes and may threaten the efficacy of carbapenems in the near future. ESBL- and carbapenemase-encoding plasmids frequently bear resistance determinants for other antimicrobial classes, including aminoglycosides (aminoglycoside-modifying enzymes or 16S rRNA methylases) and fluoroquinolones (Qnr, AAC(6')-Ib-cr or efflux pumps), a key feature that fosters the spread of multidrug resistance in Enterobacteriaceae. In non-fermenting GNB such as Pseudomonas aeruginosa, Acinetobacter baumannii and Stenotrophomonas maltophilia, multidrug resistance may emerge following the sole occurrence of sequential chromosomal mutations, which may lead to the overproduction of intrinsic beta-lactamases, hyper-expression of efflux pumps, target modifications and permeability alterations. P. aeruginosa and A. baumannii also have the ability to acquire mobile genetic elements encoding resistance determinants, including carbapenemases. Available options for the treatment of ICU-acquired infections due to carbapenem-resistant GNB are currently scarce, and recent reports emphasizing the spread of colistin resistance in environments with high

  12. Androgen receptor functions in castration-resistant prostate cancer and mechanisms of resistance to new agents targeting the androgen axis

    PubMed Central

    Yuan, X; Cai, C; Chen, S; Chen, S; Yu, Z; Balk, SP

    2016-01-01

    The metabolic functions of androgen receptor (AR) in normal prostate are circumvented in prostate cancer (PCa) to drive tumor growth, and the AR also can acquire new growth-promoting functions during PCa development and progression through genetic and epigenetic mechanisms. Androgen deprivation therapy (ADT, surgical or medical castration) is the standard treatment for metastatic PCa, but patients invariably relapse despite castrate androgen levels (castration-resistant PCa, CRPC). Early studies from many groups had shown that AR was highly expressed and transcriptionally active in CRPC, and indicated that steroids from the adrenal glands were contributing to this AR activity. More recent studies showed that CRPC cells had increased expression of enzymes mediating androgen synthesis from adrenal steroids, and could synthesize androgens de novo from cholesterol. Phase III clinical trials showing a survival advantage in CRPC for treatment with abiraterone (inhibitor of the enzyme CYP17A1 required for androgen synthesis that markedly reduces androgens and precursor steroids) and for enzalutamide (new AR antagonist) have now confirmed that AR activity driven by residual androgens makes a major contribution to CRPC, and led to the recent Food and Drug Administration approval of both agents. Unfortunately, patients treated with these agents for advanced CRPC generally relapse within a year and AR appears to be active in the relapsed tumors, but the molecular mechanisms mediating intrinsic or acquired resistance to these AR-targeted therapies remain to be defined. This review outlines AR functions that contribute to PCa development and progression, the roles of intratumoral androgen synthesis and AR structural alterations in driving AR activity in CRPC, mechanisms of action for abiraterone and enzalutamide, and possible mechanisms of resistance to these agents. PMID:23752196

  13. Update on antifungal drug resistance mechanisms of Aspergillus fumigatus.

    PubMed

    Chamilos, G; Kontoyiannis, D P

    2005-12-01

    Although the arsenal of agents with anti-Aspergillus activity has expanded over the last decade, mortality due to invasive aspergillosis (IA) remains unacceptably high. Aspergillus fumigatus still accounts for the majority of cases of IA; however less susceptible to antifungals non-fumigatus aspergilli began to emerge. Antifungal drug resistance of Aspergillus might partially account for treatment failures. Recent advances in our understanding of mechanisms of antifungal drug action in Aspergillus, along with the standardization of in vitro susceptibility testing methods, has brought resistance testing to the forefront of clinical mycology. In addition, molecular biology has started to shed light on the mechanisms of resistance of A. fumigatus to azoles and the echinocandins, while genome-based assays show promise for high-throughput screening for genotypic antifungal resistance. Several problems remain, however, in the study of this complex area. Large multicenter clinical studies--point prevalence or longitudinal--to capture the incidence and prevalence of antifungal resistance in A. fumigatus isolates are lacking. Correlation of in vitro susceptibility with clinical outcome and susceptibility breakpoints has not been established. In addition, the issue of cross-resistance between the newer triazoles is of concern. Furthermore, in vitro resistance testing for polyenes and echinocandins is difficult, and their mechanisms of resistance are largely unknown. This review examines challenges in the diagnosis, epidemiology, and mechanisms of antifungal drug resistance in A. fumigatus. PMID:16488654

  14. Epigenetic mechanisms of cell adhesion-mediated drug resistance in multiple myeloma.

    PubMed

    Furukawa, Yusuke; Kikuchi, Jiro

    2016-09-01

    Multiple myeloma cells acquire the resistance to anti-cancer drugs through physical and functional interactions with the bone marrow microenvironment via two overlapping mechanisms. First, bone marrow stromal cells (BMSCs) produce soluble factors, such as interleukin-6 and insulin-like growth factor-1, to activate signal transduction pathways leading to drug resistance (soluble factor-mediated drug resistance). Second, BMSCs up-regulate the expression of cell cycle inhibitors, anti-apoptotic members of the Bcl-2 family and ABC drug transporters in myeloma cells upon direct adhesion [cell adhesion-mediated drug resistance (CAM-DR)]. Elucidation of the mechanisms underlying drug resistance may greatly contribute to the advancement of cancer therapies. Recent investigations, including ours, have revealed the involvement of epigenetic alterations in drug resistance especially CAM-DR. For example, we found that class I histone deacetylases (HDACs) determine the sensitivity of proteasome inhibitors and the histone methyltransferase EZH2 regulates the transcription of anti-apoptotic genes during the acquisition of CAM-DR by myeloma cells. In addition, another histone methyltransferase MMSET was shown to confer drug resistance to myeloma cells by facilitating DNA repair. These findings provide a rationale for the inclusion of epigenetic drugs, such as HDAC inhibitors and histone methylation modifiers, in combination chemotherapy for MM patients to increase the therapeutic index. PMID:27411688

  15. Microbial resistance to disinfectants: mechanisms and significance

    SciTech Connect

    Hoff, J.C.; Akin, E.W.

    1986-11-01

    Drinking water disinfection provides the final barrier to transmission of a wide variety of potentially waterborne infectious agents including pathogenic bacteria, viruses, and protozoa. These agents differ greatly in their innate resistance to inactivation by disinfectants, ranging from extremely sensitive bacteria to highly resistant protozoan cysts. The close similarity between microorganism inactivation rates and the kinetics of chemical reactions has long been recognized. Ideally, under carefully controlled conditions, microorganism inactivation rates simulate first-order chemical reaction rates, making it possible to predict the effectiveness of disinfection under specific conditions. In practice, changes in relative resistance and deviations from first-order kinetics are caused by a number of factors, including microbial growth conditions, aggregation, and association with particulate materials. The net effect of all these factors is a reduction in the effectiveness and predictability of disinfection processes. To ensure effective pathogen control, disinfectant concentrations and contact times greater than experimentally determined values may be required. Of the factors causing enhanced disinfection resistance, protection by association with particulate matter is the most significant. Therefore, removal of particulate matter is an important step in increasing the effectiveness of disinfection processes.

  16. Microbial resistance to disinfectants: mechanisms and significance.

    PubMed Central

    Hoff, J C; Akin, E W

    1986-01-01

    Drinking water disinfection provides the final barrier to transmission of a wide variety of potentially waterborne infectious agents including pathogenic bacteria, viruses, and protozoa. These agents differ greatly in their innate resistance to inactivation by disinfectants, ranging from extremely sensitive bacteria to highly resistant protozoan cysts. The close similarity between microorganism inactivation rates and the kinetics of chemical reactions has long been recognized. Ideally, under carefully controlled conditions, microorganism inactivation rates simulate first-order chemical reaction rates, making it possible to predict the effectiveness of disinfection under specific conditions. In practice, changes in relative resistance and deviations from first-order kinetics are caused by a number of factors, including microbial growth conditions, aggregation, and association with particulate materials. The net effect of all these factors is a reduction in the effectiveness and predictability of disinfection processes. To ensure effective pathogen control, disinfectant concentrations and contact times greater than experimentally determined values may be required. Of the factors causing enhanced disinfection resistance, protection by association with particulate matter is the most significant. Therefore, removal of particulate matter is an important step in increasing the effectiveness of disinfection processes. Images FIGURE 6. PMID:3816738

  17. miR-200c/Bmi1 axis and epithelial–mesenchymal transition contribute to acquired resistance to BRAF inhibitor treatment

    PubMed Central

    Liu, Shujing; Tetzlaff, Michael T.; Wang, Tao; Yang, Ruifeng; Xie, Lin; Zhang, Gao; Krepler, Clemens; Xiao, Min; Beqiri, Marilda; Xu, Wei; Karakousis, Giorgos; Schuchter, Lynn; Amaravadi, Ravi K.; Xu, Weiting; Wei, Zhi; Herlyn, Meenhard; Yao, Yuan; Zhang, Litao; Wang, Yingjie; Zhang, Lin; Xu, Xiaowei

    2015-01-01

    Summary Resistance to BRAF inhibitors (BRAFi) is one of the major challenges for targeted therapies for BRAF-mutant melanomas. However, little is known about the role of microRNAs in conferring BRAFi resistance. Herein, we demonstrate that miR-200c expression is significantly reduced whereas miR-200c target genes including Bmi1, Zeb2, Tubb3, ABCG5, and MDR1 are significantly increased in melanomas that acquired BRAFi resistance compared to pretreatment tumor biopsies. Similar changes were observed in BRAFi-resistant melanoma cell lines. Overexpression of miR-200c or knock-down of Bmi1 in resistant melanoma cells restores their sensitivities to BRAFi, leading to deactivation of the PI3K/AKT and MAPK signaling cascades, and acquisition of epithelial– mesenchymal transition-like phenotypes, including upregulation of E-cadherin, downregulation of N-cadherin, and ABCG5 and MDR1 expression. Conversely, knock-down of miR-200c or overexpression of Bmi1 in BRAFi-sensitive melanoma cells activates the PI3K/AKT and MAPK pathways, upregulates N-cadherin, ABCG5, and MDR1 expression, and downregulates E-cadherin expression, leading to BRAFi resistance. Together, our data identify miR-200c as a critical signaling node in BRAFi-resistant melanomas impacting the MAPK and PI3K/AKT pathways, suggesting miR-200c as a potential therapeutic target for overcoming acquired BRAFi resistance. PMID:25903073

  18. HLA class I downregulation is associated with enhanced NK-cell killing of melanoma cells with acquired drug resistance to BRAF inhibitors.

    PubMed

    Sottile, Rosa; Pangigadde, Pradeepa N; Tan, Thomas; Anichini, Andrea; Sabbatino, Francesco; Trecroci, Francesca; Favoino, Elvira; Orgiano, Laura; Roberts, James; Ferrone, Soldano; Kärre, Klas; Colucci, Francesco; Carbone, Ennio

    2016-02-01

    The frequent development of drug resistance to targeted therapies in cancer patients has stimulated interest in strategies counteracting resistance. Combining immunotherapies with targeted therapies is one such strategy. In this context, we asked whether human NK cells can target melanoma cells that have acquired resistance to selective inhibitors targeting activating mutants of the B-Raf kinase (BRAF inhibitors, BRAFi). We generated drug-resistant cell variants in vitro from human BRAF-mutant melanoma cell lines MEL-HO, COLO-38, SK-MEL-37, 1520 and from primary melanoma cells freshly isolated from two patients. All drug-resistant cell variants remained susceptible to lysis by IL-2-activated NK cells; and two BRAFi-resistant lines (BRAFi-R) became significantly more susceptible to NK-cell lysis than their parental lines. This was associated with significant HLA class I antigen downregulation and PD-L1 upregulation on the drug-resistant lines. Although blocking HLA class I enhanced the extent of lysis of both BRAFi-R and parental cells to NK-cell-mediated lysis, antibody-mediated inhibition of PD1-PD-L1 interactions had no detectable effect. HLA class I antigen expression on BRAFi-R melanoma variants thus appears to play a major role in their susceptibility to NK-cell cytotoxicity. These findings suggest that NK-cell-based immunotherapy may be a viable approach to treat melanoma patients with acquired resistance to BRAF inhibitors. PMID:26564811

  19. HLA class I downregulation is associated with enhanced NK‐cell killing of melanoma cells with acquired drug resistance to BRAF inhibitors

    PubMed Central

    Sottile, Rosa; Pangigadde, Pradeepa N.; Tan, Thomas; Anichini, Andrea; Sabbatino, Francesco; Trecroci, Francesca; Favoino, Elvira; Orgiano, Laura; Roberts, James; Ferrone, Soldano; Kärre, Klas; Colucci, Francesco

    2015-01-01

    The frequent development of drug resistance to targeted therapies in cancer patients has stimulated interest in strategies counteracting resistance. Combining immunotherapies with targeted therapies is one such strategy. In this context, we asked whether human NK cells can target melanoma cells that have acquired resistance to selective inhibitors targeting activating mutants of the B‐Raf kinase (BRAF inhibitors, BRAFi). We generated drug‐resistant cell variants in vitro from human BRAF‐mutant melanoma cell lines MEL‐HO, COLO‐38, SK‐MEL‐37, 1520 and from primary melanoma cells freshly isolated from two patients. All drug‐resistant cell variants remained susceptible to lysis by IL‐2‐activated NK cells; and two BRAFi‐resistant lines (BRAFi‐R) became significantly more susceptible to NK‐cell lysis than their parental lines. This was associated with significant HLA class I antigen downregulation and PD‐L1 upregulation on the drug‐resistant lines. Although blocking HLA class I enhanced the extent of lysis of both BRAFi‐R and parental cells to NK‐cell‐mediated lysis, antibody‐mediated inhibition of PD1–PD‐L1 interactions had no detectable effect. HLA class I antigen expression on BRAFi‐R melanoma variants thus appears to play a major role in their susceptibility to NK‐cell cytotoxicity. These findings suggest that NK‐cell‐based immunotherapy may be a viable approach to treat melanoma patients with acquired resistance to BRAF inhibitors. PMID:26564811

  20. The vitamin D receptor and inducible nitric oxide synthase associated pathways in the development of acquired resistance to Cooperia oncophora infection in cattle

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cooperia oncophora is an economically important gastrointestinal nematode in ruminants. Acquired resistance to Cooperia oncophora infection in cattle develops rapidly resulting from prior infections. Naïve cattle, when given a primary infection of high-dose infective L3 larvae, develop a strong immu...

  1. Mechanism of Insect Resistance to the Microbial Insecticide Bacillus thuringiensis

    NASA Astrophysics Data System (ADS)

    van Rie, J.; McGaughey, W. H.; Johnson, D. E.; Barnett, B. D.; van Mellaert, H.

    1990-01-01

    Receptor binding studies show that resistance of a laboratory-selected Plodia interpunctella strain to a Bacillus thuringiensis insecticidal crystal protein (ICP) is correlated with a 50-fold reduction in affinity of the membrane receptor for this protein. The strain is sensitive to a second type of ICP that apparently recognizes a different receptor. Understanding the mechanism of resistance will provide strategies to prevent or delay resistance and hence prolong the usefulness of B. thuringiensis ICPs as environmentally safe insecticides.

  2. Evolution of herbicide resistance mechanisms in grass weeds.

    PubMed

    Matzrafi, Maor; Gadri, Yaron; Frenkel, Eyal; Rubin, Baruch; Peleg, Zvi

    2014-12-01

    Herbicide resistant weeds are becoming increasingly common, threatening global food security. Here, we present BrIFAR: a new model system for the functional study of mechanisms of herbicide resistance in grass weeds. We have developed a large collection of Brachypodium accessions, the BrI collection, representing a wide range of habitats. Wide screening of the responses of the accessions to four major herbicide groups (PSII, ACCase, ALS/AHAS and EPSPS inhibitors) identified 28 herbicide-resistance candidate accessions. Target-site resistance to PSII inhibitors was found in accessions collected from habitats with a known history of herbicide applications. An amino acid substitution in the psbA gene (serine264 to glycine) conferred resistance and also significantly affected the flowering and shoot dry weight of the resistant accession, as compared to the sensitive accession. Non-target site resistance to ACCase inhibitors was found in accessions collected from habitats with a history of herbicide application and from a nature reserve. In-vitro enzyme activity tests and responses following pre-treatment with malathion (a cytochrome-P450 inhibitor) indicated sensitivity at the enzyme level, and give strong support to diclofop-methyl and pinoxaden enhanced detoxification as NTS resistance mechanism. BrIFAR can promote better understanding of the evolution of mechanisms of herbicide resistance and aid the implementation of integrative management approaches for sustainable agriculture. PMID:25443832

  3. Resistance mechanisms against arthropod herbivores in cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cotton plants from the genus Gossypium are grown on more than 30 million hectares worldwide and are a major source of fiber. The plants possess a wide-range of indirect and direct-defense mechanisms against arthropod pests. Direct defense mechanisms include morphological traits such as trichomes and...

  4. What have the mechanisms of resistance to glyphosate taught us?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The intensive use of glyphosate alone to manage weeds has selected populations that are glyphosate resistant. The three mechanisms of glyphosate resistance that have been elucidated are 1) target site mutations; 2) gene amplification; and 3) altered translocation due to sequestration. What have we...

  5. Anthelmintic Resistance in Haemonchus contortus: History, Mechanisms and Diagnosis.

    PubMed

    Kotze, A C; Prichard, R K

    2016-01-01

    Haemonchus contortus has shown a great ability to develop resistance to anthelmintic drugs. In many instances, resistance has appeared less than 10years after the introduction of a new drug class. Field populations of this species now show resistance to all major anthelmintic drug classes, including benzimidazoles (BZs), imidazothiazoles and macrocyclic lactones. In addition, resistance to the recently introduced amino-acetonitrile derivative class (monepantel) has already been reported. The existence of field populations showing resistance to all three major drug classes, and the early appearance of resistance to monepantel, threatens the sustainability of sheep and goat production systems worldwide. This chapter reviews the history of the development of resistance to the various anthelmintics in H. contortus and examines the mechanisms utilized by this species to resist the effects of these drugs. Some of these mechanisms are well understood, particularly for BZ drugs, while our knowledge and understanding of others are increasing. Finally, we summarize methods available for the diagnosis of resistance. While such diagnosis currently relies largely on the faecal egg count reduction test, which suffers from issues of expense and sensitivity, we describe past and current efforts to utilize cheaper and less laborious phenotypic assays with free-living life stages, and then describe progress on the development of molecular assays to provide sensitive resistance-detection tests. PMID:27238009

  6. The battle against multi-resistant strains: Renaissance of antimicrobial essential oils as a promising force to fight hospital-acquired infections.

    PubMed

    Warnke, Patrick H; Becker, Stephan T; Podschun, Rainer; Sivananthan, Sureshan; Springer, Ingo N; Russo, Paul A J; Wiltfang, Joerg; Fickenscher, Helmut; Sherry, Eugene

    2009-10-01

    Hospital-acquired infections and antibiotic-resistant bacteria continue to be major health concerns worldwide. Particularly problematic is methicillin-resistant Staphylococcus aureus (MRSA) and its ability to cause severe soft tissue, bone or implant infections. First used by the Australian Aborigines, Tea tree oil and Eucalyptus oil (and several other essential oils) have each demonstrated promising efficacy against several bacteria and have been used clinically against multi-resistant strains. Several common and hospital-acquired bacterial and yeast isolates (6 Staphylococcus strains including MRSA, 4 Streptococcus strains and 3 Candida strains including Candida krusei) were tested for their susceptibility for Eucalyptus, Tea tree, Thyme white, Lavender, Lemon, Lemongrass, Cinnamon, Grapefruit, Clove Bud, Sandalwood, Peppermint, Kunzea and Sage oil with the agar diffusion test. Olive oil, Paraffin oil, Ethanol (70%), Povidone iodine, Chlorhexidine and hydrogen peroxide (H(2)O(2)) served as controls. Large prevailing effective zones of inhibition were observed for Thyme white, Lemon, Lemongrass and Cinnamon oil. The other oils also showed considerable efficacy. Remarkably, almost all tested oils demonstrated efficacy against hospital-acquired isolates and reference strains, whereas Olive and Paraffin oil from the control group produced no inhibition. As proven in vitro, essential oils represent a cheap and effective antiseptic topical treatment option even for antibiotic-resistant strains as MRSA and antimycotic-resistant Candida species. PMID:19473851

  7. Arabidopsis TTR1 causes LRR-dependent lethal systemic necrosis, rather than systemic acquired resistance, to Tobacco ringspot virus.

    PubMed

    Nam, Moon; Koh, Serry; Kim, Sung Uk; Domier, Leslie L; Jeon, Jae Heung; Kim, Hong Gi; Lee, Su-Heon; Bent, Andrew F; Moon, Jae Sun

    2011-11-01

    Most Arabidopsis ecotypes display tolerance to the Tobacco ringspot virus (TRSV), but a subset of Arabidopsis ecotypes, including Estland (Est), develop lethal systemic necrosis (LSN), which differs from the localized hypersensitive responses (HRs) or systemic acquired resistance (SAR) characteristic of incompatible reactions. Neither viral replication nor the systemic movement of TRSV was restricted in tolerant or sensitive Arabidopsis ecotypes; therefore, the LSN phenotype shown in the sensitive ecotypes might not be due to viral accumulation. In the present study, we identified the Est TTR1 gene (tolerance to Tobacco ringspot virus 1) encoding a TIR-NBS-LRR protein that controls the ecotype-dependent tolerant/sensitive phenotypes by a map-based cloning method. The tolerant Col-0 ecotype Arabidopsis transformed with the sensitive Est TTR1 allele developed an LSN phenotype upon TRSV infection, suggesting that the Est TTR1 allele is dominant over the tolerant ttr1 allele of Col-0. Multiple sequence alignments of 10 tolerant ecotypes from those of eight sensitive ecotypes showed that 10 LRR amino acid polymorphisms were consistently distributed across the TTR1/ttr1 alleles. Site-directed mutagenesis of these amino acids in the LRR region revealed that two sites, L956S and K1124Q, completely abolished the LSN phenotype. VIGS study revealed that TTR1 is dependent on SGT1, rather than EDS1. The LSN phenotype by TTR1 was shown to be transferred to Nicotiana benthamiana, demonstrating functional conservation of TTR1 across plant families, which are involved in SGT-dependent defense responses, rather than EDS1-dependent signaling pathways. PMID:22057987

  8. Arabidopsis TTR1 Causes LRR-Dependent Lethal Systemic Necrosis, rather than Systemic Acquired Resistance, to Tobacco Ringspot Virus

    PubMed Central

    Nam, Moon; Koh, Serry; Kim, Sung Uk; Domier, Leslie L.; Jeon, Jae Heung; Kim, Hong Gi; Lee, Su-Heon; Bent, Andrew F.; Moon, Jae Sun

    2011-01-01

    Most Arabidopsis ecotypes display tolerance to the Tobacco ringspot virus (TRSV), but a subset of Arabidopsis ecotypes, including Estland (Est), develop lethal systemic necrosis (LSN), which differs from the localized hypersensitive responses (HRs) or systemic acquired resistance (SAR) characteristic of incompatible reactions. Neither viral replication nor the systemic movement of TRSV was restricted in tolerant or sensitive Arabidopsis ecotypes; therefore, the LSN phenotype shown in the sensitive ecotypes might not be due to viral accumulation. In the present study, we identified the Est TTR1 gene (tolerance to Tobacco ringspot virus 1) encoding a TIR-NBS-LRR protein that controls the ecotype-dependent tolerant/sensitive phenotypes by a map-based cloning method. The tolerant Col-0 ecotype Arabidopsis transformed with the sensitive Est TTR1 allele developed an LSN phenotype upon TRSV infection, suggesting that the Est TTR1 allele is dominant over the tolerant ttr1 allele of Col-0. Multiple sequence alignments of 10 tolerant ecotypes from those of eight sensitive ecotypes showed that 10 LRR amino acid polymorphisms were consistently distributed across the TTR1/ttr1 alleles. Site-directed mutagenesis of these amino acids in the LRR region revealed that two sites, L956S and K1124Q, completely abolished the LSN phenotype. VIGS study revealed that TTR1 is dependent on SGT1, rather than EDS1. The LSN phenotype by TTR1 was shown to be transferred to Nicotiana benthamiana, demonstrating functional conservation of TTR1 across plant families, which are involved in SGT-dependent defense responses, rather than EDS1-dependent signaling pathways. PMID:22057987

  9. Valproic acid, an inhibitor of class I histone deacetylases, reverses acquired Erlotinib-resistance of lung adenocarcinoma cells: a Connectivity Mapping analysis and an experimental study.

    PubMed

    Zhuo, Wenlei; Zhang, Liang; Zhu, Yi; Xie, Qichao; Zhu, Bo; Chen, Zhengtang

    2015-01-01

    Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKI) have been used as a powerful targeting therapeutic agent for treatment of lung adenocarcinoma for years. Nevertheless, the efficacy of TKI was hampered by the appearance of acquired TKI-resistance. In the present study, we aimed to search, predict, and screen the agents that can overcome the acquired TKI-resistance of lung adenocarcinoma by using the expression profiles of differentially expressed genes (DEGs) and Connectivity map (CMAP). The profiles of DEGs were obtained by searching GEO microarray database, and then, they were submitted to CMAP for analysis in order to predict and screen the agent that might reverse the TKI-resistance of lung cancer cells. Next, the effects of the selected agent on TKI-resistant cancer cells were tested and the possible signaling pathways were also evaluated. As a result, valproic acid (VPA) was selected. Then, we used a low-concentration of VPA that has little effect on the cell growth for analysis. Interestingly, the results showed that treatment with a combination of VPA and Erlotinib significantly led to a decrease in cell viability and an increase in cell apoptosis for TKI-resistant HCC827-ER cells, relative to those treated with VPA or Erlotinib alone. Further experiments confirmed that inhibition of MAPK and AKT might be involved in this process. Analyzing the DEGs through the CMAP is a good strategy for exploitation of anti-tumor agents. VPA might markedly increase the sensitivity of TKI-resistant lung adenocarcinoma cells to Erlotinib, thus reversing the acquired TKI-resistance of cancer cells and raising VPA as a potential agent for TKI-resistant lung cancer therapy. PMID:26328250

  10. Rapid vacuolar sequestration: the horseweed glyphosate resistance mechanism

    PubMed Central

    Ge, Xia; Avignon, D André d’; Ackerman, Joseph JH; Sammons, R Douglas

    2010-01-01

    BACKGROUND Glyphosate-resistant (GR) weed species are now found with increasing frequency and threaten the critically importantGR weed management system. RESULTS The reported 31P NMR experiments on glyphosate-sensitive (S) and glyphosate-resistant (R) horseweed, Conyza canadensis (L.) Cronq., show significantly more accumulation of glyphosate within the R biotype vacuole. CONCLUSIONS Selective sequestration of glyphosate into the vacuole confers the observed horseweed resistance to glyphosate. This observation represents the first clear evidence for the glyphosate resistance mechanism in C. canadensis. PMID:20063320

  11. Elevated Cellular PD1/PD-L1 Expression Confers Acquired Resistance to Cisplatin in Small Cell Lung Cancer Cells.

    PubMed

    Yan, Fei; Pang, Jiuxia; Peng, Yong; Molina, Julian R; Yang, Ping; Liu, Shujun

    2016-01-01

    Although small cell lung cancer (SCLC) is highly responsive to chemotherapies (e.g., cisplatin-etoposide doublet), virtually almost all responsive SCLC patients experience disease recurrence characterized by drug resistance. The mechanisms underlying cisplatin resistance remain elusive. Here we report that cell-intrinsic expression of PD1 and PD-L1, two immune checkpoints, is required for sustained expansion of SCLC cells under cisplatin selection. Indeed, PD1 and PD-L1 were expressed at a higher level in lung cancer cell lines, tumor tissues, and importantly, in SCLC cells resistant to cisplatin (H69R, H82R), when compared to respective controls. Genetic abrogation of PD1 and PD-L1 in H69R and H82R cells decreased their proliferation rate, and restored their sensitivity to cisplatin. Mechanistically, PD-L1 upregulation in H69R and H82R cells was attributed to the overexpression of DNA methyltransferase 1 (DNMT1) or receptor tyrosine kinase KIT, as knockdown of DNMT1 or KIT in H69R and H82R cells led to PD-L1 downregulation. Consequently, combined knockdown of PD-L1 with KIT or DNMT1 resulted in more pronounced inhibition of H69R and H82R cell growth. Thus, cell intrinsic PD1/PD-L1 signaling may be a predictor for poor efficacy of cisplatin treatment, and targeting the cellular PD1/PD-L1 axis may improve chemosensitization of aggressive SCLC. PMID:27610620

  12. Trends towards lower antimicrobial susceptibility and characterization of acquired resistance among clinical isolates of Brachyspira hyodysenteriae in Spain.

    PubMed

    Hidalgo, Álvaro; Carvajal, Ana; Vester, Birte; Pringle, Märit; Naharro, Germán; Rubio, Pedro

    2011-07-01

    The antimicrobial susceptibility of clinical isolates of Brachyspira hyodysenteriae in Spain was monitored, and the underlying molecular mechanisms of resistance were investigated. MICs of tylosin, tiamulin, valnemulin, lincomycin, and tylvalosin were determined for 87 B. hyodysenteriae isolates recovered from 2008 to 2009 by broth dilution. Domain V of the 23S rRNA gene and the ribosomal protein L3 gene were sequenced in 20 isolates for which the tiamulin MIC was ≥ 4 μg/ml, presenting decreased susceptibility, and in 18 tiamulin-susceptible isolates (MIC ≤ 0.125 μg/ml), and all isolates were typed by multiple-locus variable-number tandem repeats analysis. A comparison with antimicrobial susceptibility data from 2000 to 2007 showed an increase in pleuromutilin resistance over time, doubling the number of isolates with decreased susceptibility to tiamulin. No alteration in susceptibility was detected for lincomycin, and the MIC of tylosin remained high (MIC(50) > 128 μg/ml). The decreased susceptibility to tylosin and lincomycin can be explained by mutations at position A2058 of the 23S rRNA gene (Escherichia coli numbering). A2058T was the predominant mutation, but A2058G also was found together with a change of the neighboring base pair at positions 2057 to 2611. The role of additional point mutations in the vicinity of the peptidyl transferase center and mutations in the L3 at amino acids 148 and 149 and their possible involvement in antimicrobial susceptibility are considered. An association between G2032A and high levels of tiamulin and lincomycin MICs was found, suggesting an increasing importance of this mutation in antimicrobial resistance of clinical isolates of B. hyodysenteriae. PMID:21555771

  13. Mechanisms of tumor resistance to EGFR-targeted therapies

    PubMed Central

    Hopper-Borge, Elizabeth A; Nasto, Rochelle E; Ratushny, Vladimir; Weiner, Louis M; Golemis, Erica A

    2009-01-01

    Background Much effort has been devoted to development of cancer therapies targeting EGFR, based on its role in regulating cell growth. Small-molecule and antibody EGFR inhibitors have clinical roles based on their efficacy in a subset of cancers, generally as components of combination therapies. Many cancers are either initially resistant to EGFR inhibitors or become resistant during treatment, limiting the efficacy of these reagents. Objective/Methods To review cellular resistance mechanisms to EGFR-targeted therapies. Results/Conclusions The best validated of these mechanisms include activation of classic ATP-binding casette (ABC) multidrug transporters; activation or mutation of EGFR; and overexpression or activation of signaling proteins operating in relation to EGFR. We discuss current efforts and potential strategies to override these sources of resistance. We describe emerging systems-biology-based concepts of alternative resistance to EGFR-targeted therapies, and discuss their implications for use of EGFR-targeted and other targeted therapies. PMID:19236156

  14. Molecular Mechanisms of Chromium in Alleviating Insulin Resistance

    PubMed Central

    Hua, Yinan; Clark, Suzanne; Ren, Jun; Sreejayan, Nair

    2011-01-01

    Type 2 diabetes is often associated with obesity, dyslipidemia, and cardiovascular anomalies and is a major health problem approaching global epidemic proportions. Insulin resistance, a prediabetic condition, precedes the onset of frank type 2 diabetes and offers potential avenues for early intervention to treat the disease. Although lifestyle modifications and exercise can reduce the incidence of diabetes, compliance has proved to be difficult, warranting pharmacological interventions. However, most of the currently available drugs that improve insulin sensitivity have adverse effects. Therefore, attractive strategies to alleviate insulin resistance include dietary supplements. One such supplement is chromium, which has been shown reduce insulin resistance in some, but not all, studies. Furthermore, the molecular mechanisms of chromium in alleviating insulin resistance remain elusive. This review examines emerging reports on the effect of chromium, as well as molecular and cellular mechanisms by which chromium may provide beneficial effects in alleviating insulin resistance. PMID:22423897

  15. Integrin β1-mediated acquired gefitinib resistance in non-small cell lung cancer cells occurs via the phosphoinositide 3-kinase-dependent pathway

    PubMed Central

    DENG, QIN-FANG; SU, BO; ZHAO, YIN-MIN; TANG, LIANG; ZHANG, JIE; ZHOU, CAI-CUN

    2016-01-01

    The present study aimed to explore the role of integrin β1 and the relevant signaling pathways in acquired gefitinib resistance in non-small cell lung cancer (NSCLC). The inhibitory effects of gefitinib, with or without LY294002, on cellular proliferation were evaluated by 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide assay. Cell cycle progression and apoptosis were analyzed by flow cytometry, while western blotting was used to evaluate the expression of EGFR, phosphorylated (phospho)-EGFR, protein kinase B (Akt), phospho-Akt, extracellular signal-regulated kinase (Erk) and phospho-Erk. The gene expression profiles of PC9 and PC9/G cells were determined by DNA microarray. Integrin β1 was knocked down in PC9/G cells by transiently transfected short interfering RNA (siRNA). A scrambled siRNA sequence was used as a control. Apoptosis of transfected cells was determined by Annexin V-phycoerythrin-Cy5/propidium iodide staining. Sequencing products were amplified by nested PCR. The resistant index of PC9/G cells to gefitinib was ~138- to 256-fold higher than that of PC9 cells, and this resistance was accompanied by significant increase in integrin β1 expression in PC9/G cells. Knockdown of integrin β1 with short hairpin RNA in PC9/G cells markedly inhibited proliferation and enhanced apoptosis in response to gefitinib, restoring the sensitivity of PC9/G cells gefitinib. Phosphoinositide 3-kinase (PI3K)/Akt activation was observed in PC9/G cells in the presence of gefitinib and the sensitivity of PC9/G cells to gefitinib was also able to be restored by PI3K/Akt pathway inhibitor LY294002. Finally, knockdown of integrin β1 significantly reduced the levels of phospho-Akt. These findings suggest that integrin β1 signaling via the PI3K/Akt pathway may be a significant mechanism underlying gefitinib resistance, and may potentially present an alternative therapeutic target for the treatment of NSCLC unresponsive to EGFR inhibitors. PMID:26870244

  16. Synergistic inhibitory effects by the combination of gefitinib and genistein on NSCLC with acquired drug-resistance in vitro and in vivo.

    PubMed

    Zhu, Hang; Cheng, Hua; Ren, Yuan; Liu, Zhan Guo; Zhang, Yi Fang; De Luo, Bing

    2012-04-01

    In clinical practice, most patients with non small cell lung cancer (NSCLC) who respond to tyrosine kinase inhibitors eventually progress because of an acquired resistance mutation, T790M, in epidermal growth factor receptor (EGFR). Thus, it is important to identify a new drug to reduce resistance. The aim of this study was to test whether genistein combined with gefitinib is effective against NSCLC in a cell line carrying T790M, and to clarify the underlying mechanisms. The human lung cancer cell line H1975 was used as an in vitro and in vivo model. Cells were treated with gefitinib, genistein, or a combination at a range of concentrations. Cell proliferation was calculated to assess the anticancer effects of the compounds in vitro. Flow cytometry and Western blotting were employed to determine the inhibitory effects on proliferation and the induction of apoptosis. The in vivo effects of the compounds were examined using a xenografted nude mouse model for validation. Gefitinib together with genistein enhanced both growth inhibition and apoptosis; however, the greatest synergistic effect was observed at low concentrations. p-EGFR, p-Akt, and p-mTOR expressions in vitro were reduced more by the combined use of the drugs, whereas caspase-3 and PARP activities were increased. Significantly more tumor growth inhibition was detected following combination treatment in the in vivo model. These findings suggest that genistein enhanced the antitumor effects of gefitinib in a NSCLC cell line carrying the T790M mutation. This synergistic activity may be due to increased inhibition of the downstream molecular and pro-apoptotic effects of EGFR. PMID:22160570

  17. Mortality among tuberculosis patients with acquired resistance to second-line anti-tuberculosis drugs — United States, 1993–2008

    PubMed Central

    Ershova, Julia V.; Kurbatova, Ekaterina V.; Moonan, Patrick K.; Cegielski, J. Peter

    2016-01-01

    Background Resistance to second-line anti-tuberculosis drugs (SLD) severely compromises treatment options of drug-resistant tuberculosis (TB). We assessed the association between acquisition of resistance (AR) to second-line injectable drugs (SLI) or fluoroquinolones (FQ) and mortality among TB cases confirmed by positive culture results with available initial and final drug susceptibility test (DST) results. Methods We analyzed data from U.S. National TB Surveillance System, 1993–2008. Acquired resistance was defined as drug susceptibility at initial DST but resistance to the same drug at final DST. We compared survival with Kaplan-Meier curves and analyzed the association between AR and mortality using a univariate extended Cox proportional hazards model adjusted for age. Results Of 2,329 cases with both initial and final DST to SLI, 49 (2.1%) acquired resistance; 13/49 (26.5%) had treatment terminated by death versus 222 (10.0%) of those without AR to SLI (P<0.001). Of 1,187 cases with both initial and final DST to FQ, 32 (2.8%) acquired resistance; 12/32 (37.5%) had treatment terminated by death versus 121 (10.9%) of those without AR to FQ (P=0.001). Controlling for age, mortality was significantly greater among cases with AR to SLD than among cases without AR (adjusted hazard ratio (aHR)[SLI], 2.8; 95% confidence interval (CI),1.4–5.4; aHR[FQ], 1.9; 95% CI,1.0–3.5). MDR TB at treatment initiation, positive HIV status, and extrapulmonary disease were also significantly associated with mortality. Conclusion Mortality was significantly greater among TB cases with AR to SLD. Providers should consider AR to SLD early in treatment, monitor DST results, and avoid premature deaths. PMID:24846639

  18. Mechanisms of resistance to anti-epidermal growth factor receptor inhibitors in metastatic colorectal cancer.

    PubMed

    Sforza, Vincenzo; Martinelli, Erika; Ciardiello, Fortunato; Gambardella, Valentina; Napolitano, Stefania; Martini, Giulia; Della Corte, Carminia; Cardone, Claudia; Ferrara, Marianna L; Reginelli, Alfonso; Liguori, Giuseppina; Belli, Giulio; Troiani, Teresa

    2016-07-28

    The prognosis of patients with metastatic colorectal cancer (mCRC) remain poor despite the impressive improvement of treatments observed over the last 20 years that led to an increase in median overall survival from 6 mo, with the only best supportive care, to approximately 30 mo with the introduction of active chemotherapy drugs and targeted agents. The monoclonal antibodies (moAbs) cetuximab and panitumumab, directed against the epidermal growth factor receptor (EGFR), undoubtedly represent a major step forward in the treatment of mCRC, given the relevant efficacy in terms of progression-free survival, overall survival, response rate, and quality of life observed in several phase III clinical trials among different lines of treatment. However, the anti-EGFR moAbs were shown only to be effective in a subset of patients. For instance, KRAS and NRAS mutations have been identified as biomarkers of resistance to these drugs, improving the selection of patients who might derive a benefit from these treatments. Nevertheless, several other alterations might affect the response to these drugs, and unfortunately, even the responders eventually become resistant by developing secondary (or acquired) resistance in approximately 13-18 mo. Several studies highlighted that the landscape of responsible alterations of both primary and acquired resistance to anti-EGFR drugs biochemically converge into MEK-ERK and PIK3CA-AKT pathways. In this review, we describe the currently known mechanisms of primary and acquired resistance to anti-EGFR moAbs together with the various strategies evaluated to prevent, overcame or revert them. PMID:27605871

  19. Mechanisms of resistance to anti-epidermal growth factor receptor inhibitors in metastatic colorectal cancer

    PubMed Central

    Sforza, Vincenzo; Martinelli, Erika; Ciardiello, Fortunato; Gambardella, Valentina; Napolitano, Stefania; Martini, Giulia; della Corte, Carminia; Cardone, Claudia; Ferrara, Marianna L; Reginelli, Alfonso; Liguori, Giuseppina; Belli, Giulio; Troiani, Teresa

    2016-01-01

    The prognosis of patients with metastatic colorectal cancer (mCRC) remain poor despite the impressive improvement of treatments observed over the last 20 years that led to an increase in median overall survival from 6 mo, with the only best supportive care, to approximately 30 mo with the introduction of active chemotherapy drugs and targeted agents. The monoclonal antibodies (moAbs) cetuximab and panitumumab, directed against the epidermal growth factor receptor (EGFR), undoubtedly represent a major step forward in the treatment of mCRC, given the relevant efficacy in terms of progression-free survival, overall survival, response rate, and quality of life observed in several phase III clinical trials among different lines of treatment. However, the anti-EGFR moAbs were shown only to be effective in a subset of patients. For instance, KRAS and NRAS mutations have been identified as biomarkers of resistance to these drugs, improving the selection of patients who might derive a benefit from these treatments. Nevertheless, several other alterations might affect the response to these drugs, and unfortunately, even the responders eventually become resistant by developing secondary (or acquired) resistance in approximately 13-18 mo. Several studies highlighted that the landscape of responsible alterations of both primary and acquired resistance to anti-EGFR drugs biochemically converge into MEK-ERK and PIK3CA-AKT pathways. In this review, we describe the currently known mechanisms of primary and acquired resistance to anti-EGFR moAbs together with the various strategies evaluated to prevent, overcame or revert them. PMID:27605871

  20. Pseudomonas aeruginosa: arsenal of resistance mechanisms, decades of changing resistance profiles, and future antimicrobial therapies.

    PubMed

    El Zowalaty, Mohamed E; Al Thani, Asmaa A; Webster, Thomas J; El Zowalaty, Ahmed E; Schweizer, Herbert P; Nasrallah, Gheyath K; Marei, Hany E; Ashour, Hossam M

    2015-01-01

    Antimicrobial resistance is one of the most serious public health issues facing humans since the discovery of antimicrobial agents. The frequent, prolonged, and uncontrolled use of antimicrobial agents are major factors in the emergence of antimicrobial-resistant bacterial strains, including multidrug-resistant variants. Pseudomonas aeruginosa is a leading cause of nosocomial infections. The abundant data on the increased resistance to antipseudomonal agents support the need for global action. There is a paucity of new classes of antibiotics active against P. aeruginosa. Here, we discuss recent antibacterial resistance profiles and mechanisms of resistance by P. aeruginosa. We also review future potential methods for controlling antibiotic-resistant bacteria, such as phage therapy, nanotechnology and antipseudomonal vaccines. PMID:26439366

  1. [Molecular characterization of resistance mechanisms: methicillin resistance Staphylococcus aureus, extended spectrum β-lactamases and carbapenemases].

    PubMed

    Oteo, Jesús; Belén Aracil, María

    2015-07-01

    Multi-drug resistance in bacterial pathogens increases morbidity and mortality in infected patients and it is a threat to public health concern by their high capacity to spread. For both reasons, the rapid detection of multi-drug resistant bacteria is critical. Standard microbiological procedures require 48-72 h to provide the antimicrobial susceptibility results, thus there is emerging interest in the development of rapid detection techniques. In recent years, the use of selective and differential culture-based methods has widely spread. However, the capacity for detecting antibiotic resistance genes and their low turnaround times has made molecular methods a reference for diagnosis of multidrug resistance. This review focusses on the molecular methods for detecting some mechanisms of antibiotic resistance with a high clinical and epidemiological impact: a) Enzymatic resistance to broad spectrum β-lactam antibiotics in Enterobacteriaceae, mainly extended spectrum β-lactamases (ESBL) and carbapenemases; and b) methicillin resistance in Staphylococcus aureus. PMID:26320993

  2. Cloning and expression analysis of cDNAs corresponding to genes activated in cucumber showing systemic acquired resistance after BTH treatment

    PubMed Central

    Bovie, Catherine; Ongena, Marc; Thonart, Philippe; Dommes, Jacques

    2004-01-01

    Background Infection of plants by necrotizing pathogens can lead to the rapid and localized induction of a complex set of defense responses resulting in a restriction of pathogen growth and spread. Subsequently, an increase of plant resistance against a broad spectrum of pathogens is observed systemically. This plant immunity is known as Systemic Acquired Resistance. To identify components of the transduction pathway, we cloned and analysed the expression pattern of several mRNAs accumulating in cucumber plants after induction of Systemic Acquired Resistance. Results We tested on cucumber different compounds known to induce systemic acquired resistance. Among these, BTH (benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester) proved to be very effective. mRNA RT-PCR differential display was used to identify mRNA sequences induced 24 hours after the application of 10 μM BTH to cucumber plants. A cDNA library constructed from cucumber plants sprayed with 10 μM BTH was screened to get corresponding full length cDNAs. Among the identified cDNAs were those coding for a putative ras-related GTP-binding protein, a putative beta-1,4-N-Acetylglucosaminyltranferase III and a putative pathogenesis related protein. The time course of accumulation of the three corresponding mRNAs was analysed by northern blotting in plants treated by BTH or in plants infected by Colletotrichum lagenarium. Conclusions The mRNA RT-PCR differential display technique allowed the identification of three genes possibly involved in Systemic Acquired Resistance in cucumber. Pathogenesis-related proteins are known to be involved in plant defence against pathogens. GTP-binding protein and N-acetylglucosaminyltranferase III have been reported to be components of signal transduction pathways in mammals and plants. PMID:15331019

  3. Fungal Resistance to Plant Antibiotics as a Mechanism of Pathogenesis

    PubMed Central

    Morrissey, John P.; Osbourn, Anne E.

    1999-01-01

    Many plants produce low-molecular-weight compounds which inhibit the growth of phytopathogenic fungi in vitro. These compounds may be preformed inhibitors that are present constitutively in healthy plants (also known as phytoanticipins), or they may be synthesized in response to pathogen attack (phytoalexins). Successful pathogens must be able to circumvent or overcome these antifungal defenses, and this review focuses on the significance of fungal resistance to plant antibiotics as a mechanism of pathogenesis. There is increasing evidence that resistance of fungal pathogens to plant antibiotics can be important for pathogenicity, at least for some fungus-plant interactions. This evidence has emerged largely from studies of fungal degradative enzymes and also from experiments in which plants with altered levels of antifungal secondary metabolites were generated. Whereas the emphasis to date has been on degradative mechanisms of resistance of phytopathogenic fungi to antifungal secondary metabolites, in the future we are likely to see a rapid expansion in our knowledge of alternative mechanisms of resistance. These may include membrane efflux systems of the kind associated with multidrug resistance and innate resistance due to insensitivity of the target site. The manipulation of plant biosynthetic pathways to give altered antibiotic profiles will also be valuable in telling us more about the significance of antifungal secondary metabolites for plant defense and clearly has great potential for enhancing disease resistance for commercial purposes. PMID:10477313

  4. Genetic dissection of azole resistance mechanisms in Candida albicans and their validation in a mouse model of disseminated infection.

    PubMed

    MacCallum, Donna M; Coste, Alix; Ischer, Françoise; Jacobsen, Mette D; Odds, Frank C; Sanglard, Dominique

    2010-04-01

    Principal mechanisms of resistance to azole antifungals include the upregulation of multidrug transporters and the modification of the target enzyme, a cytochrome P450 (Erg11) involved in the 14alpha-demethylation of ergosterol. These mechanisms are often combined in azole-resistant Candida albicans isolates recovered from patients. However, the precise contributions of individual mechanisms to C. albicans resistance to specific azoles have been difficult to establish because of the technical difficulties in the genetic manipulation of this diploid species. Recent advances have made genetic manipulations easier, and we therefore undertook the genetic dissection of resistance mechanisms in an azole-resistant clinical isolate. This isolate (DSY296) upregulates the multidrug transporter genes CDR1 and CDR2 and has acquired a G464S substitution in both ERG11 alleles. In DSY296, inactivation of TAC1, a transcription factor containing a gain-of-function mutation, followed by sequential replacement of ERG11 mutant alleles with wild-type alleles, restored azole susceptibility to the levels measured for a parent azole-susceptible isolate (DSY294). These sequential genetic manipulations not only demonstrated that these two resistance mechanisms were those responsible for the development of resistance in DSY296 but also indicated that the quantitative level of resistance as measured in vitro by MIC determinations was a function of the number of genetic resistance mechanisms operating in any strain. The engineered strains were also tested for their responses to fluconazole treatment in a novel 3-day model of invasive C. albicans infection of mice. Fifty percent effective doses (ED(50)s) of fluconazole were highest for DSY296 and decreased proportionally with the sequential removal of each resistance mechanism. However, while the fold differences in ED(50) were proportional to the fold differences in MICs, their magnitude was lower than that measured in vitro and depended on

  5. Insecticide resistance in vector Chagas disease: evolution, mechanisms and management.

    PubMed

    Mougabure-Cueto, Gastón; Picollo, María Inés

    2015-09-01

    Chagas disease is a chronic parasitic infection restricted to America. The disease is caused by the protozoa Trypanosoma cruzi, which is transmitted to human through the feces of infected triatomine insects. Because no treatment is available for the chronic forms of the disease, vector chemical control represents the best way to reduce the incidence of the disease. Chemical control has been based principally on spraying dwellings with insecticide formulations and led to the reduction of triatomine distribution and consequent interruption of disease transmission in several areas from endemic region. However, in the last decade it has been repeatedly reported the presence triatomnes, mainly Triatoma infestans, after spraying with pyrethroid insecticides, which was associated to evolution to insecticide resistance. In this paper the evolution of insecticide resistance in triatomines is reviewed. The insecticide resistance was detected in 1970s in Rhodnius prolixus and 1990s in R. prolixus and T. infestans, but not until the 2000s resistance to pyrthroids in T. infestans associated to control failures was described in Argentina and Bolivia. The main resistance mechanisms (i.e. enhanced metabolism, altered site of action and reduced penetration) were described in the T. infestans resistant to pyrethrods. Different resistant profiles were demonstrated suggesting independent origin of the different resistant foci of Argentina and Bolivia. The deltamethrin resistance in T. infestans was showed to be controlled by semi-dominant, autosomally inherited factors. Reproductive and developmental costs were also demonstrated for the resistant T. infestans. A discussion about resistance and tolerance concepts and the persistence of T. infestans in Gran Chaco region are presented. In addition, theoretical concepts related to toxicological, evolutionary and ecological aspects of insecticide resistance are discussed in order to understand the particular scenario of pyrethroid

  6. Different mechanisms of resistance modulate sulfite tolerance in wine yeasts.

    PubMed

    Nadai, Chiara; Treu, Laura; Campanaro, Stefano; Giacomini, Alessio; Corich, Viviana

    2016-01-01

    From a technological point of view, yeast resistance to sulfite is of great interest and represents an important technological character for winemaking. Several mechanisms are involved, and strain-dependent strategies to obtain SO2 resistance can deeply influence wine quality, although this choice is less relevant in determining the technological performance of the strain during fermentation. In this study, to better understand the strain-specific mechanisms of resistance, 11 Saccharomyces cerevisiae strains, whose genomes have been previously sequenced, were selected. Their attitude towards sulfites, in terms of resistance and production, was evaluated, and RNA-sequencing of four selected strains was performed during fermentation process in synthetic grape must in the presence of SO2. Results demonstrated that at molecular level, the physical effect of SO2 triggered multiple stress responses in the cell and high tolerance to general enological stressing condition increased SO2 resistance. Adaptation mechanism due to high basal gene expression level rather than specific gene induction in the presence of sulfite seemed to be responsible in modulating strain resistance. This mechanism involved higher basal gene expression level of specific cell wall proteins, enzymes for lipid biosynthesis, and enzymes directly involved in SO2 assimilation pathway and efflux. PMID:26615396

  7. Label-free SRM-based relative quantification of antibiotic resistance mechanisms in Pseudomonas aeruginosa clinical isolates

    PubMed Central

    Charretier, Yannick; Köhler, Thilo; Cecchini, Tiphaine; Bardet, Chloé; Cherkaoui, Abdessalam; Llanes, Catherine; Bogaerts, Pierre; Chatellier, Sonia; Charrier, Jean-Philippe; Schrenzel, Jacques

    2015-01-01

    Both acquired and intrinsic mechanisms play a crucial role in Pseudomonas aeruginosa antibiotic resistance. Many clinically relevant resistance mechanisms result from changes in gene expression, namely multidrug efflux pump overproduction, AmpC β-lactamase induction or derepression, and inactivation or repression of the carbapenem-specific porin OprD. Changes in gene expression are usually assessed using reverse-transcription quantitative real-time PCR (RT-qPCR) assays. Here, we evaluated label-free Selected Reaction Monitoring (SRM)-based mass spectrometry to directly quantify proteins involved in antibiotic resistance. We evaluated the label-free SRM using a defined set of P. aeruginosa isolates with known resistance mechanisms and compared it with RT-qPCR. Referring to efflux systems, we found a more robust relative quantification of antibiotic resistance mechanisms by SRM than RT-qPCR. The SRM-based approach was applied to a set of clinical P. aeruginosa isolates to detect antibiotic resistance proteins. This multiplexed SRM-based approach is a rapid and reliable method for the simultaneous detection and quantification of resistance mechanisms and we demonstrate its relevance for antibiotic resistance prediction. PMID:25713571

  8. Label-free SRM-based relative quantification of antibiotic resistance mechanisms in Pseudomonas aeruginosa clinical isolates.

    PubMed

    Charretier, Yannick; Köhler, Thilo; Cecchini, Tiphaine; Bardet, Chloé; Cherkaoui, Abdessalam; Llanes, Catherine; Bogaerts, Pierre; Chatellier, Sonia; Charrier, Jean-Philippe; Schrenzel, Jacques

    2015-01-01

    Both acquired and intrinsic mechanisms play a crucial role in Pseudomonas aeruginosa antibiotic resistance. Many clinically relevant resistance mechanisms result from changes in gene expression, namely multidrug efflux pump overproduction, AmpC β-lactamase induction or derepression, and inactivation or repression of the carbapenem-specific porin OprD. Changes in gene expression are usually assessed using reverse-transcription quantitative real-time PCR (RT-qPCR) assays. Here, we evaluated label-free Selected Reaction Monitoring (SRM)-based mass spectrometry to directly quantify proteins involved in antibiotic resistance. We evaluated the label-free SRM using a defined set of P. aeruginosa isolates with known resistance mechanisms and compared it with RT-qPCR. Referring to efflux systems, we found a more robust relative quantification of antibiotic resistance mechanisms by SRM than RT-qPCR. The SRM-based approach was applied to a set of clinical P. aeruginosa isolates to detect antibiotic resistance proteins. This multiplexed SRM-based approach is a rapid and reliable method for the simultaneous detection and quantification of resistance mechanisms and we demonstrate its relevance for antibiotic resistance prediction. PMID:25713571

  9. Mechanisms of lichen resistance to metallic pollution

    SciTech Connect

    Sarret, C.; Manceau, A.; Eybert-Berard, L.; Cuny, D.; Haluwyn, C. van; Deruelle, S.; Hazemann, J.L.; Menthonnex, J.J. |; Soldo, Y.

    1998-11-01

    Some lichens have a unique ability to grow in heavily contaminated areas due to the development of adaptative mechanisms allowing a high tolerance to metals. Here the authors report on the chemical forms of Pb and Zn in the metal hyperaccumulator Diploschistes muscorum and of Pb in the metal tolerant lichen Xanthoria parietina. The speciation of Zn and Pb has been investigated by powder X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) spectroscopy using the advanced third-generation synchrotron radiation source of the European synchrotron radiation facility (ESRF in Grenoble). This study reveals that in both lichens cells are protected from toxicity by complexation of heavy metals, but the strategies differ: in D. muscorum, Pb and Zn are accumulated through an enhanced synthesis of oxalate, which precipitates toxic elements as insoluble salts, whereas in X. parietina, Pb is complexed to carboxylic groups of the fungal cell walls. The authors conclude that hyperaccumulation of metals results from a reactive mechanism of organic acid production, whereas metallo-tolerance is achieved by a passive complexation to existing functional groups.

  10. Targeting AKT with the allosteric AKT inhibitor MK-2206 in non-small cell lung cancer cells with acquired resistance to cetuximab.

    PubMed

    Iida, Mari; Brand, Toni M; Campbell, David A; Starr, Megan M; Luthar, Neha; Traynor, Anne M; Wheeler, Deric L

    2013-06-01

    The epidermal growth factor receptor (EGFR) is a central regulator of tumor progression in human cancers. Cetuximab is an anti-EGFR monoclonal antibody that has been approved for use in oncology. Despite clinical success the majority of patients do not respond to cetuximab and those who initially respond frequently acquire resistance. To understand how tumor cells acquire resistance to cetuximab we developed a model of resistance using the non-small cell lung cancer line NCI-H226. We found that cetuximab-resistant (Ctx (R) ) clones manifested strong activation of EGFR, PI3K/AKT and MAPK. To investigate the role of AKT signaling in cetuximab resistance we analyzed the activation of the AKT pathway effector molecules using a human AKT phospho-antibody array. Strong activation was observed in Ctx (R) clones for several key AKT substrates including c-jun, GSK3β, eIF4E, rpS6, IKKα, IRS-1 and Raf1. Inhibition of AKT signaling by siAKT1/2 or by the allosteric AKT inhibitor MK-2206 resulted in robust inhibition of cell proliferation in all Ctx (R) clones. Moreover, the combinational treatment of cetuximab and MK-2206 resulted in further decreases in proliferation than either drug alone. This combinatorial treatment resulted in decreased activity of both AKT and MAPK thus highlighting the importance of simultaneous pathway inhibition to maximally affect the growth of Ctx (R) cells. Collectively, our findings demonstrate that AKT activation is an important pathway in acquired resistance to cetuximab and suggests that combinatorial therapy directed at both the AKT and EGFR/MAPK pathways may be beneficial in this setting. PMID:23760490

  11. Targeting AKT with the allosteric AKT inhibitor MK-2206 in non-small cell lung cancer cells with acquired resistance to cetuximab

    PubMed Central

    Iida, Mari; Brand, Toni M.; Campbell, David A.; Starr, Megan M.; Luthar, Neha; Traynor, Anne M.; Wheeler, Deric L.

    2013-01-01

    The epidermal growth factor receptor (EGFR) is a central regulator of tumor progression in human cancers. Cetuximab is an anti-EGFR monoclonal antibody that has been approved for use in oncology. Despite clinical success the majority of patients do not respond to cetuximab and those who initially respond frequently acquire resistance. To understand how tumor cells acquire resistance to cetuximab we developed a model of resistance using the non-small cell lung cancer line NCI-H226. We found that cetuximab-resistant (CtxR) clones manifested strong activation of EGFR, PI3K/AKT and MAPK. To investigate the role of AKT signaling in cetuximab resistance we analyzed the activation of the AKT pathway effector molecules using a human AKT phospho-antibody array. Strong activation was observed in CtxR clones for several key AKT substrates including c-jun, GSK3β, eIF4E, rpS6, IKKα, IRS-1 and Raf1. Inhibition of AKT signaling by siAKT1/2 or by the allosteric AKT inhibitor MK-2206 resulted in robust inhibition of cell proliferation in all CtxR clones. Moreover, the combinational treatment of cetuximab and MK-2206 resulted in further decreases in proliferation than either drug alone. This combinatorial treatment resulted in decreased activity of both AKT and MAPK thus highlighting the importance of simultaneous pathway inhibition to maximally affect the growth of CtxR cells. Collectively, our findings demonstrate that AKT activation is an important pathway in acquired resistance to cetuximab and suggests that combinatorial therapy directed at both the AKT and EGFR/MAPK pathways may be beneficial in this setting. PMID:23760490

  12. Evolutionary malignant resistance of cells to damaging factors as common biological defence mechanism in neoplastic development. Review of conception.

    PubMed

    Monceviciute-Eringiene, E

    2000-09-01

    Cells have some inborn resistance to harmful factors, which could be called physiological or natural resistance. The mechanisms of multixenobiotic resistance (MXR) and multidrug resistance (MDR) have common features in the formation of acquired resistance in microorganisms, carcinogenesis, tumour metastases and chemotherapy or irradiation. ATP-dependent membrane P-glycoprotein, as an MDR efflux pump, glutathione S-transferases and other products of evolutionary resistance-related genes arised for exportation and detoxification of cytotoxic xenobiotics and drugs are transmitted from bacteria to man. On the one hand, this evolutionary MXR as a common biological defence mechanism is a "driving" power to conserve homeostasis of cells, tissues and organs. On the other hand, mutation, selection and simplification of properties are the causes of functional and morphological changes in tumour cells which regress to a more primitive mode of existence (atavism) for adaptation to survival. In the present work are presented data on the forms of E. coli resistant to antibiotics and of sarcoma 45 resistant to alkylic preparations. They may be helpful in revealing the causes of resistance and acquired accelerated growth of cells. The development of tumours as fibromas 14-15 years following injection of a vital dye trypan blue into human skin supports our conception that neoplastic growth is a particular case of the evolutionary resistance of cells adapted to the damaging factors. So, tumour cells adopting the enhancement mechanisms of general biological persistent resistance, i. e. undergoing repeated cycles of malignancy enhancement, adapt themselves to survive under the changed unfavourable conditions. PMID:11144527

  13. Drug resistance mechanisms and their regulation in non-albicans Candida species.

    PubMed

    Kołaczkowska, Anna; Kołaczkowski, Marcin

    2016-06-01

    Fungal pathogens use various mechanisms to survive exposure to drugs. Prolonged treatment very often leads to the stepwise acquisition of resistance. The limited number of antifungal therapeutics and their mostly fungistatic rather than fungicidal character facilitates selection of resistant strains. These are able to cope with cytotoxic molecules by acquisition of appropriate mutations, re-wiring gene expression and metabolic adjustments. Recent evidence points to the paramount importance of the permeability barrier and cell wall integrity in the process of adaptation to high drug concentrations. Molecular details of basal and acquired drug resistance are best characterized in the most frequent human fungal pathogen, Candida albicans Effector genes directly related to the acquisition of elevated tolerance of this species to azole and echinocandin drugs are well described. The emergence of high-level drug resistance against intrinsically lower susceptibility to azoles in yeast species other than C. albicans is, however, of particular concern. This is due to their steadily increasing contribution to high mortality rates associated with disseminated infections. Recent findings concerning underlying mechanisms associated with elevated drug resistance suggest a link to cell wall and plasma membrane metabolism in non-albicans Candida species. PMID:26801081

  14. Benznidazole-resistance in Trypanosoma cruzi: Evidence that distinct mechanisms can act in concert☆

    PubMed Central

    Campos, Mônica C.O.; Leon, Leonor L.; Taylor, Martin C.; Kelly, John M.

    2014-01-01

    Benznidazole is the main drug used to treat Trypanosoma cruzi infections. However, frequent instances of treatment failure have been reported. To better understand potential resistance mechanisms, we analysed three clones isolated from a single parasite population that had undergone benznidazole-selection. These clones exhibited differing levels of benznidazole-resistance (varying between 9 and 26-fold), and displayed cross-resistance to nifurtimox (2 to 4-fold). Each clone had acquired a stop-codon-generating mutation in the gene which encodes the nitroreductase (TcNTR) that is responsible for activating nitroheterocyclic pro-drugs. In addition, one clone had lost a copy of the chromosome containing TcNTR. However, these processes alone are insufficient to account for the extent and diversity of benznidazole-resistance. It is implicit from our results that additional mechanisms must also operate and that T. cruzi has an intrinsic ability to develop drug-resistance by independent sequential steps, even within a single population. This has important implications for drug development strategies. PMID:24462750

  15. New approaches for understanding mechanisms of drug resistance in schistosomes

    PubMed Central

    GREENBERG, ROBERT M.

    2013-01-01

    SUMMARY Schistosomes are parasitic flatworms that cause schistosomiasis, a neglected tropical disease that affects hundreds of millions worldwide. Treatment and control of schistosomiasis relies almost entirely on the single drug praziquantel (PZQ), making the prospect of emerging drug resistance particularly worrisome. This review will survey reports of PZQ (and other drug) resistance in schistosomes and other platyhelminths, and explore mechanisms by which drug resistance might develop. Newer genomic and post-genomic strategies that offer the promise of better understanding of how drug resistance might arise in these organisms will be discussed. These approaches could also lead to insights into the mode of action of these drugs and potentially provide markers for monitoring the emergence of resistance. PMID:23552512

  16. Lack of dissemination of acquired resistance to β-lactams in small wild mammals around an isolated village in the Amazonian forest.

    PubMed

    Grall, Nathalie; Barraud, Olivier; Wieder, Ingrid; Hua, Anna; Perrier, Marion; Babosan, Ana; Gaschet, Margaux; Clermont, Olivier; Denamur, Erick; Catzeflis, François; Decré, Dominique; Ploy, Marie-Cécile; Andremont, Antoine

    2015-10-01

    In this study, we quantitatively evaluated the spread of resistance to β-lactams and of integrons in small rodents and marsupials living at various distances from a point of antibiotic's use. Rectal swabs from 114 animals were collected in Trois-Sauts, an isolated village in French Guiana, and along a 3 km transect heading through the non-anthropized primary forest. Prevalence of ticarcillin-resistant enterobacteria was 36% (41/114). Klebsiella spp., naturally resistant to ticarcillin, were found in 31.1% (23/73) of animals from the village and in an equal ratio of 31.7% (13/41) of animals trapped along the transect. By contrast Escherichia coli with acquired resistance to ticarcillin were found in 13.7% (10/73) of animals from the village and in only 2.4% (1/41) of those from the transect (600 m from the village). There was a huge diversity of E. coli and Klebsiella pneumoniae strains with very unique and infrequent sequence types. The overall prevalence of class 1 integrons carriage was 19.3% (22/114) homogenously distributed between animals from the village and the transect, which suggests a co-selection by a non-antibiotic environmental factor. Our results indicate that the anthropogenic acquired antibiotic resistance did not disseminate in the wild far from the point of selective pressure. PMID:25858231

  17. Acquired resistance to EGFR tyrosine kinase inhibitors in EGFR mutant lung cancer: Distinct natural history of patients with tumors harboring the T790M mutation

    PubMed Central

    Oxnard, Geoffrey R.; Arcila, Maria E.; Sima, Camelia S.; Riely, Gregory J.; Chmielecki, Juliann; Kris, Mark G.; Pao, William; Ladanyi, Marc; Miller, Vincent A.

    2010-01-01

    Purpose Patients with EGFR-mutant lung adenocarcinoma develop acquired resistance to EGFR tyrosine kinase inhibitors (TKIs) after a median of 10–16 months. In half of these cases a second EGFR mutation, T790M, underlies acquired resistance. We undertook this study to examine the clinical course of patients harboring the T790M mutation following progression on TKI. Experimental design EGFR-mutant lung cancer patients with acquired resistance to EGFR TKIs were identified as part of a prospective re-biopsy protocol where post-progression tumor specimens were collected for molecular analysis. Post-progression survival and characteristics of disease progression were compared in patients with and without T790M. Results We identified T790M in the initial re-biopsy specimens from 58/93 patients (62%, 95% confidence interval 52%–72%). T790M was more common in biopsies of lung/pleura tissue and lymph nodes than in more distant sites (p=0.014). Median post-progression survival was 16 months (interquartile range 9–29 months); patients with T790M had a significantly longer post-progression survival (p=0.036). Patients without T790M more often progressed in a previously uninvolved organ system (p=0.014) and exhibited a poorer performance status at time of progression (p=0.007). Conclusions Among patients with acquired resistance to EGFR TKIs, the presence of T790M defines a clinical subset with a relatively favorable prognosis and more indolent progression. Knowledge of T790M status is therefore important for the clinical care of these patients as well as for the optimal design and interpretation of clinical trials in this setting. PMID:21135146

  18. TrxR1 inhibition overcomes both hypoxia-induced and acquired bortezomib resistance in multiple myeloma through NF-кβ inhibition.

    PubMed

    Raninga, Prahlad V; Di Trapani, Giovanna; Vuckovic, Slavica; Tonissen, Kathryn F

    2016-02-16

    Multiple myeloma (MM) is a B-cell malignancy characterized by an accumulation of abnormal clonal plasma cells in the bone marrow. Introduction of the proteasome-inhibitor bortezomib has improved MM prognosis and survival; however hypoxia-induced or acquired bortezomib resistance remains a clinical problem. This study highlighted the role of thioredoxin reductase 1 (TrxR1) in the hypoxia-induced and acquired bortezomib resistance in MM. Higher TrxR1 gene expression correlated with high-risk disease, adverse overall survival, and poor prognosis in myeloma patients. We demonstrated that hypoxia induced bortezomib resistance in myeloma cells and increased TrxR1 protein levels. Inhibition of TrxR1 using auranofin overcame hypoxia-induced bortezomib resistance and restored the sensitivity of hypoxic-myeloma cells to bortezomib. Hypoxia increased NF-кβ subunit p65 nuclear protein levels and TrxR1 inhibition decreased hypoxia-induced NF-кβ p65 protein levels in the nucleus and reduced the expression of NF-кβ-regulated genes. In addition, higher TrxR1 protein levels were observed in bortezomib-resistant myeloma cells compared to the naïve cells, and its inhibition using either auranofin or TrxR1-specific siRNAs reversed bortezomib resistance. TrxR1 inhibition reduced p65 mRNA and protein expression in bortezomib-resistant myeloma cells, and also decreased the expression of NF-кβ-regulated anti-apoptotic and proliferative genes. Thus, TrxR1 inhibition overcomes both hypoxia-induced and acquired bortezomib resistance by inhibiting the NF-кβ signaling pathway. Our findings demonstrate that elevated TrxR1 levels correlate with the acquisition of bortezomib resistance in MM. We propose considering TrxR1-inhibiting drugs, such as auranofin, either for single agent or combination therapy to circumvent bortezomib-resistance and improve survival outcomes of MM patients. PMID:26743692

  19. Redox Regulation of Multidrug Resistance in Cancer Chemotherapy: Molecular Mechanisms and Therapeutic Opportunities

    PubMed Central

    2009-01-01

    Abstract The development of multidrug resistance to cancer chemotherapy is a major obstacle to the effective treatment of human malignancies. It has been established that membrane proteins, notably multidrug resistance (MDR), multidrug resistance protein (MRP), and breast cancer resistance protein (BCRP) of the ATP binding cassette (ABC) transporter family encoding efflux pumps, play important roles in the development of multidrug resistance. Overexpression of these transporters has been observed frequently in many types of human malignancies and correlated with poor responses to chemotherapeutic agents. Evidence has accumulated showing that redox signals are activated in response to drug treatments that affect the expression and activity of these transporters by multiple mechanisms, including (a) conformational changes in the transporters, (b) regulation of the biosynthesis cofactors required for the transporter's function, (c) regulation of the expression of transporters at transcriptional, posttranscriptional, and epigenetic levels, and (d) amplification of the copy number of genes encoding these transporters. This review describes various specific factors and their relevant signaling pathways that are involved in the regulation. Finally, the roles of redox signaling in the maintenance and evolution of cancer stem cells and their implications in the development of intrinsic and acquired multidrug resistance in cancer chemotherapy are discussed. Antioxid. Redox Signal. 11, 99–133. PMID:18699730

  20. Mechanisms involved in quinolone resistance in Mycoplasma mycoides subsp. capri.

    PubMed

    Antunes, Nuno T; Assunção, Patrícia; Poveda, José B; Tavío, María M

    2015-06-01

    Mycoplasma mycoides subsp. capri is a causative agent of contagious agalactia in goats. In this study, M. mycoides subsp. capri mutants were selected for resistance to fluoroquinolones (norfloxacin, enrofloxacin and ciprofloxacin) by serial passes in broth with increasing concentrations of antibiotic. Mutations conferring cross-resistance to the three fluoroquinolones were found in the quinolone resistance determining regions of the four genes encoding DNA gyrase and topoisomerase IV. Different mutations in the DNA gyrase GyrA subunit suggest a different mechanism of inhibition between norfloxacin and the other tested fluoroquinolones. The presence of an adenosine triphosphate-dependent efflux system was suggested through the use of the inhibitor orthovanadate. PMID:25951987

  1. Drug resistance. Population transcriptomics of human malaria parasites reveals the mechanism of artemisinin resistance.

    PubMed

    Mok, Sachel; Ashley, Elizabeth A; Ferreira, Pedro E; Zhu, Lei; Lin, Zhaoting; Yeo, Tomas; Chotivanich, Kesinee; Imwong, Mallika; Pukrittayakamee, Sasithon; Dhorda, Mehul; Nguon, Chea; Lim, Pharath; Amaratunga, Chanaki; Suon, Seila; Hien, Tran Tinh; Htut, Ye; Faiz, M Abul; Onyamboko, Marie A; Mayxay, Mayfong; Newton, Paul N; Tripura, Rupam; Woodrow, Charles J; Miotto, Olivo; Kwiatkowski, Dominic P; Nosten, François; Day, Nicholas P J; Preiser, Peter R; White, Nicholas J; Dondorp, Arjen M; Fairhurst, Rick M; Bozdech, Zbynek

    2015-01-23

    Artemisinin resistance in Plasmodium falciparum threatens global efforts to control and eliminate malaria. Polymorphisms in the kelch domain-carrying protein K13 are associated with artemisinin resistance, but the underlying molecular mechanisms are unknown. We analyzed the in vivo transcriptomes of 1043 P. falciparum isolates from patients with acute malaria and found that artemisinin resistance is associated with increased expression of unfolded protein response (UPR) pathways involving the major PROSC and TRiC chaperone complexes. Artemisinin-resistant parasites also exhibit decelerated progression through the first part of the asexual intraerythrocytic development cycle. These findings suggest that artemisinin-resistant parasites remain in a state of decelerated development at the young ring stage, whereas their up-regulated UPR pathways mitigate protein damage caused by artemisinin. The expression profiles of UPR-related genes also associate with the geographical origin of parasite isolates, further suggesting their role in emerging artemisinin resistance in the Greater Mekong Subregion. PMID:25502316

  2. Pathophysiological mechanisms of death resistance in colorectal carcinoma

    PubMed Central

    Huang, Ching-Ying; Yu, Linda Chia-Hui

    2015-01-01

    Colon cancers develop adaptive mechanisms to survive under extreme conditions and display hallmarks of unlimited proliferation and resistance to cell death. The deregulation of cell death is a key factor that contributes to chemoresistance in tumors. In a physiological context, balance between cell proliferation and death, and protection against cell damage are fundamental processes for maintaining gut epithelial homeostasis. The mechanisms underlying anti-death cytoprotection and tumor resistance often bear common pathways, and although distinguishing them would be a challenge, it would also provide an opportunity to develop advanced anti-cancer therapeutics. This review will outline cell death pathways (i.e., apoptosis, necrosis, and necroptosis), and discuss cytoprotective strategies in normal intestinal epithelium and death resistance mechanisms of colon tumor. In colorectal cancers, the intracellular mechanisms of death resistance include the direct alteration of apoptotic and necroptotic machinery and the upstream events modulating death effectors such as tumor suppressor gene inactivation and pro-survival signaling pathways. The autocrine, paracrine and exogenous factors within a tumor microenvironment can also instigate resistance against apoptotic and necroptotic cell death in colon cancers through changes in receptor signaling or transporter uptake. The roles of cyclooxygenase-2/prostaglandin E2, growth factors, glucose, and bacterial lipopolysaccharides in colorectal cancer will be highlighted. Targeting anti-death pathways in the colon cancer tissue might be a promising approach outside of anti-proliferation and anti-angiogenesis strategies for developing novel drugs to treat refractory tumors. PMID:26557002

  3. Non-Invasive Methods to Monitor Mechanisms of Resistance to Tyrosine Kinase Inhibitors in Non-Small-Cell Lung Cancer: Where Do We Stand?

    PubMed Central

    Ulivi, Paola

    2016-01-01

    The induction of resistance mechanisms represents an important problem for the targeted therapy of patients with non-small-cell lung cancer (NSCLC). The best-known resistance mechanism induced during treatment with epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) is EGFR T790M mutation for which specific drugs are have been developed. However, other molecular alterations have also been reported as induced resistance mechanisms to EGFR-TKIs. Similarly, there is growing evidence of acquired resistance mechanisms to anaplastic lymphoma kinase (ALK)-TKI treatment. A better understanding of these acquired resistance mechanisms is essential in clinical practice as patients could be treated with specific drugs that are active against the induced alterations. The use of free circulating tumor nucleic acids or circulating tumor cells (CTCs) enables resistance mechanisms to be characterized in a non-invasive manner and reduces the need for tumor re-biopsy. This review discusses the main resistance mechanisms to TKIs and provides a comprehensive overview of innovative strategies to evaluate known resistance mechanisms in free circulating nucleic acids or CTCs and potential future orientations for these non-invasive approaches. PMID:27455248

  4. Interaction of gatifloxacin with efflux transporters: a possible mechanism for drug resistance

    PubMed Central

    Kwatra, Deep; Vadlapatla, Ramya Krishna; Vadlapudi, Aswani Dutt; Pal, Dhananjay; Mitra, Ashim K.

    2010-01-01

    The purpose of the study is to screen the interactions of fourth generation fluoroquinolone-gatifloxacin with efflux pumps i.e. P-gp, MRP2 and BCRP. Mechanism of gatifloxacin interaction with efflux transporters may explain its acquired resistance. Such clarification may lead to the development of strategies to overcome efflux and enhance its bioavailability at target site. This process will aid in the reduction of dose volume, further eliminating the chances of systemic toxicity from topical gatifloxacin eye drops. MDCK cell lines transfected with the targeted efflux transporters were used for this study. [14C] Erythromycin was selected as a model substrate for P-gp and MRP2 whereas Hoechst 33342 was employed as a substrate for BCRP. Uptake and transport studies of these substrates were performed in the presence of gatifloxacin to delineate its interaction with efflux transporters. Further the efflux ratio in the presence of gatifloxacin was calculated from bidirectional transport studies. The concentration of [14C] erythromycin and Hoechst 33342 were measured using scintillation counter and fluorescence plate reader respectively. A concentration dependent inhibition effect in the presence of gatifloxacin was revealed on [14C] erythromycin uptake. The efflux ratio (BL-AP/AP-BL) of substrates was found to approach unity at higher gatifloxacin concentrations. Increased concentration of gatifloxacin did not elevate uptake of Hoechst 33342. All these studies were validated with known inhibitors as positive control. Uptake and transport studies support the hypothesis that gatifloxacin is a substrate for P-gp, MRP2 but not for BCRP. Possible interactions of gatifloxacin with P-gp and MRP2 may be a possible mechanism for acquired resistance of gatifloxacin. This information can be further extended to design prodrugs or formulations in order to prevent development of acquired resistance and improve therapeutic efficacy with its reduction in side effects. PMID:20573570

  5. Acquired resistance to rechallenge injury in rats recovered from subclinical renal damage with uranyl acetate-Importance of proliferative activity of tubular cells

    SciTech Connect

    Sun, Yuan; Fujigaki, Yoshihide; Sakakima, Masanori; Hishida, Akira

    2010-02-15

    Animals recovered from acute renal failure are resistant to subsequent insult. We investigated whether rats recovered from mild proximal tubule (PT) injury without renal dysfunction (subclinical renal damage) acquire the same resistance. Rats 14 days after recovering from subclinical renal damage, which was induced by 0.2 mg/kg of uranyl acetate (UA) (sub-toxic dose), were rechallenged with 4 mg/kg of UA (nephrotoxic dose). Fate of PT cells and renal function were examined in response to nephrotoxic dose of UA. All divided cells after sub-toxic dose of UA insult were labeled with bromodeoxyuridine (BrdU) for 14 days then the number of PT cells with or without BrdU-labeling was counted following nephrotoxic dose of UA insult. Rats recovered from subclinical renal damage gained resistance to nephrotoxic dose of UA with reduced renal dysfunction, less severity of peak damage (necrotic and TUNEL+ apoptotic cells) and accelerated PT cell proliferation, but with earlier peak of PT damage. The decrease in number of PT cells in the early phase of rechallenge injury with nephrotoxic UA was more in rats pretreated with sub-toxic dose of UA than vehicle pretreated rats. The exaggerated loss of PT cells was mainly caused by the exaggerated loss of BrdU+ divided cells. In contrast, accelerated cell proliferation in rats recovered from sub-toxic dose of UA was observed mainly in BrdU- non-divided cells. The findings suggest that rats recovered from subclinical renal damage showed partial acquired resistance to nephrotoxic insult. Accelerated recovery with increased proliferative activity of non-divided PT cells after subclinical renal damage may mainly contribute to acquired resistance.

  6. Acquired resistance of pancreatic cancer cells to treatment with gemcitabine and HER-inhibitors is accompanied by increased sensitivity to STAT3 inhibition

    PubMed Central

    IOANNOU, NIKOLAOS; SEDDON, ALAN M.; DALGLEISH, ANGUS; MACKINTOSH, DAVID; SOLCA, FLAVIO; MODJTAHEDI, HELMOUT

    2016-01-01

    Drug-resistance is a major contributing factor for the poor prognosis in patients with pancreatic cancer. We have shown previously that the irreversible ErbB family blocker afatinib, is more effective than the reversible EGFR tyrosine kinase inhibitor erlotinib in inhibiting the growth of human pancreatic cancer cells. The aim of this study was to develop human pancreatic cancer cell (BxPc3) variants with acquired resistance to treatment with gemcitabine, afatinib, or erlotinib, and to investigate the molecular changes that accompany the acquisition of a drug-resistant phenotype. We also investigated the therapeutic potential of various agents in the treatment of such drug-resistant variants. Three variant forms of BxPc3 cells with acquired resistance to gemcitabine (BxPc3GEM), afatinib (BxPc3AFR) or erlotinib (BxPc3OSIR) were developed following treatment with increasing doses of such drugs. The expression level, mutational and phosphorylation status of various growth factor receptors and downstream cell signaling molecules were determined by FACS, human phopsho-RTK array, and western blot analysis while the sulforhodamine B assay was used for determining the effect of various agents on the growth of such tumours. We found that all three BxPc3 variants with acquired resistance to gemcitabine (BxPc3GEM), afatinib (BxPc3AFR) or erlotinib (BxPc3OSIR) also become less sensitive to treatment with the two other agents. Acquisition of resistance to these agents was accompanied by upregulation of p-c-MET, p-STAT3, CD44, increased autocrine production of EGFR ligand amphiregulin and differential activation status of EGFR tyrosine residues as well as downregulation of total and p-SRC. Of all therapeutic interventions examined, including the addition of an anti-EGFR antibody ICR62, an anti-CD44 monoclonal antibody, and of STAT3 or c-MET inhibitors, only treatment with the STAT3 inhibitor Stattic produced a higher growth inhibitory effect in all three drug-resistant variants

  7. Known and putative mechanisms of resistance to EGFR targeted therapies in NSCLC patients with EGFR mutations—a review

    PubMed Central

    Stewart, Erin L.; Tan, Samuel Zhixing; Liu, Geoffrey

    2015-01-01

    Lung cancer is the leading cause of cancer related deaths in Canada with non-small cell lung cancer (NSCLC) being the predominant form of the disease. Tumor characterization can identify cancer-driving mutations as treatment targets. One of the most successful examples of cancer targeted therapy is inhibition of mutated epidermal growth factor receptor (EGFR), which occurs in ~10-30% of NSCLC patients. While this treatment has benefited many patients with activating EGFR mutations, almost all who initially benefited will eventually acquire resistance. Approximately 50% of cases of acquired resistance (AR) are due to a secondary T790M mutation in exon 20 of the EGFR gene; however, many of the remaining mechanisms of resistance are still unknown. Much work has been done to elucidate the remaining mechanisms of resistance. This review aims to highlight both the mechanisms of resistance that have already been identified in patients and potential novel mechanisms identified in preclinical models which have yet to be validated in the patient settings. PMID:25806347

  8. Antileukemic Activity and Mechanism of Drug Resistance to the Marine Salinispora tropica Proteasome Inhibitor Salinosporamide A (Marizomib)

    PubMed Central

    Niewerth, Denise; Jansen, Gerrit; Riethoff, Lesley F. V.; van Meerloo, Johan; Kale, Andrew J.; Moore, Bradley S.; Assaraf, Yehuda G.; Anderl, Janet L.; Zweegman, Sonja; Kaspers, Gertjan J. L.

    2014-01-01

    Salinosporamide A (NPI-0052, marizomib) is a naturally occurring proteasome inhibitor derived from the marine actinobacterium Salinispora tropica, and represents a promising clinical agent in the treatment of hematologic malignancies. Recently, these actinobacteria were shown to harbor self-resistance properties to salinosporamide A by expressing redundant catalytically active mutants of the 20S proteasome β-subunit, reminiscent of PSMB5 mutations identified in cancer cells with acquired resistance to the founding proteasome inhibitor bortezomib (BTZ). Here, we assessed the growth inhibitory potential of salinosporamide A in human acute lymphocytic leukemia CCRF-CEM cells, and its 10-fold (CEM/BTZ7) and 123-fold (CEM/BTZ200) bortezomib-resistant sublines harboring PSMB5 mutations. Parental cells displayed sensitivity to salinosporamide A (IC50 = 5.1 nM), whereas their bortezomib-resistant sublines were 9- and 17-fold cross-resistant to salinosporamide A, respectively. Notably, combination experiments of salinosporamide A and bortezomib showed synergistic activity in CEM/BTZ200 cells. CEM cells gradually exposed to 20 nM salinosporamide A (CEM/S20) displayed stable 5-fold acquired resistance to salinosporamide A and were 3-fold cross-resistant to bortezomib. Consistent with the acquisition of a PSMB5 point mutation (M45V) in CEM/S20 cells, salinosporamide A displayed a markedly impaired capacity to inhibit β5-associated catalytic activity. Last, compared with parental CEM cells, CEM/S20 cells exhibited up to 2.5-fold upregulation of constitutive proteasome subunits, while retaining unaltered immunoproteasome subunit expression. In conclusion, salinosporamide A displayed potent antileukemic activity against bortezomib-resistant leukemia cells. β-Subunit point mutations as a common feature of acquired resistance to salinosporamide A and bortezomib in hematologic cells and S. tropica suggest an evolutionarily conserved mechanism of resistance to proteasome

  9. Potential of L-Buthionine Sulfoximine to Enhance the Apoptotic Action of Estradiol to Reverse Acquired Antihormonal Resistance in Metastatic Breast Cancer

    PubMed Central

    Lewis-Wambi, Joan S; Swaby, Ramona; Kim, Helen; Jordan, V. Craig

    2010-01-01

    L-buthionine sulfoximine (BSO) is a potent inhibitor of glutathione biosynthesis and studies have shown that it is capable of enhancing the apoptotic effects of several chemotherapeutic agents. Previous studies have shown that long term antihormonal therapy leads to acquired drug resistance and that estrogen, which is normally a survival signal, is a potent apoptotic agent in these resistant cells. Interestingly, we have developed an antihormone resistant breast cancer cell line, MCF-7:2A, which is resistant to estrogen-induced apoptosis but has elevated levels of glutathione. In the present study, we examined whether BSO is capable of sensitizing antihormone resistant MCF-7:2A cells to estrogen-induced apoptosis. Our results showed that treatment of MCF-7:2A cells with 1 nM E2 plus 100 μM BSO combination for 1 week reduced the growth of these cells by almost 80-90% whereas the individual treatments had no significant effect on growth. TUNEL and DAPI staining showed that the inhibitory effect of the combination treatment was due to apoptosis. Our data indicates that glutathione participates in retarding apoptosis in antihormone-resistant human breast cancer cells and that depletion of this molecule by BSO may be critical in predisposing resistant cells to estrogen-induced apoptosis. PMID:19167492

  10. Overview of Community-Acquired Pneumonia and the Role of Inflammatory Mechanisms in the Immunopathogenesis of Severe Pneumococcal Disease

    PubMed Central

    Steel, Helen C.; Anderson, Ronald; Feldman, Charles

    2013-01-01

    Community-acquired pneumonia (CAP) remains a leading cause of morbidity and mortality among the infectious diseases. Despite the implementation of national pneumococcal polyvalent vaccine-based immunisation strategies targeted at high-risk groups, Streptococcus pneumoniae (the pneumococcus) remains the most common cause of CAP. Notwithstanding the HIV pandemic, major challenges confronting the control of CAP include the range of bacterial and viral pathogens causing this condition, the ever-increasing problem of antibiotic resistance worldwide, and increased vulnerability associated with steadily aging populations in developed countries. These and other risk factors, as well as diagnostic strategies, are covered in the first section of this review. Thereafter, the review is focused on the pneumococcus, specifically the major virulence factors of this microbial pathogen and their role in triggering overexuberant inflammatory responses which contribute to the immunopathogenesis of invasive disease. The final section of the review is devoted to a consideration of pharmacological, anti-inflammatory strategies with adjunctive potential in the antimicrobial chemotherapy of CAP. This is focused on macrolides, corticosteroids, and statins with respect to their modes of anti-inflammatory action, current status, and limitations. PMID:24453422

  11. 2,3,7,8-Tetrachlorodibenzo-p-dioxin induced cell-specific drug transporters with acquired cisplatin resistance in cisplatin sensitive cancer cells.

    PubMed

    Gotovdorj, Tuvshinjargal; Lee, Eunil; Lim, Yongchul; Cha, Eun Jeong; Kwon, Daeho; Hong, Eunyoung; Kim, YunJeong; Oh, Min-Yeong

    2014-09-01

    2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) can induce drug transporter genes such as the ATP-binding cassette G member 2 (ABCG2), which contributes to multidrug resistance. We investigated the effect of TCDD pretreatment on drug transporters induction from cancer cells of various origins. Cell viabilities after treatment of cisplatin were measured to evaluate acquiring cisplatin resistance by TCDD. Acquring cisplatin resistance was found only in cisplatin senstivie cancer cells including gastric SNU601, colon LS180, brain CRT-MG and lymphoma Jurkat cells which showed a significant increase in cell viability after combined treatment with TCDD and cisplatin. High increase of ABCG2 gene expression was found in SNU601 and LS180 cells with a mild increase in the expression of the ABCC3, ABCC5,and SLC29A2 genes in SNU601 cells, and of major vault protein (MVP) in LS180 cells. The AhR inhibitor kaempferol suppressed the upregulation of ABCG2 expression and reversed the TCDD-induced increase in cell viability in LS180 cells. However, in CRT-MG cells, other transporter genes including ABCC1, ABCC5, ABCA3, ABCA2, ABCB4, ABCG1, and SLC29A1 were up-regulated. These findings suggested the acquiring cisplatin resistance by TCDD associated with cancer cell-type-specific induction of drug transporters. PMID:25246735

  12. Effect of mechanical surface and heat treatments on erosion resistance

    NASA Technical Reports Server (NTRS)

    Salik, J.; Buckley, D. H.

    1980-01-01

    The effects of mechanical surface treatments as well as heat treatments on the erosion resistance of 6061 aluminum alloy and 1045 steel were studied. Mechanical surface treatments were found to have little or no effect on the erosion resistance. This is due to the formation by particle impact of a work hardened surface layer regardless of the initial surface condition. The erosion resistance of Al single crystals is found to be independent of orientation. This is due to destruction of the surface microstructure and formation of a polycrystalline surface layer by the impact of erodant particles as observed by X-ray diffraction. While upon solution treatment of annealed 6061 aluminum the increase in hardness is accompanied by an increase in erosion resistance, precipitation treatment which causes a further increase in hardness results in slightly lower erosion resistance. Using two types of erodant particles, glass beads and crushed glass, the erosion rate is found to be strongly dependent on erodant particle shape, being an order of magnitude higher for erosion with crushed glass as compared to glass beads. While for erosion with glass beads heat treatment of 1045 steel had a profound effect on its erosion resistance, little or no such effect was observed for erosion with crushed glass.

  13. Carbapenem Resistance Mechanisms in Pseudomonas aeruginosa Clinical Isolates

    PubMed Central

    Pai, Hyunjoo; Kim, Jong-Won; Kim, Jungmin; Lee, Ji Hyang; Choe, Kang Won; Gotoh, Naomasa

    2001-01-01

    In order to define the contributions of the mechanisms for carbapenem resistance in clinical strains of Pseudomonas aeruginosa, we investigated the presence of OprD, the expressions of the MexAB-OprM and MexEF-OprN systems, and the production of the β-lactamases for 44 clinical strains. All of the carbapenem-resistant isolates showed the loss of or decreased levels of OprD. Three strains overexpressed the MexAB-OprM efflux system by carrying mutations in mexR. These three strains had the amino acid substitution in MexR protein, Arg (CGG) → Gln (CAG), at the position of amino acid 70. None of the isolates, however, expressed the MexEF-OprN efflux system. For the characterization of β-lactamases, at least 13 isolates were the depressed mutants, and 12 strains produced secondary β-lactamases. Based on the above resistance mechanisms, the MICs of carbapenem for the isolates were analyzed. The MICs of carbapenem were mostly determined by the expression of OprD. The MICs of meropenem were two- to four-fold increased for the isolates which overexpressed MexAB-OprM in the background of OprD loss. However, the elevated MICs of meropenem for some individual isolates could not be explained. These findings suggested that other resistance mechanisms would play a role in meropenem resistance in clinical isolates of P. aeruginosa. PMID:11158744

  14. Resistive switching characteristics and mechanisms in silicon oxide memory devices

    NASA Astrophysics Data System (ADS)

    Chang, Yao-Feng; Fowler, Burt; Chen, Ying-Chen; Zhou, Fei; Wu, Xiaohan; Chen, Yen-Ting; Wang, Yanzhen; Xue, Fei; Lee, Jack C.

    2016-05-01

    Intrinsic unipolar SiOx-based resistance random access memories (ReRAM) characterization, switching mechanisms, and applications have been investigated. Device structures, material compositions, and electrical characteristics are identified that enable ReRAM cells with high ON/OFF ratio, low static power consumption, low switching power, and high readout-margin using complementary metal-oxide semiconductor transistor (CMOS)-compatible SiOx-based materials. These ideas are combined with the use of horizontal and vertical device structure designs, composition optimization, electrical control, and external factors to help understand resistive switching (RS) mechanisms. Measured temperature effects, pulse response, and carrier transport behaviors lead to compact models of RS mechanisms and energy band diagrams in order to aid the development of computer-aided design for ultralarge-v scale integration. This chapter presents a comprehensive investigation of SiOx-based RS characteristics and mechanisms for the post-CMOS device era.

  15. Antimicrobial resistance profiles and mechanisms of resistance in Campylobacter jejuni isolates from pets.

    PubMed

    Acke, Els; McGill, Kevina; Quinn, Teresa; Jones, Boyd R; Fanning, Seamus; Whyte, Paul

    2009-01-01

    The presence of antimicrobial resistance in 51 Campylobacter jejuni isolates obtained from cats and dogs was determined by E-testing. Resistance to nalidixic acid (37.3% of isolates), ciprofloxacin (19.6%), tetracycline (13.7%), ampicillin (13.7%), erythromycin (11.8%), and chloramphenicol (5.9%) was detected. Resistance to two antimicrobials or more was present in 31.4% of isolates, and one isolate was resistant to all six antimicrobials. Of the isolates with ciprofloxacin and/or nalidixic acid resistance, 54.5% had the gyrA substitution Thr-86-Ile on sequencing. The tet o gene was detected in 75.0% isolates with high-level resistance to tetracycline. With the observed antimicrobial resistance in C. jejuni isolates from pets in this study, and the detection of identical mechanisms for quinolone and tetracycline resistance in pets and humans, pets should be considered a potential source of (multi)resistant C. jejuni infections in humans. PMID:19580444

  16. FDG-PET is a good biomarker of both early response and acquired resistance in BRAFV600 mutant melanomas treated with vemurafenib and the MEK inhibitor GDC-0973

    PubMed Central

    2012-01-01

    Background The BRAF inhibitor, vemurafenib, has recently been approved for the treatment of metastatic melanoma in patients harboring BRAFV600 mutations. Currently, dual BRAF and MEK inhibition are ongoing in clinical trials with the goal of overcoming the acquired resistance that has unfortunately developed in some vemurafenib patients. FDG-PET measures of metabolic activity are increasingly employed as a pharmacodynamic biomarker