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1

Epstein-Barr virus-derived EBNA2 regulates STAT3 activation  

SciTech Connect

The Epstein-Barr virus (EBV)-encoded latency protein EBNA2 is a nuclear transcriptional activator that is essential for EBV-induced cellular transformation. Here, we show that EBNA2 interacts with STAT3, a signal transducer for an interleukin-6 family cytokine, and enhances the transcriptional activity of STAT3 by influencing its DNA-binding activity. Furthermore, EBNA2 cooperatively acts on STAT3 activation with LMP1. These data demonstrate that EBNA2 acts as a transcriptional coactivator of STAT3.

Muromoto, Ryuta; Ikeda, Osamu; Okabe, Kanako; Togi, Sumihito; Kamitani, Shinya [Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-Ku Kita 12 Nishi 6, Sapporo 060-0812 (Japan); Fujimuro, Masahiro [Department of Molecular Cell Biology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Chuo 409-3898 (Japan); Harada, Shizuko [Department of Virology I, National Institute of Infectious Diseases, Toyama 1-23-1, Shinjuku-ku, Tokyo 162-8640 (Japan); Oritani, Kenji [Department of Hematology and Oncology, Graduate School of Medicine, Osaka University, 2-2 Yamada-oka, Suita, Osaka 565-0871 (Japan); Matsuda, Tadashi [Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-Ku Kita 12 Nishi 6, Sapporo 060-0812 (Japan)], E-mail: tmatsuda@pharm.hokudai.ac.jp

2009-01-16

2

STAT3 as a new autophagy regulator  

PubMed Central

Signal transducers and activators of transcription 3 (STAT3) proteins are cytoplasmic transcription factors that translocate into the nucleus to induce transcription following growth factor or cytokine stimulation. Besides their normal functions, these proteins play an important role in cancer cells through the abnormal activation of cell cycle progression and the deregulation of survival and senescence pathways. New data obtained from the laboratory of Guido Kroemer identifies STAT3 as a new autophagy regulator. In the cytoplasm, in the absence of conventional phosphorylation on the tyrosine 705 residue, STAT3 interacts with the PKR kinase to inhibit eIF2A phosphorylation and so reduce autophagic pathways. This new and nonconventional function of STAT3 has an important role in normal cells but we suggest that it might also affect cancer cells and the response to chemotherapy treatment.

Jonchere, Barbara; Belanger, Audrey; Guette, Catherine; Barre, Benjamin; Coqueret, Olivier

2013-01-01

3

Host cell and EBNA-2 regulation of Epstein-Barr virus latent-cycle promoter activity in B lymphocytes.  

PubMed Central

The six latent-cycle nuclear antigens (EBNAs) of Epstein-Barr virus (EBV), whose genes share 5' leader exons and two promoters (Cp and Wp), are differentially expressed by cells of the B lineage. To examine the possibility that EBNA gene expression is regulated through selective use of Cp and Wp, we monitored the activity of promoter-chloramphenicol acetyltransferase (CAT) gene constructs transfected into EBV-positive and EBV-negative B lymphocytes and Burkitt's lymphoma cells. Wp was a much stronger promoter than Cp in EBV genome-negative B-cell lines and was used exclusively in primary B cells. When B cells were infected with transforming EBV, Cp became the stronger promoter. This switch was not observed when B cells were infected with an immortalization-deficient virus, P3HR-1, which lacks the EBNA-2 open reading frame and expresses a mutant leader protein (EBNA-LP). Cp function was transactivated when EBV-negative or P3HR-1-infected B cells were cotransfected with Cp and a 12-kb fragment of DNA (BamHI-WWYH) that spanned the P3HR-1 deletion. This activity was mapped to the EBNA-2 gene within WWYH; constructs expressing EBNA-LP did not induce Cp function, and the deletion of 405 bp from the EBNA-2 open reading frame abolished transactivation. This research demonstrates host cell and EBNA-2 regulation of latent-cycle promoter activity in B lymphocytes, a mechanism with implications for persistence of EBV-infected lymphoid cells in vivo. Images

Rooney, C M; Brimmell, M; Buschle, M; Allan, G; Farrell, P J; Kolman, J L

1992-01-01

4

Identification and characterization of cis elements in the STAT3 gene regulating STAT3 alpha and STAT3 beta messenger RNA splicing.  

PubMed

Signal transducer and activator of transcription 3 (STAT3) is an oncogene and a critical regulator of multiple cell-fate decisions, including myeloid cell differentiation. Two isoforms of STAT3 have been identified: alpha (p92) and beta (p83). These differ structurally in their C-terminal transactivation domains, resulting in distinct functional activities. The cis genetic elements that regulate the ratio of alpha to beta messenger RNA (mRNA) are unknown. In this study, cloning, sequencing, and splicing analysis of the human and murine STAT3 genes revealed a highly conserved 5' donor site for generation of both alpha and beta mRNA and distinct branch-point sequences, polypyrimidine tracts, and 3' acceptor sites (ASs) for each. The beta 3' AS was found to be located 50 nucleotides downstream of the alpha 3' AS in exon 23. Two additional cryptic 3' ASs (delta and epsilon) were also identified. Thus, we identified for the first time the cis regulatory sequences responsible for generation of STAT3 alpha and STAT3 beta mRNA. PMID:11739197

Shao, H; Quintero, A J; Tweardy, D J

2001-12-15

5

Differential regulation of miR-21 and miR-146a by Epstein-Barr virus-encoded EBNA2  

PubMed Central

The discovery of microRNA (miR) represents a novel paradigm in RNA-based regulation of gene expression and their dysregulation has become a hallmark of many a tumor. In virally associated cancers, the host–pathogen interaction could involve alteration in miR expression. Epstein–Barr virus (EBV)-encoded EBNA2 is indispensable for the capacity of the virus to transform B cells in vitro. Here, we studied how it affects cellular miRs. Extensive miR profiling of the virus-infected and EBNA2-transfected B lymphoma cells revealed that oncomiR miR-21 is positively regulated by this viral protein. Conversely, Burkitt's lymphoma (BL) cell lines infected with EBNA2 lacking P3HR1 strain did not show any increase in miR-21. EBNA2 increased phosphorylation of AKT and this was directly correlated with increased miR-21. In contrast, miR-146a was downregulated by EBNA2 in B lymphoma cells. Low miR-146a expression correlates with an elevated level of IRAK1 and type I interferon in EBNA2 transfectants. Taken together, the present data suggest that EBNA2 might contribute to EBV-induced B-cell transformation by altering miR expression and in particular by increasing oncomiR-like miR-21 and by affecting the antiviral responses of the innate immune system through downregulation of its key regulator miR-146a.

Rosato, P; Anastasiadou, E; Garg, N; Lenze, D; Boccellato, F; Vincenti, S; Severa, M; Coccia, E M; Bigi, R; Cirone, M; Ferretti, E; Campese, A F; Hummel, M; Frati, L; Presutti, C; Faggioni, A; Trivedi, P

2012-01-01

6

Stat3 Inhibition Attenuates Mechanical Allodynia through Transcriptional Regulation of Chemokine Expression in Spinal Astrocytes  

PubMed Central

Background Signal transducer and activator of transcription 3 (Stat3) is known to induce cell proliferation and inflammation by regulating gene transcription. Recent studies showed that Stat3 modulates nociceptive transmission by reducing spinal astrocyte proliferation. However, it is unclear whether Stat3 also contributes to the modulation of nociceptive transmission by regulating inflammatory response in spinal astrocytes. This study aimed at investigating the role of Stat3 on neuroinflammation during development of pain in rats after intrathecal injection of lipopolysaccharide (LPS). Methods Stat3 specific siRNA oligo and synthetic selective inhibitor (Stattic) were applied to block the activity of Stat3 in primary astrocytes or rat spinal cord, respectively. LPS was used to induce the expression of proinflammatory genes in all studies. Immunofluorescence staining of cells and slices of spinal cord was performed to monitor Stat3 activation. The impact of Stat3 inhibition on proinflammatory genes expression was determined by cytokine antibody array, enzyme-linked immunosorbent assay and real-time polymerase chain reaction. Mechanical allodynia, as determined by the threshold pressure that could induce hind paw withdrawal after application of standardized von Frey filaments, was used to detect the effects of Stat3 inhibition after pain development with intrathecal LPS injection. Results Intrathecal injection of LPS activated Stat3 in reactive spinal astrocytes. Blockade of Stat3 activity attenuated mechanical allodynia significantly and was correlated with a lower number of reactive astrocytes in the spinal dorsal horn. In vitro study demonstrated that Stat3 modulated inflammatory response in primary astrocytes by transcriptional regulation of chemokine expression including Cx3cl1, Cxcl5, Cxcl10 and Ccl20. Similarly, inhibition of Stat3 reversed the expression of these chemokines in the spinal dorsal horn. Conclusions Stat3 acted as a transcriptional regulator of reactive astrocytes by modulating chemokine expression. Stat3 regulated inflammatory response in astrocytes and contributed to pain modulation. Blockade of Stat3 represents a new target for pain control.

Liu, Xiaodong; Tian, Yuanyuan; Lu, Na; Gin, Tony; Cheng, Christopher H. K.; Chan, Matthew T. V.

2013-01-01

7

Cross-talk between KLF4 and STAT3 regulates axon regeneration  

NASA Astrophysics Data System (ADS)

Cytokine-induced activation of signal transducer and activator of transcription 3 (STAT3) promotes the regrowth of damaged axons in the adult central nervous system (CNS). Here we show that KLF4 physically interacts with STAT3 upon cytokine-induced phosphorylation of tyrosine 705 (Y705) on STAT3. This interaction suppresses STAT3-dependent gene expression by blocking its DNA-binding activity. The deletion of KLF4 in vivo induces axon regeneration of adult retinal ganglion cells (RGCs) via Janus kinase (JAK)–STAT3 signalling. This regeneration can be greatly enhanced by exogenous cytokine treatment, or removal of an endogenous JAK–STAT3 pathway inhibitor called suppressor of cytokine signalling 3 (SOCS3). These findings reveal an unexpected cross-talk between KLF4 and activated STAT3 in the regulation of axon regeneration that might have therapeutic implications in promoting repair of injured adult CNS.

Qin, Song; Zou, Yuhua; Zhang, Chun-Li

2013-10-01

8

Dendritic Cell (DC)-Specific Targeting Reveals Stat3 as a Negative Regulator of DC Function  

PubMed Central

Dendritic cells (DCs) must achieve a critical balance between activation and tolerance, a process influenced by cytokines and growth factors. IL-10, which transduces signals through Stat3, has emerged as one important negative regulator of DC activation. To directly examine the role Stat3 plays in regulating DC activity, the Stat3 gene was targeted for deletion with a CD11c-cre transgene. Stat3 CKO mice developed cervical lymphadenopathy as well as a mild ileocolitis that persisted throughout life and was associated with impaired weight gain. Consistent with this, Stat3-deficient DCs demonstrated enhanced immune activity, including increased cytokine production, Ag-dependent T-cell activation and resistance to IL-10–mediated suppression. These results reveal a cell-intrinsic negative regulatory role of Stat3 in DCs and link increased DC activation with perturbed immune homeostasis and chronic mucosal inflammation.

Melillo, Jessica A.; Song, Li; Bhagat, Govind; Blazquez, Ana Belen; Plumlee, Courtney R.; Lee, Carolyn; Berin, Cecilia; Reizis, Boris; Schindler, Christian

2011-01-01

9

Regulation of Sox2 by STAT3 initiates commitment to the neural precursor cell fate.  

PubMed

STAT3, a member of the signal transducer and activator or transcription (STAT) family of proteins, plays a major role in gliogenesis; however, its functions during differentiation of neural precursor cells (NPCs) are unclear. Our data demonstrate that STAT3 is present and active in the developing mouse central nervous system (CNS) as early as E7.5, several days prior to gliogenesis. We hypothesize that STAT3 is functioning very early in neural development to regulate NPC differentiation. To test this hypothesis, STAT3 dominant negative embryonic stem (ES) cells were generated and subjected to neural differentiation. The loss of STAT3 resulted in production of significantly fewer NPCs along with decreased expression of the neural stem cell marker nestin. Further investigation revealed the existence of a novel signaling pathway during early neural development in which STAT3 directly regulates the Sox2 promoter leading to Sox2 expression and subsequent nestin expression and commitment to the NPC fate. PMID:18447642

Foshay, Kara M; Gallicano, G Ian

2008-04-01

10

Self-regulation of Stat3 activity coordinates cell-cycle progression and neural crest specification  

PubMed Central

A complex set of extracellular signals is required for neural crest (NC) specification. However, how these signals function to coordinate cell-cycle progression and differentiation remains poorly understood. Here, we report in Xenopus a role for the transcription factor signal transducers and activators of transcription-3 (Stat3) in this process downstream of FGF signalling. Depletion of Stat3 inhibits NC gene expression and cell proliferation, whereas overexpression expands the NC domain and promotes cell proliferation. Stat3 is phosphorylated and activated in ectodermal cells by FGFs through binding with FGFR4. Stat3 activation is also modulated by Hairy2 and Id3 proteins that, respectively, facilitate and disrupt Stat3-FGFR4 complex formation. Furthermore, distinct levels of Stat3 activity control Hairy2 and Id3 transcription, leading to Stat3 self-regulation. Finally, high Stat3 activity maintains cells in an undifferentiated state, whereas low activity promotes cell proliferation and NC differentiation. Together, our data suggest that Stat3, downstream of FGFs and under the positive and negative feedback regulation of Hairy2 and Id3, plays an essential role in the coordination of cell-cycle progression and differentiation during NC specification.

Nichane, Massimo; Ren, Xi; Bellefroid, Eric J

2010-01-01

11

Necdin, a Negative Growth Regulator, Is a Novel STAT3 Target Gene Down-Regulated in Human Cancer  

PubMed Central

Cytokine and growth factor signaling pathways involving STAT3 are frequently constitutively activated in many human primary tumors, and are known for the transcriptional role they play in controlling cell growth and cell cycle progression. However, the extent of STAT3's reach on transcriptional control of the genome as a whole remains an important question. We predicted that this persistent STAT3 signaling affects a wide variety of cellular functions, many of which still remain to be characterized. We took a broad approach to identify novel STAT3 regulated genes by examining changes in the genome-wide gene expression profile by microarray, using cells expressing constitutively-activated STAT3. Using computational analysis, we were able to define the gene expression profiles of cells containing activated STAT3 and identify candidate target genes with a wide range of biological functions. Among these genes we identified Necdin, a negative growth regulator, as a novel STAT3 target gene, whose expression is down-regulated at the mRNA and protein levels when STAT3 is constitutively active. This repression is STAT3 dependent, since inhibition of STAT3 using siRNA restores Necdin expression. A STAT3 DNA-binding site was identified in the Necdin promoter and both EMSA and chromatin immunoprecipitation confirm binding of STAT3 to this region. Necdin expression has previously been shown to be down-regulated in a melanoma and a drug-resistant ovarian cancer cell line. Further analysis of Necdin expression demonstrated repression in a STAT3-dependent manner in human melanoma, prostate and breast cancer cell lines. These results suggest that STAT3 coordinates expression of genes involved in multiple metabolic and biosynthetic pathways, integrating signals that lead to global transcriptional changes and oncogenesis. STAT3 may exert its oncogenic effect by up-regulating transcription of genes involved in promoting growth and proliferation, but also by down-regulating expression of negative regulators of the same cellular processes, such as Necdin.

Haviland, Rachel; Eschrich, Steven; Bloom, Gregory; Ma, Yihong; Minton, Susan; Jove, Richard; Cress, W. Douglas

2011-01-01

12

APE1/Ref-1 Regulates STAT3 Transcriptional Activity and APE1/Ref-1-STAT3 Dual-Targeting Effectively Inhibits Pancreatic Cancer Cell Survival  

PubMed Central

Pancreatic cancer is a largely incurable disease, and increasing evidence supports strategies targeting multiple molecular mediators of critical functions of pancreatic ductal adenocarcinoma cells. Intracellular redox state modulates the activity of various signal transduction pathways and biological processes, including cell survival, drug resistance and responsiveness to microenvironmental factors. Recently, it has been shown that the transcription factor STAT3 is under redox control, but the mechanisms involved in its regulation are unknown. Here, we demonstrate for the first time that STAT3 DNA binding and transcriptional activity is directly regulated by the redox function of the APE1/Ref-1 endonuclease, using overexpression and redox-specific mutational strategies, and gene knockdown. Also, pharmacological blockade of APE1/Ref-1 by the redox-selective inhibitor E3330 abrogates STAT3 DNA binding. Since APE1/Ref-1 also exerts redox control on other cancer-associated transcription factors, we assessed the impact of dual-targeting of STAT3 signaling and APE1/Ref-1 redox on pancreatic cancer cell functions. We observed that disruption of APE1/Ref-1 redox activity synergizes with STAT3 blockade to potently inhibit the proliferation and viability of human PDAC cells. Mechanistically, we show that STAT3–APE1/Ref-1 dual targeting promotes marked tumor cell apoptosis, with engagement of caspase-3 signaling, which are significantly increased in comparison to the effects triggered by single target blockade. Also, we show that STAT3–APE1/Ref-1 dual blockade results in significant inhibition of tumor cell migration. Overall, this work demonstrates that the transcriptional activity of STAT3 is directly regulated by the redox function of APE1/Ref-1, and that concurrent blockade of STAT3 and APE1/Ref-1 redox synergize effectively inhibit critical PDAC cell functions.

Cardoso, Angelo A.; Jiang, Yanlin; Luo, Meihua; Reed, April M.; Shahda, Safi; He, Ying; Maitra, Anirban; Kelley, Mark R.; Fishel, Melissa L.

2012-01-01

13

GSTP1 negatively regulates Stat3 activation in epidermal growth factor signaling  

PubMed Central

Glutathione S-transferases (GSTs) are the enzymes that defend cells against the damage mediated by oxidant and electrophilic carcinogens. GST? (GSTP1) is a member of the GST family and the hypermethylation GSTP1 CpG island DNA is detected in human hepatocellular carcinoma (HCC) tissues, which contributes to the negative expression of GSTP1 mRNA and protein. GSTP1 expression is considered to be an early event in HCC. Stat3, a member of the signal transduction and activator of transcription (Stat) family, is important for promoting the proliferation, survival and other biological processes of cells triggered by cytokines and growth factors. Activated Stat3 may participate in oncogenesis. Previous studies have demonstrated that overexpression of phosphorylated Stat3 is important in the proliferation of HCC cells, suggesting that disturbance of the Stat3 pathway may be an early event. We hypothesize that the suppression of GSTP1 expression in HCC cells increases Stat3 activation. In order to test this hypothesis, HepG2 cells were genetically modified to transiently express high levels of GSTP1. The transient expression of GSTP1 specifically downregulated epidermal growth factor (EGF)-mediated tyrosine phosphorylation of Stat3, and subsequently suppressed the transcriptional activity of Stat3. By contrast, GSTP1 RNAi was able to lead to an increase in the phosphorylation of Stat3. In addition, overexpression of GSTP1 was capable of reducing the survival of HepG2 cells and inducing cell cycle arrest. This inhibition was mediated by a direct interaction between GSTP1 and Stat3. Overall, our results suggest that GSTP1 is important in the regulation of the transcriptional activity of Stat3, and that it is also a regulator of the cell cycle via EGF signaling.

KOU, XIANJUAN; CHEN, NING; FENG, ZHIYONG; LUO, LAN; YIN, ZHIMIN

2013-01-01

14

STAT3 in Epithelial Cells Regulates Inflammation and Tumor Progression to Malignant State in Colon.  

PubMed

Chronic inflammation is an important risk factor for the development of colorectal cancer; however, the mechanism of tumorigenesis especially tumor progression to malignancy in the inflamed colon is still unclear. Our study shows that epithelial signal transducer and activator of transcription 3 (STAT3), persistently activated in inflamed colon, is not required for inflammation-induced epithelial overproliferation and the development of early-stage tumors; however, it is essential for tumor progression to advanced malignancy. We found that one of the mechanisms that epithelial STAT3 regulates in tumor progression might be to modify leukocytic infiltration in the large intestine. Activation of epithelial STAT3 promotes the infiltration of the CD8+ lymphocyte population but inhibits the recruitment of regulatory T (Treg) lymphocytes. The loss of Stat3 in epithelial cells promoted the expression of cytokines/chemokines including CCL19, CCL28, and RANTES, which are known to be able to recruit Treg lymphocytes. Linked to these changes was the pathway mediated by sphingosine 1-phosphate receptor 1 and sphingosine 1-phosphate kinases, which is activated in colonic epithelial cells in inflamed colon with functional STAT3 but not in epithelial cells deleted of STAT3. Our data suggest that epithelial STAT3 plays a critical role in inflammation-induced tumor progression through regulation of leukocytic recruitment especially the infiltration of Treg cells in the large intestine. PMID:24027425

Nguyen, Andrew V; Wu, Yuan-Yuan; Liu, Qiang; Wang, Donghai; Nguyen, Stephanie; Loh, Ricky; Pang, Joey; Friedman, Kenneth; Orlofsky, Amos; Augenlicht, Leonard; Pollard, Jeffrey W; Lin, Elaine Y

2013-09-01

15

STAT3 in Epithelial Cells Regulates Inflammation and Tumor Progression to Malignant State in Colon1  

PubMed Central

Chronic inflammation is an important risk factor for the development of colorectal cancer; however, the mechanism of tumorigenesis especially tumor progression to malignancy in the inflamed colon is still unclear. Our study shows that epithelial signal transducer and activator of transcription 3 (STAT3), persistently activated in inflamed colon, is not required for inflammation-induced epithelial overproliferation and the development of early-stage tumors; however, it is essential for tumor progression to advanced malignancy. We found that one of the mechanisms that epithelial STAT3 regulates in tumor progression might be to modify leukocytic infiltration in the large intestine. Activation of epithelial STAT3 promotes the infiltration of the CD8+ lymphocyte population but inhibits the recruitment of regulatory T (Treg) lymphocytes. The loss of Stat3 in epithelial cells promoted the expression of cytokines/chemokines including CCL19, CCL28, and RANTES, which are known to be able to recruit Treg lymphocytes. Linked to these changes was the pathway mediated by sphingosine 1-phosphate receptor 1 and sphingosine 1-phosphate kinases, which is activated in colonic epithelial cells in inflamed colon with functional STAT3 but not in epithelial cells deleted of STAT3. Our data suggest that epithelial STAT3 plays a critical role in inflammation-induced tumor progression through regulation of leukocytic recruitment especially the infiltration of Treg cells in the large intestine.

Nguyen, Andrew V; Wu, Yuan-Yuan; Liu, Qiang; Wang, Donghai; Nguyen, Stephanie; Loh, Ricky; Pang, Joey; Friedman, Kenneth; Orlofsky, Amos; Augenlicht, Leonard; Pollard, Jeffrey W; Lin, Elaine Y

2013-01-01

16

Association of early phase of colorectal carcinogenesis with STAT3 activation and its relevance in apoptosis regulation  

Microsoft Academic Search

Expression of STAT3\\/pSTAT3 in colorectal cancer (CRC) patients of Indian origin was studied to assess its significance in early detection and apoptosis regulation. Colorectal tissues with malignant lesions were STAT3\\/pSTAT3 positive in 66% of the cases and among these positive cases, well differentiated, moderately differentiated and poorly differentiated cancers were 86%, 60% and 0% respectively. All CRC specimens studied were

Rathindranath Baral; Anamika Bose; Chinmoyee Ray; Sonali Paul; Smarajit Pal; Enamul Haque; Bhagawan Mishra; Debolina Pal; Jatin Kumar Nagpal; Chinmay Kumar Panda; Bibhu Ranjan Das

2009-01-01

17

STAT3 regulation of and by microRNAs in development and disease  

PubMed Central

MicroRNAs (miRNAs) are endogenously expressed small non-coding RNAs acting at the post-transcriptional level where they promote mRNA degradation and block protein translation. Recent findings suggest that complex transcriptional and post-transcriptional circuits control miRNAs. STAT3 has emerged as an important regulator of their expression and biogenesis and, in turn, STAT3 signaling pathways are controlled by distinct miRNAs. We summarize the current knowledge on STAT3 mediated processing of individual miRNAs and contrariwise, the modulation of the STAT3 pathway by miRNAs in development and in pathophysiological conditions such as immune processes, infection, cancer, cardiovascular disease and pulmonary hypertension.

Haghikia, Arash; Hoch, Melanie; Stapel, Britta; Hilfiker-Kleiner, Denise

2012-01-01

18

Interleukin-21 regulates expression of key Epstein-Barr virus oncoproteins, EBNA2 and LMP1, in infected human B cells  

SciTech Connect

Epstein-Barr virus (EBV) persists for the life of the host by accessing the long-lived memory B cell pool. It has been proposed that EBV uses different combinations of viral proteins, known as latency types, to drive infected B cells to make the transition from resting B cells to memory cells. This process is normally antigen-driven. A major unresolved question is what factors coordinate expression of EBV latency proteins. We have recently described novel type III latency EBV{sup +} B cell lines (OCI-BCLs) that were induced to differentiate into late plasmablasts/early plasma cells in culture with interleukin-21 (IL-21), mimicking normal B cell development. The objective of this study was to determine whether IL-21-mediated signals also regulate the expression of key EBV latent proteins during this window of development. Here we show that IL-21-reduced gene and protein expression of growth-transforming EBV nuclear antigen 2 (EBNA2) in OCI-BCLs. By contrast, the expression of CD40-like, latent membrane protein 1 (LMP1) strongly increased in these cells suggesting an EBNA2-independent mode of regulation. Same results were also observed in Burkitt's lymphoma line Jijoye and B95-8 transformed lymphoblastoid cell lines. The effect of IL-21 on EBNA2 and LMP1 expression was attenuated by a pharmacological JAK inhibitor indicating involvement of JAK/STAT signalling in this process. Our study also shows that IL-21 induced transcription of ebna1 from the viral Q promoter (Qp)

Konforte, Danijela [Division of Stem Cell and Developmental Biology, Princess Margaret Hospital, Ontario Cancer Institute, University Health Network, Toronto, M5G 2M9 (Canada); Department of Immunology, University of Toronto, Toronto, M5S 1A8 (Canada)], E-mail: danijela.konforte@utoronto.ca; Simard, Nathalie; Paige, Christopher J. [Division of Stem Cell and Developmental Biology, Princess Margaret Hospital, Ontario Cancer Institute, University Health Network, Toronto, M5G 2M9 (Canada); Department of Immunology, University of Toronto, Toronto, M5S 1A8 (Canada)

2008-04-25

19

STAT3 signalling is required for leptin regulation of energy balance but not reproduction  

Microsoft Academic Search

Secretion of leptin from adipocytes communicates body energy status to the brain by activating the leptin receptor long form (LRb). LRb regulates energy homeostasis and neuroendocrine function; the absence of LRb in db\\/db mice results in obesity, impaired growth, infertility and diabetes. Tyr 1138 of LRb mediates activation of the transcription factor STAT3 during leptin action. To investigate the contribution

Sarah H. Bates; Walter H. Stearns; Trevor A. Dundon; Markus Schubert; Annette W. K. Tso; Yongping Wang; Alexander S. Banks; Hugh J. Lavery; Asma K. Haq; Eleftheria Maratos-Flier; Benjamin G. Neel; Michael W. Schwartz; Martin G. Myers

2003-01-01

20

Protein kinase Cvarepsilon mediates Stat3Ser727 phosphorylation, Stat3-regulated gene expression, and cell invasion in various human cancer cell lines through integration with MAPK cascade (RAF-1, MEK1/2, and ERK1/2).  

PubMed

Protein kinase C epsilon (PKCvarepsilon), a novel calcium-independent PKC isoform, has been shown to be a transforming oncogene. PKCvarepsilon-mediated oncogenic activity is linked to its ability to promote cell survival. However, the mechanisms by which PKCvarepsilon signals cell survival remain elusive. We found that signal transducers and activators of transcription 3 (Stat3), which is constitutively activated in a wide variety of human cancers, is a protein partner of PKCvarepsilon. Stat3 has two conserved amino-acid (Tyr705 and Ser727) residues, which are phosphorylated during Stat3 activation. PKCvarepsilon interacts with Stat3alpha isoform, which has Ser727, and not with Stat3beta isoform, which lacks Ser727. PKCvarepsilon-Stat3 interaction and Stat3Ser727 phosphorylation was initially observed during induction of squamous cell carcinomas and in prostate cancer. Now we present that (1) PKCvarepsilon physically interacts with Stat3alpha isoform in various human cancer cells: skin melanomas (MeWo and WM266-4), gliomas (T98G and MO59K), bladder (RT-4 and UM-UC-3), colon (Caco-2), lung (H1650), pancreatic (PANC-1), and breast (MCF-7 and MDA:MB-231); (2) inhibition of PKCvarepsilon expression using specific siRNA inhibits Stat3Ser727 phosphorylation, Stat3-DNA binding, Stat3-regulated gene expression as well as cell invasion; and (3) PKCvarepsilon mediates Stat3Ser727 phosphorylation through integration with the MAPK cascade (RAF-1, MEK1/2, and ERK1/2). The results indicate that PKCvarepsilon-mediated Stat3Ser727 phosphorylation is essential for constitutive activation of Stat3 and cell invasion in various human cancers. PMID:20228845

Aziz, M H; Hafeez, B B; Sand, J M; Pierce, D B; Aziz, S W; Dreckschmidt, N E; Verma, A K

2010-03-15

21

Avicin D: A Protein Reactive Plant Isoprenoid Dephosphorylates Stat 3 by Regulating Both Kinase and Phosphatase Activities  

PubMed Central

Avicins, a class of electrophilic triterpenoids with pro-apoptotic, anti-inflammatory and antioxidant properties, have been shown to induce redox-dependant post-translational modification of cysteine residues to regulate protein function. Based on (a) the cross-talk that occurs between redox and phosphorylation processes, and (b) the role of Stat3 in the process of apoptosis and carcinogenesis, we chose to study the effects of avicins on the processes of phosphorylation/dephosphorylation in Stat3. Avicins dephosphorylate Stat3 in a variety of human tumor cell lines, leading to a decrease in the transcriptional activity of Stat3. The expression of Stat3-regulated proteins such as c-myc, cyclin D1, Bcl2, survivin and VEGF were reduced in response to avicin treatment. Underlying avicin-induced dephosphorylation of Stat3 was dephosphorylation of JAKs, as well as activation of protein phosphatase-1. Downregulation of both Stat3 activity and expression of Stat 3-controlled pro-survival proteins, contributes to the induction of apoptosis in avicin treated tumor cells. Based on the role of Stat3 in inflammation and wounding, and the in vivo inhibition of VEGF by avicins in a mouse skin carcinogenesis model, it is likely that avicin-induced inhibition of Stat3 activity results in the suppression of the pro-inflammatory and pro-oxidant stromal environment of tumors. Activation of PP-1, which also acts as a cellular economizer, combined with the redox regulation by avicins, can aid in redirecting metabolism from growth promoting anabolic to energy sparing pathways.

Haridas, Valsala; Nishimura, Goshi; Xu, Zhi-Xiang; Connolly, Fiona; Hanausek, Margaret; Walaszek, Zbigniew; Zoltaszek, Robert; Gutterman, Jordan U.

2009-01-01

22

Opposing roles of STAT1 and STAT3 in T cell-mediated hepatitis: regulation by SOCS  

PubMed Central

T cell–mediated fulminant hepatitis is a life-threatening event for which the underlying mechanism is not fully understood. Injection of concanavalin A (Con A) into mice recapitulates the histological and pathological sequelae of T cell–mediated hepatitis. In this model, both signal transducer and activator of transcription factor 1 (STAT1) and STAT3 are activated in the liver. Disruption of the STAT1 gene by way of genetic knockout attenuates liver injury, suppresses CD4+ and NK T cell activation, and downregulates expression of proapoptotic interferon regulatory factor-1 protein and suppressor of cytokine signaling-1 (SOCS1), but enhances STAT3 activation and STAT3-controlled antiapoptotic signals. Studies from IFN-?–deficient mice indicate that IFN-? not only is the major cytokine responsible for STAT1 activation but also partially accounts for STAT3 activation. Moreover, downregulation of STAT3 activation in IL-6–deficient mice is associated with decreased STAT3-controlled antiapoptotic signals and expression of SOCS3, but upregulation of STAT1 activation and STAT1-induced proapoptotic signals and exacerbation of liver injury. Taken together, these findings suggest that STAT1 plays a harmful role in Con A–mediated hepatitis by activation of CD4+ and NK T cells and directly inducing hepatocyte death, whereas STAT3 protects against liver injury by suppression of IFN-? signaling and induction of antiapoptotic protein Bcl-XL. STAT1 and STAT3 in hepatocytes also negatively regulate one another through the induction of SOCS.

Hong, Feng; Jaruga, Barbara; Kim, Won Ho; Radaeva, Svetlana; El-Assal, Osama N.; Tian, Zhigang; Nguyen, Van-Anh; Gao, Bin

2002-01-01

23

Involvement of STAT3-regulated hepatic soluble factors in attenuation of stellate cell activity and liver fibrogenesis in mice.  

PubMed

Glycoprotein 130 (gp130)/signal transducer and activator of transcription 3 (STAT3) signaling in hepatocytes controls a variety of physiological and pathological processes including liver regeneration, apoptosis resistance and metabolism. Recent research has shed light on the importance of acute phase proteins (APPs) regulated by hepatic gp130/STAT3 in host defense through suppression of innate immune responses during systemic inflammation. To examine whether these STAT3-regulated soluble factors directly affect liver fibrogenic responses during liver injury, hepatocyte-specific STAT3 knockout (L-STAT3 KO) mice and control littermates were subjected to bile duct ligation (BDL) and examined 10 days later. In contrast to controls, L-STAT3 KO mice failed to produce APPs, such as serum amyloid A and haptoglobin, after BDL. Whereas L-STAT3 KO mice displayed similar levels of cholestasis, inflammatory cell infiltration and regeneration in the liver, they developed exacerbated liver injury and fibrosis with significant increases in expression of alpha-smooth muscle actin and type I collagen genes. In vitro experiments revealed that attenuated expression of APPs in primary hepatocytes isolated from L-STAT3 KO mice with IL-6 exposure, compared to wild-type hepatocytes. The cultured supernatant from IL-6-treated wild-type hepatocytes inhibited expression of alpha-smooth muscle actin and type I collagen genes in activated hepatic stellate cells (HSCs), whereas this did not occur with the supernatant from IL-6-treated knockout hepatocytes or with control medium. In conclusion, the absence of STAT3 in hepatocytes leads to exacerbation of liver fibrosis during cholestasis. Soluble factors released from hepatocytes, dependent on STAT3, collectively play a protective role in liver fibrogenesis through an inhibitory effect on activated HSCs. PMID:21356197

Shigekawa, Minoru; Takehara, Tetsuo; Kodama, Takahiro; Hikita, Hayato; Shimizu, Satoshi; Li, Wei; Miyagi, Takuya; Hosui, Atsushi; Tatsumi, Tomohide; Ishida, Hisashi; Kanto, Tatsuya; Hiramatsu, Naoki; Hayashi, Norio

2011-02-26

24

Integrin ?3-mediated Src activation regulates apoptosis in IEC-6 cells via Akt and STAT3  

PubMed Central

Intestinal epithelial (IEC-6) cells are resistant to apoptosis following the inhibition of ODC (ornithine decarboxylase) and subsequent polyamine depletion. The depletion of polyamines rapidly activates NF-?B (nuclear factor ?B) and STAT3 (signal transducer and activator of transcription 3), which is responsible for the observed decrease in apoptosis. Since both NF-?B and STAT3 signalling pathways can be activated by Src kinase, we examined its role in the antiapoptotic response. Inhibition of ODC by DFMO (?-difluoromethylornithine) increased the activity of Src and ERK1/2 (extracellular-signal-regulated kinase 1/2) within 30 min, which was prevented by exogenous polyamines added to the DFMO-containing medium. Conversely, epidermal growth factor-mediated Src and ERK1/2 activation was not prevented by the addition of polyamines. Inhibition of Src with PP2 {4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine} and a DN-Src (dominant-negative Src) construct prevented the activation of Akt, JAK (Janus kinase) and STAT3. Spontaneous apoptosis was increased in DN-Src-expressing cells and the protective effect of polyamine depletion was lost. Polyamine depletion by DFMO increased integrin ?3 Tyr785 phosphorylation. Cells plated on fibronectin had significantly higher ?3 phosphorylation and Src activation compared with plastic. Exogenous polyamines added to the fibronectin matrix prevented Src activation. Arg-Gly-Asp-Ser inhibited ?3, Src and Akt phosphorylation and sensitized polyamine-depleted cells to tumour necrosis factor ?/cycloheximide-mediated apoptosis. Fibronectin activated Src and subsequently protected cells from apoptosis. Together, these results suggest that the inhibition of ODC rapidly removes a small pool of available polyamines triggering the activation of ?3 integrin, which in turn activates Src. The subsequent Akt and JAK activation is accompanied by translocation of NF-?B and STAT3 to the nucleus and the synthesis of antiapoptotic proteins.

Bhattacharya, Sujoy; Ray, Ramesh M.; Johnson, Leonard R.

2006-01-01

25

Caveolin-2 regulation of STAT3 transcriptional activation in response to insulin  

Microsoft Academic Search

The regulatory function of caveolin-2 in signal transducer and activator of transcription 3 (STAT3) signaling by insulin was investigated. Insulin-induced increase in phosphorylation of STAT3 was reduced by caveolin-2 siRNA. Mutagenesis studies identified that phosphorylation of tyrosines 19 and 27 on caveolin-2 is required for the STAT3 activation. Caveolin-2 Y27A mutation decreased insulin-induced phosphorylation of STAT3 interacting with caveolin-2. pY27-Caveolin-2

Hayeong Kwon; Kyuho Jeong; Eun Mi Hwang; Jae-Yong Park; Seong-Geun Hong; Wan-Sung Choi; Yunbae Pak

2009-01-01

26

The STAT3-Ser/Hes3 signaling axis: an emerging regulator of endogenous regeneration and cancer growth  

PubMed Central

Stem cells, by definition, are able to both self-renew (give rise to more cells of their own kind) and demonstrate multipotential (the ability to differentiate into multiple cell types). To accommodate this unique dual ability, stem cells interpret signal transduction pathways in specialized ways. Notable examples include canonical and non-canonical branches of the Notch signaling pathway, with each controlling different downstream targets (e.g., Hes1 vs. Hes3) and promoting either differentiation or self-renewal. Similarly, stem cells utilize STAT3 signaling uniquely. Most mature cells studied thus far rely on tyrosine phosphorylation (STAT3-Tyr) to promote survival and growth; in contrast, STAT3-Tyr induces the differentiation of neural stem cells (NSCs). NSCs use an alternative phosphorylation site, STAT3-Ser, to regulate survival and growth, a site that is largely redundant for this function in most other cell types. STAT3-Ser regulates Hes3, and together they form a convergence point for several signals, including Notch, Tie2, and insulin receptor activation. Disregulation and manipulation of the STAT3-Ser/Hes3 signaling pathway is important in both tumorigenesis and regenerative medicine, and worthy of extensive study.

Poser, Steven W.; Park, Deric M.; Androutsellis-Theotokis, Andreas

2013-01-01

27

Phosphotyrosyl peptides block Stat3-mediated DNA binding activity, gene regulation, and cell transformation.  

PubMed

Signal transducers and activators of transcription (STATs) comprise a family of cytoplasmic signaling proteins that participates in normal cellular responses to cytokines and growth factors. Frequently, however, constitutive activation of certain STAT family members, particularly Stat3, has accompanied a wide variety of human malignancies. To identify small molecule inhibitors of Stat3, we investigated the ability of the Stat3 SH2 domain-binding peptide, PY*LKTK (where Y* represents phosphotyrosine), to disrupt Stat3 activity in vitro. The presence of PY*LKTK, but not PYLKTK or PFLKTK, in nuclear extracts results in significant reduction in the levels of DNA binding activities of Stat3, to a lesser extent of Stat1, and with no effect on that of Stat5. Analyses of alanine scanning mutagenesis and deletion derivatives of PY*LKTK reveal that the Leu residue at the Y+1 position and a substituent at the Y-1 position (but not necessarily Pro) are essential for the disruption of active Stat3, thereby mapping the minimum active sequence to the tripeptide, XY*L. Studies involving bead-coupled PY*LKTK peptide demonstrate that this phosphopeptide directly complexes with Stat3 monomers in vitro, suggesting that PY*LKTK disrupts Stat3:Stat3 dimers. As evidence for the functional importance of peptide-directed inhibition of Stat3, PY*LKTK-mts (mts, membrane translocating sequence) selectively inhibits constitutive and ligand-induced Stat3 activation in vivo. Furthermore, PY*LKTK-mts suppresses transformation by the Src oncoprotein, which has been shown previously to require constitutive Stat3 activation. Altogether, we have identified a minimal peptide that inhibits Stat3 signaling and provides the conceptual basis for use of this peptide as a lead for novel peptidomimetic drug design. PMID:11579100

Turkson, J; Ryan, D; Kim, J S; Zhang, Y; Chen, Z; Haura, E; Laudano, A; Sebti, S; Hamilton, A D; Jove, R

2001-09-28

28

The Wnt/?-Catenin Pathway Cross-Talks with STAT3 Signaling to Regulate Survival of Retinal Pigment Epithelium Cells  

PubMed Central

Wnt/?-catenin signaling is an essential pathway that regulates numerous cellular processes, including cell survival. The molecular mechanisms contributing to pro-survival Wnt signaling are mostly unknown. Signal transducer and activator of transcription proteins (STATs) are a well-described family of transcription factors. STAT3 induces expression of anti-apoptotic genes in many tissues and is a downstream mediator of protective growth factors and cytokines. In this study, we investigated whether pro-survival Wnt signaling is mediated by STAT3. The Wnt3a ligand activated Wnt signaling in the retinal pigment epithelium ARPE-19 cell line and significantly increased the viability of cells exposed to oxidative stress. Furthermore, Wnt3a increased STAT3 activation and nuclear translocation, as measured by an antibody against phosphorylated STAT3. Reducing STAT3 levels with siRNA eliminated Wnt3a-dependent protection from oxidative stress. Together, these data demonstrate a previously unknown link between Wnt3a-mediated activation of STAT3 and cell survival, and indicate cross-talk between two important pro-survival signaling pathways.

Nakamura, Rei E. I.; Yi, Hyun; Surapaneni, Krishna; Hackam, Abigail S.

2012-01-01

29

Role of STAT3 in regulation of hepatic gluconeogenic genes and carbohydrate metabolism in vivo  

Microsoft Academic Search

The transcription factor, signal transducer and activator of transcription-3 (STAT-3) contributes to various physiological processes. Here we show that mice with liver-specific deficiency in STAT-3, achieved using the Cre-loxP system, show insulin resistance associated with increased hepatic expression of gluconeogenic genes. Restoration of hepatic STAT-3 expression in these mice, using adenovirus-mediated gene transfer, corrected the metabolic abnormalities and the alterations

Hiroshi Inoue; Wataru Ogawa; Michitaka Ozaki; Sanae Haga; Michihiro Matsumoto; Kensuke Furukawa; Naoko Hashimoto; Yoshiaki Kido; Toshiyuki Mori; Hiroshi Sakaue; Kiyoshi Teshigawara; Shiyu Jin; Haruhisa Iguchi; Ryuji Hiramatsu; Derek LeRoith; Kiyoshi Takeda; Shizuo Akira; Masato Kasuga

2004-01-01

30

STAT3 regulates arginase-I in myeloid-derived suppressor cells from cancer patients.  

PubMed

Myeloid-derived suppressor cells (MDSC) play a key immunosuppressive role in various types of cancer, including head and neck squamous cell carcinoma (HNSCC). In this study, we characterized CD14+HLA-DR(-/lo) cells sorted from the tumors, draining lymph nodes, and peripheral blood of HNSCC patients. CD14+HLA-DR(-/lo) cells were phenotyped as CD11b+, CD33+, CD34+, arginase-I+, and ROS+. In all 3 compartments, they suppressed autologous, antigen-independent T cell proliferation in a differential manner. The abundance of MDSC correlated with stage, but did not correlate with previous treatment with radiation or subsites of HNSCC. Interestingly, MDSC from all 3 compartments showed high phosphorylated STAT3 levels that correlated with arginase-I expression levels and activity. Stattic, a STAT3-specific inhibitor, and STAT3-targeted siRNA abrogated MDSC’s suppressive function. Inhibition of STAT3 signaling also resulted in decreased arginase-I activity. Analysis of the human arginase-I promoter region showed multiple STAT3-binding elements, and ChIP demonstrated that phosphorylated STAT3 binds to multiple sites in the arginase-I promoter. Finally, rescue of arginase-I activity after STAT3 blockade restored MDSC’s suppressive function. Taken together, these results demonstrate that the suppressive function of arginase-I in both infiltrating and circulating MDSC is a downstream target of activated STAT3. PMID:23454751

Vasquez-Dunddel, David; Pan, Fan; Zeng, Qi; Gorbounov, Mikhail; Albesiano, Emilia; Fu, Juan; Blosser, Richard L; Tam, Ada J; Bruno, Tullia; Zhang, Hao; Pardoll, Drew; Kim, Young

2013-04-01

31

Regulation of the innate and adaptive immune responses by Stat3 signaling in tumor cells  

Microsoft Academic Search

Although tumor progression involves processes such as tissue invasion that can activate inflammatory responses, the immune system largely ignores or tolerates disseminated cancers. The mechanisms that block initiation of immune responses during cancer development are poorly understood. We report here that constitutive activation of Stat-3, a common oncogenic signaling pathway, suppresses tumor expression of proinflammatory mediators. Blocking Stat-3 in tumor

Tianhong Wang; Guilian Niu; Marcin Kortylewski; Lyudmila Burdelya; Kenneth Shain; Shumin Zhang; Raka Bhattacharya; Dmitry Gabrilovich; Richard Heller; Domenico Coppola; William Dalton; Richard Jove; Drew Pardoll; Hua Yu

2003-01-01

32

Signal Transducer and Activator of Transcription 3 (STAT3) Protein Suppresses Adenoma-to-carcinoma Transition in Apcmin/+ Mice via Regulation of Snail-1 (SNAI) Protein Stability*  

PubMed Central

STAT3 was recently reported to suppress tumor invasion in Apcmin/+ mice. We investigated the mechanisms by which STAT3 inhibits intestinal epithelial tumors using Apcmin/+/Stat3IEC-KO mice (intestinal epithelial cell (IEC)-specific deletion of STAT3 in the Apcmin/+ background) to determine the role of STAT3 in carcinogenesis in vivo as well as colorectal cancer cell lines in vitro. To inhibit invasion of IEC tumors, STAT3 functions as a molecular adaptor rather than a transcription factor. Accordingly, the tumors in Apcmin/+/Stat3IEC-KO mice undergo adenoma-to-carcinoma transition and acquire an invasive phenotype. Similarly, STAT3 knockdown in a colorectal cell line enhances IEC invasion. We demonstrate that STAT3 down-regulates SNAI (Snail-1) expression levels and hence suppresses epithelial-mesenchymal transition of colorectal cancer cells. Mechanistically, STAT3 facilitates glycogen synthase kinase (GSK) 3?-mediated degradation of SNAI by regulating phosphorylation of GSK3?. Our data identified a new role for STAT3 in the adenoma-to-carcinoma sequence of intestinal tumors.

Lee, Jongdae; Kim, Joanna C. K.; Lee, Shee-Eun; Quinley, Christine; Kim, HyeRi; Herdman, Scott; Corr, Maripat; Raz, Eyal

2012-01-01

33

B Cells Promote Tumor Progression via STAT3 Regulated-Angiogenesis  

PubMed Central

The role of B cells in cancer and the underlying mechanisms remain to be further explored. Here, we show that tumor-associated B cells with activated STAT3 contribute to tumor development by promoting tumor angiogenesis. B cells with or without Stat3 have opposite effects on tumor growth and tumor angiogenesis in both B16 melanoma and Lewis Lung Cancer mouse models. Ex vivo angiogenesis assays show that B cell-mediated tumor angiogenesis is mainly dependent on the induction of pro-angiogenic gene expression, which requires Stat3 signaling in B cells. Furthermore, B cells with activated STAT3 are mainly found in or near tumor vasculature and correlate significantly with overall STAT3 activity in human tumors. Moreover, the density of B cells in human tumor tissues correlates significantly with expression levels of several STAT3-downstream pro-angiogenic genes, as well as the degree of tumor angiogenesis. Together, these findings define a novel role of B cells in promoting tumor progression through angiogenesis and identify STAT3 in B cells as potential therapeutic target for anti-angiogenesis therapy.

Pal, Sumanta; Jove, Veronica; Deng, Jiehui; Zhang, Wang; Hoon, Dave S. B.; Wakabayashi, Mark; Forman, Stephen; Yu, Hua

2013-01-01

34

The STAT3 Pathway  

NSDL National Science Digital Library

Signal transducer and activator of transcription 3 (STAT3) is widely expressed and activated by various growth-regulating signals, as well as diverse cytokines, that activate gp130 signaling receptors. Hence, STAT3 is critical for embryonic development and stem cell biology, as well as inflammation, growth regulation, and multiple immune regulatory and homeostatic functions. STAT3 is also found in its activated state in a large number of human cancers and has been correlated with oncogenic activity and tumor maintenance in several systems. The Connections Map highlights activation of STAT3 by interleukin 6 and shows that STAT3 serves as an integration point for components in multiple signaling pathways in addition to those involving JAKs, for example, the small guanosine triphosphatase Ras, heterotrimeric guanine nucleotide-binding protein (G proteins) of the Gi/o family, and the nonreceptor tyrosine kinases of the Src family. Science Viewpoint D. S. Aaronson, C. M. Horvath, A road map for those who don't know JAK-STAT. Science 296, 1653-1655 (2002). [Abstract] [Full Text

David S. Aaronson (Mount Sinai School of Medicine;Immunobiology Center REV); Curt M. Horvath (Mount Sinai School of Medicine;Immunobiology Center REV)

2003-08-26

35

HLA-G regulates the invasive properties of JEG-3 choriocarcinoma cells by controlling STAT3 activation.  

PubMed

The expression of human leucocyte antigen-G (HLA-G) in trophoblasts plays a crucial role in successful embryonic implantation, and reduced HLA-G expression might contribute to adverse obstetric outcomes. In this study, we silenced HLA-G expression using RNA interference in JEG-3 cells, resulting in a notably attenuated invasion capacity of the cells in a Transwell assay; however, no alterations in cell proliferation or apoptosis were observed. The down-regulation of HLA-G dampened the activation of signal transducer and activator of transcription 3 (STAT3), whereas the up-regulation of HLA-G promoted STAT3 activation and invasion in JEG-3 cells treated with human galectin-1. Most importantly, interleukin-6 (IL-6), but not galectin-1, was shown to rescue invasion deficiency in a dose-dependent manner. Thus, we demonstrate that HLA-G is able to regulate JEG-3 cell invasion by influencing STAT3 activation, which may underlie the implantation defects accompanying HLA-G hypo-expression in pre-eclampsia. PMID:24054889

Liu, X; Gu, W; Li, X

2013-09-17

36

Signal transducer and activator of transcription 3 (Stat3) contributes to T-cell homeostasis by regulating pro-survival Bcl-2 family genes.  

PubMed

The naive T-cell pool in peripheral lymphoid tissues is fairly stable in terms of number, diversity and functional capabilities in spite of the absence of prominent stimuli. This stability is attributed to continuous tuning of the composition of the T-cell pool by various homeostatic signals. Despite extensive research into the link between signal transducer and activator of transcription 3 (Stat3) and T-cell survival, little is known about how Stat3 regulates homeostasis by maintaining the required naive T-cell population in peripheral lymphoid organs. We assessed whether the elimination of Stat3 in T cells limits T-cell survival. We demonstrated that the proportion and number of single-positive thymocytes as well as T cells in the spleen and lymph nodes were significantly decreased in the Stat3-deficient group as a result of the enhanced susceptibility of Stat3-deleted T lymphocytes to apoptosis. Importantly, expression of the anti-apoptotic Bcl-2 and Bcl-xL was markedly decreased in Stat3-deleted single-positive thymocytes and T lymphocytes, suggesting that Stat3 helps to maintain the T-cell pool in the resting condition by promoting the expression of Bcl-2 family genes. These findings suggest the importance of Stat3 in the integration of homeostatic cues for the maintenance and functional tuning of the T-cell pool. PMID:23746113

Lee, Jin-Ku; Won, Cheolhee; Yi, Eun Hee; Seok, Seung-Hyeok; Kim, Myoung-Hwan; Kim, Sang-Jeong; Chung, Myung-Hee; Lee, Hyun Gyu; Ikuta, Koichi; Ye, Sang-Kyu

2013-11-01

37

Signal Transducer and Activator of Transcription 3 (STAT3) Regulates Human Telomerase Reverse Transcriptase (hTERT) Expression in Human Cancer and Primary Cells  

Microsoft Academic Search

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that plays a critical role in cytokine and growth factor signaling and is frequently activated in human tumors. Human telomerase reverse transcriptase (hTERT) is also often overexpressed in tumor cells and mediates cellular immortalization. Here we report that STAT3 directly regulates the expression of hTERT in a variety

Liza Konnikova; Marina C. Simeone; Matthew M. Kruger; Maciej Kotecki; Brent H. Cochran

2005-01-01

38

The Stat3/Socs3a Pathway is a Key Regulator of Hair Cell Regeneration in Zebrafish  

PubMed Central

All nonmammalian vertebrates studied can regenerate inner ear mechanosensory receptors, i.e. hair cells (Corwin and Cotanche, 1988; Lombarte et al., 1993; Baird et al., 1996), but mammals only possess a very limited capacity for regeneration after birth (Roberson and Rubel, 1994). As a result, mammals suffer from permanent deficiencies in hearing and balance once their inner ear hair cells are lost. The mechanisms of hair cell regeneration are poorly understood. Because the inner ear sensory epithelium is highly conserved in all vertebrates (Fritzsch et al., 2007), we chose to study hair cell regeneration mechanism in adult zebrafish, hoping the results would be transferrable to inducing hair cell regeneration in mammals. We defined the comprehensive network of genes involved in hair cell regeneration in the inner ear of adult zebrafish with the powerful transcriptional profiling technique, Digital Gene Expression (DGE), which leverages the power of next-generation sequencing ('t Hoen et al., 2008). We also identified a key pathway, stat3/socs3, and demonstrated its role in promoting hair cell regeneration through stem cell activation, cell division, and differentiation. In addition, transient pharmacological up-regulation of stat3 signaling accelerated hair cell regeneration without over-producing cells. Taking other published datasets into account (Sano et al., 1999; Schebesta et al., 2006; Zhu et al., 2008; Riehle et al., 2008; Dierssen et al., 2008; Qin et al., 2009), we propose that the stat3/socs3 pathway is a key response in all tissue regeneration and thus an important therapeutic target for a broad application in tissue repair and injury healing.

Liang, Jin; Wang, Dongmei; Renaud, Gabriel; Wolfsberg, Tyra G.; Wilson, Alexander F.; Burgess, Shawn M.

2012-01-01

39

Integrin beta3-mediated Src activation regulates apoptosis in IEC-6 cells via Akt and STAT3.  

PubMed

Intestinal epithelial (IEC-6) cells are resistant to apoptosis following the inhibition of ODC (ornithine decarboxylase) and subsequent polyamine depletion. The depletion of polyamines rapidly activates NF-kappaB (nuclear factor kappaB) and STAT3 (signal transducer and activator of transcription 3), which is responsible for the observed decrease in apoptosis. Since both NF-kappaB and STAT3 signalling pathways can be activated by Src kinase, we examined its role in the antiapoptotic response. Inhibition of ODC by DFMO (alpha-difluoromethylornithine) increased the activity of Src and ERK1/2 (extracellular-signal-regulated kinase 1/2) within 30 min, which was prevented by exogenous polyamines added to the DFMO-containing medium. Conversely, epidermal growth factor-mediated Src and ERK1/2 activation was not prevented by the addition of polyamines. Inhibition of Src with PP2 {4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine} and a DN-Src (dominant-negative Src) construct prevented the activation of Akt, JAK (Janus kinase) and STAT3. Spontaneous apoptosis was increased in DN-Src-expressing cells and the protective effect of polyamine depletion was lost. Polyamine depletion by DFMO increased integrin beta3 Tyr785 phosphorylation. Cells plated on fibronectin had significantly higher beta3 phosphorylation and Src activation compared with plastic. Exogenous polyamines added to the fibronectin matrix prevented Src activation. Arg-Gly-Asp-Ser inhibited beta3, Src and Akt phosphorylation and sensitized polyamine-depleted cells to tumour necrosis factor alpha/cycloheximide-mediated apoptosis. Fibronectin activated Src and subsequently protected cells from apoptosis. Together, these results suggest that the inhibition of ODC rapidly removes a small pool of available polyamines triggering the activation of beta3 integrin, which in turn activates Src. The subsequent Akt and JAK activation is accompanied by translocation of NF-kappaB and STAT3 to the nucleus and the synthesis of antiapoptotic proteins. PMID:16669788

Bhattacharya, Sujoy; Ray, Ramesh M; Johnson, Leonard R

2006-08-01

40

An essential role for the Stat3 in regulating IgG immune complex-induced pulmonary inflammation  

Technology Transfer Automated Retrieval System (TEKTRAN)

Growing evidence suggests that transcription factor signal transducer and activator of transcription (Stat) 3 may play an important regulatory role during inflammation. However, the function of Stat3 in acute lung injury (ALI) is largely unknown. In the current study, by using an adenoviral vector e...

41

Silencing STAT3 may inhibit cell growth through regulating signaling pathway, telomerase, cell cycle, apoptosis and angiogenesis in hepatocellular carcinoma: potential uses for gene therapy.  

PubMed

The genesis and development of hepatocellular carcinoma (HCC) is related to the abnormity of signaling pathway, telomerase, cell cycle, apoptosis, angiogenesis, and others, in which STAT3 signaling pathway plays a key role. The HCC cell line HepG2 was transfected with small interfering RNA (siRNA) directed against STAT3. After 72 h, cell growth and cycle were analysed by MTT and Flow cytometry. Then, the protein was extracted and the protein expression of STAT3, Smad3, p44/42, TERT, caspase-3, XIAP, Grp-78, HSP-27, MMP-2, MMP-9, VEGF-A, cyclin A, and cyclin E was detected by Western blot. After the transfection, HCC cell growth was inhibited during the 24-72 h time period and the cell cycle was arrested in G0/G1. STAT3 protein expression was inhibited at 72 h after the transfection. Interestingly, Smad3, p-caspase-3, p-p44/42, Grp78, cyclin A, and cyclin E protein expression was increased at 72 h, while TERT, caspase-3, XIAP, MMP-2, MMP-9, and VEGF-A protein expression decreased at 72 h. However, P44/42, and HSP27 protein expression showed no change following transfection. The results demonstrated that STAT3 signaling pathway may participate in HCC genesis and development through regulating the protein expression of other signaling pathway, telomerase, apoptosis, cell cycle and angiogenesis; thereby, blockade of the Stat3 pathway represents a potential strategy for future treatment. Keywords: STAT3, signaling pathway, telomerase, cell cycle, apoptosis, angiogenesis. PMID:21275467

Wang, X H; Liu, B R; Qu, B; Xing, H; Gao, S L; Yin, J M; Wang, X F; Cheng, Y Q

2011-01-01

42

Touched and Moved by STAT3  

NSDL National Science Digital Library

STAT3, a member of the signal transducer and activator of transcription (STAT) family of transcription factors, is a known regulator of cell motility through its transcriptional activating functions. However, new evidence suggests a novel role for non–tyrosine-phosphorylated and cytoplasmically localized STAT3 in mediating cell migration by disrupting an interaction between microtubules and one of its partners, stathmin. The association of STAT3 with stathmin potentiates microtubule polymerization and cell movement.

S. Paul Gao (New York NY;Memorial Sloan-Kettering Cancer Center REV); Jacqueline F. Bromberg (New York NY;Memorial Sloan-Kettering Cancer Center REV)

2006-07-11

43

STAT3 SIGNALING: Anticancer Strategies and Challenges  

PubMed Central

Multiple lines of evidence place STAT3 at a central node in the development, progression, and maintenance of many human tumors, and STAT3 has been validated as an anti-cancer target in several contexts. STAT3 modulates the transcription of a variety of genes involved in the regulation of critical functions, including cell differentiation, proliferation, apoptosis, angiogenesis, metastasis, and immune responses. For many cancers, elevated levels of activated STAT3 have been associated with a poor prognosis. We review approaches that have been pursued to target STAT3, and we highlight some of the promises and challenges associated with developing an anticancer drug that might therapeutically inhibit the STAT3 signaling pathway.

Johnston, Paul A.; Grandis, Jennifer R.

2011-01-01

44

Mouse skeletal muscle fiber-type specific macroautophagy and muscle wasting is regulated by a Fyn/STAT3/Vps34 signaling pathway  

PubMed Central

SUMMARY Skeletal muscle atrophy induced by aging (sarcopenia), inactivity and prolonged fasting states (starvation) is predominantly restricted to glycolytic type II muscle fibers and typical spares oxidative type I fibers. However, the mechanisms accounting for muscle fiber type specificity of atrophy have remained enigmatic. In the current study, we that although the Fyn tyrosine kinase activated the mTORC1 signaling complex, it also induced marked atrophy of glycolytic fibers with relatively less effect on oxidative muscle fibers. This was due to inhibition of macroautophagy via an mTORC1-independent but STAT3-dependent reduction in Vps34 protein levels and decreased Vps34/p150/Beclin1/Atg14 complexes. Physiologically, in the fed sate endogenous Fyn kinase activity was increased in glycolytic but not oxidative skeletal muscle. In parallel, Y705-STAT3 phosphorylation increased with decreased Vps34 protein levels. Moreover, fed/starved regulation of Y705-STAT3 phosphorylation and Vps34 protein levels was prevented in skeletal muscle of Fyn null mice. These data demonstrate a novel Fyn/STAT3/Vps34 pathway that is responsible for fiber type specific regulation of macroautophagy and skeletal muscle atrophy.

Yamada, Eijiro; Bastie, Claire C.; Koga, Hiroshi; Wang, Yichen; Cuervo, Ana Maria; Pessin, Jeffrey E.

2012-01-01

45

Essential role of cooperative NF-?B and Stat3 recruitment to ICAM-1 intronic consensus elements in the regulation of radiation-induced invasion and migration in glioma.  

PubMed

Although radiotherapy improves survival in patients, glioblastoma multiformes (GBMs) tend to relapse with augmented tumor migration and invasion even after ionizing radiation (IR). Aberrant nuclear factor-?B (NF-?B) and signal transducer and activator of transcription factor 3 (Stat3) activation and interaction have been suggested in several human tumors. However, possible NF-?B/Stat3 interaction and the role of Stat3 in maintenance of NF-?B nuclear retention in GBM still remain unknown. Stat3 and NF-?B (p65) physically interact with one another in the nucleus in glioma tumors. Most importantly, glutathione S-transferase pull-down assays identified that Stat3 binds to the p65 transactivation domain and is present in the NF-?B DNA-binding complex. Irradiation significantly elevated nuclear phospho-p65/phospho-Stat3 interaction in correlation with increased intercellular adhesion molecule-1 (ICAM-1) and soluble-ICAM-1 levels, migration and invasion in human glioma xenograft cell lines 4910 and 5310. Chromatin immunopreicipitation and promoter luciferase activity assays confirmed the critical role of adjacent NF-?B (+399) and Stat3 (+479) binding motifs in the proximal intron-1 in elevating IR-induced ICAM-1 expression. Specific inhibition of Stat3 or NF-?B with Stat3.siRNA or JSH-23 severely inhibited IR-induced p65 recruitment onto ICAM-1 intron-1 and suppressed migratory properties in both the cell lines. On the other hand, Stat3C- or IR-induced Stat3 promoter recruitment was significantly decreased in p65-knockdown cells, thereby suggesting the reciprocal regulation between p65 and Stat3. We also observed a significant increase in NF-?B enrichment on ICAM-1 intron-1 and ICAM-1 transactivation in Stat3C overexpressing cells. In in vivo orthotopic experiments, suppression of tumor growth in Stat3.si+IR-treated mice was associated with the inhibition of IR-induced p-p65/p-Stat3 nuclear colocalization and ICAM-1 levels. To our knowledge, this is the first study showing the crucial role of NF-?B/Stat3 nuclear association in IR-induced ICAM-1 regulation and implies that targeting NF-?B/Stat3 interaction may have future therapeutic significance in glioma treatment. PMID:23178493

Kesanakurti, D; Chetty, C; Rajasekhar Maddirela, D; Gujrati, M; Rao, J S

2012-11-26

46

Protein Kinase C Zeta Regulates Human Pancreatic Cancer Cell Transformed Growth and Invasion through a STAT3-Dependent Mechanism  

PubMed Central

Pancreatic cancer is a very aggressive disease with few therapeutic options. In this study, we investigate the role of protein kinase C zeta (PKC?) in pancreatic cancer cells. PKC? has been shown to act as either a tumor suppressor or tumor promoter depending upon the cellular context. We find that PKC? expression is either maintained or elevated in primary human pancreatic tumors, but is never lost, consistent with PKC? playing a promotive role in the pancreatic cancer phenotype. Genetic inhibition of PKC? reduced adherent growth, cell survival and anchorage-independent growth of human pancreatic cancer cells in vitro. Furthermore, PKC? inhibition reduced orthotopic tumor size in vivo by inhibiting tumor cell proliferation and increasing tumor necrosis. In addition, PKC? inhibition reduced tumor metastases in vivo, and caused a corresponding reduction in pancreatic cancer cell invasion in vitro. Signal transducer and activator of transcription 3 (STAT3) is often constitutively active in pancreatic cancer, and plays an important role in pancreatic cancer cell survival and metastasis. Interestingly, inhibition of PKC? significantly reduced constitutive STAT3 activation in pancreatic cancer cells in vitro and in vivo. Pharmacologic inhibition of STAT3 mimicked the phenotype of PKC? inhibition, and expression of a constitutively active STAT3 construct rescued the transformed phenotype in PKC?-deficient cells. We conclude that PKC? is required for pancreatic cancer cell transformed growth and invasion in vitro and tumorigenesis in vivo, and that STAT3 is an important downstream mediator of the pro-carcinogenic effects of PKC? in pancreatic cancer cells.

Butler, Amanda M.; Scotti Buzhardt, Michele L.; Li, Shuhua; Smith, Kristin E.; Fields, Alan P.; Murray, Nicole R.

2013-01-01

47

Stat3 is a positive regulator of gap junctional intercellular communication in cultured, human lung carcinoma cells  

PubMed Central

Background Neoplastic transformation of cultured cells by a number of oncogenes such as src suppresses gap junctional, intercellular communication (GJIC); however, the role of Src and its effector Signal transducer and activator of transcription-3 (Stat3) upon GJIC in non small cell lung cancer (NSCLC) has not been defined. Immunohistochemical analysis revealed high Src activity in NSCLC biopsy samples compared to normal tissues. Here we explored the potential effect of Src and Stat3 upon GJIC, by assessing the levels of tyr418-phosphorylated Src and tyr705-phosphorylated Stat3, respectively, in a panel of NSCLC cell lines. Methods Gap junctional communication was examined by electroporating the fluorescent dye Lucifer yellow into cells grown on a transparent electrode, followed by observation of the migration of the dye to the adjacent, non-electroporated cells under fluorescence illumination. Results An inverse relationship between Src activity levels and GJIC was noted; in five lines with high Src activity GJIC was absent, while two lines with extensive GJIC (QU-DB and SK-LuCi6) had low Src levels, similar to a non-transformed, immortalised lung epithelial cell line. Interestingly, examination of the mechanism indicated that Stat3 inhibition in any of the NSCLC lines expressing high endogenous Src activity levels, or in cells where Src was exogenously transduced, did not restore GJIC. On the contrary, Stat3 downregulation in immortalised lung epithelial cells or in the NSCLC lines displaying extensive GJIC actually suppressed junctional permeability. Conclusions Our findings demonstrate that although Stat3 is generally growth promoting and in an activated form it can act as an oncogene, it is actually required for gap junctional communication both in nontransformed lung epithelial cells and in certain lung cancer lines that retain extensive GJIC.

2012-01-01

48

IL-17-mediated Bcl-2 expression regulates survival of fibroblast-like synoviocytes in rheumatoid arthritis through STAT3 activation  

PubMed Central

Introduction Fibroblast-like synoviocytes (FLSs) are a major cell population of the pannus that invades adjacent cartilage and bone in rheumatoid arthritis (RA). The study was undertaken to determine the effect of interleukin-17 (IL-17) on the survival and/or proliferation of FLSs from RA patients and to investigate whether signal tranducer and activator of transcription 3 (STAT3) is implicated in this process. Methods Bcl-2 and Bax expression in FLSs was determined using the real-time PCR and western blot analysis. The expression of Bcl-2 and phosphoSTAT3 in synovial tissues was investigated by confocal microscope. Apoptosis of FLSs was detected by Annexin V/propidium iodide staining and/or phase contrast microscopy. The proliferation of FLSs was determined by CCK-8 ELISA assay. Results The pro-apoptotic Bax is decreased and anti-apoptotic Bcl-2 is increased in FLSs from RA patients compared with those from patients with osteoarthritis (OA). IL-17 upregulated the expression of Bcl-2 in FLSs from RA patients, but not in FLSs from OA patients. STAT3 was found to mediate IL-17-induced Bcl-2 upregulation in FLSs from RA patients. Additionally, IL-17 promoted the survival and proliferation of FLSs from RA patients. Most importantly, treatment with STAT3 inhibitor reversed the protective effect of IL-17 on FLSs apoptosis induced by sodium nitroprusside (SNP). Conclusions Our data demonstrate that STAT3 is critical in IL-17-induced survival of FLS from RA patients. Therefore, therapeutic strategies that target the IL-17/STAT3 pathway might be strong candidates for RA treatment modalities.

2013-01-01

49

Identification of Major Phosphorylation Sites of Epstein-Barr Virus Nuclear Antigen Leader Protein (EBNA-LP): Ability of EBNA-LP To Induce Latent Membrane Protein 1 Cooperatively with EBNA-2 Is Regulated by Phosphorylation  

Microsoft Academic Search

Epstein-Barr virus (EBV) nuclear antigen leader protein (EBNA-LP) is a phosphoprotein suggested to play important roles in EBV-induced immortalization of B cells. One of the potential functions of EBNA-LP is a cooperative induction with EBNA-2 of viral and cellular gene expression, including that of the genes for viral latent membrane protein 1 (LMP-1) and cellular cyclin D2. We report here

AKIHIKO YOKOYAMA; MICHIKO TANAKA; GO MATSUDA; KENTARO KATO; MIKIKO KANAMORI; HIROSHI KAWASAKI; HISASHI HIRANO; ISSAY KITABAYASHI; MISAO OHKI; KANJI HIRAI; YASUSHI KAWAGUCHI

2001-01-01

50

Wnt5A Regulates Expression of Tumor Associated Antigens in Melanoma Via Changes in STAT3 Phosphorylation  

PubMed Central

There are currently no effective therapies for metastatic melanoma and targeted immunotherapy results in the remission of only a very small percentage of tumors. In this study we demonstrate that the non-canonical Wnt ligand, Wnt5A, can increase melanoma metastasis in vivo while downregulating the expression of tumor-associated antigens important in eliciting cytotoxic T lymphocyte (CTL) responses (eg., MART-1, GP100, tyrosinase). Melanosomal antigen expression is governed by MITF, PAX3 and SOX10, and is inhibited upon STAT3 activation, via decreases in PAX3 and subsequently MITF expression. Increasing Wnt5A in Wnt5A-low cells activated STAT3, and STAT3 was decreased upon Wnt5A knockdown. Downstream targets such as PAX3, MITF amd MART-1 were also affected by Wnt5A treatment or knockdown. Staining of a melanoma tissue array also highlighted the inverse relationship between MART-1 and Wnt5A expression. PKC activation by phorbol ester mimicked Wnt5A effects, and Wnt5A treatment in the presence of STAT3 or PKC inhibitors did not lower MART-1 levels. CTL activation studies demonstrated that increases in Wnt5A correspond to decreased CTL activation and vice versa, suggesting that targeting Wnt5A before immunotherapy may lead to the enhancement of current targeted immunotherapy for patients with metastatic melanoma.

Dissanayake, Samudra K.; Olkhanud, Purevdorj B.; O'Connell, Michael P.; Carter, Arnell; French, Amanda D.; Camilli, Tura C.; Emeche, Chineye D.; Hewitt, Kyle J.; Rosenthal, Devin T.; Leotlela, Poloko D.; Wade, Michael S.; Yang, Sherry W.; Brant, Larry; Nickoloff, Brian J.; Messina, Jane L.; Biragyn, Arya; Hoek, Keith S.; Taub, Dennis D.; Longo, Dan L.; Sondak, Vernon K.; Hewitt, Stephen M.; Weeraratna, Ashani T.

2008-01-01

51

Stat3 Mediates Expression of Autotaxin in Breast Cancer  

PubMed Central

We determined that signal transducer and activator of transcription 3 (Stat3) is tyrosine phosphorylated in 37% of primary breast tumors and 63% of paired metastatic axillary lymph nodes. Examination of the distribution of tyrosine phosphorylated (pStat3) in primary tumors revealed heterogenous expression within the tumor with the highest levels found in cells on the edge of tumors with relatively lower levels in the central portion of tumors. In order to determine Stat3 target genes that may be involved in migration and metastasis, we identified those genes that were differentially expressed in primary breast cancer samples as a function of pStat3 levels. In addition to known Stat3 transcriptional targets (Twist, Snail, Tenascin-C and IL-8), we identified ENPP2 as a novel Stat3 regulated gene, which encodes autotaxin (ATX), a secreted lysophospholipase which mediates mammary tumorigenesis and cancer cell migration. A positive correlation between nuclear pStat3 and ATX was determined by immunohistochemical analysis of primary breast cancer samples and matched axillary lymph nodes and in several breast cancer derived cell lines. Inhibition of pStat3 or reducing Stat3 expression led to a decrease in ATX levels and cell migration. An association between Stat3 and the ATX promoter, which contains a number of putative Stat3 binding sites, was determined by chromatin immunoprecipitation. These observations suggest that activated Stat3 may regulate the migration of breast cancer cells through the regulation of ATX.

Azare, Janeen; Doane, Ashley; Leslie, Kenneth; Chang, Qing; Berishaj, Marjan; Nnoli, Jennifer; Mark, Kevin; Al-Ahmadie, Hikmat; Gerald, William; Hassimi, Maryam; Viale, Agnes; Stracke, Mary; Lyden, David; Bromberg, Jacqueline

2011-01-01

52

The stat3/socs3a pathway is a key regulator of hair cell regeneration in zebrafish. [corrected].  

PubMed

All nonmammalian vertebrates studied can regenerate inner ear mechanosensory receptors (i.e., hair cells) (Corwin and Cotanche, 1988; Lombarte et al., 1993; Baird et al., 1996), but mammals possess only a very limited capacity for regeneration after birth (Roberson and Rubel, 1994). As a result, mammals experience permanent deficiencies in hearing and balance once their inner ear hair cells are lost. The mechanisms of hair cell regeneration are poorly understood. Because the inner ear sensory epithelium is highly conserved in all vertebrates (Fritzsch et al., 2007), we chose to study hair cell regeneration mechanism in adult zebrafish, hoping the results would be transferrable to inducing hair cell regeneration in mammals. We defined the comprehensive network of genes involved in hair cell regeneration in the inner ear of adult zebrafish with the powerful transcriptional profiling technique digital gene expression, which leverages the power of next-generation sequencing ('t Hoen et al., 2008). We also identified a key pathway, stat3/socs3, and demonstrated its role in promoting hair cell regeneration through stem cell activation, cell division, and differentiation. In addition, transient pharmacological inhibition of stat3 signaling accelerated hair cell regeneration without overproducing cells. Taking other published datasets into account (Sano et al., 1999; Schebesta et al., 2006; Dierssen et al., 2008; Riehle et al., 2008; Zhu et al., 2008; Qin et al., 2009), we propose that the stat3/socs3 pathway is a key response in all tissue regeneration and thus an important therapeutic target for a broad application in tissue repair and injury healing. PMID:22855815

Liang, Jin; Wang, Dongmei; Renaud, Gabriel; Wolfsberg, Tyra G; Wilson, Alexander F; Burgess, Shawn M

2012-08-01

53

STAT3: A Target to Enhance Antitumor Immune Response  

PubMed Central

Signal transducer and activator of transcription 3 (Stat3) has emerged as a critical regulator for tumor-associated inflammation. Activation of Stat3 negatively regulates the Th1-type immune response and promotes expansion of myeloid-derived suppressor cells (MDSCs) and regulatory T-cell functions in the tumor microenvironment. Mounting evidence suggests that Stat3 and related pathways may serve as a target for changing the tumor immunologic microenvironment to benefit cancer immunotherapies. Many recent studies support the use of certain tyrosine kinase inhibitors, through inhibition of Stat3, in decreasing immunosuppression in the tumor microenvironment. Other potential therapeutic avenues include the use of targeted delivery of Stat3 siRNA into immune cells. Here, we describe the role of Stat3 in regulating the immunologic properties of tumors as a background for Stat3-based therapeutic interventions.

Lee, Heehyoung; Pal, Sumanta Kumar; Reckamp, Karen; Figlin, Robert A.

2011-01-01

54

The Pro-Inflammatory Cytokine IL-22 Up-Regulates Keratin 17 Expression in Keratinocytes via STAT3 and ERK1/2  

PubMed Central

Background To investigate the regulation of K17 expression by the pro-inflammatory cytokine IL-22 in keratinocytes and its important role in our previously hypothesized “K17/T cell/cytokine autoimmune loop” in psoriasis. Materials and Methods K17 expression was examined in the IL-22-treated keratinocytes by real-time quantitative PCR, ELISA, Western blot and Immunofluorescence. In addition, the signaling pathways involved in K17 regulation were investigated with related inhibitors and siRNAs. In addition, K17 expression was examined in the epidermis of IL-22-injected mouse skin. Results IL-22-induced K17 expression was confirmed in keratinocytes and the epidermis of IL-22-injected mouse skin at both mRNA and protein levels, which is an important complement to the autoimmune loop. We further investigated the regulatory mechanisms and found that both STAT3 and ERK1/2 were involved in the up-regulation of K17 expression induced by IL-22. Conclusion IL-22 up-regulates K17 expression in keratinocytes in a dose-dependent manner through STAT3- and ERK1/2-dependent mechanisms. These findings indicated that IL-22 was also involved in the K17/T cell/cytokine autoimmune loop and may play an important role in the progression of psoriasis.

Shi, Xiaowei; Jin, Liang; Feng, Zhenzhen; Hu, Lei; Wu, Yan; Wang, Gang

2012-01-01

55

The role of constitutively activated STAT3 in B16 melanoma cells  

PubMed Central

Constitutively activated STAT3 is found frequently in a wide variety of human tumors, including melanoma. Moreover, constitutive STAT3 activation actively participates in tumor formation and progression, making STAT3 an attractive target for cancer therapy. We report here that in murine B16 melanoma cells, which have been previously shown to express constitutively active STAT3, the expression of a mutant form of STAT3 with the canonical tyrosine phosphorylation site (residue 705) mutated to phenylanaine has dominant-negative properties (STAT3-DN). STAT3-DN inhibits STAT3 tyrosine phosphorylation and STAT3-dependent DNA binding activity. Most importantly, STAT3-DN expression in B16 cells inhibits their invasiveness, as well as their melanogenesis by down-regulation of tyrosinase mRNA and protein expression as well as tyrosinase activity. These results suggest that STAT3 signaling plays a critical role in regulating melanoma behavior, and may represent a druggable target for melanoma therapy.

Yang, Chuan He; Fan, Meiyun; Slominski, Andrzej T; Yue, Junming; Pfeffer, Lawrence M

2010-01-01

56

STAT1 and STAT3 in tumorigenesis  

PubMed Central

The transcription factors STAT1 and STAT3 appear to play opposite roles in tumorigenesis. While STAT3 promotes cell survival/proliferation, motility and immune tolerance and is considered as an oncogene, STAT1 mostly triggers anti-proliferative and pro-apoptotic responses while enhancing anti-tumor immunity. Despite being activated downstream of common cytokine and growth factor receptors, their activation is reciprocally regulated and perturbation in their balanced expression or phosphorylation levels may re-direct cytokine/growth factor signals from proliferative to apoptotic, or from inflammatory to anti-inflammatory. Here we review the functional canonical and non-canonical effects of STAT1 and STAT3 activation in tumorigenesis and their potential cross-regulation mechanisms.

Avalle, Lidia; Pensa, Sara; Regis, Gabriella; Novelli, Francesco; Poli, Valeria

2012-01-01

57

An RNA biding protein, Y14 interacts with and modulates STAT3 activation  

SciTech Connect

Signal transducer and activator of transcription 3 (STAT3), which mediates biological actions in many physiological processes, is activated by cytokines and growth factors via specific tyrosine-phosphorylation, dimerization, and nuclear translocation. To clarify the molecular mechanisms underlying the regulation of STAT3 activation, we performed yeast two-hybrid screening. We identified Y14, an RNA-binding protein, as a novel STAT3 binding partner. Y14 bound to STAT3 through the C-terminal region of STAT3 in vivo. Importantly, small-interfering RNA-mediated reduction of endogenous Y14 expression decreased IL-6-induced tyrosine-phosphorylation, nuclear accumulation, and DNA-binding activity of STAT3, as well as IL-6/STAT3-dependent gene expression. These results indicate that Y14 interacts with STAT3 and regulates the transcriptional activation of STAT3 by influencing the tyrosine-phosphorylation of STAT3.

Ohbayashi, Norihiko; Taira, Naohisa; Kawakami, Shiho; Togi, Sumihito; Sato, Noriko; Ikeda, Osamu; Kamitani, Shinya; Muromoto, Ryuta; Sekine, Yuichi [Department of Immunology, Graduate School of Pharmaceutical Sciences Hokkaido University, Kita-ku Kita 12 Nishi 6, Sapporo 060-0812 (Japan); Matsuda, Tadashi [Department of Immunology, Graduate School of Pharmaceutical Sciences Hokkaido University, Kita-ku Kita 12 Nishi 6, Sapporo 060-0812 (Japan)], E-mail: tmatsuda@pharm.hokudai.ac.jp

2008-08-01

58

Leukotriene B4 Receptor-2 Promotes Invasiveness and Metastasis of Ovarian Cancer Cells through Signal Transducer and Activator of Transcription 3 (STAT3)-dependent Up-regulation of Matrix Metalloproteinase 2*  

PubMed Central

Ovarian cancer is the most lethal gynecologic malignancy in women. Despite the fact that the metastatic spread is associated with the majority of deaths from ovarian cancer, the molecular mechanisms regulating the invasive and metastatic phenotypes of ovarian cancer are poorly understood. In this study, we demonstrated that BLT2, a low affinity leukotriene B4 receptor, is highly expressed in OVCAR-3 and SKOV-3 human ovarian cancer cells, and that this receptor plays a key role in the invasiveness and metastasis of these cells through activation of STAT3 and consequent up-regulation of matrix metalloproteinase 2 (MMP2). In addition, our results suggest that activation of NAD(P)H oxidase-4 (NOX4) and subsequent reactive oxygen species (ROS) generation lie downstream of BLT2, mediating the stimulation of STAT3-MMP2 cascade in this process. For example, knockdown of BLT2 or NOX4 using each specific siRNA suppressed STAT3 stimulation and MMP2 expression. Similarly, inhibition of STAT3 suppressed the expression of MMP2, thus leading to attenuated invasiveness of these ovarian cancer cells. Finally, the metastasis of SKOV-3 cells in nude mice was markedly suppressed by pharmacological inhibition of BLT2. Together, our results implicate a BLT2-NOX4-ROS-STAT3-MMP2 cascade in the invasiveness and metastasis of ovarian cancer cells.

Seo, Ji-Min; Park, Sooyoung; Kim, Jae-Hong

2012-01-01

59

N-Acetylcysteine and allopurinol up-regulated the Jak/STAT3 and PI3K/Akt pathways via adiponectin and attenuated myocardial postischemic injury in diabetes.  

PubMed

N-Acetylcysteine (NAC) and allopurinol (ALP) synergistically reduce myocardial ischemia reperfusion (MI/R) injury in diabetes. However, the mechanism is unclear. We postulated that NAC and ALP attenuated diabetic MI/R injury by up-regulating phosphatidylinositol 3-kinase/Akt (PI3K/Akt) and Janus kinase 2/signal transducer and activator of transcription-3 (JAK2/STAT3) pathways subsequent to adiponectin (APN) activation. Control (C) or streptozotocin-induced diabetic rats (D) were untreated or treated with NAC and ALP followed by MI/R. D rats displayed larger infarct size accompanied by decreased phosphorylation of Akt, STAT3 and decreased cardiac nitric oxide (NO) and APN levels. NAC and ALP decreased MI/R injury in D rats, enhanced phosphorylation of Akt and STAT3, and increased NO and APN. High glucose and hypoxia/reoxygenation exposure induced cell death and Akt and STAT3 inactivation in cultured cardiomyocytes, which were prevented by NAC and ALP. The PI3K inhibitor wortmannin and Jak2 inhibitor AG490 abolished the protection of NAC and ALP. Similarly, APN restored posthypoxic Akt and STAT3 activation and decreased cell death in cardiomyocytes. Gene silencing with AdipoR2 siRNA or STAT3 siRNA but not AdipoR1 siRNA abolished the protection of NAC and ALP. In conclusion, NAC and ALP prevented diabetic MI/R injury through PI3K/Akt and Jak2/STAT3 and cardiac APN may serve as a mediator via AdipoR2 in this process. PMID:23747931

Wang, Tingting; Mao, Xiaowen; Li, Haobo; Qiao, Shigang; Xu, Aimin; Wang, Junwen; Lei, Shaoqing; Liu, Zipeng; Ng, Kwok F J; Wong, Gordon T; Vanhoutte, Paul M; Irwin, Michael G; Xia, Zhengyuan

2013-06-06

60

Mechanisms of Unphosphorylated STAT3 Transcription Factor Binding to DNA*  

PubMed Central

Phosphorylation of signal transducer and activator of transcription 3 (STAT3) on a single tyrosine residue in response to growth factors, cytokines, interferons, and oncogenes activates its dimerization, translocation to the nucleus, binding to the interferon ? (gamma)-activated sequence (GAS) DNA-binding site and activation of transcription of target genes. STAT3 is constitutively phosphorylated in various cancers and drives gene expression from GAS-containing promoters to promote tumorigenesis. Recently, roles for unphosphorylated STAT3 (U-STAT3) have been described in response to cytokine stimulation, in cancers, and in maintenance of heterochromatin stability. However, the mechanisms underlying U-STAT3 binding to DNA has not been fully investigated. Here, we explore STAT3-DNA interactions by atomic force microscopy (AFM) imaging. We observed that U-STAT3 molecules bind to the GAS DNA-binding site as dimers and monomers. In addition, we observed that U-STAT3 binds to AT-rich DNA sequence sites and recognizes specific DNA structures, such as 4-way junctions and DNA nodes, within negatively supercoiled plasmid DNA. These structures are important for chromatin organization and our data suggest a role for U-STAT3 as a chromatin/genome organizer. Unexpectedly, we found that a C-terminal truncated 67.5-kDa STAT3 isoform recognizes single-stranded spacers within cruciform structures that also have a role in chromatin organization and gene expression. This isoform appears to be abundant in the nuclei of cancer cells and, therefore, may have a role in regulation of gene expression. Taken together, our data highlight novel mechanisms by which U-STAT3 binds to DNA and supports U-STAT3 function as a transcriptional activator and a chromatin/genomic organizer.

Timofeeva, Olga A.; Chasovskikh, Sergey; Lonskaya, Irina; Tarasova, Nadya I.; Khavrutskii, Lyuba; Tarasov, Sergey G.; Zhang, Xueping; Korostyshevskiy, Valeriy R.; Cheema, Amrita; Zhang, Lihua; Dakshanamurthy, Sivanesan; Brown, Milton L.; Dritschilo, Anatoly

2012-01-01

61

A novel small-molecule disrupts Stat3 SH2 domain-phosphotyrosine interactions and Stat3-dependent tumor processes  

PubMed Central

The molecular modeling of the phosphotyrosine (pTyr)-SH2 domain interaction in the Stat3:Stat3 dimerization, combined with in silico structural analysis of the Stat3 dimerization disruptor, S3I-201, has furnished a diverse set of analogs. We present evidence from in vitro biochemical and biophysical studies that the structural analog, S3I-201.1066 directly interacts with Stat3 or the SH2 domain, with an affinity (KD) of 2.74 nM, and disrupts the binding of Stat3 to the cognate pTyr-peptide, GpYLPQTV-NH2, with an IC50 of 23 ?M. Moreover, S3I-201.1066 selectively blocks the association of Stat3 with the epidermal growth factor receptor (EGFR), and inhibits Stat3 tyrosine phosphorylation and nuclear translocation in EGF-stimulated mouse fibroblasts. In cancer cells that harbor aberrant Stat3 activity, S3I-201.1066 inhibits constitutive Stat3 DNA-binding and transcriptional activities. By contrast, S3I-201.1066 has no effect on Src activation or the EGFR-mediated activation of the Erk1/2MAPK pathway. S3I-201.1066 selectively suppresses the viability, survival, and malignant transformation of the human breast and pancreatic cancer lines and the v-Src-transformed mouse fibroblasts harboring persistently-active Stat3. Treatment with S3I-201.1066 of malignant cells harboring aberrantly-active Stat3 down-regulated the expression of c-Myc, Bcl-xL, Survivin, the matrix metalloproteinase 9, and VEGF. The in vivo administration of S3I-201.1066 induced significant antitumor response in mouse models of human breast cancer, which correlates with the inhibition of constitutively-active Stat3 and the suppression of known Stat3-regulated genes. Our studies identify a novel small-molecule that binds with a high affinity to Stat3, blocks Stat3 activation and function, and thereby induces antitumor response in human breast tumor xenografts harboring persistently-active Stat3.

Zhang, Xiaolei; Yue, Peibin; Fletcher, Steven; Zhao, Wei; Gunning, Patrick T.; Turkson, James

2011-01-01

62

Characterization of the CBF2 Binding Site within the Epstein-Barr Virus Latency C Promoter and Its Role in Modulating EBNA2-Mediated Transactivation  

PubMed Central

The Epstein-Barr virus (EBV) EBNA2 protein is a transcriptional activator that regulates viral and cellular gene expression and is also essential for EBV-driven immortalization of B lymphocytes. The EBNA2-responsive enhancer in the viral latency C promoter (Cp) binds two cellular factors, CBF1 and CBF2. The precise role of the CBF2 protein for Cp enhancer function is presently unclear. CBF2 does not appear to interact with EBNA2 and binds just downstream of CBF1 between positions ?339 and ?368 in the Cp EBNA2 enhancer. Within this region an 8-bp sequence, CAGTGCGT, can be found, and a similar sequence is also located downstream of CBF1 binding sites in other EBNA2-responsive promoters. Previous studies have indicated that mutations and methylation in this sequence affect EBNA2 responsiveness. To investigate the requirements for CBF2 binding, we synthesized a series of oligonucleotides carrying double transversion mutations spanning both the conserved core sequence and outside flanking sequences. Surprisingly, mutations outside of the conserved core sequence in 4 bases immediately flanking the 5? end, GGTT, had the most deleterious effect on CBF2 binding. Mutations in the conserved core had a gradient effect, with those near the 5? end having the most deleterious effects on CBF2 binding. In addition, the affinities of CBF2 for binding to the LMP-1, LMP-2, and CD23 promoters were also measured. These promoters contain the conserved core but lack the 5? flanking GGTT motif and bound CBF2 weakly or not at all. Using Cp reporter plasmids containing CBF2 mutant binding sites, we were also able to show that at lower doses of EBNA2, Cp transactivation required a functional CBF2 binding site but that higher doses of EBNA2 transactivated CBF2 mutant promoters to 40% of wild-type levels. These assays indicate that CBF2 is important for EBNA2-mediated transactivation of the viral latency Cp. In addition, CBF2 activity was found to be associated with two polypeptides of 27 and 33 kDa.

Fuentes-Panana, Ezequiel M.; Ling, Paul D.

1998-01-01

63

STAT3: A Target to Enhance Antitumor Immune Response  

Microsoft Academic Search

\\u000a Signal transducer and activator of transcription 3 (Stat3) has emerged as a critical regulator for tumor-associated inflammation.\\u000a Activation of Stat3 negatively regulates the Th1-type immune response and promotes expansion of myeloid-derived suppressor\\u000a cells (MDSCs) and regulatory T-cell functions in the tumor microenvironment. Mounting evidence suggests that Stat3 and related\\u000a pathways may serve as a target for changing the tumor immunologic

Heehyoung Lee; Sumanta Kumar Pal; Karen Reckamp; Robert A. Figlin; Hua Yu

64

Radiation response and regulation of apoptosis induced by a combination of TRAIL and CHX in cells lacking mitochondrial DNA: a role for NF-?B--STAT3-directed Gene Expression  

PubMed Central

Mitochondrial DNA depleted (?0) human skin fibroblasts (HSF) with suppressed oxidative phosphorylation were characterized by significant changes in the expression of 2100 nuclear genes, encoding numerous protein classes, in NF-?B and STAT3 signaling pathways, and by decreased activity of mitochondrial death pathway, compared to the parental ?+ HSF. In contrast, the extrinsic TRAIL/TRAIL-Receptor mediated death pathway remained highly active, and exogenous TRAIL in a combination with cycloheximide (CHX) induced higher levels of apoptosis in ?0 cells compared to ?+ HSF. Global gene expression analysis using microarray and qRT-PCR demonstrated that mRNA expression levels of many growth factors and their adaptor proteins (FGF13, HGF, IGFBP4, IGFBP6, IGFL2), cytokines (IL6, IL17B, IL18, IL19, IL28B) and cytokine receptors (IL1R1, IL21R, IL31RA) were substantially decreased after mitochondrial DNA depletion. Some of these genes were targets of NF-?B and STAT3, and their protein products could regulate the STAT3 signaling pathway. Alpha-irradiation further induced expression of several NF-?B/STAT3 target genes, including IL1A, IL1B, IL6, PTGS2/COX2 and MMP12, in ?+ HSF, but this response was substantially decreased in ?0 HSF. Suppression of the IKK-NF-?B pathway by the small molecular inhibitor BMS-345541 and of the JAK2-STAT3 pathway by AG490 dramatically increased TRAIL-induced apoptosis in the control and irradiated ?+ HSF. Inhibitory antibodies against IL6, the main activator of JAK2-STAT3 pathway, added into the cell media, also increased TRAIL-induced apoptosis in HSF, especially after alpha-irradiation. Collectively, our results indicated that NF-?B activation was partially lost in ?0 HSF resulting in downregulation of the basal or radiation-induced expression of numerous NF-?B targets, further suppressing IL6-JAK2-STAT3 that in concert with NF-?B regulated protection against TRAIL-induced apoptosis

Ivanov, Vladimir N.; Ghandhi, Shanaz A.; Zhou, Hongning; Huang, Sarah X.; Chai, Yunfei; Amundson, Sally A.; Hei, Tom K.

2013-01-01

65

STAT5A-mediated SOCS2 expression regulates Jak2 and STAT3 activity following c-Src inhibition in head and neck squamous carcinoma  

PubMed Central

Purpose The inhibition of c-Src results in a striking reduction in cancer cell invasion, but the effect on cell survival is modest. Defining mechanisms that limit apoptosis following c-Src inhibition could result in an ideal therapeutic approach that both inhibits invasion and leads to apoptosis. In this regard, we discovered a novel feedback loop that results in STAT3 reactivation following sustained c-Src inhibition. Here we define the mechanism underlying this feedback loop and examine the effect of inhibiting it in vivo. Methods We measured levels and activity of pathway components using PCR, Western blotting, and kinase assays following their manipulation using both molecular and pharmacologic approaches. We utilized a heterotransplant animal model in which human oral squamous cancer is maintained exclusively in vivo. Results Following c-Src inhibition, STAT5 is durably inhibited. The inhibition of STAT5A, but not STAT5B, subsequently reduces the expression of suppressors of cytokine signaling 2 (SOCS2). SOCS2 inhibits Janus kinase 2 (Jak2) activity and Jak2-STAT3 binding. SOCS2 expression is necessary for STAT3 inhibition by c-Src inhibitors. Overexpression of SOCS2 is adequate to prevent STAT3 reactivation and to enhance the cytotoxic effects of c-Src inhibition. Likewise, the combination of Jak and c-Src inhibitors led to significantly more apoptosis than either agent alone in vivo. Conclusions To our knowledge, ours is the first study that fully defines the mechanism underlying this feedback loop, in which sustained c-Src inhibition leads to diminished SOCS2 expression via sustained inhibition of STAT5A, allowing activation of Jak2 and STAT3, Jak2-STAT3 binding, and survival signals.

Sen, Banibrata; Peng, Shaohua; Woods, Denise M.; Wistuba, Ignacio; Bell, Diana; El-Nagar, Adel; Lai, Stephen Y.; Johnson, Faye M.

2011-01-01

66

STAT3 modulates cigarette smoke-induced inflammation and protease expression.  

PubMed

Signal transducer and activator of transcription-3 (STAT3) regulates inflammation, apoptosis, and protease expression, which are critical processes associated with airway injury and lung tissue destruction. However, the precise role of STAT3 in the development of airway diseases such as chronic obstructive pulmonary disease (COPD) has not been established. This study shows that cigarette smoke activates STAT3 in the lungs of mice. Since cigarette smoke activated STAT3 in the lung, we then evaluated how the loss of STAT3 would impact on smoke-mediated lung inflammation, protease expression, and apoptosis. STAT3(+/+) and STAT3(-/-) mice were exposed to 8 days of cigarette smoke. Compared to the STAT3(+/+) mice bronchoalveolar lavage fluid (BALF) cellularity was significantly elevated in the STAT3(-/-) mice both before and after cigarette smoke exposure, with the increase in cells primarily macrophages. In addition, smoke exposure induced significantly higher BALF protein levels of Interleukin-1? (IL-1?), and monocyte chemotactic protein-1 (MCP-1) and higher tissue expression of keratinocyte chemoattractant (KC) in the STAT3(-/-) mice. Lung mRNA expression of MMP-12 was increased in STAT3(-/-) at baseline. However, the smoke-induced increase in MMP-10 expression seen in the STAT3(+/+) mice was not observed in the STAT3(-/-) mice. Moreover, lung protein levels of the anti-inflammatory proteins SOCS3 and IL-10 were markedly lower in the STAT3(-/-) mice compared to the STAT3(+/+) mice. Lastly, apoptosis, as determined by caspase 3/7 activity assay, was increased in the STAT3(-/-) at baseline to levels comparable to those observed in the smoke-exposed STAT3(+/+) mice. Together, these results indicate that the smoke-mediated induction of lung STAT3 activity may play a critical role in maintaining normal lung homeostasis and function. PMID:24101903

Geraghty, Patrick; Wyman, Anne E; Garcia-Arcos, Itsaso; Dabo, Abdoulaye J; Gadhvi, Sonya; Foronjy, Robert

2013-10-01

67

STAT3 modulates cigarette smoke-induced inflammation and protease expression  

PubMed Central

Signal transducer and activator of transcription-3 (STAT3) regulates inflammation, apoptosis, and protease expression, which are critical processes associated with airway injury and lung tissue destruction. However, the precise role of STAT3 in the development of airway diseases such as chronic obstructive pulmonary disease (COPD) has not been established. This study shows that cigarette smoke activates STAT3 in the lungs of mice. Since cigarette smoke activated STAT3 in the lung, we then evaluated how the loss of STAT3 would impact on smoke-mediated lung inflammation, protease expression, and apoptosis. STAT3+/+ and STAT3?/? mice were exposed to 8 days of cigarette smoke. Compared to the STAT3+/+ mice bronchoalveolar lavage fluid (BALF) cellularity was significantly elevated in the STAT3?/? mice both before and after cigarette smoke exposure, with the increase in cells primarily macrophages. In addition, smoke exposure induced significantly higher BALF protein levels of Interleukin-1? (IL-1?), and monocyte chemotactic protein-1 (MCP-1) and higher tissue expression of keratinocyte chemoattractant (KC) in the STAT3?/? mice. Lung mRNA expression of MMP-12 was increased in STAT3?/? at baseline. However, the smoke-induced increase in MMP-10 expression seen in the STAT3+/+ mice was not observed in the STAT3?/? mice. Moreover, lung protein levels of the anti-inflammatory proteins SOCS3 and IL-10 were markedly lower in the STAT3?/? mice compared to the STAT3+/+ mice. Lastly, apoptosis, as determined by caspase 3/7 activity assay, was increased in the STAT3?/? at baseline to levels comparable to those observed in the smoke-exposed STAT3+/+ mice. Together, these results indicate that the smoke-mediated induction of lung STAT3 activity may play a critical role in maintaining normal lung homeostasis and function.

Geraghty, Patrick; Wyman, Anne E.; Garcia-Arcos, Itsaso; Dabo, Abdoulaye J.; Gadhvi, Sonya; Foronjy, Robert

2013-01-01

68

Signal transducer and activator of transcription-3/suppressor of cytokine signaling-3 (STAT3/SOCS3) axis in myeloid cells regulates neuroinflammation  

PubMed Central

Suppressor of cytokine signaling (SOCS) proteins are feedback inhibitors of the JAK/STAT pathway. SOCS3 has a crucial role in inhibiting STAT3 activation, cytokine signaling, and inflammatory gene expression in macrophages/microglia. To determine the role of SOCS3 in myeloid cells in neuroinflammation, mice with conditional SOCS3 deletion in myeloid cells (LysMCre-SOCS3fl/fl) were tested for experimental autoimmune encephalomyelitis (EAE). The myeloid-specific SOCS3-deficient mice are vulnerable to myelin oligodendrocyte glycoprotein (MOG)-induced EAE, with a severe, nonresolving atypical form of disease. In vivo, enhanced infiltration of inflammatory cells and demyelination is prominent in the cerebellum of myeloid-specific SOCS3-deficient mice, as is enhanced STAT3 signaling and expression of inflammatory cytokines/chemokines and an immune response dominated by Th1 and Th17 cells. In vitro, SOCS3-deficient macrophages exhibit heightened STAT3 activation and are polarized toward the classical M1 phenotype. SOCS3-deficient M1 macrophages provide the microenvironment to polarize Th1 and Th17 cells and induce neuronal death. Furthermore, adoptive transfer of M2 macrophages into myeloid SOCS3-deficient mice leads to delayed onset and reduced severity of atypical EAE by decreasing STAT3 activation, Th1/Th17 cells, and proinflammatory mediators in the cerebellum. These findings indicate that myeloid cell SOCS3 provides protection from EAE through deactivation of neuroinflammatory responses.

Qin, Hongwei; Yeh, Wen-I; De Sarno, Patrizia; Holdbrooks, Andrew T.; Liu, Yudong; Muldowney, Michelle T.; Reynolds, Stephanie L.; Yanagisawa, Lora L.; Fox, Thomas H.; Park, Keun; Harrington, Laurie E.; Raman, Chander; Benveniste, Etty N.

2012-01-01

69

The role of Stat3 in glioblastoma multiforme.  

PubMed

Glioblastoma multiforme (GBM) is the most common brain tumor and has the worst prognosis. Several signaling molecules have been clearly implicated in the development, progression, and aggressiveness of GBM. Here we review the role of signal transducer and activator of transcription-3 (Stat3) in GBM. We particularly focus on its expression in clinical GBM samples, its role in brain tumorigenicity in cell lines and animal models, and discuss possible therapeutic strategies targeting Stat3. This review also summarizes the current knowledge regarding the role of Stat3 regulation by upstream activators and repressors in promoting GBM progression in both translational and clinical studies. PMID:23688441

Luwor, Rodney B; Stylli, Stanley S; Kaye, Andrew H

2013-05-17

70

Identification of STAT3-independent regulatory effects for protein inhibitor of activated STAT3 by binding to novel transcription factors  

PubMed Central

Protein Inhibitor of Activated Signal Transducer and Activators of Transcription 3 (PIAS3) is a molecule that regulates STAT3 and has antiproliferative properties. Glioblastoma and squamous cell lung cancer lack PIAS3 expression. To test the hypothesis that PIAS3 transcriptional effects are STAT3-independent, we developed models for STAT3 knockdown and PIAS3 overexpression. PIAS3 expression results in a distinct transcriptional profile that does not occur with STAT3 knockdown. We identify novel transcription factor binding partners for PIAS3 including ETS, EGR1, NR1I2 and GATA1. PIAS3 binds to these factors and regulates their transcriptional effects resulting in alterations in canonical pathways including Wnt/?-catenin signaling and functions such as cell death and proliferation. A model is proposed by which PIAS3 effects EGR1 regulated pathways.

Dabir, Snehal; Kluge, Amy; Aziz, Mohammad A; Houghton, Janet A

2011-01-01

71

A membrane penetrating peptide aptamer inhibits STAT3 function and suppresses the growth of STAT3 addicted tumor cells  

PubMed Central

Cancer cells are characterized by the aberrant activation of signaling pathways governing proliferation, survival, angiogenesis, migration and immune evasion. These processes are partially regulated by the transcription factor STAT3. This factor is inappropriately activated in diverse tumor types. Since tumor cells can become dependent on its persistent activation, STAT3 is a favorable drug target. Here, we describe the functional characterization of the recombinant STAT3 inhibitor, rS3-PA. This inhibitor is based on a 20 amino acid peptide which specifically interacts with the dimerization domain of STAT3. It is integrated into a thioredoxin scaffold and fused to a protein transduction domain. Protein gel blot and immunofluorescence analyses showed that rS3-PA is efficiently taken up by cells via an endocytosis independent mechanism. Intracellularly, it reduces the phosphorylation of STAT3 and enhances its degradation. This leads to the downregulation of STAT3 target gene expression on the mRNA and protein levels. Subsequently, tumor cell proliferation, survival and migration and the induction of angiogenesis are inhibited. In contrast, normal cells remain unaffected. Systemic administration of rS3-PA at doses of 7.5 mg/kg reduced P-STAT3 levels and significantly inhibited tumor growth up to 35% in a glioblastoma xenograft mouse model.

Borghouts, Corina; Delis, Natalia; Brill, Boris; Weiss, Astrid; Mack, Laura; Lucks, Peter; Groner, Bernd

2012-01-01

72

RACK1 Recruits STAT3 Specifically to Insulin and Insulin-Like Growth Factor 1 Receptors for Activation, Which Is Important for Regulating Anchorage-Independent Growth  

Microsoft Academic Search

Current understanding of the activation of STATs is through binding between the SH2 domain of STATs and phosphotyrosine of tyrosine kinases. Here we demonstrate a novel role of RACK1 as an adaptor for insulin and insulin-like growth factor 1 receptor (IGF-1R)-mediated STAT3 activation specifically. Intracellular associa- tion of RACK1 via its N-terminal WD domains 1 to 4 (WD1-4) with insulin

Weizhou Zhang; Cong S. Zong; Ulrich Hermanto; Pablo Lopez-Bergami; Ze' ev Ronai; Lu-Hai Wang

2006-01-01

73

The transcriptional repressor ZBP-89 and the lack of Sp1/Sp3, c-Jun, and Stat3 are important for the down-regulation of the vimentin gene during C2C12 myogenesis  

PubMed Central

Currently, considerable information is available about how muscle-specific genes are activated during myogenesis, yet little is known about how non-muscle genes are down-regulated. The intermediate filament protein vimentin is known to be “turned off” during myogenesis to be replaced by desmin, the muscle-specific intermediate filament protein. Here, we demonstrate that vimentin down-regulation is the result of the combined effect of several transcription factors. Levels of the positive activators, Sp1/Sp3, which are essential for vimentin expression, decrease during myogenesis. In addition, c-Jun and Stat3, two additional positive-acting transcription factors for vimentin gene expression, are also down-regulated. Over-expression via adenoviral approaches demonstrates that the up-regulation of the repressor ZBP-89 is critical to vimentin down-regulation. Elimination of ZBP-89 via siRNA blocks the down-regulation of vimentin and Sp1/Sp3 expression. From these studies we conclude that the combinatorial effect of the down-regulation of positive-acting transcription factors such as Sp1/Sp3, c-Jun and Stat3 versus the up-regulation of the repressor ZBP-89 contributes to the “turning off” of the vimentin gene during myogenesis.

Salmon, Morgan; Zehner, Zendra E.

2009-01-01

74

Critical analysis of the potential for targeting STAT3 in human malignancy  

PubMed Central

The signal transducer and activator of transcription (STAT) family of proteins was originally discovered in the context of normal cell biology where they function to transduce intracellular and extracellular signals to the nucleus, ultimately leading to transcription of specific target genes and downstream phenotypic effects. It was quickly appreciated that the STATs, especially STAT3, play a fundamental role in human malignancy. In contrast to normal biology in which transient STAT3 signaling is strictly regulated by a tightly coordinated network of activators and deactivators, STAT3 is constitutively activated in human malignancies. Constitutive STAT3 signaling has been associated with many cancerous phenotypes across nearly all human cancers, including the upregulation of cell growth, proliferation, survival, and motility, among others. Studies involving candidate preclinical STAT3 inhibitors have further demonstrated that the reversal of these phenotypes results from pharmacologic or genetic inhibition of STAT3, suggesting that STAT3 may be a promising target for clinical interventions. Indeed, a Phase 0 clinical trial involving a STAT3 decoy oligonucleotide demonstrated that STAT3 is a drug-gable target in human tumors. Because of the ubiquity of overactive STAT3 in cancer, its role in promoting a wide variety of cancerous phenotypes, and the strong clinical and preclinical studies performed to date, STAT3 represents a promising target for the development of inhibitors for the treatment of human cancers.

Peyser, Noah D; Grandis, Jennifer R

2013-01-01

75

Conditional deletion of Stat3 promotes neurogenesis and inhibits astrogliogenesis in neural stem cells.  

PubMed

Although signal transducer and activator of transcription 3 (Stat3) plays crucial roles in the determination of neural stem cell (NSC) fate, Stat3 has multiple roles in NSC function. Moreover, Stat3 plays important roles in neuronal survival and tumorigenesis. To investigate the overall effects of Stat3 on NSC fate, NSC were isolated from Stat3(flox/flox) mouse embryos (E14-15d), in which both Stat3 alleles are flanked by LoxP sites. Isolated NSC was inoculated with an adenovirus vector expressing Cre recombinase (Ad.nCre) or a control adenovirus vector expressing beta-galactosidase (Ad.nLz). Three days later, quantitative real-time PCR (qPCR) analysis revealed that treatment with Ad.nCre eliminated stat3 mRNA expression in NSC. Promoter assay confirmed that overexpression of nCre inhibited transactivation of acute responsive element (APRE) and blocked Stat3 function in NSC. Moreover, Western blot analysis and immunocytochemical analysis revealed that elimination of Stat3 in NSC promoted neurogenesis and inhibited astrogliogenesis. In addition, we investigated the effects of Stat3 elimination in NSC on the mRNA expression of Notch family members and bHLH factors. Consequently, qPCR analysis showed that elimination of Stat3 in NSC promoted neurogenesis and inhibited astrogliogenesis through down-regulation of notch1, notch2 and hes5, but not hes1 mRNA expression. PMID:20303333

Cao, Fang; Hata, Ryuji; Zhu, Pengxiang; Nakashiro, Koh-ichi; Sakanaka, Masahiro

2010-03-18

76

STAT3 inhibitors for cancer therapy  

PubMed Central

The signal transducer and activator of transcription STAT3 is a transcription factor which plays a key role in normal cell growth and is constitutively activated in about 70% of solid and hematological cancers. Activated STAT3 is phosphorylated on tyrosine and forms a dimer through phosphotyrosine/src homology 2 (SH2) domain interaction. The dimer enters the nucleus via interaction with importins and binds target genes. Inhibition of STAT3 results in the death of tumor cells, this indicates that it is a valuable target for anticancer strategies; a view that is corroborated by recent findings of activating mutations within the gene. Yet, there is still only a small number of STAT3 direct inhibitors; in addition, the high similarity of STAT3 with STAT1, another STAT family member mostly oriented toward apoptosis, cell death and defense against pathogens, requires that STAT3-inhibitors have no effect on STAT1. Specific STAT3 direct inhibitors consist of SH2 ligands, including G quartet oligodeoxynucleotides (ODN) and small molecules, they induce cell death in tumor cells in which STAT3 is activated. STAT3 can also be inhibited by decoy ODNs (dODN), which bind STAT3 and induce cell death. A specific STAT3 dODN which does not interfere with STAT1-mediated interferon-induced cell death has been designed pointing to the STAT3 DBD as a target for specific inhibition. Comprehensive analysis of this region is in progress in the laboratory to design DBD-targeting STAT3 inhibitors with STAT3/STAT1 discriminating ability.

Fagard, Remi; Metelev, Valeri; Souissi, Ines; Baran-Marszak, Fanny

2013-01-01

77

STAT3 Inhibition in Prostate and Pancreatic Cancer Lines by STAT3 Binding Sequence Oligonucleotides: Differential Activity Between 5? and 3? Ends  

PubMed Central

Signal transducers and activators of transcription (STATs) were originally discovered as components of signal transduction pathways. Persistent aberrant activation of STAT3 is a feature of many malignancies including prostate cancer and pancreatic cancer. One consequence of persistently-activated STAT3 in malignant cells is that they depend upon it for survival, thus STAT3 is an excellent molecular target for therapy. Previously we reported that single-stranded oligonucleotides containing consensus STAT3 binding sequences (13410 and 13411) were more effective for inducing apoptosis in prostate cancer cells than antisense STAT3 oligonucleotides. Control oligonucleotides (scrambled sequences) had no effect. Here we report that authentic STAT3 binding sequences, identified from published literature, were more effective for inducing apoptosis in prostate cancer cells and pancreatic cancer cells than was oligonucleotide 13410. Moreover, the authentic STAT3 binding sequences showed differing efficacies in the malignant cell lines depending upon whether the canonical STAT3 binding sequence was truncated at the 5? or the 3? end. Finally, expression of one STAT3-regulated gene was decreased following treatment, suggesting that STAT3 may regulate the same set of genes in the two types of cancer. We conclude that truncating the 5? end left intact enough of the canonical STAT3 binding site for effective hybridization to the genome, whereas truncation of the 3? end, which is outside the canonical binding site, may have affected binding of required cofactors essential for STAT3 activity, thereby reducing the capacity of this modified oligonucleotide to induce apoptosis. Additional experiments to answer this hypothesis are underway.

Lewis, H. Dan; Winter, Ashley; Murphy, Thomas F.; Tripathi, Snehlata; Pandey, Virendra N.; Barton, Beverly E.

2008-01-01

78

Interplay between MITF, PIAS3, and STAT3 in Mast Cells and Melanocytes  

Microsoft Academic Search

Microphthalmia transcription factor (MITF) and STAT3 are two transcription factors that play a major role in the regulation of growth and function in mast cells and melanocytes. In the present study, we explored the MITF-PIAS3-STAT3 network of interactions, how these interactions regulate gene expression, and how cyto- kine-mediated phosphorylation of MITF and STAT3 is involved in the in vivo interplay

Amir Sonnenblick; Carmit Levy; Ehud Razin

2004-01-01

79

RAD001-mediated STAT3 upregulation and megakaryocytic differentiation.  

PubMed

RAD001 is currently used as an immunosuppressant and anticancer drug. Megakaryocyte (MK) differentiation includes development from pluripotent stem cells to proliferation and differentiation toward MK formation and platelet maturation. Our preliminary assay showed that RAD001 might stimulate MK differentiation; however, the exact regulatory mechanisms needed to be elucidated. By the ex vivo assay, RAD001 induced MK differentiation in human haematopoietic stem cells, with both the stimulation of CFU-GM colony formation and CD61 surface marker expression. Then, BALB/c mice were orally administrated with or without agrylin and/or RAD001 for 15 days. The platelet count and bone marrow CFU-MK colony formation were eliminated by agrylin, but unchanged in RAD001 and RAD001 plus agrylin mice. An ex vivo assay of bone marrow-derived stem cells demonstrated that RAD001 increased the number of CFU-MK colonies. The MK count in bone section indicated the decreased effect by agrylin and then recovered by RAD001. The level of plasma thrombopoietin was also enhanced in RAD001-treated mice. The effect of RAD001 on human leukaemic K562 and HEL cells showed the growth inhibition and MK differentiation activities; including morphological observation, CD41 and CD61 expression, and platelet factor 4 secretion. In RAD001-treated HEL cells, p-STAT3 expression, STAT3 translocation, and STAT3-DNA binding activity were up-regulated. Furthermore, STAT3 siRNA decreased the p-STAT3 and CD61 expression, as well as the CD61 fluorescence intensity, indicating that STAT3 may be critical in RAD001-mediated MK differentiation. Conclusion, the present study demonstrated that RAD001 might have the capacity to induce MK differentiation through the up-regulation of STAT3 signalling. PMID:23329056

Su, Yu-Chieh; Li, Szu-Chin; Peng, Hsuan-Yu; Ho, Yang-Hui; Chen, Li-Jung; Liao, Hui-Fen

2013-01-17

80

miR-17 family of microRNAs controls FGF10-mediated embryonic lung epithelial branching morphogenesis through MAPK14 and STAT3 regulation of E-Cadherin distribution  

PubMed Central

The miR-17 family of microRNAs has recently been recognized for its importance during lung development. The transgenic overexpression of the entire miR-17-92 cluster in the lung epithelium led to elevated cellular proliferation and inhibition of differentiation, while targeted deletion of miR-17-92 and miR-106b-25 clusters showed embryonic or early post-natal lethality. Herein we demonstrate that miR-17 and its paralogs, miR-20a, and miR-106b, are highly expressed during the pseudoglandular stage and identify their critical functional role during embryonic lung development. Simultaneous downregulation of these three miRNAs in explants of isolated lung epithelium altered FGF10 induced budding morphogenesis, an effect that was rescued by synthetic miR-17. E-Cadherin levels were reduced, and its distribution was altered by miR-17, miR-20a and miR-106b downregulation, while conversely, beta-catenin activity was augmented, and expression of its downstream targets, including Bmp4 as well as Fgfr2b, increased. Finally, we identified Stat3 and Mapk14 as key direct targets of miR-17, miR-20a, and miR-106b and showed that simultaneous overexpression of Stat3 and Mapk14 mimics the alteration of E-Cadherin distribution observed after miR-17, miR-20a, and miR-106b downregulation. We conclude that the mir-17 family of miRNA modulates FGF10-FGFR2b downstream signaling by specifically targeting Stat3 and Mapk14, hence regulating E-Cadherin expression, which in turn modulates epithelial bud morphogenesis in response to FGF10 signaling.

Carraro, Gianni; El-Hashash, Ahmed; Guidolin, Diego; Tiozzo, Caterina; Turcatel, Gianluca; Young, Brittany M.; De Langhe, Stijn P.; Bellusci, Saverio; Shi, Wei; Parnigotto, Pier Paolo; Warburton, David

2009-01-01

81

A novel inhibitor of the STAT3 pathway induces apoptosis in malignant glioma cells both in vitro and in vivo  

Microsoft Academic Search

Signal transducer and activator of transcription-3 (STAT3) is constitutively activated in a variety of cancer types, including malignant gliomas. STAT3 is activated by phosphorylation of a tyrosine residue, after which it dimerizes and translocates into the nucleus. There it regulates the expression of several genes responsible for proliferation and survival at the transcriptional level. A selective inhibitor of STAT3 phosphorylation,

A Iwamaru; S Szymanski; E Iwado; H Aoki; T Yokoyama; I Fokt; K Hess; C Conrad; T Madden; R Sawaya; S Kondo; W Priebe; Y Kondo

2007-01-01

82

Involvement of stat3 in mouse brain development and sexual dimorphism: A proteomics approach  

Microsoft Academic Search

Although the role of STAT3 in cell physiology and tissue development has been largely investigated, its involvement in the development and maintenance of nervous tissue and in the mechanisms of neuroprotection is not yet known. The potentially wide range of STAT3 activities raises the question of tissue- and gender-specificity as putative mechanisms of regulation. To explore the function of STAT3

Fabio Di Domenico; Gabriella Casalena; Rukhsana Sultana; Jian Cai; William M. Pierce; Marzia Perluigi; Chiara Cini; Alessandra Baracca; Giancarlo Solaini; Giorgio Lenaz; Jia Jia; Suzan Dziennis; Stephanie J. Murphy; Nabil J. Alkayed; D. Allan Butterfield

83

Mitochondrial Localized Stat3 Promotes Breast Cancer Growth via Phosphorylation of Serine 727.  

PubMed

Signal transducer and activator of transcription 3 (Stat3) is a key mediator in the development of many cancers. For 20 years, it has been assumed that Stat3 mediates its biological activities as a nuclear localized transcription factor activated by many cytokines. However, recent studies from this laboratory and others indicate that Stat3 has an independent function in the mitochondria (mitoStat3) where it controls the activity of the electron transport chain (ETC) and mediates Ras-induced transformation of mouse embryo fibroblasts. The actions of mitoStat3 in controlling respiration and Ras transformation are mediated by the phosphorylation state of serine 727. To address the role of mitoStat3 in the pathogenesis of cells that are transformed, we used 4T1 breast cancer cells, which form tumors that metastasize in immunocompetent mice. Substitution of Ser-727 for an alanine or aspartate in Stat3 that has a mitochondrial localization sequence, MLS-Stat3, has profound effects on tumor growth, complex I activity of the ETC, and accumulation of reactive oxygen species (ROS). Cells expressing MLS-Stat3(S727A) display slower tumor growth, decreased complex I activity of the ETC, and increased ROS accumulation under hypoxia compared with cells expressing MLS-Stat3. In contrast, cells expressing MLS-Stat3(S727D) show enhanced tumor growth and complex I activity and decreased production of ROS. These results highlight the importance of serine 727 of mitoStat3 in breast cancer and suggest a novel role for mitoStat3 in regulation of ROS concentrations through its action on the ETC. PMID:24019511

Zhang, Qifang; Raje, Vidisha; Yakovlev, Vasily A; Yacoub, Adly; Szczepanek, Karol; Meier, Jeremy; Derecka, Marta; Chen, Qun; Hu, Ying; Sisler, Jennifer; Hamed, Hossein; Lesnefsky, Edward J; Valerie, Kristoffer; Dent, Paul; Larner, Andrew C

2013-09-09

84

STAT3 plays a critical role in KRAS-induced pancreatic tumorigenesis  

PubMed Central

The STAT3 transcription factor is an important regulator of stem cell self-renewal, cancer cell survival, and inflammation. In the pancreas, STAT3 is dispensable for normal development whereas the majority of pancreatic ductal adenocarcinomas (PDAC) show constitutive activation of STAT3, suggesting its potential as a therapeutic target in this cancer. Here, we sought to define the mechanisms of STAT3 activation and its functional importance in PDAC pathogenesis. Large-scale screening of cancer cell lines with a JAK2 inhibitor that blocks STAT3 function revealed a >30-fold range in sensitivity in PDAC, and showed a close correlation of sensitivity with levels of tyrosine-phosphorylated STAT3 and of the gp130 receptor, an upstream signaling component. Correspondingly, upregulation of the IL6/LIF-gp130 pathway accounted for the strong STAT3 activation in PDAC subsets. To define functions of STAT3 in vivo, we developed mouse models that test the impact of conditional inactivation of STAT3 in KRAS-driven PDAC. We showed that STAT3 is required for the development of the earliest pre-malignant pancreatic lesions, acinar-to-ductal metaplasia (ADM) and pancreatic intraepithelial neoplasia (PanIN). Moreover, acute STAT3 inactivation blocked PDAC initiation in a second in vivo model. Our results demonstrate that STAT3 has critical roles throughout the course of PDAC pathogenesis, supporting the development of therapeutic approaches targeting this pathway. Moreover, our work suggests that gp130 and phospho-STAT3 expression may be effective biomarkers for predicting response to JAK2 inhibitors.

Corcoran, Ryan B.; Contino, Gianmarco; Deshpande, Vikram; Tzatsos, Alexandros; Conrad, Claudius; Benes, Cyril H.; Settleman, Jeffrey; Engelman, Jeffrey A.; Bardeesy, Nabeel

2013-01-01

85

Epstein-Barr virus leader protein enhances EBNA-2-mediated transactivation of latent membrane protein 1 expression: a role for the W1W2 repeat domain.  

PubMed Central

The Epstein-Barr virus (EBV)-encoded leader protein EBNA-LP is made up of several 66-amino-acid repeats (the W1W2 domains) linked to a unique 45-amino-acid C-terminal sequence (the Y1Y2 domain). This protein is highly expressed along with a second nuclear antigen, EBNA-2, during the initial stages of virus-induced B-cell transformation. While EBNA-2's essential role in transformation as a transcriptional activatory is well documented, very little is known about EBNA-LP function except that recombinant viruses lacking the EBNA-LP Y1Y2 exons show reduced, but still detectable, transforming ability. This was taken as evidence that EBNA-LP plays an auxiliary role but is not essential for transformation. A recent study showed that EBNA-LP could cooperate with EBNA-2 in activating cyclin D2 transcription in resting B cells (A.J. Sinclair, L Palmero, G. Peters, and P.J. Farrell, EMBO J. 13:3321-3328, 1994). Here we report that EBNA-LP can also cooperate with EBNA-2 in up-regulating expression of the major EBV effector protein of B-cell transformation, latent membrane protein 1 (LMP1). In transient-transfection assays, EBNA-LP enhanced the level of EBNA-2-induced LMP1 expression by 5- to 10-fold in one Latency I Burkitt's lymphoma cell line, Eli-BL, and was absolutely required, along with EBNA-2, to induce LMP1 in a second line, Akata-BL. These changes in LMP1 protein expression appeared to be reflected at the transcriptional level. A study of EBNA-LP mutants showed that this cooperative function mapped to the W1W2 repeat domain rather than to Y1Y2. Because a Y1Y2-deleted form of EBNA-LP may therefore retain some aspects of wild-type function, the original data from virus recombinants leave open the possibility that EBNA-LP is actually an essential transforming gene.

Nitsche, F; Bell, A; Rickinson, A

1997-01-01

86

STAT3 Revs Up the Powerhouse  

NSDL National Science Digital Library

Tyrosine phosphorylation of signal transducers and activators of transcription (STATs) promotes their dimerization and ability to bind target genes in the nucleus. However, evidence shows that one member of the STAT family, STAT3, has an additional property independent of its classical role in the nucleus. STAT3 modifed by serine phosphorylation augmented oxidative phosphorylation in mitochondria and supported cellular transformation by oncogenic Ras.

Nancy C. Reich (Stony Brook University;Molecular Genetics and Microbiology REV)

2009-09-29

87

INVOLVEMENT OF STAT3 IN MOUSE BRAIN DEVELOPMENT AND SEXUAL DIMORPHISM: A PROTEOMICS APPROACH  

PubMed Central

Although the role of STAT3 in cell physiology and tissue development has been largely investigated, its involvement in the development and maintenance of nervous tissue and in the mechanisms of neuroprotection is not yet known. The potentially wide range of STAT3 activities raise the question of tissue- and gender-specificity as putative mechanisms of regulation. To explore the function of STAT3 in the brain and the hypothesis of a gender-linked modulation of STAT3, we analyzed a neuron-specific STAT3 knockout mouse model investigating the influence of STAT3 activity in brain protein expression pattern in both males and females in the absence of neurological insult. We performed a proteomic study aimed to reveal the molecular pathways directly or indirectly controlled by STAT3 underscoring its role in brain development and maintenance. We identified several proteins, belonging to different neuronal pathways such as energy metabolism or synaptic transmission, controlled by STAT3 that confirm its crucial role in brain development and maintenance. Moreover, we investigated the different processes that could contribute to the sexual dimorphic behavior observed in the incidence of neurological and mental disease. Interestingly both STAT3 KO and gender factors influence the expression of several mitochondrial proteins conferring to mitochondrial activity high importance in the regulation of brain physiology and conceivable relevance as therapeutic target.

Di Domenico, Fabio; Casalena, Gabriella; Sultana, Rukhsana; Cai, Jian; Pierce, William M.; Perluigi, Marzia; Cini, Chiara; Baracca, Alessandra; Solaini, Giancarlo; Lenaz, Giorgio; Jia, Jia; Dziennis, Suzan; Murphy, Stephanie J.; Alkayed, Nabil J.; Butterfield, D. Allan

2010-01-01

88

Suppression of Stat3 activity sensitizes gefitinib-resistant non small cell lung cancer cells.  

PubMed

Epidermal growth factor receptor (EGFR) is a proven therapeutic target to treat a small subset of non small cell lung cancer (NSCLC) harboring activating mutations within the EGFR gene. However, many NSCLC patients are not sensitive to EGFR inhibitors, suggesting that other factors are implicated in survival of NSCLC cells. Signal transducers and activators of transcription 3 (Stat3) function as transcription factor to mediate cell survival and differentiation and the dysregulation of Stat3 has been discovered in a number of cancers. In this study, we found that a small molecule, reactivation of p53 and induction of tumor cell apoptosis (RITA), showed anti-cancer activity against gefitinib-resistant H1650 cells through a p53-independent pathway. Stat3 suppression by RITA attracted our attention to investigate the role of Stat3 in sustaining survival of H1650 cells. Pharmacological and genetic approaches were employed to down-regulate Stat3 in H1650 cells. WP1066, a known Stat3 inhibitor, was shown to exhibit inhibitory effect on the growth of H1650 cells. Meanwhile, apoptosis activation by siRNA-mediated down-regulation of Stat3 in H1650 cells provides more direct evidence for the involvement of Stat3 in viability maintenance of H1650 cells. Moreover, as a novel identified Stat3 inhibitor, RITA increased doxorubicin sensitivity of H1650 cells in vitro and in vivo, suggesting that doxorubicin accompanied with Stat3 inhibitors may be considered as an alternative strategy to treat NSCLC patients who have inherent resistance to doxorubicin. Overall, our observations reveal that targeting Stat3 may be an effective treatment for certain NSCLC cells with oncogenic addition to Stat3. PMID:21406185

Chiu, Huan-Chih; Chou, Ding-Li; Huang, Chin-Ting; Lin, Wen-Hsing; Lien, Tzu-Wen; Yen, Kuei-Jung; Hsu, John T-A

2011-03-22

89

Icaritin Shows Potent Anti-Leukemia Activity on Chronic Myeloid Leukemia In Vitro and In Vivo by Regulating MAPK/ERK/JNK and JAK2/STAT3 /AKT Signalings  

PubMed Central

Purpose To explore the effects of Icaritin on chronic myeloid leukemia (CML) cells and underlying mechanisms. Method CML cells were incubated with various concentration of Icaritin for 48 hours, the cell proliferation was analyzed by MTT and the apoptosis was assessed with Annexin V and Hoechst 33258 staining. Cell hemoglobinization was determined. Western blotting was used to evaluate the expressions of MAPK/ERK/JNK signal pathway and Jak-2/Phorpho-Stat3/Phorsph-Akt network-related protein. NOD-SCID nude mice were applied to demonstrate the anti-leukemia effect of Icaritin in vivo. Results Icaritin potently inhibited proliferation of K562 cells (IC50 was 8 µM) and primary CML cells (IC50 was 13.4 µM for CML-CP and 18 µM for CML-BC), induced CML cells apoptosis and promoted the erythroid differentiation of K562 cells with time-dependent manner. Furthermore, Icaritin was able to suppress the growth of primary CD34+ leukemia cells (CML) and Imatinib-resistant cells, and to induce apoptosis. In mouse leukemia model, Icaritin could prolong lifespan of NOD-SCID nude mice inoculated with K562 cells as effective as Imatinib without suppression of bone marrow. Icaritin could up-regulate phospho-JNK or phospho-C-Jun and down-regulate phospho-ERK, phospho-P-38, Jak-2, phospho-Stat3 and phospho-Akt expression with dose- or time-dependent manner. Icaritin had no influence both on c-Abl and phospho-c-Abl protein expression and mRNA levels of Bcr/Abl. Conclusion Icaritin from Chinese herb medicine may be a potential anti-CML agent with low adverse effect. The mechanism of anti-leukemia for Icaritin is involved in the regulation of Bcr/Abl downstream signaling. Icaritin may be useful for an alternative therapeutic choice of Imatinib-resistant forms of CML.

Zhang, Guang sen; Meng, Kun; Kuang, Wen yong; Li, Jin; Zhou, Xin fu; Li, Rui juan; Peng, Hong ling; Dai, Chong wen; Shen, Jian Kai; Gong, Fan jie; Xu, Yun xiao; Liu, Su fang

2011-01-01

90

Two distinct signaling pathways in hair cycle induction: Stat3-dependent and -independent pathways  

PubMed Central

The hair follicle is an epidermal derivative that undergoes cycles of growth, involution, and rest. The hair cycle has well-orchestrated kinetics regulated by interactions between mesenchymal and epithelial cells, although the intracellular signals remain unclear. We previously established keratinocyte-specific Stat3-disrupted mice, by which we demonstrated that signal transducer and activator of transcription 3 (Stat3) is required for wound healing and anagen progression in the hair cycle. Growth factor-dependent migration of Stat3-disrupted keratinocytes was severely impaired, suggesting that not only wound healing but also telogen-to-anagen progression required organized keratinocyte migration in response to mesenchymal stimuli. In the present study, to examine whether Stat3 activation in keratinocytes is a prerequisite for hair cycle progression, we applied methods for experimental anagen induction to Stat3-disrupted mice. It was demonstrated that anagen was successfully induced in Stat3-disrupted as well as wild-type mice by chemical or mechanical stimulation, i.e., by topical application of phorbol 12-myristate 13-acetate (PMA) or by hair plucking, respectively. This result indicated that anagen in these methods occurred in the absence of Stat3. Furthermore, PMA stimulated the migration of Stat3-disrupted keratinocytes in vitro, supporting a hypothesis that the protein kinase C (PKC) and Stat3 pathways occur independently in the postnatal anagen induction. Both Stat3-dependent and -independent migration of keratinocytes was inhibited by a phosphoinositide 3-kinase (PI3K) inhibitor, wortmannin. Therefore, we infer that entry into anagen is mediated by at least two distinct signaling pathways: Stat3-dependent pathway for spontaneous hair cycling and Stat3-independent (probably PKC-dependent) pathway for exogenously induced hair cycling, whereas both pathways require PI3K activation.

Sano, Shigetoshi; Kira, Masahiro; Takagi, Satoshi; Yoshikawa, Kunihiko; Takeda, Junji; Itami, Satoshi

2000-01-01

91

Development of a Combination Therapy for Prostate Cancer by Targeting Stat3 and HIF-1alpha.  

National Technical Information Service (NTIS)

The Stat3 pathway and the hypoxia sensing pathway are both upregulated in prostate cancer. Stat3 is a specific regulator of pro- carcinogenic inflammation and represents a promising therapeutic target for converting cancer-promoting inflammation to anti-t...

N. Jing

2011-01-01

92

Pim kinases are upregulated during Epstein-Barr virus infection and enhance EBNA2 activity  

SciTech Connect

Latent Epstein-Barr virus (EBV) infection is strongly associated with B-cell proliferative diseases such as Burkitt's lymphoma. Here we show that the oncogenic serine/threonine kinases Pim-1 and Pim-2 enhance the activity of the viral transcriptional activator EBNA2. During EBV infection of primary B-lymphocytes, the mRNA expression levels of pim genes, especially of pim-2, are upregulated and remain elevated in latently infected B-cell lines. Thus, EBV-induced upregulation of Pim kinases and Pim-stimulated EBNA2 transcriptional activity may contribute to the ability of EBV to immortalize B-cells and predispose them to malignant growth.

Rainio, Eeva-Marja [Turku Centre for Biotechnology, University of Turku/Abo Akademi University, Tykistoekatu 6B, 20520 Turku (Finland); Turku Graduate School of Biomedical Sciences, 20520 Turku (Finland); Ahlfors, Helena [Turku Centre for Biotechnology, University of Turku/Abo Akademi University, Tykistoekatu 6B, 20520 Turku (Finland); Carter, Kara L. [Department of Medicine and Microbiology, Harvard Medical School, Boston, MA 02115 (United States); Department of Molecular Genetics, Harvard Medical School, Boston, MA 02115 (United States); Channing Laboratory, Brigham and Women's Hospital, Boston, MA 02115 (United States); Ruuska, Marja [Turku Centre for Biotechnology, University of Turku/Abo Akademi University, Tykistoekatu 6B, 20520 Turku (Finland); Matikainen, Sampsa [Turku Centre for Biotechnology, University of Turku/Abo Akademi University, Tykistoekatu 6B, 20520 Turku (Finland); Department of Microbiology, National Public Health Institute, Mannerheimintie 166, 00300 Helsinki (Finland); Kieff, Elliott [Department of Medicine and Microbiology, Harvard Medical School, Boston, MA 02115 (United States); Department of Molecular Genetics, Harvard Medical School, Boston, MA 02115 (United States); Channing Laboratory, Brigham and Women's Hospital, Boston, MA 02115 (United States); Koskinen, Paeivi J. [Turku Centre for Biotechnology, University of Turku/Abo Akademi University, Tykistoekatu 6B, 20520 Turku (Finland)]. E-mail: paivi.koskinen@btk.fi

2005-03-15

93

The R(h)oads to Stat3: Stat3 activation by the Rho GTPases  

PubMed Central

The signal transducer and activator of transcription-3 (Stat3) is a member of the STAT family of cytoplasmic transcription factors. Overactivation of Stat3 is detected with high frequency in human cancer and is considered a molecular abnormality that supports the tumor phenotype. Despite concerted investigative efforts, the molecular mechanisms leading to the aberrant Stat3 activation and Stat3-mediated transformation and tumorigenesis are still not clearly defined. Recent evidence reveals a crosstalk close relationship between Stat3 signaling and members of the Rho family of small GTPases, including Rac1, Cdc42 and RhoA. Specifically, Rac1, acting in a complex with the MgcRacGAP (male germ cell RacGAP), promotes tyrosine phosphorylation of Stat3 by the IL6-receptor family/Jak kinase complex, as well as its translocation to the nucleus. Studies have further revealed that the mutational activation of Rac1 and Cdc42 results in Stat3 activation, which occurs in part through the upregulation of IL6 family cytokines that in turn stimulates Stat3 through the Jak kinases. Interestingly, evidence also shows that the engagement of cadherins, cell to cell adhesion molecules, specifically induces a striking increase in Rac1 and Cdc42 protein levels and activity, which in turn results in Stat3 activation. In this review we integrate recent findings clarifying the role of the Rho family GTPases in Stat3 activation in the context of malignant progression.

Raptis, Leda; Arulanandam, Rozanne; Geletu, Mulu; Turkson, James

2011-01-01

94

Cell confluency-induced Stat3 activation regulates NHE3 expression by recruiting Sp1 and Sp3 to the proximal NHE3 promoter region during epithelial dome formation  

PubMed Central

Activation of signal transducer and activator of transcription-3 (Stat3) during cell confluency is related to its regulatory roles in cell growth arrest- or survival-related physiological or developmental processes. We previously demonstrated that this signaling event triggers epithelial dome formation by transcriptional augmentation of sodium hydrogen exchanger-3 (NHE3) expression. However, the detailed molecular mechanism remained unclear. By using serial deletions, site-directed mutagenesis, and EMSA analysis, we now demonstrate Stat3 binding to an atypical Stat3-response element in the rat proximal NHE3 promoter, located adjacent to a cluster of Sp cis-elements (SpA/B/C), within ?77/?36 nt of the gene. SpB (?58/?55 nt) site was more effective than SpA (?72/?69 nt) site for cooperative binding of Sp1/Sp3. Increasing cell density had no effect on Sp1/Sp3 expression but resulted in their increased binding to the SpA/B/C probe along with Stat3 and concurrently with enhanced nuclear pTyr705-Stat3 level. Immunoprecipitation performed with the nuclear extracts demonstrated physical interaction of Stat3 and Sp1/Sp3 triggered by cell confluency. Stat3 inhibition by overexpression of dominant-negative Stat3-D mutant in MDCK cells or by small interfering RNA-mediated knockdown in Caco-2 cells resulted in inhibition of the cell density-induced NHE3 expression, Sp1/Sp3 binding, and NHE3 promoter activity and in decreased dome formation. Thus, during confluency, ligand-independent Stat3 activation leads to its interaction with Sp1/Sp3, their recruitment to the SpA/B/C cluster in a Stat3 DNA-binding domain-dependent fashion, increased transcription, and expression of NHE3, to coordinate cell density-mediated epithelial dome formation.

Su, Hsiao-Wen; Wang, Shainn-Wei; Ghishan, Fayez K.; Kiela, Pawel R.; Tang, Ming-Jer

2009-01-01

95

STAT3 revs up the powerhouse.  

PubMed

Tyrosine phosphorylation of signal transducers and activators of transcription (STATs) promotes their dimerization and ability to bind target genes in the nucleus. However, evidence shows that one member of the STAT family, STAT3, has an additional property independent of its classical role in the nucleus. STAT3 modifed by serine phosphorylation augmented oxidative phosphorylation in mitochondria and supported cellular transformation by oncogenic Ras. PMID:19797267

Reich, Nancy C

2009-09-29

96

IKBKE is induced by STAT3 and tobacco carcinogen and determines chemosensitivity in non-small cell lung cancer.  

PubMed

Serine/threonine kinase IKBKE is a newly identified oncogene; however, its regulation remains elusive. Here, we provide evidence that IKBKE is a downstream target of signal transducer and activator of transcription 3 (STAT3) and that tobacco components induce IKBKE expression through STAT3. Ectopic expression of constitutively active STAT3 increased IKBKE mRNA and protein levels, whereas inhibition of STAT3 reduced IKBKE expression. Furthermore, expression levels of IKBKE are significantly associated with STAT3 activation and tobacco use history in non-small cell lung cancer (NSCLC) patients examined. In addition, we show induction of IKBKE by two components of cigarette smoke, nicotine and nicotine-derived nitrosamine ketone (NNK). Upon exposure to nicotine or NNK, cells express high levels of IKBKE protein and mRNA, which are largely abrogated by inhibition of STAT3. Characterization of the IKBKE promoter revealed two STAT3-response elements. The IKBKE promoter directly bound to STAT3 and responded to nicotine and NNK stimulation. Notably, enforcing expression of IKBKE induces chemoresistance, whereas knockdown of IKBKE not only sensitizes NSCLC cells to chemotherapy but also abrogates STAT3- and nicotine-induced cell survival. These data indicate for the first time that IKBKE is a direct target of STAT3 and is induced by tobacco carcinogens through STAT3 pathway. In addition, our study also suggests that IKBKE is an important therapeutic target and could have a pivotal role in tobacco-associated lung carcinogenesis. PMID:22330135

Guo, J; Kim, D; Gao, J; Kurtyka, C; Chen, H; Yu, C; Wu, D; Mittal, A; Beg, A A; Chellappan, S P; Haura, E B; Cheng, J Q

2012-02-13

97

JAK/STAT3 pathway inhibition blocks skeletal muscle wasting downstream of IL-6 and in experimental cancer cachexia  

PubMed Central

Cachexia, the metabolic dysregulation leading to sustained loss of muscle and adipose tissue, is a devastating complication of cancer and other chronic diseases. Interleukin-6 and related cytokines are associated with muscle wasting in clinical and experimental cachexia, although the mechanisms by which they might induce muscle wasting are unknown. One pathway activated strongly by IL-6 family ligands is the JAK/STAT3 pathway, the function of which has not been evaluated in regulation of skeletal muscle mass. Recently, we showed that skeletal muscle STAT3 phosphorylation, nuclear localization, and target gene expression are activated in C26 cancer cachexia, a model with high IL-6 family ligands. Here, we report that STAT3 activation is a common feature of muscle wasting, activated in muscle by IL-6 in vivo and in vitro and by different types of cancer and sterile sepsis. Moreover, STAT3 activation proved both necessary and sufficient for muscle wasting. In C2C12 myotubes and in mouse muscle, mutant constitutively activated STAT3-induced muscle fiber atrophy and exacerbated wasting in cachexia. Conversely, inhibiting STAT3 pharmacologically with JAK or STAT3 inhibitors or genetically with dominant negative STAT3 and short hairpin STAT3 reduced muscle atrophy downstream of IL-6 or cancer. These results indicate that STAT3 is a primary mediator of muscle wasting in cancer cachexia and other conditions of high IL-6 family signaling. Thus STAT3 could represent a novel therapeutic target for the preservation of skeletal muscle in cachexia.

Bonetto, Andrea; Aydogdu, Tufan; Jin, Xiaoling; Zhang, Zongxiu; Zhan, Rui; Puzis, Leopold; Koniaris, Leonidas G.

2012-01-01

98

STAT3 mediates resistance to MEK inhibitor through microRNA miR-17  

PubMed Central

AZD6244 is a small molecule inhibitor of the MEK kinase pathway currently in clinical trials. However, the mechanisms mediating intrinsic resistance to MEK inhibition are not fully characterized. To define molecular mechanisms of MEK inhibitor resistance, we analyzed responses of 38 lung cancer cell lines following AZD6244 treatment and their genome-wide gene expression profiles and identified a panel of genes correlated with sensitivity or resistance to AZD6244 treatment. In particular, Ingenuity pathway analysis revealed that activation of the STAT3 pathway was associated with MEK inhibitor resistance. Inhibition of this pathway by JSI-124, a STAT3-specific small molecule inhibitor, or with STAT3-specific siRNA sensitized lung cancer cells to AZD6244 and induced apoptosis. Moreover, combining a STAT3 inhibitor with AZD6244 induced expression of BIM and polyADP-ribose polymerase (PARP) cleavage, whereas activation of the STAT3 pathway inhibited BIM expression and elicited resistance to MEK inhibitors. We found that the STAT3-regulated microRNA miR-17 played a critical role in MEK inhibitor resistance, such that miR-17 inhibition sensitized resistant cells to AZD6244 by inducing BIM and PARP cleavage. Together, these results indicated that STAT3-mediated overexpression of miR-17 blocked BIM expression and caused resistance to AZD6244. Our findings suggest novel approaches to overcome resistance to MEK inhibitors by combining AZD6244 with STAT3 or miR-17 inhibitors.

Dai, Bingbing; Meng, Jieru; Peyton, Michael; Girard, Luc; Bornmann, William G.; Ji, Lin; Minna, John D.; Fang, Bingliang; Roth, Jack A.

2012-01-01

99

Reversible methylation of promoter-bound STAT3 by histone-modifying enzymes.  

PubMed

Following its tyrosine phosphorylation, STAT3 is methylated on K140 by the histone methyl transferase SET9 and demethylated by LSD1 when it is bound to a subset of the promoters that it activates. Methylation of K140 is a negative regulatory event, because its blockade greatly increases the steady-state amount of activated STAT3 and the expression of many (i.e., SOCS3) but not all (i.e., CD14) STAT3 target genes. Biological relevance is shown by the observation that overexpression of SOCS3 when K140 cannot be methylated blocks the ability of cells to activate STAT3 in response to IL-6. K140 methylation does not occur with mutants of STAT3 that do not enter nuclei or bind to DNA. Following treatment with IL-6, events at the SOCS3 promoter occur in an ordered sequence, as shown by chromatin immunoprecipitations. Y705-phosphoryl-STAT3 binds first and S727 is then phosphorylated, followed by the coincident binding of SET9 and dimethylation of K140, and lastly by the binding of LSD1. We conclude that the lysine methylation of promoter-bound STAT3 leads to biologically important down-regulation of the dependent responses and that SET9, which is known to help provide an activating methylation mark to H3K4, is recruited to the newly activated SOCS3 promoter by STAT3. PMID:21098664

Yang, Jinbo; Huang, Jing; Dasgupta, Maupali; Sears, Nathan; Miyagi, Masaru; Wang, Benlian; Chance, Mark R; Chen, Xing; Du, Yuping; Wang, Yuxin; An, Lizhe; Wang, Qin; Lu, Tao; Zhang, Xiaodong; Wang, Zhenghe; Stark, George R

2010-11-23

100

STAT3 mediates resistance to MEK inhibitor through microRNA miR-17.  

PubMed

AZD6244 is a small molecule inhibitor of the MEK (MAP/ERK kinase) pathway currently in clinical trials. However, the mechanisms mediating intrinsic resistance to MEK inhibition are not fully characterized. To define molecular mechanisms of MEK inhibitor resistance, we analyzed responses of 38 lung cancer cell lines following AZD6244 treatment and their genome-wide gene expression profiles and identified a panel of genes correlated with sensitivity or resistance to AZD6244 treatment. In particular, ingenuity pathway analysis revealed that activation of the STAT3 pathway was associated with MEK inhibitor resistance. Inhibition of this pathway by JSI-124, a STAT3-specific small molecule inhibitor, or with STAT3-specific siRNA sensitized lung cancer cells to AZD6244 and induced apoptosis. Moreover, combining a STAT3 inhibitor with AZD6244 induced expression of BIM and PARP cleavage, whereas activation of the STAT3 pathway inhibited BIM expression and elicited resistance to MEK inhibitors. We found that the STAT3-regulated microRNA miR-17 played a critical role in MEK inhibitor resistance, such that miR-17 inhibition sensitized resistant cells to AZD6244 by inducing BIM and PARP cleavage. Together, these results indicated that STAT3-mediated overexpression of miR-17 blocked BIM expression and caused resistance to AZD6244. Our findings suggest novel approaches to overcome resistance to MEK inhibitors by combining AZD6244 with STAT3 or miR-17 inhibitors. PMID:21444672

Dai, Bingbing; Meng, Jieru; Peyton, Michael; Girard, Luc; Bornmann, William G; Ji, Lin; Minna, John D; Fang, Bingliang; Roth, Jack A

2011-03-28

101

Reversible methylation of promoter-bound STAT3 by histone-modifying enzymes  

PubMed Central

Following its tyrosine phosphorylation, STAT3 is methylated on K140 by the histone methyl transferase SET9 and demethylated by LSD1 when it is bound to a subset of the promoters that it activates. Methylation of K140 is a negative regulatory event, because its blockade greatly increases the steady-state amount of activated STAT3 and the expression of many (i.e., SOCS3) but not all (i.e., CD14) STAT3 target genes. Biological relevance is shown by the observation that overexpression of SOCS3 when K140 cannot be methylated blocks the ability of cells to activate STAT3 in response to IL-6. K140 methylation does not occur with mutants of STAT3 that do not enter nuclei or bind to DNA. Following treatment with IL-6, events at the SOCS3 promoter occur in an ordered sequence, as shown by chromatin immunoprecipitations. Y705-phosphoryl-STAT3 binds first and S727 is then phosphorylated, followed by the coincident binding of SET9 and dimethylation of K140, and lastly by the binding of LSD1. We conclude that the lysine methylation of promoter-bound STAT3 leads to biologically important down-regulation of the dependent responses and that SET9, which is known to help provide an activating methylation mark to H3K4, is recruited to the newly activated SOCS3 promoter by STAT3.

Yang, Jinbo; Huang, Jing; Dasgupta, Maupali; Sears, Nathan; Miyagi, Masaru; Wang, Benlian; Chance, Mark R.; Chen, Xing; Du, Yuping; Wang, Yuxin; An, Lizhe; Wang, Qin; Lu, Tao; Zhang, Xiaodong; Wang, Zhenghe; Stark, George R.

2010-01-01

102

CYLD enhances severe listeriosis by impairing IL-6/STAT3-dependent fibrin production.  

PubMed

The facultative intracellular bacterium Listeria monocytogenes (Lm) may cause severe infection in humans and livestock. Control of acute listeriosis is primarily dependent on innate immune responses, which are strongly regulated by NF-?B, and tissue protective factors including fibrin. However, molecular pathways connecting NF-?B and fibrin production are poorly described. Here, we investigated whether the deubiquitinating enzyme CYLD, which is an inhibitor of NF-?B-dependent immune responses, regulated these protective host responses in murine listeriosis. Upon high dose systemic infection, all C57BL/6 Cyld(-/-) mice survived, whereas 100% of wildtype mice succumbed due to severe liver pathology with impaired pathogen control and hemorrhage within 6 days. Upon in vitro infection with Lm, CYLD reduced NF-?B-dependent production of reactive oxygen species, interleukin (IL)-6 secretion, and control of bacteria in macrophages. Furthermore, Western blot analyses showed that CYLD impaired STAT3-dependent fibrin production in cultivated hepatocytes. Immunoprecipitation experiments revealed that CYLD interacted with STAT3 in the cytoplasm and strongly reduced K63-ubiquitination of STAT3 in IL-6 stimulated hepatocytes. In addition, CYLD diminished IL-6-induced STAT3 activity by reducing nuclear accumulation of phosphorylated STAT3. In vivo, CYLD also reduced hepatic STAT3 K63-ubiquitination and activation, NF-?B activation, IL-6 and NOX2 mRNA production as well as fibrin production in murine listeriosis. In vivo neutralization of IL-6 by anti-IL-6 antibody, STAT3 by siRNA, and fibrin by warfarin treatment, respectively, demonstrated that IL-6-induced, STAT3-mediated fibrin production significantly contributed to protection in Cyld(-/-) mice. In addition, in vivo Cyld siRNA treatment increased STAT3 phosphorylation, fibrin production, pathogen control and survival of Lm-infected WT mice illustrating that therapeutic inhibition of CYLD augments the protective NF-?B/IL-6/STAT3 pathway and fibrin production. PMID:23825949

Nishanth, Gopala; Deckert, Martina; Wex, Katharina; Massoumi, Ramin; Schweitzer, Katrin; Naumann, Michael; Schlüter, Dirk

2013-06-27

103

Dangerous liaisons: STAT3 and NF-?B collaboration and crosstalk in cancer  

PubMed Central

Transcriptional factors of the NF-?B family and STAT3 are ubiquitously expressed and control numerous physiological processes including development, differentiation, immunity, metabolism and cancer. Both NF-?B and STAT3 are rapidly activated in response to various stimuli including stresses and cytokines, although they are regulated by entirely different signaling mechanisms. Once activated, NF-?B and STAT3 control the expression of anti-apoptotic, pro-proliferative and immune response genes. Some of these genes overlap and require transcriptional cooperation between the two factors. The activation of and interaction between STAT3 and NF-?B plays a key role in controlling the dialog between the malignant cell and its microenvironment, especially with inflammatory/immune cells that infiltrate tumors. Quite often, cytokines whose expression is induced in response to NF-?B in immune cells of the tumor microenvironment lead to STAT3 activation in both malignant and immune cells. While within malignant and pre-malignant cells STAT3 exerts important oncogenic functions, within inflammatory cells it may also suppress tumor promotion through its anti-inflammatory effects. Other interactions and forms of crosstalk between NF-?B and STAT3 include physical interaction between the two, cooperation of these factors at gene promoters/enhancers, the NF-?B dependent expression of inhibitors of STAT3 activation and the participation of STAT3 in inflammatory cells in the negative regulation NF-?B. Despite these versatile and occasionally antagonistic interactions, NF-?B and STAT3 cooperate to promote the development and progression of colon, gastric and liver cancers. In addition to explaining the molecular pathogenesis of cancer, these interactions also offer opportunities for the design of new therapeutic interventions.

Grivennikov, Sergei; Karin, Michael

2009-01-01

104

STAT3 serine phosphorylation by ERK-dependent and -independent pathways negatively modulates its tyrosine phosphorylation.  

PubMed Central

Recent studies have indicated that serine phosphorylation regulates the activities of STAT1 and STAT3. However, the kinase(s) responsible and the role of serine phosphorylation in STAT function remain unresolved. In the present studies, we examined the growth factor-dependent serine phosphorylation of STAT1 and STAT3. We provide in vitro and in vivo evidence that the ERK family of mitogen-activated protein (MAP) kinases, but not JNK or p38, specifically phosphorylate STAT3 at serine 727 in response to growth factors. Evidence for additional mitogen-regulated serine phosphorylation is also provided. STAT1 is a relatively poor substrate for all MAP kinases tested both in vitro and in vivo. STAT3 serine phosphorylation, not its tyrosine phosphorylation, results in retarded mobility of the STAT3 protein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Importantly, serine 727 phosphorylation negatively modulates STAT3 tyrosine phosphorylation, which is required for dimer formation, nuclear translocation, and the DNA binding activity of this transcriptional regulator. Interestingly, the cytokine interleukin-6 also stimulates STAT3 serine phosphorylation, but in contrast to growth factors, this occurs by an ERK-independent process.

Chung, J; Uchida, E; Grammer, T C; Blenis, J

1997-01-01

105

STAT3 signaling in pulmonary arterial hypertension  

PubMed Central

Pulmonary artery hypertension (PAH) is a proliferative disorder associated with enhanced pulmonary artery smooth muscle cell proliferation and suppressed apoptosis. The sustainability of this phenotype requires the activation of pro-survival transcription factor like the signal transducers and activators of transcription-3 (STAT3). Using multidisciplinary and translational approaches, we and others have demonstrated that STAT3 activation in both human and experimental models of PAH accounts for the modulation of the expression of several proteins already known as implicated in PAH pathogenesis, as well as for signal transduction to other transcription factors. Furthermore, recent data demonstrated that STAT3 could be therapeutically targeted in different animal models and some molecules are actually in clinical trials for cancer or PAH treatment.

Paulin, Roxane; Meloche, Jolyane; Bonnet, Sebastien

2012-01-01

106

Monocytes Induce STAT3 Activation in Human Mesenchymal Stem Cells to Promote Osteoblast Formation  

PubMed Central

A major therapeutic challenge is how to replace bone once it is lost. Bone loss is a characteristic of chronic inflammatory and degenerative diseases such as rheumatoid arthritis and osteoporosis. Cells and cytokines of the immune system are known to regulate bone turnover by controlling the differentiation and activity of osteoclasts, the bone resorbing cells. However, less is known about the regulation of osteoblasts (OB), the bone forming cells. This study aimed to investigate whether immune cells also regulate OB differentiation. Using in vitro cell cultures of human bone marrow-derived mesenchymal stem cells (MSC), it was shown that monocytes/macrophages potently induced MSC differentiation into OBs. This was evident by increased alkaline phosphatase (ALP) after 7 days and the formation of mineralised bone nodules at 21 days. This monocyte-induced osteogenic effect was mediated by cell contact with MSCs leading to the production of soluble factor(s) by the monocytes. As a consequence of these interactions we observed a rapid activation of STAT3 in the MSCs. Gene profiling of STAT3 constitutively active (STAT3C) infected MSCs using Illumina whole human genome arrays showed that Runx2 and ALP were up-regulated whilst DKK1 was down-regulated in response to STAT3 signalling. STAT3C also led to the up-regulation of the oncostatin M (OSM) and LIF receptors. In the co-cultures, OSM that was produced by monocytes activated STAT3 in MSCs, and neutralising antibodies to OSM reduced ALP by 50%. These data indicate that OSM, in conjunction with other mediators, can drive MSC differentiation into OB. This study establishes a role for monocyte/macrophages as critical regulators of osteogenic differentiation via OSM production and the induction of STAT3 signalling in MSCs. Inducing the local activation of STAT3 in bone cells may be a valuable tool to increase bone formation in osteoporosis and arthritis, and in localised bone remodelling during fracture repair.

Nicolaidou, Vicky; Wong, Mei Mei; Redpath, Andia N.; Ersek, Adel; Baban, Dilair F.; Williams, Lynn M.; Cope, Andrew P.; Horwood, Nicole J.

2012-01-01

107

XZH-5 Inhibits STAT3 Phosphorylation and Enhances the Cytotoxicity of Chemotherapeutic Drugs in Human Breast and Pancreatic Cancer Cells  

PubMed Central

Constitutive activation of Signal Transducers and Activators of Transcription 3 (STAT3) signaling is frequently detected in breast and pancreatic cancer. Inhibiting constitutive STAT3 signaling represents a promising molecular target for therapeutic approach. Using structure-based design, we developed a non-peptide cell-permeable, small molecule, termed as XZH-5, which targeted STAT3 phosphorylation. XZH-5 was found to inhibit STAT3 phosphorylation (Tyr705) and induce apoptosis in human breast and pancreatic cancer cell lines expressing elevated levels of phosphorylated STAT3. XZH-5 could also inhibit interleukin-6-induced STAT3 phosphorylation in cancer cell lines expressing low phosphorylated STAT3. Inhibition of STAT3 signaling by XZH-5 was confirmed by the down-regulation of downstream targets of STAT3, such as Cyclin D1, Bcl-2, and Survivin at mRNA level. In addition, XZH-5 inhibited colony formation, cell migration, and enhanced the cytotoxicity of chemotherapeutic drugs when combined with Doxorubicin or Gemcitabine. Our results indicate that XZH-5 may be a potential therapeutic agent for breast and pancreatic cancers with constitutive STAT3 signaling.

Liu, Aiguo; Liu, Yan; Jin, Zhigang; Hu, Qun; Lin, Li; Jou, David; Yang, Jing; Xu, Zhenghu; Wang, Hong; Li, Chenglong; Lin, Jiayuh

2012-01-01

108

Stat3 and G-CSF-induced myeloid differentiation.  

PubMed

Granulocyte colony-stimulating factor (G-CSF) is the cytokine critical for directing neutrophilic granulocyte differentiation. Early G-CSF signaling events in myeloid cells involves activation of STATs, proteins that serve the dual function of signal transduction and activation of transcription, especially the activation of Stat3. A dominant-negative mutant construct of Stat3 inhibited G-CSF-mediated neutrophilic differentiation indicating that Stat3 is a essential component for driving the G-CSF-mediated differentiation program in myeloid cells. Three isoforms of Stat3 have been identified, alpha(p92), beta(p83) and gamma(p72) each derived from a single gene. Stat3alpha is the predominant isoform expressed in most cells. Stat3beta is derived from Stat3alpha by alternative RNA splicing. Stat3gamma is derived from Stat3alpha by limited proteolysis. Mapping of Stat3alpha and Stat3beta activation in M1 murine myeloid leukemia cells revealed that their optimal activation required G-CSFR constructs containing both Y704 and Y744. These amino acid residues has previously been demonstrated to be essential for G-CSF-induced differentiation in this cells. Phosphopeptide affinity and phosphopeptide inhibition studies indicate that Stat3alpha and Stat3beta are recruited to the G-CSF receptor complex through their interaction with the receptor at phosphotyrosines Y704 and Y744. Y744 is followed at the +3 position by Cys (C). This sequence YXXC, represents a novel motif implicated in the recruitment and activation of Stat3alpha, Stat3beta and Stat3gamma by the hG-CSFR. Structurally, Stat3alpha, Stat3beta and Stat3gamma differ from each other in their C-terminal transactivation domain. In the beta isoform, the Stat3alpha transactivation domain is replaced by 7 amino acid residues which enable Stat3beta to interact with c-Jun. In the gamma isoform, the Stat3alpha transactivation domain is removed by limited proteolysis creating a dominant negative isoform. In immature human myeloid cells capable of differentiating into neutrophils in response to G-CSF, G-CSF did not activate Stat3alpha; rather. it activated predominantly Stat3beta. These findings combined with recent reports linking Stat3alpha with proliferation and transformation suggest that the beta isoform of Stat3 may be more critical for G-CSF-mediated differentiation. Activation of Stat3gamma occurred predominantly in terminally differentiated neutrophils suggesting that it may be part of a controlled proteolytic mechanism modulating pro-proliferative protein(s) in mature myeloid cells. PMID:9711905

Chakraborty, A; Tweardy, D J

1998-08-01

109

BOTH ENDOGENOUS AND EXOGENOUS TESTOSTERONE DECREASE MYOCARDIAL STAT3 ACTIVATION AND SOCS3 EXPRESSION FOLLOWING ACUTE ISCHEMIA AND REPERFUSION  

PubMed Central

Background Signal transducer and activator of transduction 3 (STAT3) pathway has been shown to be cardioprotective. We observed decreased STAT3/suppressor of cytokine signaling 3 (SOCS3) in male hearts, which was associated with worse post-ischemic myocardial function compared to females. However, it is unclear whether this down-regulation of myocardial STAT3/SOCS3 is due to testosterone in males. We hypothesized that following ischemia/reperfusion (I/R): 1) endogenous testosterone decreases myocardial STAT3 and SOCS3 in males; 2) administration of exogenous testosterone reduces myocardial STAT3/SOCS3 in female and castrated male hearts. Methods To study this, hearts from I/R injury (Langendorff) were homogenized and assessed for phosphorylated-STAT3 (p-STAT3), total-STAT3 (T-STAT3), SOCS3 and GAPDH by western blot. Groups: age-matched adult males, females, castrated males, males with androgen receptor blocker-flutamide implantation, females and castrated males with chronic (3-week) 5alpha-dihydrotestosterone (DHT) release pellet implantation or acute (5-minute) testosterone infusion (ATI) prior to ischemia (n=5–9/group). Results Castration or flutamide treatment significantly increased SOCS3 expression in male hearts after I/R. However, only castration increased myocardial STAT3 activation. Notably, DHT replacement or ATI markedly decreased myocardial STAT3/SOCS3 in castrated males and females subjected to I/R. Conclusion These results suggest that endogenous and exogenous testosterone decrease myocardial STAT3 activation and SOCS3 expression following I/R. This represents the initial demonstration of testosterone-downregulated STAT3/SOCS3 signaling in myocardium.

Wang, Meijing; Wang, Yue; Abarbanell, Aaron; Tan, Jiangjing; Weil, Brent; Herrmann, Jeremy; Meldrum, Daniel R.

2009-01-01

110

STAT3 and the Hyper-IgE syndrome  

PubMed Central

During recent years a number of primary immunodeficiencies resulting from impaired function of JAK-STAT molecules have been described. One of these is the Hyper-IgE syndrome (HIES) characterized by elevated IgE levels, eczema, recurrent staphylococcal skin and pulmonary infections and pleiotropic somatic manifestations. In 2007 the genetic basis of HIES was revealed by identification of dominant negative STAT3 mutations in HIES patients. Subsequently impaired function of Tyk2 and DOCK8 have been implicated in milder forms of HIES. Since STAT3 acts as a central transcription factor downstream of multiple cytokine and growth factor receptors and thus regulates antimicrobial responses and cell survival, impaired STAT3 function results in immunodeficiency and in some cases tumorigenesis. However, as the immunological and molecular basis of HIES is being unraveled, important biological and immunological insight into JAK-STAT signaling is emerging that may have implications for our understanding of the pathogenesis and clinical management of patients with HIES.

Mogensen, Trine H.

2013-01-01

111

Auranofin blocks interleukin-6 signalling by inhibiting phosphorylation of JAK1 and STAT3  

PubMed Central

Auranofin (AF) is a sulphur-containing gold compound. Because of its anti-inflammatory and immunosuppressive activities, AF has been widely used for the therapeutic treatment of rheumatoid arthritis. However, little is known about its mechanism of action. To elucidate the molecular mechanism underlying the anti-inflammatory effect of AF, we studied the effects of AF on cellular responses to interleukin-6 (IL-6). In HepG2 human hepatoma cells, AF markedly inhibited IL-6-induced phosphorylation of janus kinase 1 (JAK1) and signal transducer and activator of transcription 3 (STAT3) and STAT3 translocation into the nucleus. Consistent with this, AF diminished IL-6-induced production of the acute-phase proteins, haptoglobin, fibrinogen, C3 complement and ?1-acid glycoprotein, and gene expression of vascular endothelial growth factor, all of whose transcriptional activities are regulated by STAT3. The inhibitory activity of AF on STAT3 phosphorylation was also demonstrated in primary cells, i.e. fibroblast-like synoviocytes from rheumatoid arthritis patients, human umbilical vein endothelial cells and rat astrocytes. Auranofin-mediated inhibition of STAT3 phosphorylation was recovered by pretreatment with antioxidants containing thiol groups. These findings suggest that the anti-inflammatory action of AF is associated with a blockade of JAK1/STAT3 signalling. Thiol-group-reactive proteins may be involved in AF-induced suppression of JAK1/STAT3 phosphorylation.

Kim, Nam-Hoon; Lee, Mun-Yong; Park, Seon-Joo; Choi, Jeong-Sun; Oh, Mi-Kyung; Kim, In-Sook

2007-01-01

112

MEK inhibition affects STAT3 signaling and invasion in human melanoma cell lines.  

PubMed

Elevated activity of the mitogen-activated protein kinase (MAPK) signaling cascade is found in the majority of human melanomas and is known to regulate proliferation, survival and invasion. Current targeted therapies focus on decreasing the activity of this pathway; however, we do not fully understand how these therapies impact tumor biology, especially given that melanoma is a heterogeneous disease. Using a three-dimensional (3D), collagen-embedded spheroid melanoma model, we observed that MEK and BRAF inhibitors can increase the invasive potential of ?20% of human melanoma cell lines. The invasive cell lines displayed increased receptor tyrosine kinase (RTK) activity and activation of the Src/FAK/signal transducers and activators of transcription-3 (STAT3) signaling axis, also associated with increased cell-to-cell adhesion and cadherin engagement following MEK inhibition. Targeting various RTKs, Src, FAK and STAT3 with small molecule inhibitors in combination with a MEK inhibitor prevented the invasive phenotype, but only STAT3 inhibition caused cell death in the 3D context. We further show that STAT3 signaling is induced in BRAF-inhibitor-resistant cells. Our findings suggest that MEK and BRAF inhibitors can induce STAT3 signaling, causing potential adverse effects such as increased invasion. We also provide the rationale for the combined targeting of the MAPK pathway along with inhibitors of RTKs, SRC or STAT3 to counteract STAT3-mediated resistance phenotypes.Oncogene advance online publication, 29 April 2013; doi:10.1038/onc.2013.131. PMID:23624919

Vultur, A; Villanueva, J; Krepler, C; Rajan, G; Chen, Q; Xiao, M; Li, L; Gimotty, P A; Wilson, M; Hayden, J; Keeney, F; Nathanson, K L; Herlyn, M

2013-04-29

113

STAT3 inhibitor WP1066 as a novel therapeutic agent for renal cell carcinoma  

Microsoft Academic Search

Background:Signal transducer and activator of transcription 3 (STAT3) regulates the expression of genes that mediate cell survival, proliferation, and angiogenesis and is aberrantly activated in various types of malignancies, including renal cell carcinoma (RCC). We examined whether it could be a novel therapeutic target for RCC by using the STAT3 inhibitor WP1066.Methods:The antitumour activities and related mechanisms of WP1066 were

A Horiguchi; T Asano; K Kuroda; A Sato; J Asakuma; K Ito; M Hayakawa; M Sumitomo

2010-01-01

114

STATs in cancer inflammation and immunity: a leading role for STAT3  

Microsoft Academic Search

Commensurate with their roles in regulating cytokine-dependent inflammation and immunity, signal transducer and activator of transcription (STAT) proteins are central in determining whether immune responses in the tumour microenvironment promote or inhibit cancer. Persistently activated STAT3 and, to some extent, STAT5 increase tumour cell proliferation, survival and invasion while suppressing anti-tumour immunity. The persistent activation of STAT3 also mediates tumour-promoting

Hua Yu; Drew Pardoll; Richard Jove

2009-01-01

115

Inhibition of STAT3 Expression and Signaling in Resveratrol-Differentiated Medulloblastoma Cells1  

PubMed Central

In this study, the potential influence of resveratrol (3,5,4?-trihydroxy-trans-stilbene) in signal transducer and activator of transcription 3 (STAT3) signaling of medulloblastoma cells was evaluated by checking the status of STAT3 signaling and its downstream gene expression in two medulloblastoma cell lines (UW228-2 and UW228-3) with and without resveratrol treatment. The results revealed that resveratrol induced neuronal differentiation of medulloblastoma cells. Signal transducer and activator of transcription 3 expression and phosphorylation were detected in normally cultured UW228-2 and UW228-3 cells that were apparently attenuated after resveratrol treatment. The expression of STAT3 downstream genes, survivin, cyclin D1, Cox-2, and c-Myc, was suppressed but Bcl-2 was enhanced by resveratrol. Meanwhile, the production and secretion of leukemia inhibitory factor, a STAT3 activator, became active in resveratrol-treated cells. To further ascertain the significance of STAT3 signaling for medulloblastoma cells, AG490, a selective inhibitor of STAT3 phosphorylation, was used to treat UW228-3 cells. Phosphorylation of STAT3 was inhibited by AG490 accompanied with growth suppression, differentiation-like changes, and down-regulation of survivin, cyclin D1, Cox-2, and c-Myc. Our data thus suggest the importance of STAT3 signaling in maintenance and survival of medulloblastoma cells. This signaling may be the major target of resveratrol. Enhanced leukemia inhibitory factor and Bcl-2 expressions in resveratrol-treated cells might reflect a compensatory response to the loss of STAT3 function.

Yu, Li-Jun; Wu, Mo-Li; Li, Hong; Chen, Xiao-Yan; Wang, Qian; Sun, Yuan; Kong, Qing-You; Liu, Jia

2008-01-01

116

The Induction of APC with a Distinct Tolerogenic Phenotype via Contact-Dependent STAT3 Activation  

PubMed Central

Background Activation of the signal transducer and activator of transcription 3 (STAT3) within antigen presenting cells (APCs) is linked to abnormal APCs differentiation and function. We have previously shown that STAT3 is activated within APC by a novel contact-dependent mechanism, which plays a key role in mediating the immunomodulatory effects of hMSC. In order to better understand the underlying mechanisms that control APC maturation in a contact dependent manner, we extended our observation to tumor cells. Tumors were shown to secrete a variety of tumor-derived factors that activate STAT3 within infiltrating APCs. We now tested whether tumor cells can activate STAT3 within APC using the contact-dependent mechanism, in addition to soluble factors, and compared these two STAT3 activating pathways. Principal Findings We demonstrate that in addition to tumor-derived secreted factors tumor cells activate STAT3 by a mechanism that is based on cell-cell interaction. We further demonstrate that these two STAT3 activating mechanisms differ in their JAK usage and their susceptibility to JSI-124 inhibition thereby representing two distinct pathways. Significantly, although both pathways activate STAT3, they modulate DCs maturation in a different manner that results in disparate phenotypic outcomes. Whereas the soluble-dependent pathway results in an immature phenotype, the contact-dependent pathway results in an apparently mature phenotype. Albeit their mature-like phenotype these latter cells express the tolerogenic markers ILT3 and ILT4 and possess T cell inhibitory activity. Significance This data suggests that, in at least certain cellular microenvironments, cell:cell interactions represent a novel way to activate STAT3 signaling, uncouple APC activation events and consequently regulate immunity and tolerance. Significantly, we have now demonstrated that this contact-dependent signaling pathway differs from that mediated by soluble factors and cytokines, inducing disparate phenotypic outcome, suggesting these two mechanisms have different and possibly complementary biological functions.

Gur-Wahnon, Devorah; Borovsky, Zipora; Liebergall, Meir; Rachmilewitz, Jacob

2009-01-01

117

CD24 controls Src/STAT3 activity in human tumors.  

PubMed

CD24 is a glycosyl-phosphatidylinositol-anchored membrane protein that is frequently over-expressed in a variety of human carcinomas and is correlated with poor prognosis. In cancer cell lines, changes of CD24 expression can alter several cellular properties in vitro and tumor growth in vivo. However, little is known about how CD24 mediates these effects. Here we have analyzed the functional consequences of CD24 knock-down or over-expression in human cancer cell lines. Depletion of CD24 reduced cell proliferation and adhesion, enhanced apoptosis, and regulated the expression of various genes some of which were identified as STAT3 target genes. Loss of CD24 reduced STAT3 and FAK phosphorylation. Diminished STAT3 activity was confirmed by specific reporter assays. We found that reduced STAT3 activity after CD24 knock-down was accompanied by altered Src phosphorylation. Silencing of Src, similar to CD24, targeted the expression of prototype STAT3-regulated genes. Likewise, the over-expression of CD24 augmented Src-Y416 phosphorylation, the recruitment of Src into lipid rafts and the expression of STAT3-dependent target genes. An antibody to CD24 was effective in reducing tumor growth of A549 lung cancer and BxPC3 pancreatic cancer xenografts in mice. Antibody treatment affected the level of Src-phosphorylation in the tumor and altered the expression of STAT3 target genes. Our results provide evidence that CD24 regulates STAT3 and FAK activity and suggest an important role of Src in this process. Finally, the targeting of CD24 by antibodies could represent a novel route for tumor therapy. PMID:22760497

Bretz, Niko P; Salnikov, Alexei V; Perne, Claudia; Keller, Sascha; Wang, Xiaoli; Mierke, Claudia T; Fogel, Mina; Erbe-Hofmann, Natalie; Schlange, Thomas; Moldenhauer, Gerhard; Altevogt, Peter

2012-07-04

118

Ultraviolet Radiation and 12-O-Tetradecanoylphorbol-13-Acetate-Induced Interaction of Mouse Epidermal Protein Kinase C? With Stat3 Involve Integration With Erk1/2  

PubMed Central

We have reported that protein kinase C epsilon (PKC?) expression level in epidermis dictates the susceptibility of mice to the development of squamous cell carcinomas (SCC) elicited either by repeated exposure to ultraviolet radiation (UVR) or by the DMBA-TPA tumor promotion protocol. To find clues about the mechanism by which PKC? mediates susceptibility to UVR-induced development of SCC, we found that PKC?-over-expressing transgenic mice, as compared to their wild-type littermates, when exposed to UVR, elicit enhanced phosphorylation of Stat3 at Ser727 residues. Stat3 is constitutively activated in SCC and UVR fails to induce SCC in Stat3 mutant mice. Stat3Ser727 phosphorylation is essential for Stat3 transcriptional activity (Cancer Res. 67: 1385, 2007). We now present severa novel findings including that PKC? integrates with its downstream partner ERK1/2 to phosphorylate Stat3Ser727. In these experiments, mice were either exposed to UVR (2 kJ/m2/dose) emitted by Kodacel-filtered FS-40 sun lamps or treated with TPA (5 nmol). Both UVR and TPA treatment stimulated PKC?-Stat3 interaction, Stat3Ser727 phosphorylation and Stat3-regulated gene COX-2 expression. PKC?-Stat3 interaction and Stat3Ser727 phosphorylation was also observed in SCC elicited by repeated UVR exposures of mice. PKC?-Stat3 interaction was PKC? specific. UVR or TPA-stimulated Stat3Ser727 phosphorylation accompanied interaction of PKC? with ERK1/2 in intact mouse skin in vivo. Deletion of PKC? in wild-type mice attenuated both TPA and UVR-induced expression of phosphoforms of ERK1/2 and Stat3Ser727. These results indicate that PKC? integrates with ERK1/2 to mediate both TPA and UVR-induced epidermal Stat3Ser727 phosphorylation. PKC? and Stat3 may be potential molecular targets for SCC prevention.

Sand, Jordan Marshall; Hafeez, Bilal Bin; Aziz, Moammir Hasan; Siebers, Emily Marie; Dreckschmidt, Nancy Ellen; Verma, Ajit Kumar

2012-01-01

119

TIS21(/BTG2/PC3) inhibits interleukin-6 expression via downregulation of STAT3 pathway.  

PubMed

Cancer cell growth was increased when co-cultured with fibroblasts, however, no effect was observed when co-cultured with TIS21-overexpressed fibroblast. Therefore, the role of TIS21 played in cancer microenvironment was investigated. TIS21 decreased interleukin-6 (IL-6) expression in human dermal fibroblast (HDF). Adenoviral transduction of TIS21 gene to HDF decreased the secretion of IL-6, whereas knockdown of the gene increased IL-6 expression. Furthermore, TIS21 overexpression inhibited STAT3 binding to IL-6 promoter region as well as JAK2-STAT3 signaling by inhibiting reactive oxygen species (ROS) generation by being localized in mitochondria. Mitochondria-target TIS21 (MT-TIS21) also inhibited IL-6 expression by downregulating STAT3 phosphorylation, whereas NF-?B pathway was not influenced by TIS21 expression. These results indicate that TIS21 negatively regulated cancer cell growth by inhibiting IL-6 expression through downregulation of STAT3 activation. PMID:23917204

Quy, Linh Nguyen; Choi, Yong Won; Kim, Yeong Hwa; Chwae, Yong-Joon; Park, Tae Jun; Lim, In Kyoung

2013-08-01

120

EGCG Enhances the Therapeutic Potential of Gemcitabine and CP690550 by Inhibiting STAT3 Signaling Pathway in Human Pancreatic Cancer  

PubMed Central

Background Signal Transducer and Activator of Transcription 3 (STAT3) is an oncogene, which promotes cell survival, proliferation, motility and progression in cancer cells. Targeting STAT3 signaling may lead to the development of novel therapeutic approaches for human cancers. Here, we examined the effects of epigallocathechin gallate (EGCG) on STAT3 signaling in pancreatic cancer cells, and assessed the therapeutic potential of EGCG with gemcitabine or JAK3 inhibitor CP690550 (Tasocitinib) for the treatment and/or prevention of pancreatic cancer. Methodology/Principal Findings Cell viability and apoptosis were measured by XTT assay and TUNEL staining, respectively. Gene and protein expressions were measured by qRT-PCR and Western blot analysis, respectively. The results revealed that EGCG inhibited the expression of phospho and total JAK3 and STAT3, STAT3 transcription and activation, and the expression of STAT3-regulated genes, resulting in the inhibition of cell motility, migration and invasion, and the induction of caspase-3 and PARP cleavage. The inhibition of STAT3 enhanced the inhibitory effects of EGCG on cell motility and viability. Additionally, gemcitabine and CP690550 alone inhibited STAT3 target genes and synergized with EGCG to inhibit cell viability and induce apoptosis in pancreatic cancer cells. Conclusions/Significance Overall, these results suggest that EGCG suppresses the growth, invasion and migration of pancreatic cancer cells, and induces apoptosis by interfering with the STAT3 signaling pathway. Moreover, EGCG further enhanced the therapeutic potential of gemcitabine and CP690550 against pancreatic cancer.

Tang, Su-Ni; Fu, Junsheng; Shankar, Sharmila; Srivastava, Rakesh K.

2012-01-01

121

ChatStat 3.1.6  

NSDL National Science Digital Library

If you have a website, there may have been times where you would have liked to talk with visitors who have browsed on in to say hello. ChatStat 3.16 offers users the ability to conduct live chat sessions with website visitors, along with free dynamic web analytic software. Visitors can also chat with other operators via instant message and even let visitors request a "call back". This application is compatible with computers running Windows NT and newer.

2008-01-01

122

Gene expression and biological processes influenced by deletion of Stat3 in pulmonary type II epithelial cells  

PubMed Central

Background The signal transducer and activator of transcription 3 (STAT3) mediates gene expression in response to numerous growth factors and cytokines, playing an important role in many cellular processes. To better understand the molecular mechanisms by which Stat3 influences gene expression in the lung, the effect of pulmonary epithelial cell specific deletion of Stat3 on genome wide mRNA expression profiling was assessed. Differentially expressed genes were identified from Affymetrix Murine GeneChips analysis and subjected to gene ontology classification, promoter analysis, pathway mapping and literature mining. Results Total of 791 mRNAs were significantly increased and 314 mRNAs were decreased in response to the deletion of Stat3?/? in the lung. STAT is the most enriched cis-elements in the promoter regions of those differentially expressed genes. Deletion of Stat3 induced genes influencing protein metabolism, transport, chemotaxis and apoptosis and decreased the expression of genes mediating lipid synthesis and metabolism. Expression of Srebf1 and 2, genes encoding key regulators of fatty acid and steroid biosynthesis, was decreased in type II cells from the Stat3?/? mice, consistent with the observation that lung surfactant phospholipids content was decreased. Stat3 influenced both pro- and anti-apoptotic pathways that determine cell death or survival. Akt, a potential transcriptional target of Stat3, was identified as an important participant in Stat3 mediated pathways including Jak-Stat signaling, apoptosis, Mapk signaling, cholesterol and fatty acid biosynthesis. Conclusion Deletion of Stat3 from type II epithelial cells altered the expression of genes regulating diverse cellular processes, including cell growth, apoptosis and lipid metabolism. Pathway analysis indicates that STAT3 regulates cellular homeostasis through a complex regulatory network that likely enhances alveolar epithelial cell survival and surfactant/lipid synthesis, necessary for the protection of the lung during injury.

Xu, Yan; Ikegami, Machiko; Wang, Yanhua; Matsuzaki, Yohei; Whitsett, Jeffrey A

2007-01-01

123

?-Caryophyllene oxide Inhibits Constitutive and Inducible STAT3 Signaling Pathway Through Induction of the SHP-1 Protein Tyrosine Phosphatase.  

PubMed

Constitutive activation of STAT3 is frequently observed and closely linked with proliferation, survival, invasion, metastasis and angiogenesis in tumor cells. In the present study, we investigated whether ?-caryophyllene oxide (CPO), a sesquiterpene isolated primarily from the essential oils of medicinal plants such as guava (Psidium guajava), and oregano (Origanum vulgare L.), can mediate its effect through interference with the STAT3 activation pathway in cancer cells. The effect of CPO on STAT3 activation, associated protein kinases and phosphatase, STAT3-regulated gene products and apoptosis was investigated using both functional proteomics tumor pathway technology platform and different tumor cell lines. We found that CPO suppressed constitutive STAT3 activation in multiple myeloma (MM), breast and prostate cancer cell lines, with a significant dose- and time-dependent effects observed in MM cells. The suppression was mediated through the inhibition of activation of upstream kinases c-Src and JAK1/2. Also, vanadate treatment reversed CPO-induced down-regulation of STAT3, suggesting the involvement of a tyrosine phosphatase. Indeed, we found that CPO induced the expression of tyrosine phosphatase SHP-1 that correlated with the down-regulation of constitutive STAT3 activation. Interestingly, deletion of SHP-1 gene by siRNA abolished the ability of CPO to inhibit STAT3 activation. The inhibition of STAT3 activation by CPO inhibited proliferation, induced apoptosis and abrogated the invasive potential of tumor cells. Our results suggest for the first time that CPO is a novel blocker of STAT3 signaling cascade and thus has an enormous potential for the treatment of various cancers harboring constitutively activated STAT3. © 2013 Wiley Periodicals, Inc. PMID:23765383

Kim, Chulwon; Cho, Somi K; Kapoor, Shweta; Kumar, Ansu; Vali, Shireen; Abbasi, Taher; Kim, Sung-Hoon; Sethi, Gautam; Ahn, Kwang Seok

2013-06-13

124

STAT3 in CD4+ T helper Cell differentiation and Inflammatory Diseases  

PubMed Central

Jak/STAT pathways influence cell-fate decisions made by differentiating naïve T-cells, regulate the intensity and duration of inflammatory responses and are implicated in pathogenic mechanisms of a number of chronic inflammatory diseases. Among the STATs, the STAT3 protein has emerged as an important determinant of whether the naïve T cell differentiates into regulatory (Treg) or an inflammatory (Th17) T cell lineage. STAT3 also has potent anti-inflammatory effects and regulates critical cellular processes such as, cell growth, apoptosis and transcription of inflammatory genes. Dysregulation of STAT3 pathway has therefore been implicated in the development of chronic inflammatory diseases, as well as, a number of malignant and neurodegenerative diseases. This review focuses on recent findings regarding the role of STAT3 in immunity, with particular emphasis on T cell lineage specification and disease etiology. New insights from animal models of uveitis, multiple sclerosis and inflammatory bowel diseases are discussed as exemplars of critical roles that STAT3 pathways play in inflammatory diseases and on how inhibiting STAT3 can be exploited to mitigate pathogenic autoimmunity.

Egwuagu, Charles E.

2009-01-01

125

STAT3 activation in response to IL-6 is prolonged by the binding of IL-6 receptor to EGF receptor  

PubMed Central

The activation of STAT3 by tyrosine phosphorylation, essential for normal development and for a normal inflammatory response to invading pathogens, is kept in check by negative regulators. Abnormal constitutive activation of STAT3, which contributes to the pathology of cancer and to chronic inflammatory diseases such as rheumatoid arthritis, occurs when negative regulation is not fully effective. SOCS3, the major negative regulator of STAT3, is induced by tyrosine-phosphorylated STAT3 and terminates STAT3 phosphorylation about 2 h after initial exposure of cells to members of the IL-6 family of cytokines by binding cooperatively to the common receptor subunit gp130 and JAKs 1 and 2. We show here that when the epidermal growth factor receptor (EGFR) is present and active, STAT3 is rephosphorylated about 4 h after exposure of cells to IL-6 or oncostatin M and remains active for many hours. Newly synthesized IL-6 drives association of the IL-6 receptor and gp130 with EGFR, leading to EGFR-dependent rephosphorylation of STAT3, which is not inhibited by the continued presence of SOCS3. This second wave of STAT3 activation supports sustained expression of a subset of IL-6-induced proteins, several of which play important roles in inflammation and cancer, in which both IL-6 secretion and EGFR levels are often elevated.

Wang, Yuxin; van Boxel-Dezaire, Anette H. H.; Cheon, HyeonJoo; Yang, Jinbo; Stark, George R.

2013-01-01

126

Distinct transcriptional regulatory modules underlie STAT3's cell type-independent and cell type-specific functions  

PubMed Central

Transcription factors (TFs) regulate gene expression by binding to short DNA sequence motifs, yet their binding specificities alone cannot explain how certain TFs drive a diversity of biological processes. In order to investigate the factors that control the functions of the pleiotropic TF STAT3, we studied its genome-wide binding patterns in four different cell types: embryonic stem cells, CD4+ T cells, macrophages and AtT-20 cells. We describe for the first time two distinct modes of STAT3 binding. First, a small cell type-independent mode represented by a set of 35 evolutionarily conserved STAT3-binding sites that collectively regulate STAT3’s own functions and cell growth. We show that STAT3 is recruited to sites with E2F1 already pre-bound before STAT3 activation. Second, a series of different transcriptional regulatory modules (TRMs) assemble around STAT3 to drive distinct transcriptional programs in the four cell types. These modules recognize cell type-specific binding sites and are associated with factors particular to each cell type. Our study illustrates the versatility of STAT3 to regulate both universal- and cell type-specific functions by means of distinct TRMs, a mechanism that might be common to other pleiotropic TFs.

Hutchins, Andrew Paul; Diez, Diego; Takahashi, Yoshiko; Ahmad, Shandar; Jauch, Ralf; Tremblay, Michel Lucien; Miranda-Saavedra, Diego

2013-01-01

127

QUICK identification and SPR validation of signal transducers and activators of transcription 3 (Stat3) interacting proteins.  

PubMed

Signal transducers and activators of transcription 3 (Stat3) has been reported to be involved in the pathogenesis of various human diseases and is constitutively active in human multiple myeloma (MM) U266 cells. The Stat3-regulated mechanisms involved in these processes, however, are not fully defined. To further understand the regulation of Stat3 activity, we performed a systematic proteomic analysis of Stat3 interacting proteins in U266 cells. This analysis, termed quantitative immunoprecipitation combined with knockdown (QUICK), combines RNAi, stable isotope labeling with amino acids in cell culture (SILAC), immunoprecipitation, and quantitative MS. As a result, quantitative mass spectrometry analysis allowed us to distinguish specific Stat3 interacting proteins from background proteins and led to the identification of a total of 38 proteins. Three Stat3 interacting proteins - 14-3-3?, PRKCB and Hsp90 - were further confirmed by reciprocal co-immunoprecipitations and surface plasmon resonance (SPR) analysis. Our results therefore not only uncover a number of Stat3 interacting proteins that possess a variety of cellular functions, but also provide new insight into the mechanisms that regulate Stat3 activity and function in MM cells. PMID:22075167

Zheng, Peng; Zhong, Qiu; Xiong, Qian; Yang, Mingkun; Zhang, Jia; Li, Chongyang; Bi, Li-Jun; Ge, Feng

2011-10-30

128

STAT3 activation in response to IL-6 is prolonged by the binding of IL-6 receptor to EGF receptor.  

PubMed

The activation of STAT3 by tyrosine phosphorylation, essential for normal development and for a normal inflammatory response to invading pathogens, is kept in check by negative regulators. Abnormal constitutive activation of STAT3, which contributes to the pathology of cancer and to chronic inflammatory diseases such as rheumatoid arthritis, occurs when negative regulation is not fully effective. SOCS3, the major negative regulator of STAT3, is induced by tyrosine-phosphorylated STAT3 and terminates STAT3 phosphorylation about 2 h after initial exposure of cells to members of the IL-6 family of cytokines by binding cooperatively to the common receptor subunit gp130 and JAKs 1 and 2. We show here that when the epidermal growth factor receptor (EGFR) is present and active, STAT3 is rephosphorylated about 4 h after exposure of cells to IL-6 or oncostatin M and remains active for many hours. Newly synthesized IL-6 drives association of the IL-6 receptor and gp130 with EGFR, leading to EGFR-dependent rephosphorylation of STAT3, which is not inhibited by the continued presence of SOCS3. This second wave of STAT3 activation supports sustained expression of a subset of IL-6-induced proteins, several of which play important roles in inflammation and cancer, in which both IL-6 secretion and EGFR levels are often elevated. PMID:24082147

Wang, Yuxin; van Boxel-Dezaire, Anette H H; Cheon, Hyeonjoo; Yang, Jinbo; Stark, George R

2013-09-30

129

Phosphorylation of STAT3 serine-727 by cyclin-dependent kinase 1 is critical for nocodazole-induced mitotic arrest.  

PubMed

Signal transducer and activator of transcription 3 (STAT3) mediates cellular responses to diverse cytokines and growth factors by modulating the expression of specific target genes. While phosphorylation of STAT3 at Tyr-705 has been demonstrated to be a prerequisite for STAT3 dimerization, nuclear translocation, and activation of gene transcription, the role of Ser-727 in regulation of STAT3 activity is controversial. Kinetworks KPSS-1.1 phospho-site screening of nocodazole-treated HeLa cells revealed that STAT3 Ser-727 phosphorylation was enhanced during mitosis, and this correlated with a reduction of Tyr-705 phosphorylation. Overexpression of STAT3 mutants in which these phosphorylation sites were separately abolished revealed that phosphorylation at these sites appeared to be mutually antagonistic. The nocodazole-induced STAT3 Ser-727 phosphorylation was reduced by selective inhibition of CDK1 phosphotransferase activity, and CDK1 could directly phosphorylate GST-STAT3 Ser-727 in vitro and co-immunoprecipitate with STAT3 in vivo. Blocking Ser-727 phosphorylation enhanced STAT3 DNA-binding activity toward its target gene promoters, implying a negative effect of Ser-727 phosphorylation on its transcriptional activity. Interference of Ser-727 phosphorylation resulted in an exit from mitotic arrest induced by nocodazole treatment and a cell cycle arrest at the G1 phase, as indicated by the accumulation of 2N cell population and enhanced expression of G1 cell cycle regulators including p21(CIP1/WAF1), p27(Kip1), and cyclin E. Taken together, our observations point to a novel role of STAT3 Ser-727 phosphorylation in control of the onset and maintenance of the M phase during the cell cycle through downregulation of CDK inhibitors. PMID:16669628

Shi, Xiaoqing; Zhang, Hong; Paddon, Harry; Lee, Gloria; Cao, Xinmin; Pelech, Steven

2006-05-01

130

STAT3-iNOS Signaling Mediates EGFRvIII-Induced Glial Proliferation and Transformation.  

PubMed

Malignant gliomas, including glioblastoma multiforme, constitute the most common and aggressive primary brain tumors in adults. The transcription factor signal transducer and activator of transcription 3 (STAT3) plays an essential role in glioblastoma pathogenesis downstream of the major oncogenic protein epidermal growth factor receptor variant III (EGFRvIII). However, the critical gene targets of STAT3 that mediate EGFRvIII-induced glial transformation have remained unknown. Here, we identify inducible nitric oxide synthase (iNOS) as a novel target gene of STAT3 in EGFRvIII-expressing mouse astrocytes. Endogenous STAT3 occupies the endogenous iNOS promoter and stimulates iNOS transcription in EGFRvIII-expressing astrocytes. STAT3 does not appear to control iNOS transcription in astrocytes deficient in the major glioblastoma tumor suppressor protein phosphatase and tensin homolog (PTEN), suggesting that STAT3 regulates iNOS transcription specifically in EGFRvIII-expressing astrocytes. Importantly, inhibition of iNOS by distinct approaches, including knockdown by RNA interference, reduces cell population growth and invasiveness of EGFRvIII-expressing astrocytes. In addition, upon iNOS knockdown or administration of a small-molecule inhibitor of iNOS, EGFRvIII-expressing astrocytes form smaller tumors in vivo. These findings suggest that inhibition of iNOS may have potential therapeutic value for EGFRvIII-activated brain tumors. PMID:22674257

Puram, Sidharth V; Yeung, Caleb M; Jahani-Asl, Arezu; Lin, Chieyu; de la Iglesia, Nuria; Konopka, Genevieve; Jackson-Grusby, Laurie; Bonni, Azad

2012-06-01

131

The import of the transcription factor STAT3 into mitochondria depends on GRIM-19, a component of the electron transport chain.  

PubMed

The signal transducer and activator of transcription 3 (STAT3), a nuclear transcription factor, is also present in mitochondria and regulates cellular respiration in a transcriptional-independent manner. The mechanism of STAT3 import into mitochondria remains obscure. In this report we show that mitochondrial-localized STAT3 resides in the inner mitochondrial membrane. In vitro import studies show that the gene associated with retinoid interferon induced cell mortality 19 (GRIM-19), a complex I subunit that acts as a chaperone to recruit STAT3 into mitochondria. In addition, GRIM-19 enhances the integration of STAT3 into complex I. A S727A mutation in STAT3 reduces its import and assembly even in the presence of GRIM-19. Together, our studies unveil a novel chaperone function for GRIM-19 in the recruitment of STAT3 into mitochondria. PMID:23271731

Tammineni, Prasad; Anugula, Chandrashekhar; Mohammed, Fareed; Anjaneyulu, Murari; Larner, Andrew C; Sepuri, Naresh Babu Venkata

2012-12-27

132

EBV nuclear antigen EBNALP dismisses transcription repressors NCoR and RBPJ from enhancers and EBNA2 increases NCoR-deficient RBPJ DNA binding.  

PubMed

EBV nuclear antigen 2 (EBNA2) and EBV nuclear antigen LP (EBNALP) are critical for B-lymphocyte transformation to lymphoblastoid cell lines (LCLs). EBNA2 activates transcription through recombination signal-binding immunoglobulin ?J region (RBPJ), a transcription factor associated with NCoR repressive complexes, and EBNALP is implicated in repressor relocalization. EBNALP coactivation with EBNA2 was found to dominate over NCoR repression. EBNALP associated with NCoR and dismissed NCoR, NCoR and RBPJ, or NCoR, RBPJ, and EBNA2 from matrix-associated deacetylase (MAD) bodies. In non-EBV-infected BJAB B lymphoma cells that stably express EBNA2, EBNALP, or EBNA2 and EBNALP, EBNALP was associated with hairy and enhancer of split 1 (hes1), cd21, cd23, and arginine and glutamate-rich 1 (arglu1) enhancer or promoter DNA and was associated minimally with coding DNA. With the exception of RBPJ at the arglu1 enhancer, NCoR and RBPJ were significantly decreased at enhancer and promoter sites in EBNALP or EBNA2 and EBNALP BJAB cells. EBNA2 DNA association was unaffected by EBNALP, and EBNALP was unaffected by EBNA2. EBNA2 markedly increased RBPJ at enhancer sites without increasing NCoR. EBNALP further increased hes1 and arglu1 RNA levels with EBNA2 but did not further increase cd21 or cd23 RNA levels. EBNALP in which the 45 C-terminal residues critical for transformation and transcriptional activation were deleted associated with NCoR but was deficient in dismissing NCoR from MAD bodies and from enhancer and promoter sites. These data strongly support a model in which EBNA2 association with NCoR-deficient RBPJ enhances transcription and EBNALP dismisses NCoR and RBPJ repressive complexes from enhancers to coactivate hes1 and arglu1 but not cd21 or cd23. PMID:21518914

Portal, Daniel; Zhao, Bo; Calderwood, Michael A; Sommermann, Thomas; Johannsen, Eric; Kieff, Elliott

2011-04-25

133

Stat3-induced S1PR1 expression is critical for persistent Stat3 activation in tumors  

PubMed Central

IL-6/Jak2 signaling is viewed critical for persistent Stat3 activation in cancer. However, IL-6-induced Stat3 activity is transient in normal physiology. Here we identify a mechanism important for persistent Stat3 activation in tumor cells and the tumor microenvironment. We show that sphingosine-1-phosphate receptor 1 (S1PR1), a G-protein-coupled receptor for lysophospholipid sphingosine-1-phosphate (S1P), is elevated in Stat3-positive tumors. Stat3 is a transcription factor for the S1pr1 gene. Enhanced S1pr1 expression activates Stat3 and upregulates Il6 gene expression, thereby accelerating tumor growth and metastasis. Conversely, silencing S1pr1 in tumor cells or immune cells inhibits tumor Stat3 activity, tumor growth and metastasis. S1P/S1PR1-induced Stat3 activation is persistent, in contrast to transient Stat3 activation by IL-6. S1PR1 activates Stat3 in part by upregulating Jak2 tyrosine kinase activity. We demonstrate that Stat3-induced S1pr1 expression, as well as S1P/S1PR1 pathway, is important for persistent Stat3 activation in cancer cells and the tumor microenvironment and for malignant progression.

Lee, Heehyoung; Deng, Jiehui; Kujawski, Maciej; Yang, Chunmei; Liu, Yong; Herrmann, Andreas; Kortylewski, Marcin; Horne, David; Somlo, George; Forman, Stephen; Jove, Richard; Yu, Hua

2011-01-01

134

Investigation of the protein alkylation sites of the STAT3:STAT3 inhibitor Stattic by mass spectrometry.  

PubMed

STAT3 (Signal Transducer and Activator of Transcription factor 3) is constitutively active in a wide range of human tumours. Stattic is one of the first non-peptidic small molecules reported to inhibit formation of the STAT3:STAT3 protein dimer complex. A mass spectrometry method has been developed to investigate the binding of Stattic to the un-phosphorylated STAT3?tc (U-STAT3) protein. Alkylation of four cysteine residues has been observed with possible reaction at a fifth which could account for the mechanism of action. PMID:23810499

Heidelberger, Sibylle; Zinzalla, Giovanna; Antonow, Dyeison; Essex, Samantha; Basu, B Piku; Palmer, Jonathan; Husby, Jarmila; Jackson, Paul J M; Rahman, Khondaker M; Wilderspin, Andrew F; Zloh, Mire; Thurston, David E

2013-05-29

135

Anomalous behaviour of the STAT3 binding site in the human c-myc P2 promoter  

SciTech Connect

The Signal Transducer and Activator of Transcription 3 (STAT3) is necessary for ES cell renewal, plays critical roles during vertebrate development, and has oncogenic potential. STAT3 also mediates cytokine responses notably in the induction of acute phase response genes in the liver. Thus STAT3 is a pleiotropic regulator during cell proliferation and a cell-specific mediator of pro-inflammatory responses. How STAT3 fulfils both roles is unclear. To address this question we attempted to characterise pre-initiation complexes (PICs) on STAT3-responsive promoters containing the c-myc P2 promoter element (P2E) or c-fos Serum-Inducible Element (SIE). Although both promoters mediated cytokine responses in HepG2 cells, poor binding of STAT1 and STAT3 in vitro precluded isolation of active promoter complexes on the P2E. The inability of STAT3 to bind the P2E in vitro correlated with failure of the P2E to mediate cytokine-responsive gene expression in several other cell types. Thus the c-myc P2E behaves as a dual-purpose STAT3 element with anomalous characteristics in HepG2 cells.

Vougier, Stephanie; Cheung, S.-H.; Li Li; Hodgson, Glenn [Centre for Biochemistry and Cell Biology, School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH (United Kingdom); Shaw, Peter E [Centre for Biochemistry and Cell Biology, School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre, Nottingham NG7 2UH (United Kingdom)], E-mail: peter.shaw@nottingham.ac.uk

2007-12-21

136

STAT3 activation in monocytes accelerates liver cancer progression  

PubMed Central

Background Signal transducer and activator of transcription 3 (STAT3) is an important transcription factor ubiquitously expressed in different cell types. STAT3 plays an essential role in cell survival, proliferation, and differentiation. Aberrantly hyper-activated STAT3 signaling in cancer cells and in the tumor microenvironment has been detected in a wide variety of human cancers and is considered an important factor for cancer initiation, development, and progression. However, the role of STAT3 activation in monocytes in the development of HCC has not been well understood. Methods Immunohistochemical analysis of phosphorylated STAT3 was performed on tissue microarray from HCC patients. Using a co-culture system in vivo, HCC cell growth was determined by the MTT assay. In vivo experiments were conducted with mice given diethylinitrosamine (DEN), which induces HCC was used to investigate the role of STAT3 expression in monocytes on tumor growth. Real-time PCR was used to determine the expression of cell proliferation and cell arrest associated genes in the tumor and nontumor tissue from liver. Results Phosphorylated STAT3 was found in human hepatocellular carcinoma tissue samples and was expressed in tumor cells and also in monocytes. Phosphorylated STAT3 expression in monocyte was significantly correlated to advanced clinical stage of HCC and a poor prognosis. Using a co-culture system in vivo, monocytes promoted HCC cell growth via the IL-6/STAT3 signaling pathway. The STAT3 inhibitor, NSC 74859, significantly suppressed tumor growth in vivo in mice with diethylinitrosamine (DEN)-induced HCC. In this animal model, blockade of STAT3 with NSC 74859 induced tumor cell apoptosis, while inhibiting both tumor cells and monocytes proliferation. Furthermore, NSC 74859 treatment suppressed cancer associated inflammation in DEN-induce HCC. Conclusion Our data suggest constitutively activated STAT3 monocytes promote liver tumorigenesis in clinical patients and animal experiments. Thus, STAT3 in tumor infiltrating inflammatory cells may an attractive target for liver cancer therapy.

2011-01-01

137

Two Naturally Occurring Terpenes, Dehydrocostuslactone and Costunolide, Decrease Intracellular GSH Content and Inhibit STAT3 Activation  

PubMed Central

The main purpose of the present study is to envisage the molecular mechanism of inhibitory action ofdehydrocostuslactone (DCE) andcostunolide (CS), two naturally occurring sesquiterpene lactones, towards the activation of signal transducer and activator of transcription 3 (STAT3). We report that, in human THP-1 cell line, they inhibit IL-6-elicited tyrosine phosphorylation of STAT3 and its DNA binding activity with EC50 of 10 µM with concomitantdown-regulation ofthe phosphorylation of the tyrosine Janus kinases JAK1, JAK2 and Tyk2. Furthermore, these compounds that contain an ?-?-unsatured carbonyl moiety and function as potent Michael reaction acceptor, induce a rapid drop in intracellular glutathione (GSH) concentration by direct interaction with it, thereby triggering S-glutathionylation of STAT3. Dehydrocostunolide (HCS), the reduced form of CS lacking only the ?-?-unsaturated carbonyl group, fails to exert any inhibitory action. Finally, the glutathione ethylene ester (GEE), the cell permeable GSH form, reverts the inhibitory action of DCE and CS on STAT3 tyrosine phosphorylation. We conclude that these two sesquiterpene lactones are able to induce redox-dependent post-translational modification of cysteine residues of STAT3 protein in order to regulate its function.

Butturini, Elena; Cavalieri, Elisabetta; Carcereri de Prati, Alessandra; Darra, Elena; Rigo, Antonella; Shoji, Kazuo; Murayama, Norie; Yamazaki, Hiroshi; Watanabe, Yasuo; Suzuki, Hisanori; Mariotto, Sofia

2011-01-01

138

Towards a quantitative understanding of the MITF-PIAS3-STAT3 connection  

PubMed Central

Background Expression of the two transcription factors microphthalmia-associated transcription factor (MITF) and signal transducer and activator of transcription 3 (STAT3) are tightly connected to cell proliferation and survival, and are important for melanocyte development. The co-regulation of MITF and STAT3 via their binding to a common inhibitor Protein Inhibitor of Activated STAT3 (PIAS3) is intriguing. A better quantitative understanding of this regulation is likely to be important for elucidation of the melanocyte biology. Results We present a mathematical model describing the MITF-PIAS3-STAT3 signalling network. A default parameter set was developed, partly informed by the literature and partly by constraining the model to mimic reported behavioural features of the system. In addition, a set of experiment-specific parameters was derived for each of 28 experiments reported in the literature. The model seems capable of accounting for most of these experiments in terms of observed temporal development of protein amounts and phosphorylation states. Further, the results also suggest that this system possesses some regulatory features yet to be elucidated. Conclusions We find that the experimentally observed crosstalk between MITF and STAT3 via PIAS3 in melanocytes is faithfully reproduced in our model, offering mechanistic explanations for this behaviour, as well as providing a scaffold for further studies of MITF signalling in melanoma.

2012-01-01

139

STAT3 activation in photoreceptors by leukemia inhibitory factor is associated with protection from light damage.  

PubMed

Members of the interleukin-6 cytokine family, including leukemia inhibitory factor (LIF), signal through gp130. The neuroprotective role of gp130 activation has been widely demonstrated in both CNS and PNS, but the mechanism by which this is accomplished is not well established. We investigated temporal and cell-specific activation of signaling pathways induced by LIF in the mature mouse retina. Intravitreal injection of LIF preserved photoreceptor function and prevented photoreceptor cell death from light-induced oxidative damage in a dose-dependent manner (2 days post-injection). A therapeutic dose of LIF induced rapid and sustained activation of signal transducer and activator of transcription (STAT) 3. Activated STAT3 was localized to all the retinal neurons and glial cells, including photoreceptors. Activation of extracellular signal-regulated kinase 1 and 2 was robust but transient in Müller glial cells, and undetectable at the time of light exposure. Akt was not activated by LIF. We also show that at the time of neuroprotection, STAT3 but not extracellular signal-regulated kinase 1 and 2 or the Akt pathways was active in LIF-treated retinas, and activated STAT3 was clearly localized in transcriptionally active areas of photoreceptor nuclei. Our data suggest that photoreceptor protection in response to LIF can be directly mediated by activation of STAT3 in photoreceptors. PMID:18088375

Ueki, Yumi; Wang, Jiangang; Chollangi, Srinivas; Ash, John D

2007-12-10

140

Effects of STAT3 Gene Silencing and Rapamycin on Apoptosis in Hepatocarcinoma Cells  

PubMed Central

The PI3K/Akt/mTOR and JAK/STAT3 signaling pathways are important for regulating apoptosis, and are frequently activated in cancers. In this study, we targeted STAT3 and mTOR in human hepatocellular carcinoma Bel-7402 cells and examined the subsequent alterations in cellular apoptosis. The expression of STAT3 was silenced with small interfering RNA (siRNA)-expressing plasmid. The activity of mTOR was inhibited using rapamycin. Following treatment, Annexin V/propidium iodide staining followed by flow cytometry and Hoechst33258 immunofluorescence staining was used to examine cellular apoptosis. JC-1 staining was used to monitor depolarization of mitochondrial membrane (??m). Furthermore, the expression of activated caspase 3 protein was analyzed by Western blotting. Compared to non-treated or control siRNA-transfected cells, significantly higher levels of apoptosis were detected in siSTAT3-transfected or rapamycin-treated cells (P < 0.05), which was further enhanced in cells targeted for both molecules (P < 0.05). The pro-apoptotic effects were accompanied with concomitant depolarization of mitochondrial membrane and up-regulation of activated caspase 3. Combined treatments using rapamycin and STAT3 gene silencing significantly increases apoptosis in Bel-7402 cells, displaying more dramatic effect than any single treatment. This study provides evidence for targeting multiple molecules in cancer therapy.

Zhang, Yi; Zhang, Jun-Wei; Lv, Guo-Yue; Xie, Shu-Li; Wang, Guang-Yi

2012-01-01

141

PKM2, STAT3 and HIF-1?: The Warburg's vicious circle.  

PubMed

The M2 isoform of pyruvate kinase, highly expressed in tumor cells, is known to engage a feed forward loop with the glycolysis master transcription factor HIF-1?. Gao and co-authors recently showed that dimeric PKM2 localizes to the nucleus in highly proliferating cancer cells, where it regulates in vivo growth by acting as a protein kinase and directly activating STAT3. STAT3 is therefore a novel player of the PKM2/HIF-1? feedback loop, since HIF-induced PKM2 activates STAT3 that in turn induces HIF-1? expression. These findings have profound implications for understanding the complex connections between gene regulation, metabolism, survival and proliferation in cancer. PMID:24058770

Demaria, Marco; Poli, Valeria

2012-07-01

142

Resistance to chemotherapy via Stat3-dependent overexpression of Bcl-2 in metastatic breast cancer cells.  

PubMed

Disruption of apoptosis may allow metastatic cell survival and confer resistance to chemotherapeutic drugs. We have analysed the molecular pathways that activate these survival genes in specific sites of metastasis. Estrogen receptor-negative breast cancer cell line MDA-MB435 and two metastatic sublines derived from lung (435L) and brain (435B) were analysed for the expression of members of the Bcl-2 family of apoptosis regulators. The levels of Bcl-2 were higher in the metastatic sublines than in parental cells, which correlated with the activation of Stat3, but not with the expression and/or activation of known bcl-2 transcription factors (CREB and WT1). In the brain subline, both expression of Bcl-2 and Stat3 activation were induced by epidermal growth factor and abrogated after treatment with kinase inhibitors specific for epidermal growth factor receptor or Jak2. Furthermore, transfection of 435B with a dominant-negative Stat3 markedly reduced the expression of Bcl-2 protein, whereas transient expression of a constitutively active Stat3 increased Bcl-2 in parental 435 cells. In addition, blockade of Stat3 activation by treatment with epidermal growth factor receptor and Jak2 kinase inhibitors or transfection with a dominant negative Stat3, sensitizes 435B cells to chemotherapy-induced apoptosis. Our data suggest that an increased activation of the Stat3-Bcl-2 pathway in estrogen receptor-negative metastatic breast cancer cell lines confer a survival advantage to these cells and contribute to their chemoresistance. PMID:12400004

Real, Pedro J; Sierra, Angels; De Juan, Ana; Segovia, Jose C; Lopez-Vega, Jose M; Fernandez-Luna, Jose L

2002-10-31

143

6-Bromoindirubin-3'-oxime inhibits JAK/STAT3 signaling and induces apoptosis of human melanoma cells  

PubMed Central

Signal Transducer and Activator of Transcription 3 (STAT3) is persistently activated and contributes to malignant progression in various cancers. Janus kinases (JAKs) phosphorylate STAT3 in response to stimulation with cytokines or growth factors. The STAT3 signaling pathway has been validated as a promising target for development of anti-cancer therapeutics. Small-molecule inhibitors of JAK/STAT3 signaling represent potential molecular-targeted cancer therapeutic agents. In this study, we investigated the role of JAK/STAT3 signaling in 6-bromoindirubin-3'-oxime (6BIO) mediated growth inhibition of human melanoma cells and assessed 6BIO as an anticancer drug candidate. We found that 6BIO is a pan-JAK inhibitor that induced apoptosis of human melanoma cells. 6BIO directly inhibited JAK family kinase activity both in vitro and in cancer cells. Apoptosis of human melanoma cells induced by 6BIO was associated with reduced phosphorylation of JAKs and STAT3 in both a dose- and time-dependent manners. Consistent with inhibition of STAT3 signaling, the anti-apoptotic protein Mcl-1 was down-regulated. In contrast to the decreased levels of phosphorylation of JAKs and STAT3, phosphorylation levels of the AKT and MAPK signaling proteins were not inhibited in cells treated with 6BIO. Importantly, 6BIO suppressed tumor growth in vivo with low toxicity in a mouse xenograft model of melanoma. Taken together, these results demonstrate that 6BIO is a novel pan-JAK inhibitor that can selectively inhibit STAT3 signaling and induced tumor cell apoptosis. Our findings support further development of 6BIO as a potential anti-cancer therapeutic agent that targets JAK/STAT3 signaling in tumor cells.

Liu, Lucy; Nam, Sangkil; Tian, Yan; Yang, Fan; Wu, Jun; Wang, Yan; Scuto, Anna; Polychronopoulos, Panos; Magiatis, Prokopios; Skaltsounis, Leandros; Jove, Richard

2011-01-01

144

Hepatoprotective versus Oncogenic Functions of STAT3 in Liver Tumorigenesis  

PubMed Central

Aberrantly hyperactivated STAT3 has been found in human liver cancers as an oncogene; however, STAT3 has also been shown to exert hepatoprotective effects during liver injury. The balancing act that STAT3 plays between hepatoprotection and liver tumorigenesis remains poorly defined. In this study, the diethylnitrosamine (DEN)-induced liver tumor model and the chronic carbon tetrachloride (CCl4)–induced liver fibrosis model were both used to investigate the role of STAT3 in liver tumorigenesis. Hepatocyte-specific STAT3 knockout mice were resistant to liver tumorigenesis induced by a single DEN injection, whose tumorigenesis was associated with minimal chronic liver inflammation, injury, and fibrosis. In contrast, long-term CCl4 treatment resulted in severe hepatic oxidative damage, inflammation, and fibrosis but rarely induced liver tumor formation in wild-type mice. Despite the oncogenic function of STAT3 in DEN-induced liver tumor, hepatocyte-specific STAT3 knockout mice were more susceptible to liver tumorigenesis after 16 weeks of CCl4 injection, which was associated with higher levels of liver injury, inflammation, fibrosis, and oxidative DNA damage compared with wild-type mice. These findings suggest that the hepatoprotective feature of STAT3 prevents hepatic damage and fibrosis under the condition of persistent inflammatory stress, consequently suppressing injury-driven liver tumor initiation. Once liver tumor cells have developed, STAT3 likely acts as an oncogenic factor to promote tumor growth.

Wang, Hua; Lafdil, Fouad; Wang, Lei; Park, Ogyi; Yin, Shi; Niu, Junyang; Miller, Andrew M.; Sun, Zhaoli; Gao, Bin

2011-01-01

145

Determinants of the extent and duration of STAT3 signaling  

PubMed Central

Multiple molecular mechanisms have been identified that are responsible for the deregulation of the quantitative aspects of JAK-STAT signaling. These mechanisms enhance the extent and the duration of, e.g., STAT3 activation and have profound consequences on the phenotypes of the affected cells. The fine tuning of STAT3 signaling is required to maintain its physiological functions and its deregulation is associated with diverse pathological states. Deregulation can be exerted by the gain of function of components mediating the activation of STAT3 or the loss of function of molecules involved in the deactivation steps of STAT3. Gain of function mutations can involve tyrosine kinases that phosphorylate STAT3, mutations in cytokine and growth factor receptors causing their ligand independent activation, mutations in STAT3 that enhance and prolong its tyrosine phosphorylation and the autocrine or paracrine production and secretion of cytokines, most notably IL-6. Diminished deactivation of phosphorylated STAT3 can be due to the reduced expression of tyrosine phosphatases, inactivating mutations in these enzymes, silencing or functional inactivation of SOCS molecules, post-transcriptional inhibition of PIAS3 expression or deletion mutations in the lymphocyte adaptor protein, LNK. STAT3 variants that exhibit autonomous transactivation potential have been detected in 40% of patients with T-cell large granular lymphocytic leukemia in clonally expanded CD8+ T cells. These patients also were preferentially affected by neutropenia and rheumatoid disorders and the results suggest that activating STAT3 mutations in T lymphocytes could be a cause of autoimmune diseases.

2012-01-01

146

MiR-124 Suppresses Growth of Human Colorectal Cancer by Inhibiting STAT3.  

PubMed

Emerging evidence indicate that microRNAs (miRNAs) may play important roles in cancer. Aberrant expression of miRNAs has been frequently identified in different human malignancies, including colorectal cancer (CRC). However, the mechanism by which deregulated miRNAs impact the development of CRC remains largely elusive. In this study, we show that miR-124 is significantly down-regulated in CRC compared to adjacent non-tumor colorectal tissues. MiR-124 suppresses the expression of STAT3 by directly binding to its 3'-untranslated region (3'-UTR). Overexpression of miR-124 led to increased apoptosis of CRC cells and reduced tumor growth in vitro and in vivo. Knocking down STAT3 expression by specific siRNA suppressed the growth of CRC cells in vitro and in vivo, resembling that of miR-124 overexpression. Moreover, overexpression of STAT3 in miR-124-transfected CRC cells effectively rescued the inhibition of cell proliferation caused by miR-124. These data suggest that miR-124 serves as a tumor suppressor by targeting STAT3, and call for the use of miR-124 as a potential therapeutic tool for CRC, where STAT3 is often hyper-activated. PMID:23940556

Zhang, Jufeng; Lu, Yanxin; Yue, Xupeng; Li, Huiming; Luo, Xia; Wang, Ying; Wang, Kepeng; Wan, Jun

2013-08-05

147

MiR-124 Suppresses Growth of Human Colorectal Cancer by Inhibiting STAT3  

PubMed Central

Emerging evidence indicate that microRNAs (miRNAs) may play important roles in cancer. Aberrant expression of miRNAs has been frequently identified in different human malignancies, including colorectal cancer (CRC). However, the mechanism by which deregulated miRNAs impact the development of CRC remains largely elusive. In this study, we show that miR-124 is significantly down-regulated in CRC compared to adjacent non-tumor colorectal tissues. MiR-124 suppresses the expression of STAT3 by directly binding to its 3?-untranslated region (3?-UTR). Overexpression of miR-124 led to increased apoptosis of CRC cells and reduced tumor growth in vitro and in vivo. Knocking down STAT3 expression by specific siRNA suppressed the growth of CRC cells in vitro and in vivo, resembling that of miR-124 overexpression. Moreover, overexpression of STAT3 in miR-124-transfected CRC cells effectively rescued the inhibition of cell proliferation caused by miR-124. These data suggest that miR-124 serves as a tumor suppressor by targeting STAT3, and call for the use of miR-124 as a potential therapeutic tool for CRC, where STAT3 is often hyper-activated.

Yue, Xupeng; Li, Huiming; Luo, Xia; Wang, Ying; Wang, Kepeng; Wan, Jun

2013-01-01

148

EBNA2 Amino Acids 3 to 30 Are Required for Induction of LMP-1 and Immortalization Maintenance  

PubMed Central

Epstein-Barr virus (EBV) nuclear antigen 2 (EBNA2), a direct transcriptional activator of viral and cellular genes, is required for EBV-induced B-cell transformation. The functional role of conserved regions within the amino terminus of the protein preceding the poly-proline region has yet to be fully characterized. Thus, we tested whether the EBNA2 amino-terminal 30 amino acid residues, containing evolutionarily conserved region 1, are required for stimulating viral and cellular gene expression necessary for B-cell transformation in a viral transcomplementation assay. We found that these residues are required for its ability to induce LMP-1 expression in lymphoblastoid cell lines (LCLs), to stimulate LMP-1 promoter reporter plasmids in transient-cotransfection assays, and to rescue LCL growth following inactivation of endogenous wild-type EBNA2 protein. Deletion of amino acid residues 3 to 30 also impaired its ability to self-associate in coimmunoprecipitation assays. These data indicate that EBNA2 residues 3 to 30 comprise an essential domain required for induction of LMP-1 expression and, consequently, for maintenance of the immortalized phenotype of LCLs. The ability to self-associate into dimers or multimers conferred by this domain may be an important mechanism for these effects.

Gordadze, Alexey V.; Onunwor, Chisaroka W.; Peng, RongSheng; Poston, David; Kremmer, Elisabeth; Ling, Paul D.

2004-01-01

149

Conditional deletion of Stat3 in mammary epithelium impairs the acute phase response and modulates immune cell numbers during post-lactational regression.  

PubMed

Mammary gland regression following weaning (involution) is associated with extensive cell death and the acquisition of an inflammatory signature. Characterizing the interplay between mammary epithelial cells, the re-emerging stroma and immune cells has implications for the understanding of the pathogenesis of pregnancy-associated breast cancer. Stat3 has a role in orchestrating cell death and involution, and we sought to determine whether expression of Stat3 by the mammary epithelium also influences the innate immune environment and inflammatory cell influx in the gland. We examined mice in which Stat3 is conditionally deleted only in the mammary epithelium. Distinct sets of genes associated with the acute phase response and innate immunity are markedly up-regulated during first phase involution in a Stat3-dependent manner. During second phase involution, chitinase 3-like 1, which has been associated with wound healing and chronic inflammatory conditions, is dramatically up-regulated by Stat3. Also at this time, the number of mammary macrophages and mast cells increases per unit area, and this increase is impaired in the absence of epithelial Stat3. Furthermore, expression of arginase-1 and Ym1, markers of alternatively activated macrophages, is significantly decreased in the absence of Stat3, whilst iNOS, a marker associated with classically activated macrophages, shows significantly increased expression in the Stat3-deleted glands. Thus, Stat3 is a key transcriptional regulator of genes associated with innate immunity and wound healing and influences mammary macrophage and mast cell numbers. The presence of epithelial Stat3 appears to polarize the macrophages and epithelial cells towards an alternatively activated phenotype, since in the absence of Stat3, the gland retains a phenotype associated with classically activated macrophages. These findings have relevance to the study of pregnancy-associated breast cancer and the role of Stat3 signalling in recruitment of alternatively activated tumour-associated macrophages in breast cancer. PMID:22081431

Hughes, Katherine; Wickenden, Julie A; Allen, Judith E; Watson, Christine J

2012-01-27

150

Differential interleukin-6/Stat3 signaling as a function of cellular context mediates Ras-induced transformation  

PubMed Central

Introduction Tyrosine phosphorylated signal transducer and activator of transcription 3 (pStat3) is expressed in numerous cancers and is required for mediating tumorigenesis. Autocrine and paracrine interleukin (IL)-6 signaling is the principal mechanism by which Stat3 is persistently phosphorylated in epithelial tumors including breast, lung, colon and gastric cancer. The Ras oncogene mediates cellular transformation without evidence of pStat3 in cultured cells. However, non-tyrosine phosphorylated Stat3 was shown to function as a transcriptional activator, localize to the mitochondria and regulate ATP synthesis and mediate cell migration. Here we examined the role of Stat3 in Ras mediated transformation. Methods Ha-rasV12 transformed mammary epithelial cells (MCF10A-Ras) cells were transduced with a Stat3shRNA, IL-6shRNA and/or treated with inhibitors of Janus kinases (JAKs) to examine the role of the IL-6 signaling pathway in Ras mediated migration, invasion and tumorigenesis. Results Cellular migration, invasion, anchorage independent growth and tumorigenesis were largely abrogated in the Stat3-reduced cells compared to control cells. Analysis of MCF10A-Ras tumors revealed high levels of pStat3 and interleukin-6. Tumors derived from transgenic MMTV-K-Ras mice were also found to express pStat3 and IL-6. MCF10A-Ras cells, when grown in a three-dimensional Matrigel culture system revealed the appearance of the junctional protein E-Cadherin as a consequence of reducing Stat3 levels or inhibiting Stat3 activity. Decreasing IL-6 levels in the MCF10A-Ras cells abrogated tumorigenesis and reduced cell migration. By isolating Ras-expressing primary tumors and serially passaging these cells in two-dimensional culture led to a decrease in IL-6 and pStat3 levels with the reappearance of E-Cadherin. Conclusions The cellular and environmental context can lead to differential IL-6/pStat3 signaling and a dependency on this cytokine and transcription factor for migration, invasion and tumorigenesis.

2010-01-01

151

STAT3 activation by IL-6 from mesenchymal stem cells promotes the proliferation and metastasis of osteosarcoma.  

PubMed

We previously demonstrated that human mesenchymal stem cells (MSCs) promote the growth of osteosarcoma in the bone microenvironment. The aim of the present study was to further determine the effect of IL-6/STAT3 signaling on the progression of osteosarcoma. First, conditioned medium from MSCs was used to stimulate the growth of osteosarcoma cells (Saos-2) in vitro. We found that STAT3 was activated and that the activation could be blocked by an IL-6-neutralizing antibody. The inhibition of STAT3 in Saos-2 cells by siRNA or AG490 decreased cell proliferation, migration and invasion, down-regulated the mRNA expression of Cyclin D, Bcl-xL and Survivin and enhanced the apoptotic response. Furthermore, a nude mouse osteosarcoma model was established by injecting luciferase-labeled Saos-2 cells into the tibia, and the effect of STAT3 on tumor growth was determined by treating the mice with AG490. In vivo bioluminescence images showed that tumor growth was dramatically reduced in the AG490 group. In addition, STAT3 inhibition decreased the lung metastasis rate and prolonged the survival of these mice. After treatment with AG490, the protein levels of IL-6, p-STAT3 and PCNA were decreased, and the level of apoptosis in the tumor was increased. Altogether, these data indicate that MSCs in the bone microenvironment might promote the progression of osteosarcoma and protect tumor cells from drug-induced apoptosis through IL-6/STAT3 signaling. PMID:22743617

Tu, Bing; Du, Lin; Fan, Qi-Ming; Tang, Ze; Tang, Ting-Ting

2012-06-26

152

Innate Stat3-mediated induction of the antimicrobial protein Reg3? is required for host defense against MRSA pneumonia  

PubMed Central

Pulmonary Staphylococcus aureus (SA) infections are a public health concern and a major complication of hyper-IgE syndrome, caused by mutations in STAT3. In contrast to previous findings of skin infection, we observed that clearance of SA from the lung did not require T, B, or NK cells but did require Stat3 activation. Immunohistochemistry showed robust Stat3 phosphorylation in the lung epithelium. We identified that a critical Stat3 target gene in lung epithelium is Reg3g (regenerating islet-derived 3 ?), a gene which is highly expressed in gastrointestinal epithelium but whose role in pulmonary host defense is uncharacterized. Stat3 regulated Reg3g transcription through direct binding at the Reg3g promoter region. Recombinant Reg3? bound to SA and had both bacteriostatic and bactericidal activity in a dose-dependent fashion. Stat3 inhibition in vivo reduced Reg3g transcripts in the lung, and more importantly, recombinant Reg3? rescued mice from defective SA clearance. These findings reveal an antibacterial function for lung epithelium through Stat3-mediated induction of Reg3?.

Choi, Sun-Mi; McAleer, Jeremy P.; Zheng, Mingquan; Pociask, Derek A.; Kaplan, Mark H.; Qin, Shulin; Reinhart, Todd A.

2013-01-01

153

Suppression of epithelial apoptosis and delayed mammary gland involution in mice with a conditional knockout of Stat3  

PubMed Central

Mammary gland involution is characterized by extensive apoptosis of the epithelial cells. At the onset of involution, Stat3 is specifically activated. To address the function of this signaling molecule in mammary epithelial apoptosis, we have generated a conditional knockout of Stat3 using the Cre-lox recombination system. Following weaning, a decrease in apoptosis and a dramatic delay of involution occurred in Stat3 null mammary tissue. Involution is normally associated with a significant increase in IGFBP-5 levels. This was observed in control glands, but not in the absence of Stat3. IGFBP-5 has been suggested to induce apoptosis by sequestering IGF-1 to casein micelles, thereby inhibiting its survival function. Our findings suggest that IGFBP-5 is a direct or indirect target for Stat3 and its upregulation is essential to normal involution. No marked differences were seen in the regulation of Stat5, Bcl-xL, or Bax in the absence of Stat3. Precocious activation of Stat1 and increases in levels of p53 and p21 occurred and may act as compensatory mechanisms for the eventual initiation of involution observed in Stat3 null mammary glands. This is the first demonstration of the importance of a Stat factor in signaling the initiation of physiological apoptosis in vivo.

Chapman, Rachel S.; Lourenco, Paula C.; Tonner, Elizabeth; Flint, David J.; Selbert, Stefan; Takeda, Kiyoshi; Akira, Shizuo; Clarke, Alan R.; Watson, Christine J.

1999-01-01

154

IL-10-Mediated Tristetraprolin Induction is part of a feedback loop that controls Macrophage STAT3 activation and cytokine production1  

PubMed Central

In activated macrophages, the anti-inflammatory cytokine IL-10 inhibits expression of molecules that propagate inflammation in a manner that depends on transcription factor STAT3. Expression of IL-10 is regulated post-transcriptionally by the RNA-binding protein tristetraprolin (TTP), which destabilizes IL-10 mRNA in activated macrophages. Using LPS-activated bone marrow-derived murine macrophages, we demonstrate that TTP is a negative regulator of the IL-10/STAT3 anti-inflammatory response. LPS-stimulated TTP-deficient macrophages overproduced IL-10, contained increased amounts of activated STAT3, and showed reduced expression of inflammatory cytokines, including cytokines encoded by TTP-target mRNAs. Thus, in LPS-stimulated TTP-deficient macrophages, increased IL-10/STAT3 anti-inflammatory control was dominant over the mRNA-stabilization of specific TTP targets. The TTP gene promoter contains a conserved STAT3 binding site and IL-10 induces STAT3 recruitment to this site. Correspondingly, STAT3 was required for efficient IL-10-induced TTP expression. Hence, by inducing TTP expression, STAT3 activates a negative regulatory loop that controls the IL-10/STAT3 anti-inflammatory response.

Gaba, Anthony; Grivennikov, Sergei I.; Do, Mahn Vu; Stumpo, Deborah J.; Blackshear, Perry J.; Karin, Michael

2012-01-01

155

Cytokine-Induction of Tumor Necrosis Factor Receptor 2 (TNFR2) is Mediated by STAT3 in Colon Cancer Cells  

PubMed Central

The IL-6/STAT3 and TNF?/NF?B pathways are emerging as critical mediators of inflammation-associated colon cancer. TNFR2 expression is increased in inflammatory bowel diseases, the azoxymethane/dextran sodium sulfate (AOM/DSS) model of colitis-associated cancer, and by combined IL-6 and TNF?. The molecular mechanisms that regulate TNFR2 remain undefined. This study used colon cancer cell lines to test the hypothesis that IL-6 and TNF? induce TNFR2 via STAT3 and/or NF?B. Basal and IL-6 + TNF?-induced TNFR2 were decreased by pharmacological STAT3 inhibition. NF?B inhibition had little effect on IL-6 + TNF?-induced TNFR2, but did inhibit induction of endogenous IL-6 and TNFR2 in cells treated with TNF? alone. Chromatin immunoprecipitation (ChIP) revealed cooperative effects of IL-6 + TNF? to induce STAT3 binding to a -1578 STAT response element in the TNFR2 promoter, but no effect on NF?B binding to consensus sites. Constitutively active STAT3 was sufficient to induce TNFR2 expression. Over-expression of SOCS3, a cytokine-inducible STAT3 inhibitor, which reduces tumorigenesis in preclinical models of colitis-associated cancer, decreased cytokine-induced TNFR2 expression and STAT3 binding to the -1578 STAT response element. SOCS3 over-expression also decreased proliferation of colon cancer cells and dramatically decreased anchorage-independent growth of colon cancer cells, even cells over-expressing TNFR2. Collectively, these studies demonstrate that IL-6 and TNF?-induced TNFR2 expression in colon cancer cells is mediated primarily by STAT3, and provide evidence that TNFR2 may contribute to the tumor-promoting roles of STAT3.

Hamilton, Kathryn E.; Simmons, James G.; Ding, Shengli; Van Landeghem, Laurianne; Lund, P. Kay

2011-01-01

156

STAT3 expression correlates with prognosis of thymic epithelial tumors  

PubMed Central

Background More and more evidences demonstrate the significance of Signal transducers and activators of transcription 3(STAT3) in oncogenesis and tumor development. However, little systematic researches have been reported on the correlation between STAT3 and thymic epithelial tumor (TET). Methods Expression of STAT3 protein in 80 thymic epithelial tumors was detected by immunohistochemistry (IHC). The difference of STAT3 expression was compared by the ?2 test. Estimation of survival was calculated using the Kaplan-Meier method, and the statistical differences were analyzed using the Log-rank test. Results Positive expression of STAT3 protein was significantly associated with Masaoka staging and WHO histological classification (P?STAT3-positive tumors, compared with 4.55% in negative ones (P?STAT3-positive subjects (61.11%) than in negative ones (97.73%) (P?STAT3 (35.00%, 35.00%) was statistically lower than that of the negative ones (92.31%, 91.67%). Cox regression analysis revealed that positive expression of STAT3 protein was an independent prognostic factor of thymic epithelial tumors (HR?=?9.325, P?=?0.044). Conclusion Positive expression of STAT3 protein increases along with the rising malignant degree of thymic epithelial tumors. It may be considered as an independent prognostic parameter with good prognostic value to evaluate the possibility of recurrence/metastasis in patients with thymic epithelial tumor.

2013-01-01

157

Deficiency of Erbin induces resistance of cervical cancer cells to anoikis in a STAT3-dependent manner  

PubMed Central

Epithelial cell polarization and integration are essential to their function and loss of epithelial polarity and tissue architecture correlates with the development of aggressive tumors. Erbin is a basolateral membrane-associated protein. The roles of Erbin in establishing cell polarization and regulating cell adhesion have been suggested. Erbin is also a negative regulator in Ras-Raf-ERK (extracellular signal-regulated kinase) signaling pathway. However, the potential functions of Erbin in human cancer are basically unknown. In the present study, we show, for the first time, that loss of Erbin endows cervical cancer cells with resistance to anoikis both in vitro and in vivo and promotes the growth and metastasis of human cervical cancer xenografts in nude mice. We found that knockdown of Erbin induced the phosphorylation, nuclear translocation and transcriptional activities of signal transducer and activator of transcription factor 3 (STAT3) in cervical cancer cells. Overexpression of STAT3C or induction of endogenous STAT3 activation by interleukin (IL)-6 evidently inhibited anoikis of cervical cancer cells, whereas WP1066, a potent inhibitor of Janus-activated kinase 2 (Jak2)/STAT3, effectively blocked the effect of Erbin knockdown on cell survival under anchorage-independent conditions, indicating that loss of Erbin confers resistance of cervical cancer cells to anoikis in a STAT3-dependent manner. Interestingly, IL-6 induced STAT3 activation and Erbin expression simultaneously. Overexpression of STAT3C also significantly upregulated the level of Erbin, whereas the Jak2 inhibitor AG490 remarkably blocked not only STAT3 phosphorylation but also IL-6-induced Erbin expression. Knockdown of Erbin augmented the effects of IL-6 on STAT3 activation and anoikis resistance. In addition, by immunohistochemical analysis of Erbin expression, we demonstrate that the expression of Erbin is significantly decreased or even lost in cervical cancer tissues. These data reveal that Erbin is a novel negative regulator of STAT3, and the IL-6/STAT3/Erbin loop has a crucial role in cervical cancer progression and metastasis.

Hu, Y; Chen, H; Duan, C; Liu, D; Qian, L; Yang, Z; Guo, L; Song, L; Yu, M; Hu, M; Shi, M; Guo, N

2013-01-01

158

?-Tocotrienol is a novel inhibitor of constitutive and inducible STAT3 signalling pathway in human hepatocellular carcinoma: potential role as an antiproliferative, pro-apoptotic and chemosensitizing agent  

PubMed Central

BACKGROUND AND PURPOSE Activation of signal transducer and activator of transcription 3 (STAT3) play a critical role in the survival, proliferation, angiogenesis and chemoresistance of tumour cells. Thus, agents that suppress STAT3 phosphorylation have potential as cancer therapies. In the present study, we investigated whether the apoptotic, antiproliferative and chemosensitizing effects of ?-tocotrienol are associated with its ability to suppress STAT3 activation in hepatocellular carcinoma (HCC). EXPERIMENTAL APPROACH The effect of ?-tocotrienol on STAT3 activation, associated protein kinases and phosphatase, STAT3-regulated gene products, cellular proliferation and apoptosis in HCC cells was investigated. KEY RESULTS ?-Tocotrienol inhibited both the constitutive and inducible activation of STAT3 with minimum effect on STAT5. ?-Tocotrienol also inhibited the activation of Src, JAK1 and JAK2 implicated in STAT3 activation. Pervanadate reversed the ?-tocotrienol-induced down-regulation of STAT3, suggesting the involvement of a protein tyrosine phosphatase. Indeed, we found that ?-tocotrienol induced the expression of the tyrosine phosphatase SHP-1 and deletion of the SHP-1 gene by small interfering RNA abolished the ability of ?-tocotrienol to inhibit STAT3 activation. ?-Tocotrienol also down-regulated the expression of STAT3-regulated gene products, including cyclin D1, Bcl-2, Bcl-xL, survivin, Mcl-1 and vascular endothelial growth factor. Finally, ?-tocotrienol inhibited proliferation, induced apoptosis and significantly potentiated the apoptotic effects of chemotherapeutic drugs (paclitaxel and doxorubicin) used for the treatment of HCC. CONCLUSIONS AND IMPLICATIONS Overall, these results suggest that ?-tocotrienol is a novel blocker of the STAT3 activation pathway, with a potential role in future therapies for HCC and other cancers.

Rajendran, Peramaiyan; Li, Feng; Manu, Kanjoormana Aryan; Shanmugam, Muthu K; Loo, Ser Yue; Kumar, Alan Prem; Sethi, Gautam

2011-01-01

159

Mouse hematopoietic cell-targeted STAT3 deletion: stem/progenitor cell defects, mitochondrial dysfunction, ROS overproduction, and a rapid aging-like phenotype  

PubMed Central

Nuclear transcription factor Stat3 is important for proper regulation of hematopoietic stem cell (HSC) and hematopoietic progenitor cell (HPC) proliferation, survival, and cytokine signaling responses. A new, noncanonical role for Stat3 in mitochondrial function has been discovered recently. However, there is little information on the role(s) of mitochondrial Stat3 in HSC/HPC function, especially potential effects of Stat3/mitochondrial dysregulation in human diseases. We investigated hematopoietic cell–targeted deletion of the STAT3 gene in HSCs/HPCs with a focus on mitochondrial function. We found that STAT3?/? mice, which have a very shortened lifespan, dysfunctional/dysregulated mitochondrial function and excessive reactive oxygen species production in HSCs/HPCs that coincides with pronounced defects in function. These animals have a blood phenotype with similarities to premature aging and to human diseases of myelodysplastic syndrome and myeloproliferative neoplasms such as erythroid dysplasia, anemia, excessive myeloproliferation, and lymphomyeloid ratio shifts. We show herein that the lifespan of STAT3?/? animals is lengthened by treatment with a reactive oxygen species scavenger, which lessened the severity of the blood phenotype. These data suggest a need for more detailed studies of role(s) of Stat3 in HSC/HPC mitochondrial function in human diseases and raise the idea that mitochondrial Stat3 could be used as a potential therapeutic target.

Messina-Graham, Steven; Moh, Akira; Cooper, Scott; Hangoc, Giao; Fu, Xin-Yuan; Broxmeyer, Hal E.

2012-01-01

160

Benzoxathiol derivative BOT-4-one suppresses L540 lymphoma cell survival and proliferation via inhibition of JAK3/STAT3 signaling  

PubMed Central

Persistently activated JAK/STAT3 signaling pathway plays a pivotal role in various human cancers including major carcinomas and hematologic tumors, and is implicated in cancer cell survival and proliferation. Therefore, inhibition of JAK/STAT3 signaling may be a clinical application in cancer therapy. Here, we report that 2-cyclohexylimino-6-methyl-6,7-dihydro-5H-benzo [1,3]oxathiol-4-one (BOT-4-one), a small molecule inhibitor of JAK/STAT3 signaling, induces apoptosis through inhibition of STAT3 activation. BOT-4-one suppressed cytokine (upd)-induced tyrosine phosphorylation and transcriptional activity of STAT92E, the sole Drosophila STAT homolog. Consequently, BOT-4-one significantly inhibited STAT3 tyrosine phosphorylation and expression of STAT3 downstream target gene SOCS3 in various human cancer cell lines, and its effect was more potent in JAK3-activated Hodgkin's lymphoma cell line than in JAK2-activated breast cancer and prostate cancer cell lines. In addition, BOT-4-one-treated Hodgkin's lymphoma cells showed decreased cell survival and proliferation by inducing apoptosis through down-regulation of STAT3 downstream target anti-apoptotic gene expression. These results suggest that BOT-4-one is a novel small molecule inhibitor of JAK3/STAT3 signaling and may have therapeutic potential in the treatment of human cancers harboring aberrant JAK3/STAT3 signaling, specifically Hodgkin's lymphoma.

Kim, Byung Hak; Min, Yun Sook; Choi, Jung Sook; Baeg, Gyeong-Hun; Kim, Youngsoo; Shin, Jong Wook; Kim, Tae-Yoon

2011-01-01

161

Protective Role of STAT3 in NMDA and Glutamate-Induced Neuronal Death: Negative Regulatory Effect of SOCS3  

PubMed Central

The present study investigates the involvement of the IL-6 family of cytokines, activation of the transcription factor Signal Transducer and Activator of Transcription-3 (STAT3), and the role of Suppressor Of Cytokine Signaling-3 (SOCS3) in regulating excitotoxic neuronal death in vitro. Biochemical evidence demonstrates that in primary cortical neurons and SH-SY5Y neuroblastoma cells, IL-6 cytokine family members, OSM and IL-6 plus the soluble IL-6R (IL-6/R), prevent NMDA and glutamate-induced neuronal toxicity. As well, OSM and IL-6/R induce tyrosine and serine phosphorylation of STAT3 in primary cortical neurons and SH-SY5Y cells. Studies using Pyridine 6 (P6), a pan-JAK inhibitor, demonstrate that the protective effect of OSM and IL-6/R on neuronal death is mediated by the JAK/STAT3 signaling pathway. In parallel to STAT3 phosphorylation, OSM and IL-6/R induce SOCS3 expression at the mRNA and protein level. P6 treatment inhibits SOCS3 expression, indicating that STAT3 is required for OSM and IL-6/R-induced SOCS3 expression. Lentiviral delivery of SOCS3, an inhibitor of STAT3 signaling, into primary neurons and SH-SY5Y cells inhibits OSM and IL-6/R-induced phosphorylation of STAT3, and also reverses the protective effect of OSM and IL-6/R on NMDA and glutamate-induced neurotoxicity in primary cortical neurons. In addition, treatment with IL-6 cytokines increases expression of the anti-apoptotic protein Bcl-xL and induces activation of the Akt signaling pathway, which are also negatively regulated by SOCS3 expression. Thus, IL-6/R and OSM-induced SOCS3 expression may be an important factor limiting the neuroprotective effects of activated STAT3 against NMDA and glutamate-induced neurotoxicity.

Park, Keun W.; Nozell, Susan E.; Benveniste, Etty N.

2012-01-01

162

Stat3 isoforms, alpha and beta, demonstrate distinct intracellular dynamics with prolonged nuclear retention of Stat3beta mapping to its unique C-terminal end.  

PubMed

Two isoforms of Stat3 (signal transducer and activator of transcription 3) are expressed in cells, alpha (p92) and beta (p83), both derived from a single gene by alternative mRNA splicing. The 55-residue C-terminal transactivation domain of Stat3alpha is deleted in Stat3beta and replaced by seven unique C-terminal residues (CT7) whose function remains uncertain. We subcloned the open reading frames of Stat3alpha and Stat3beta into the C terminus of green fluorescent protein (GFP). Fluorescent microscopic analysis of HEK293T cells transiently transfected with GFP-Stat3alpha or GFP-Stat3beta revealed similar kinetics and cytokine concentration dependence of nuclear accumulation; these findings were confirmed by high throughput microscope analysis of murine embryonic fibroblasts that lacked endogenous Stat3 but stably expressed either GFP-Stat3alpha or GFP-Stat3beta. However, although time to half-maximal cytoplasmic reaccumulation after cytokine withdrawal was 15 min for GFP-Stat3alpha, it was >180 min for GFP-Stat3beta. Furthermore, although the intranuclear mobility of GFP-Stat3alpha was rapid and increased with cytokine stimulation, the intranuclear mobility of GFP-Stat3beta in unstimulated cells was slower than that of GFP-Stat3alpha in unstimulated cells and was slowed further following cytokine stimulation. Deletion of the unique CT7 domain from Stat3beta eliminated prolonged nuclear retention but did not alter its intranuclear mobility. Thus, Stat3alpha and Stat3beta have distinct intracellular dynamics, with Stat3beta exhibiting prolonged nuclear retention and reduced intranuclear mobility especially following ligand stimulation. Prolonged nuclear retention, but not reduced intranuclear mobility, mapped to the CT7 domain of Stat3beta. PMID:17855361

Huang, Ying; Qiu, Jihui; Dong, Shuo; Redell, Michele S; Poli, Valeria; Mancini, Michael A; Tweardy, David J

2007-09-12

163

STAT3-mediated astrogliosis protects myelin development in neonatal brain injury  

PubMed Central

Objective Pathological findings in neonatal brain injury associated with preterm birth include focal and/or diffuse white matter injury (WMI). Despite the heterogeneous nature of this condition, reactive astrogliosis and microgliosis are frequently observed. Thus, molecular mechanisms by which glia activation contribute to WMI were investigated. Methods Postmortem brains of neonatal brain injury were investigated in order to identify molecular features of reactive astrocytes. The contribution of astrogliosis to WMI was further tested in a mouse model in genetically-engineered mice. Results Activated STAT3 signaling in reactive astrocytes was found to be a common feature in postmortem brains of neonatal brain injury. In a mouse model of neonatal WMI, conditional deletion of STAT3 in astrocytes resulted in exacerbated WMI, which was associated with delayed maturation of oligodendrocytes. Mechanistically, the delay occurred in association with over-expression of TGF?-1 in microglia, which in healthy controls, decreased with myelin maturation in age-dependent manner. TGF?-1 directly and dose-dependently inhibited the maturation of purified oligodendrocyte progenitors, and pharmacological inhibition of TGF?-1 signaling in vivo reversed the delay in myelin development. Factors secreted from STAT3-deficient astrocytes promoted elevated TGF?-1 production in cultured microglia compared to wild type astrocytes. Interpretation These results suggest that myelin development is regulated by a mechanism involving cross-talk between microglia and oligodendrocyte progenitors. Reactive astrocytes may modify this signaling in STAT3-dependent manner, preventing the pathological expression of TGF?-1 in microglia and the impairment of oligodendrocyte maturation.

Nobuta, Hiroko; Ghiani, Cristina A.; Paez, Pablo M.; Spreuer, Vilma; Dong, Hongmei; Korsak, Rose A.; Manukyan, Armine; Li, Jiaxi; Vinters, Harry V.; Huang, Eric J.; Rowitch, David H.; Sofroniew, Michael V.; Campagnoni, Anthony T.; de Vellis, Jean; Waschek, James A.

2012-01-01

164

Lipopolysaccharide-induced interleukin-6 production is controlled by glycogen synthase kinase-3 and STAT3 in the brain  

PubMed Central

Background Septic shock is a prevalent condition that, when not lethal, often causes disturbances in cognition, mood, and behavior, particularly due to central actions of the inflammatory cytokine interleukin-6 (IL-6). To identify potential targets to control brain IL-6, we tested if IL-6 produced by glia is regulated by signal transducer and activator of transcription-3 (STAT3) and glycogen synthase kinase-3 (GSK3). Methods Lipopolysaccharide (LPS) was used to induce inflammatory responses in mice or cultured primary glia. IL-6 was measured by ELISA and other inflammatory molecules were measured using an array. Results Mouse brain IL-6 levels increased after central, as well as peripheral, LPS administration, consistent with glia producing a portion of brain IL-6. STAT3 in the brain was activated after peripheral or central LPS administration, and in LPS-stimulated cultured primary glia. Inhibition of STAT3 expression, function, or activation reduced by ~80% IL-6 production by primary glia, demonstrating the dependence on active STAT3. GSK3 promotes STAT3 activation, and array analysis of inflammatory molecules produced by LPS-stimulated primary glia demonstrated that IL-6 was the cytokine most diminished (>90%) by GSK3 inhibition. Inhibition of GSK3, and knockdown of GSK3?, not GSK3?, greatly inhibited IL-6 production by LPS-stimulated primary glia. Conversely, expression of active STAT3 and active GSK3 promoted IL-6 production. In vivo inhibition of GSK3 reduced serum and brain IL-6 levels, brain STAT3 activation, and GFAP upregulation following LPS administration. Conclusion STAT3 and GSK3 cooperatively promote neuroinflammation, providing novel targets for anti-inflammatory intervention.

Beurel, Eleonore; Jope, Richard S

2009-01-01

165

Significance and relationship between Cripto-1 and p-STAT3 expression in gastric cancer and precancerous lesions  

PubMed Central

AIM: To explore the relationship between Cripto-1 (CR-1) and tyrosine phosphorylation STAT3 (p-STAT3) expressions in gastric cancer (GC) and gastric carcinogensis and metastasis. METHODS: The PV9000 immunohistochemical method was used to detect the expression of CR-1 and p-STAT3 in 178 cases of GC, 95 matched normal gastric mucosa, 40 chronic atrophic gastritis (CAG), 48 intestinal metaplasia (IM) and 25 dysplasia (DYS). RESULTS: The positive rates of CR-1 and p-STAT3 expression were significantly higher in CAG (65.0% and 60.0%), in IM (83.3% and 77.1%), DYS (80.0% and 68%) and GC (71.3% and 60.1%) than in normal gastric mucosa (43.2% and 41.1%, P < 0.05), respectively. The expressions of CR-1 and p-STAT3 (78.3% and 66.7%) were significantly higher in GC with lymph node metastasis than in those without metastasis (53.1% and 42.9%, P < 0.05). CR-1 expression was also related to histological and Lauren’s types of GC (P < 0.001). Furthermore, there was positive relationship between CR-1 and p-STAT3 expressions in GC (rk = 0.189, P = 0.002). CONCLUSION: The up-regulation of CR-1 and p-STAT3 may play important roles in gastric carcinogenesis and lymph node metastasis. CR-1 and p-STAT3 expression in GC was positively correlated, and the relevant molecular mechanism requires further investigations.

Zhang, Jian-Guo; Zhao, Jing; Xin, Yan

2010-01-01

166

Dimethylfumarate Suppresses Adipogenic Differentiation in 3T3-L1 Preadipocytes through Inhibition of STAT3 Activity  

PubMed Central

The excessive accumulation of adipocytes contributes to the development of obesity and obesity-related diseases. The interactions of several transcription factors, such as C/EBP?, PPAR?, C/EBP?, Nrf2, and STAT3, are required for adipogenic differentiation. Dimethylfumarate (DMF), an immune modulator and antioxidant, may function as an inhibitor of STAT3 and an activator of Nrf2. This study examined whether DMF inhibits adipogenic differentiation of 3T3-L1 preadipocytes by inhibiting STAT3 or activating Nrf2. DMF suppressed 3T3-L1 preadipocyte differentiation to mature adipocytes in a dose-dependent manner as determined by Oil Red O staining. The mRNA and protein levels of adipogenic genes, including C/EBP?, C/EBP?, PPAR?, SREBP-1c, FAS, and aP2, were significantly lower in DMF-treated 3T3-L1 preadipocytes. Suppression of adipogenic differentiation by DMF treatment resulted primarily from inhibition of the early stages of differentiation. DMF inhibits clonal expansion during adipogenic differentiation through induction of a G1 cell cycle arrest. Additionally, DMF regulates cell cycle-related proteins, such as p21, pRb, and cyclin D. DMF treatment markedly inhibited differentiation medium-induced STAT3 phosphorylation and inhibited STAT3 transcriptional activation of a reporter construct composed of four synthetic STAT3-response elements. Moreover, inhibition of endogenous Nrf2 activity using a dominant negative Nrf2 did not abolish the DMF-induced inhibition of adipogenic differentiation of 3T3-L1 preadipocytes. In summary, DMF is a negative regulator of adipogenic differentiation based on its regulation of adipogenic transcription factors and cell cycle proteins. This negative regulation by DMF is mediated by STAT3 inhibition, but is unlikely to involve Nrf2 activation.

Go, Younghoon; Oh, Chang Joo; Jeoung, Nam Ho; Park, Keun-Gyu; Lee, In-Kyu

2013-01-01

167

Dimethylfumarate suppresses adipogenic differentiation in 3T3-L1 preadipocytes through inhibition of STAT3 activity.  

PubMed

The excessive accumulation of adipocytes contributes to the development of obesity and obesity-related diseases. The interactions of several transcription factors, such as C/EBP?, PPAR?, C/EBP?, Nrf2, and STAT3, are required for adipogenic differentiation. Dimethylfumarate (DMF), an immune modulator and antioxidant, may function as an inhibitor of STAT3 and an activator of Nrf2. This study examined whether DMF inhibits adipogenic differentiation of 3T3-L1 preadipocytes by inhibiting STAT3 or activating Nrf2. DMF suppressed 3T3-L1 preadipocyte differentiation to mature adipocytes in a dose-dependent manner as determined by Oil Red O staining. The mRNA and protein levels of adipogenic genes, including C/EBP?, C/EBP?, PPAR?, SREBP-1c, FAS, and aP2, were significantly lower in DMF-treated 3T3-L1 preadipocytes. Suppression of adipogenic differentiation by DMF treatment resulted primarily from inhibition of the early stages of differentiation. DMF inhibits clonal expansion during adipogenic differentiation through induction of a G1 cell cycle arrest. Additionally, DMF regulates cell cycle-related proteins, such as p21, pRb, and cyclin D. DMF treatment markedly inhibited differentiation medium-induced STAT3 phosphorylation and inhibited STAT3 transcriptional activation of a reporter construct composed of four synthetic STAT3-response elements. Moreover, inhibition of endogenous Nrf2 activity using a dominant negative Nrf2 did not abolish the DMF-induced inhibition of adipogenic differentiation of 3T3-L1 preadipocytes. In summary, DMF is a negative regulator of adipogenic differentiation based on its regulation of adipogenic transcription factors and cell cycle proteins. This negative regulation by DMF is mediated by STAT3 inhibition, but is unlikely to involve Nrf2 activation. PMID:23637829

Kang, Hyeon-Ji; Seo, Hyun-Ae; Go, Younghoon; Oh, Chang Joo; Jeoung, Nam Ho; Park, Keun-Gyu; Lee, In-Kyu

2013-04-18

168

Chrysanthemum indicum L. extract induces apoptosis through suppression of constitutive STAT3 activation in human prostate cancer DU145 cells.  

PubMed

Chrysanthemum indicum L. has been shown to possess antiinflammatory and anticancer activities, but its molecular targets/pathways are not yet fully understood in tumor cells. In the present study, the potential effects of C. indicum on signal transducer and activator of transcription 3 (STAT3) signaling pathway in different tumor cells were examined. The solvent fractions (hexane, CH?Cl?, EtOAc, and BuOH,) were obtained from a crude extract (80% EOH extract) of C. indicum. The methylene chloride fraction of C. indicum (MCI) exhibited strong cytotoxic activity as compared with the other fractions and clearly suppressed constitutive STAT3 activation against both DU145 and U266 cells, but not MDA-MB-231 cells. The suppression of constitutive STAT3 activation by MCI is associated with blocking upstream JAK1 and JAK2, but not Src. MCI downregulated the expression of STAT3-regulated gene products; this is correlated with the accumulation of the cell cycle at sub-G1 phase, the induction of caspase-3 activation, and apoptosis. Moreover, the major components of the MCI were bioactive compounds such as sudachitin, hesperetin, chrysoeriol, and acacetin. Sudachitin, chrysoeriol, and acacetin also exerted significantly cytotoxicity, clearly suppressed constitutive STAT3 activation, and induced apoptosis, although hesperetin did not show any significant effect in DU145 cells. Overall, our results demonstrate that MCI could induce apoptosis through inhibition of the JAK1/2 and STAT3 signaling pathways. PMID:22438130

Kim, Chulwon; Kim, Moo-Chang; Kim, Sung-Moo; Nam, Dongwoo; Choi, Seung-Hoon; Kim, Sung-Hoon; Ahn, Kyoo Seok; Lee, Eun Ha; Jung, Sang Hoon; Ahn, Kwang Seok

2012-03-22

169

Signal transducer and activator of transcription 3 (STAT3) degradation by proteasome controls a developmental switch in neurotrophin dependence.  

PubMed

Neonatal brains develop through a program that eliminates about half of the neurons. During this period, neurons depend on neurotrophins for their survival. Recently, we reported that, at the conclusion of the naturally occurring death period, neurons become neurotrophin-independent and, further, that this developmental switch is achieved by the emergence of a second survival pathway mediated by signal transducer and activator of transcription 3 (STAT3). Here I show that calcineurin plays a key role in controlling the developmental switch in mouse hippocampal neurons. Calcineurin promotes the degradation of STAT3 via the ubiquitin-proteasome pathway. Inhibition of calcineurin acutely increases total levels of STAT3 as well as its activated forms, resulting in decreased levels of the tumor suppressor p53 and its proapoptotic target, Bax. In vivo and in vitro, calcineurin regulates levels of STAT3 and neurotrophin dependence. TMF/ARA 160 (TATA element modulatory factor/androgen receptor co-activator 160), the key mediator of STAT3 ubiquitination, is required for calcineurin-dependent STAT3 degradation. Thus, these results show that the ubiquitin-proteasome pathway controls the critical developmental switch of neurotrophin dependence in the newborn hippocampus. PMID:23733189

Murase, Sachiko

2013-06-03

170

Physical and functional interactions between Daxx and STAT3  

Microsoft Academic Search

Signal transducer and activator of transcription 3 (STAT3) play key roles in the intracellular signaling pathways of the interleukin (IL)-6 family of cytokines, which exhibit a diverse set of cellular responses, including cell proliferation and differentiation. Dysregulated IL-6\\/STAT3 signaling is involved in the pathogenesis of several diseases, for example autoimmune diseases and tumors. Type I interferon (IFN) induces the expression

R Muromoto; K Nakao; T Watanabe; N Sato; Y Sekine; K Sugiyama; K Oritani; K Shimoda; T Matsuda

2006-01-01

171

Binding of the heterogeneous ribonucleoprotein K (hnRNP K) to the Epstein-Barr virus nuclear antigen 2 (EBNA2) enhances viral LMP2A expression.  

PubMed

The Epstein-Barr Virus (EBV) -encoded EBNA2 protein, which is essential for the in vitro transformation of B-lymphocytes, interferes with cellular processes by binding to proteins via conserved sequence motifs. Its Arginine-Glycine (RG) repeat element contains either symmetrically or asymmetrically di-methylated arginine residues (SDMA and ADMA, respectively). EBNA2 binds via its SDMA-modified RG-repeat to the survival motor neurons protein (SMN) and via the ADMA-RG-repeat to the NP9 protein of the human endogenous retrovirus K (HERV-K (HML-2) Type 1). The hypothesis of this work was that the methylated RG-repeat mimics an epitope shared with cellular proteins that is used for interaction with target structures. With monoclonal antibodies against the modified RG-repeat, we indeed identified cellular homologues that apparently have the same surface structure as methylated EBNA2. With the SDMA-specific antibodies, we precipitated the Sm protein D3 (SmD3) which, like EBNA2, binds via its SDMA-modified RG-repeat to SMN. With the ADMA-specific antibodies, we precipitated the heterogeneous ribonucleoprotein K (hnRNP K). Specific binding of the ADMA- antibody to hnRNP K was demonstrated using E. coli expressed/ADMA-methylated hnRNP K. In addition, we show that EBNA2 and hnRNP K form a complex in EBV- infected B-cells. Finally, hnRNP K, when co-expressed with EBNA2, strongly enhances viral latent membrane protein 2A (LMP2A) expression by an unknown mechanism as we did not detect a direct association of hnRNP K with DNA-bound EBNA2 in gel shift experiments. Our data support the notion that the methylated surface of EBNA2 mimics the surface structure of cellular proteins to interfere with or co-opt their functional properties. PMID:22879910

Gross, Henrik; Hennard, Christine; Masouris, Ilias; Cassel, Christian; Barth, Stephanie; Stober-Grässer, Ute; Mamiani, Alfredo; Moritz, Bodo; Ostareck, Dirk; Ostareck-Lederer, Antje; Neuenkirchen, Nils; Fischer, Utz; Deng, Wen; Leonhardt, Heinrich; Noessner, Elfriede; Kremmer, Elisabeth; Grässer, Friedrich A

2012-08-03

172

Binding of the Heterogeneous Ribonucleoprotein K (hnRNP K) to the Epstein-Barr Virus Nuclear Antigen 2 (EBNA2) Enhances Viral LMP2A Expression  

PubMed Central

The Epstein-Barr Virus (EBV) -encoded EBNA2 protein, which is essential for the in vitro transformation of B-lymphocytes, interferes with cellular processes by binding to proteins via conserved sequence motifs. Its Arginine-Glycine (RG) repeat element contains either symmetrically or asymmetrically di-methylated arginine residues (SDMA and ADMA, respectively). EBNA2 binds via its SDMA-modified RG-repeat to the survival motor neurons protein (SMN) and via the ADMA-RG-repeat to the NP9 protein of the human endogenous retrovirus K (HERV-K (HML-2) Type 1). The hypothesis of this work was that the methylated RG-repeat mimics an epitope shared with cellular proteins that is used for interaction with target structures. With monoclonal antibodies against the modified RG-repeat, we indeed identified cellular homologues that apparently have the same surface structure as methylated EBNA2. With the SDMA-specific antibodies, we precipitated the Sm protein D3 (SmD3) which, like EBNA2, binds via its SDMA-modified RG-repeat to SMN. With the ADMA-specific antibodies, we precipitated the heterogeneous ribonucleoprotein K (hnRNP K). Specific binding of the ADMA- antibody to hnRNP K was demonstrated using E. coli expressed/ADMA-methylated hnRNP K. In addition, we show that EBNA2 and hnRNP K form a complex in EBV- infected B-cells. Finally, hnRNP K, when co-expressed with EBNA2, strongly enhances viral latent membrane protein 2A (LMP2A) expression by an unknown mechanism as we did not detect a direct association of hnRNP K with DNA-bound EBNA2 in gel shift experiments. Our data support the notion that the methylated surface of EBNA2 mimics the surface structure of cellular proteins to interfere with or co-opt their functional properties.

Gross, Henrik; Hennard, Christine; Masouris, Ilias; Cassel, Christian; Barth, Stephanie; Stober-Grasser, Ute; Mamiani, Alfredo; Moritz, Bodo; Ostareck, Dirk; Ostareck-Lederer, Antje; Neuenkirchen, Nils; Fischer, Utz; Deng, Wen; Leonhardt, Heinrich; Noessner, Elfriede; Kremmer, Elisabeth; Grasser, Friedrich A.

2012-01-01

173

Phosphorylation of signal transducer and activator of transcription 3 (STAT3) correlates with Her-2 status, carbonic anhydrase 9 expression and prognosis in esophageal cancer.  

PubMed

The signal-transcriptional factor signal transducer and activator of transcription (STAT3) is overexpressed in various tumor entities and promotes tumor progression and metastasis. The tyrosine-kinase receptor Her-2 was shown to activate STAT3-expression and is overexpressed in a subtype of esophageal cancer (EC). STAT3 also regulates carbonic anhydrase IX (CAIX) expression in vivo, promoting IL-6-dependent tumor invasion.Tumor-tissue from 324 patients with EC and 45 patients with precursor lesions were analyzed for the expressions of tyrosine-705 phosphorylated STAT3 (pSTAT3). Data on Her-2-status and CAIX expression were available from previous studies. pSTAT3 was overexpressed in 40 % of adenocarcinomas (AC) and 50 % of squamous cell carcinomas of the esophagus and was associated with worse overall (OS) (p = 0.001) and disease free survival (DFS) (p = 0.001). In Barrett's mucosa without/low-grade dysplasia, pSTAT3 was expressed in 14 % compared to 27 % in patients with high-grade dysplasia (p = 0.018). A significant association between Her-2 and pSTAT3 was found in ACs (p = 0.013), showing that patients with tumors expressing both proteins have significantly worse OS (p = 0.0039) and DFS (p = 0.029). One hundred-fifty (46.3 %) cancer cases were considered as positive for CAIX expression, and a strong correlation between pSTAT3 and CAIX expression was seen (p < 0.001). pSTAT3 plays an important role in the development of AC. Expression of pSTAT3 correlates with Her-2 status and CAIX expression and is associated with tumor progression and worse outcome, offering expectantly therapeutical implications. PMID:22484976

Schoppmann, Sebastian F; Jesch, Bettina; Friedrich, Julia; Jomrich, Gerd; Maroske, Florian; Birner, Peter

2012-04-08

174

In vivo activation of STAT3 in cutaneous T-cell lymphoma. Evidence for an antiapoptotic function of STAT3  

Microsoft Academic Search

A characteristic feature of neoplastic transformation is a perpetual activation of oncogenic proteins. Here, we studied signal transducers and activators of transcription (STAT) in patients with mycosis fungoides (MF)\\/cutaneous T-cell lymphoma (CTCL). Malignant lymphocytes in dermal infiltrates of CTCL tumors showed frequent and intense nuclear staining with anti-PY-STAT3 antibody, indicating a constitutive activation of STAT3 in vivo in tumor stages.

V H Sommer; O J Clemmensen; O Nielsen; M Wasik; P Lovato; C Brender; K W Eriksen; A Woetmann; C G Kaestel; M H Nissen; C Ropke; S Skov; N Ødum

2004-01-01

175

Essential role of STAT3 in postnatal survival and growth revealed by mice lacking STAT3 serine 727 phosphorylation.  

PubMed

A large number of extracellular polypeptides bound to their cognate receptors activate the transcription factor STAT3 by phosphorylation of tyrosine 705. Supplemental activation occurs when serine 727 is also phosphorylated. STAT3 deletion in mice leads to embryonic lethality. We have produced mice with alanine substituted for serine 727 in STAT3 (the SA allele) to examine the function of serine 727 phosphorylation in vivo. Embryonic fibroblasts from SA/SA mice had approximately 50% of the transcriptional response of wild-type cells. However, SA/SA mice were viable and grossly normal. STAT3 wild-type/null (+/-) animals were also normal and were interbred with SA/SA mice to study SA/- mice. The SA/- mice progressed through gestation, showing 10 to 15% reduced birth weight, three-fourths died soon after birth, and the SA/- survivors reached only 50 to 60% of normal size at 1 week of age. The lethality and decreased growth were accompanied by altered insulin-like growth factor 1 (IGF-1) levels in serum, establishing a role for the STAT3 serine phosphorylation acting through IGF-1 in embryonic and perinatal growth. The SA/- survivors have decreased thymocyte number associated with increased apoptosis, but unexpectedly normal STAT3-dependent liver acute phase response. These animals offer the opportunity to study defined reductions in the transcriptional capacity of a widely used signaling pathway. PMID:14673173

Shen, Yuhong; Schlessinger, Karni; Zhu, Xuejun; Meffre, Eric; Quimby, Fred; Levy, David E; Darnell, J E

2004-01-01

176

Novel CD47: SIRP? Dependent Mechanism for the Activation of STAT3 in Antigen-Presenting Cell.  

PubMed

Cell surface CD47 interacts with its receptor, signal-regulatory-protein ? (SIRP?) that is expressed predominantly on macrophages, to inhibit phagocytosis of normal, healthy cells. This "don't eat me" signal is mediated through tyrosine phosphorylation of SIRP? at the cytoplasmic ITIM motifs and the recruitment of the phosphatase, SHP-1. We previously revealed a novel mechanism for the activation of the STAT3 pathway and the regulation of human APC maturation and function that is based on cell:cell interaction. In this study, we present evidence supporting the notion that CD47:SIRP? serves as a cell surface receptor: ligand pair involved in this contact-dependent STAT3 activation and regulation of APC maturation. We show that upon co-culturing APC with various primary and tumor cell lines STAT3 phosphorylation and IL-10 expression are induced, and such regulation could be suppressed by specific CD47 siRNAs and shRNAs. Significantly, >50% reduction in CD47 expression abolished the contact-dependent inhibition of T cell activation. Furthermore, co-immunoprecipitation experiments revealed a physical association between SIRP? and STAT3. Thus, we suggest that in addition to signaling through the ITIM-SHP-1 complex that transmit an anti-phagocytotic, CD47:SIRP? also triggers STAT3 signaling that is linked to an immature APC phenotype and peripheral tolerance under steady state and pathological conditions. PMID:24073274

Toledano, Natan; Gur-Wahnon, Devorah; Ben-Yehuda, Adi; Rachmilewitz, Jacob

2013-09-20

177

Novel CD47: SIRP? Dependent Mechanism for the Activation of STAT3 in Antigen-Presenting Cell  

PubMed Central

Cell surface CD47 interacts with its receptor, signal-regulatory-protein ? (SIRP?) that is expressed predominantly on macrophages, to inhibit phagocytosis of normal, healthy cells. This “don’t eat me” signal is mediated through tyrosine phosphorylation of SIRP? at the cytoplasmic ITIM motifs and the recruitment of the phosphatase, SHP-1. We previously revealed a novel mechanism for the activation of the STAT3 pathway and the regulation of human APC maturation and function that is based on cell:cell interaction. In this study, we present evidence supporting the notion that CD47:SIRP? serves as a cell surface receptor: ligand pair involved in this contact-dependent STAT3 activation and regulation of APC maturation. We show that upon co-culturing APC with various primary and tumor cell lines STAT3 phosphorylation and IL-10 expression are induced, and such regulation could be suppressed by specific CD47 siRNAs and shRNAs. Significantly, >50% reduction in CD47 expression abolished the contact-dependent inhibition of T cell activation. Furthermore, co-immunoprecipitation experiments revealed a physical association between SIRP? and STAT3. Thus, we suggest that in addition to signaling through the ITIM-SHP-1 complex that transmit an anti-phagocytotic, CD47:SIRP? also triggers STAT3 signaling that is linked to an immature APC phenotype and peripheral tolerance under steady state and pathological conditions.

Toledano, Natan; Gur-Wahnon, Devorah; Ben-Yehuda, Adi; Rachmilewitz, Jacob

2013-01-01

178

Pterostilbene exerts antitumor activity against human osteosarcoma cells by inhibiting the JAK2/STAT3 signaling pathway.  

PubMed

Osteosarcoma is a high-grade malignant bone tumor. Pterostilbene (PTE) is a natural, dimethylated analog of resveratrol with higher bioavailability. While PTE has been shown to have potent antitumor activity against various types of cancer, the molecular mechanisms underlying the effects of PTE remain largely unknown. The Janus kinase 2/Signal Transducer and Activator of Transcription 3 (JAK2/STAT3) signaling pathway plays a crucial role in tumorigenesis and immune development. In this study, we assessed the antitumor activity of PTE against human osteosarcoma cells and explored the role of JAK2/STAT3 and apoptosis-related signaling pathways on the activity of PTE. PTE treatment resulted in a dose- and time-dependent inhibition of osteosarcoma cell viability. Additionally, PTE exhibited strong antitumor activity, as evidenced not only by reductions in tumor cell adhesion, migration and mitochondrial membrane potential (MMP) but also by increases in the apoptotic index, reactive oxygen species (ROS) and several biochemical parameters. Furthermore, PTE treatment directly inhibited the phosphorylation of JAK2 at Tyr 1007 and the downstream activation of STAT3. PTE also down-regulated the expression of STAT3 target genes, including the anti-apoptotic proteins Bcl-xL and Mcl-1, leading to the up-regulation of mitochondrial apoptosis pathway-related proteins (Bax, Bak, cytosolic Cytochrome c, and cleaved Caspase3) and cyclin-dependent kinase inhibitors such as p21 and p27. PTE, used in combination with a known JAK2/STAT3 inhibitor, AG490, further decreased the viability of osteosarcoma cells. Taken together, PTE is a potent inhibitor of osteosarcoma cell growth that targets the JAK2/STAT3 signaling pathway. These data suggest that inhibition of JAK2/STAT3 signaling is a novel mechanism of action for PTE during therapeutic intervention in osteosarcoma cancers. PMID:23313376

Liu, Yanwu; Wang, Lingjuan; Wu, Yaoping; Lv, Changwei; Li, Xinkui; Cao, Xiaorui; Yang, Min; Feng, Dapeng; Luo, Zhuojing

2013-01-08

179

Gprc5a deletion enhances the transformed phenotype in normal and malignant lung epithelial cells by eliciting persistent Stat3 signaling induced by autocrine Lif  

PubMed Central

Signal transduction and activator of transcription 3 (Stat3) is activated by cytokines and growth factors in lung cancers and regulates expression of genes implicated in cell growth, survival, and transformation. Previously, we found that mice with a deletion of the G protein-coupled receptor, family C, group 5, member a (Gprc5a) gene develop lung tumors indicating that Gprc5a is a tumor suppressor. Herein, we show that epithelial cells from Gprc5a knockout mouse lung (Gprc5a?/? cells) survive better in vitro in medium deprived of exogenous growth factors and form more colonies in semi-solid medium than their counterparts from wildtype mice (Gprc5a+/+ cells). Stat3 Tyrosine 705 phosphorylation and expression of several Stat3-regulated anti-apoptotic genes were higher in Gprc5a?/? than in Gprc5a+/+ cells. Both cell types secreted Leukemia inhibitory factor (Lif), however, whereas Stat3 activation was persistent in Gprc5a?/? cells it was transient in Gprc5a+/+ cells. Lung adenocarcinoma cells isolated from Gprc5a?/? mice also exhibited autocrine Lif-mediated Stat3 activation. The level of Socs3, the endogenous Stat3 inhibitory protein, was higher in Gprc5a+/+ than in Gprc5a?/? cells and expression of the tumor suppressor stabilized Socs3. Inhibition of Stat3 signaling in Gprc5a?/? normal and cancer cells by the Jak2 inhibitor AG490 or by a dominant negative Stat3(Y705F) increased starvation-induced apoptosis and inhibited colony formation. These results demonstrate that persistent Stat3 activation is important for the survival and transformation of Gprc5a?/? lung cells and suggest that the tumor suppressive effects of Gprc5a are mediated, at least in part, by inhibition of Stat3 signaling via Socs3 stabilization.

Chen, Yulong; Deng, Jiong; Fujimoto, Junya; Kadara, Humam; Men, Taoyan; Lotan, Dafna; Lotan, Reuben

2010-01-01

180

Transcription Factor STAT3 in Leptin Target Neurons of the Rat Hypothalamus  

Microsoft Academic Search

Leptin is an adipose tissue-derived hormone that regulates body weight via interactions with hypothalamic neuronal circuitries expressing specific leptin receptors (Ob-R). The Ob-Rs act via the JAK-STAT (Janus kinase-signal transducers and activators of transcription) pathway of signal transduction. Recent evidence suggests that primarily the transcription factor STAT3 mediates leptin’s action in the hypothalamus. We have investigated the presence and cellular

Marie-Louise Håkansson; Björn Meister

1998-01-01

181

Stat3? mitigates development of atherosclerosis in apolipoprotein E-deficient mice.  

PubMed

The transcription factor Stat3 is an activator of systemic inflammatory genes. Two isoforms of Stat3 are generated by alternative splicing, Stat3? and Stat3?. The ? isoform lacks the transactivation domain but retains other functions, including dimerization and DNA binding. Stat3?-deficient mice exhibit elevated expression of systemic inflammatory genes and are hyperresponsive to lipopolysaccharide, suggesting that Stat3? functions predominantly as a suppressor of systemic inflammation. To test whether Stat3? deficiency would provoke pathologic effects associated with chronic inflammation, we asked whether selective removal of Stat3? would exacerbate the development of atherosclerosis in apolipoprotein E-deficient mice. In apoE(-/-)Stat3?(-/-) mice atherosclerotic plaque formation was significantly enhanced relative to apoE(-/-)Stat3?(+/+) controls. The ability of Stat3? deficiency to promote atherosclerosis was more pronounced in female mice, but could be unmasked in males by feeding a high fat diet. Infiltrating macrophages were not increased in aortas of apoE(-/-)Stat3?(-/-) mice. In contrast, the proportion of pro-inflammatory TH17 cells was significantly elevated in aortic infiltrates from apoE(-/-)Stat3?(-/-) mice, relative to paired apoE(-/-)Stat3?(+/+) littermates. These observations indicate that Stat3? can suppress pathologic sequelae associated with chronic inflammation. Our findings further suggest that in Stat3?-deficient mice the unopposed action of Stat3? may enhance atherogenesis in part by promoting differentiation of TH17 cells. PMID:23619910

Lee, Jihyun; Baldwin, William M; Lee, Chih-Yuan; Desiderio, Stephen

2013-04-26

182

Effect of bisphenol A on the EGFR-STAT3 pathway in MCF-7 breast cancer cells.  

PubMed

The aim of this study was to explore the effect of bisphenol A (BPA) on the EGFR-STAT3 pathway in breast cancer. We applied 3-(4,5-dimethylthiazol-2-yl)2,5-diphenyl tetrazolium bromide (MTT) cytotoxicity assay to the analysis of the responsiveness of MCF-7 cells to BPA. Gene expression was assayed at the transcriptional and translational levels by reverse transcription-PCR and Western blotting. We explored the effects of BPA on MCF-7 cell proliferation through inhibition of the related genes, STAT3, using RNA interference, and EGFR, using its inhibitor AG1478. The optimal concentration and time point of BPA-induced proliferation in MCF-7 cells are 1 µM and 24 h, respectively. BPA significantly increased the expression of STAT3 at a concentration of 1 µM following treatment for 48 h and the expression of STAT3 was down-regulated after blocking EGFR. When STAT3 was blocked in MCF-7 cells, BPA did not appear to induce cell proliferation. Treatment with BPA (1 µM) in the presence of AG1478 for 48 h resulted in the stimulation of cell growth in MCF-7 cells, similar to that of the BPA alone treatment. BPA increases STAT3 expression, which is a major factor in the pathway of BPA-induced proliferation, and STAT3 activation contributes to BPA-induced breast cancer cell proliferation. However, EGFR mediates negative signaling for BPA-induced breast cancer cell proliferation. PMID:21909620

Zhang, Wei; Fang, Yanqiu; Shi, Xu; Zhang, Minglei; Wang, Xiaoqi; Tan, Yan

2011-09-09

183

Misguidance and modulation of axonal regeneration by Stat3 and Rho/ROCK signaling in the transparent optic nerve.  

PubMed

The use of the visual system played a major role in the elucidation of molecular mechanisms controlling axonal regeneration in the injured CNS after trauma. In this model, CNTF was shown to be the most potent known neurotrophic factor for axonal regeneration in the injured optic nerve. To clarify the role of the downstream growth regulator Stat3, we analyzed axonal regeneration and neuronal survival after an optic nerve crush in adult mice. The infection of retinal ganglion cells with adeno-associated virus serotype 2 (AAV2) containing wild-type (Stat3-wt) or constitutively active (Stat3-ca) Stat3 cDNA promoted axonal regeneration in the injured optic nerve. Axonal growth was analyzed in whole-mounted optic nerves in three dimensions (3D) after tissue clearing. Surprisingly, with AAV2.Stat3-ca stimulation, axons elongating beyond the lesion site displayed very irregular courses, including frequent U-turns, suggesting massive directionality and guidance problems. The pharmacological blockade of ROCK, a key signaling component for myelin-associated growth inhibitors, reduced axonal U-turns and potentiated AAV2.Stat3-ca-induced regeneration. Similar results were obtained after the sustained delivery of CNTF in the axotomized retina. These results show the important role of Stat3 in the activation of the neuronal growth program for regeneration, and they reveal that axonal misguidance is a key limiting factor that can affect long-distance regeneration and target interaction after trauma in the CNS. The correction of axonal misguidance was associated with improved long-distance axon regeneration in the injured adult CNS. PMID:23868067

Pernet, V; Joly, S; Jordi, N; Dalkara, D; Guzik-Kornacka, A; Flannery, J G; Schwab, M E

2013-07-18

184

Cytokine Signaling through Stat3 Activates Integrins, Promotes Adhesion, and Induces Growth Arrest in the Myeloid Cell Line 32D*  

PubMed Central

Hematopoietic cell development and function is dependent on cytokines and on intercellular interactions with the microenvironment. Although the intracellular signaling pathways stimulated by cytokine receptors are well described, little is known about the mechanisms through which these pathways modulate hematopoietic cell adhesion events in the microenvironment. Here we show that cytokine-activated Stat3 stimulates the expression and function of cell surface adhesion molecules in the myeloid progenitor cell line 32D. We generated an erythropoietin receptor (EpoR) isoform (ER343/401-S3) that activates Stat3 rather than Stat5 by substituting the Stat3 binding/activation sequence motif from gp130 for the sequences surrounding tyrosines 343 and 401 in the receptor cytoplasmic region. Activation of Stat3 leads to homotypic cell aggregation, increased expression of intercellular adhesion molecule 1 (ICAM-1), CD18, and CD11b, and activation of signaling through CD18-containing integrins. Unlike the wild type EpoR, ER343/401-S3 is unable to support long term Epo-dependent proliferation in 32D cells. Instead, Epo-treated ER343/401-S3 cells undergo G1 arrest and express elevated levels of the cyclin-dependent kinase inhibitor p27Kip1. Sustained activation of Stat3 in these cells is required for their altered morphology and growth properties since constitutive SOCS3 expression abrogates homotypic cell aggregation, signaling through CD18-containing integrins, G1 arrest, and accumulation of p27Kip1. Collectively, our results demonstrate that cytokine-activated Stat3 stimulates the expression and function of cell surface adhesion molecules, indicating that a role for Stat3 is to regulate intercellular contacts in myeloid cells.

Wooten, David K.; Xie, Xiaoling; Bartos, David; Busche, Ruth A.; Longmore, Gregory D.; Watowich, Stephanie S.

2008-01-01

185

Stat3 is involved in control of MASP2 gene expression  

SciTech Connect

Little is known about determinants regulating expression of Mannan-binding lectin associated serine protease-2 (MASP-2), the effector component of the lectin pathway of complement activation. Comparative bioinformatic analysis of the MASP2 promoter regions in human, mouse, and rat, revealed conservation of two putative Stat binding sites, termed StatA and StatB. Site directed mutagenesis specific for these sites was performed. Transcription activity was decreased 5-fold when StatB site was mutated in the wildtype reporter gene construct. Gel retardation and competition assays demonstrated that proteins contained in the nuclear extract prepared from HepG2 specifically bound double-stranded StatB oligonucleotides. Supershift analysis revealed Stat3 to be the major specific binding protein. We conclude that Stat3 binding is important for MASP2 promoter activity.

Unterberger, Claudia [Clinical Cooperation Group Inflammatory Lung Diseases - GSF-National Research Center for Environment and Health, Asklepios Fachkliniken, Gauting (Germany); Hanson, Steven [Anthropology and Human Genetics, Department Biology II, Ludwig-Maximilians-Universitaet Munich (Germany); Department of Infection, Immunity and Inflammation, University of Leicester, University Road, Leicester LE1 9HN (United Kingdom); Klingenhoff, Andreas [Genomatix Software GmbH, Munich (Germany); Oesterle, Daniela [Anthropology and Human Genetics, Department Biology II, Ludwig-Maximilians-Universitaet Muenchen (Germany); Frankenberger, Marion [Clinical Cooperation Group Inflammatory Lung Diseases - GSF-National Research Center for Environment and Health, Asklepios Fachkliniken, Gauting (Germany); Endo, Yuichi [Department of Biochemistry, Fukushima Medical University School of Medicine, Fukushima (Japan); Matsushita, Misao [Department of Applied Biochemistry, Tokai University, Hiratsuka (Japan); Fujita, Teizo [Department of Biochemistry, Fukushima Medical University School of Medicine, Fukushima (Japan); Schwaeble, Wilhelm [Department of Infection, Immunity and Inflammation, University of Leicester, University Road, Leicester LE1 9HN (United Kingdom); Weiss, Elisabeth H. [Anthropology and Human Genetics, Department Biology II, Ludwig-Maximilians-Universitaet Muenchen (Germany); Ziegler-Heitbrock, Loems [Clinical Cooperation Group Inflammatory Lung Diseases - GSF-National Research Center for Environment and Health, Asklepios Fachkliniken, Gauting (Germany); Department of Infection, Immunity and Inflammation, University of Leicester, University Road, Leicester LE1 9HN (United Kingdom); Stover, Cordula [Department of Infection, Immunity and Inflammation, University of Leicester, University Road, Leicester LE1 9HN (United Kingdom)], E-mail: cms13@le.ac.uk

2007-12-28

186

Inhibition of Jak-STAT3 pathway enhances bufalin-induced apoptosis in colon cancer SW620 cells  

PubMed Central

Background The purpose of the research is to investigate the roles of Jak-STAT3 signaling pathway in bufalin-induced apoptosis in colon cancer SW620 cells. Methods The inhibitory effects of bufalin on cell proliferation were determined by MTT (Methyl thiazolyltetrazolium) assay. The morphological changes of cells were measured by Wright-Giemsa staining. The cell cycle arrest and apoptosis were tested by flow cytometry analysis. Western Blot was used to determine the protein expression of the apoptosis inhibitors livin and caspase-3, the apoptosis-related proteins Bax and Bcl-2, as well as the key protein kinases in the Jak-stat3 signaling pathway, stat3 and p-stat3. Results (1) Bufalin inhibited the proliferation of SW620 cells. IC50 at 24 h, 48 h and 72 h were 76.72 ± 6.21 nmol/L, 34.05 ± 4.21 nmol/L and 16.7 ± 6.37 nmol/L. (2) Bufalin induced SW620 cell cycle arrest and apoptosis, indicated by the appearance of apoptotic bodies; (3) The results from flow cytometry demonstrated that there was cell cycle G2/M phase arrest in 20 nmol/L bufalin treatment group (36.29 ± 2.11% vs 18.39 ± 1.74%, P<0.01); there was a sub-diploid apoptosis peak in 80 nmol/L bufalin treatment group (19.69 ± 1.63% vs 0.99 ± 0.23%, P <0.01). The apoptosis rate was 34.63 ± 2.57% (vs 19.69 ± 1.63%, P = 0.002) in JAK kinase inhibitor AG490 plus bufalin treatment group. (4) During the process of bufalin-induced apoptosis in SW620 cells, transient activation of p-stat3 inhibited the activation of stat3, up-regulated Bax expression, down-regulated livin and Bcl-2 expression (P<0.01), and activated caspase-3. Inhibition of Jak-stat3 signaling pathway by pre-treatment with AG490 significantly enhanced the bufalin-induced apoptosis (P<0.01), further up-regulated Bax protein expression, down-regulated livin and Bcl-2 protein expression and enhanced caspase-3 activation. Conclusions Bufalin not only inhibited the growth of colon cancer SW620 cells, but also induced apoptosis of SW620 cells. Activation of caspase-3, up-regulation of Bax, down-regulation of livin and Bcl-2, as well as inhibition of Jak-stat3 signaling pathway might be the important mechanisms for the bufalin-induced apoptosis.

2012-01-01

187

TLR4 Mediates MAPK-STAT3 Axis Activation in Bladder Epithelial Cells.  

PubMed

The role of Toll-like receptor 4 (TLR4) in immune cells is well characterized, but its biological properties in bladder epithelial cells (BECs), especially reciprocal crosstalk between mitogen-activated protein (MAP) kinase pathway and signal transducer and activator of transcription (STAT)3-mediated signal transduction elicited by TLR4 have not been demonstrated so far. The present studies were to demonstrate the signal transduction and inflammatory cytokine response elicited through activation of TLR4 in BECs with a special focus on the crosstalk between the MAPK-pathway and STAT3-mediated signals and its regulatory relevance for the inflammatory response towards lipopolysaccharide (LPS). We selected human bladder cancer T24 cell line in the present study and examined its expression of TLR4 by reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry. The expression of p38, extracellular signal regulated kinase (ERK), c-Jun NH2-terminal kinase (JNK), and STAT3 were performed by RT-PCR, quantitative PCR, and Western blotting. Signal transduction was analyzed by Western blotting. Interleukin-6 (IL-6) and interleukin-10 (IL-10) secretion in culture supernatants were tested by human enzyme-linked immunosorbent assay (ELISA) kit. BECs of rat infection in vivo model and patients with cystitis glandularis (CG) were analyzed as described above. Our study demonstrated that TLR4 was significantly upregulated following LPS treatment, with the maximum mRNA expression occurring at 4 h after stimulation. Activation of TLR4 signaling by LPS resulted in phosphorylation of MAPK and STAT pathways and upregulation of IL-10 in dose- and time-dependent manners in T24 cells. Pretreatment of cells with SB203580 (inhibitor of p38) and SP600125 (inhibitor of JNK) attenuated LPS-induced IL-10 expression, whereas it markedly inhibited the STAT3 expression. IL-10 mRNA expression was increased in inflamed lesions compared to noninflamed tissue in rats and patients with CG disease. Our results demonstrate that activation of TLR4 signaling in BECs induces IL-10 expression via activation of p38 and JNK, and the activation of STAT-3 was upregulated. Our data indicated that the reciprocal crosstalk between the MAPK pathway and STAT3-mediated signal transduction forms a critical axis successively activated by LPS in BECs. PMID:23612802

Ying, Huang; Da, Liu; Yu-Xiu, Shi; Yu, Xia; Li-Xia, Liu; Li-Mei, Xie; Wei-Dong, Ren

2013-10-01

188

Discovery of P3971 an Orally Efficacious Novel Anticancer Agent Targeting HIF-1? and STAT3 Pathways.  

PubMed

Hypoxia-inducible factor-1? (HIF-1?) and signal transducer and activator of transcription 3 (STAT3) are transcription factors and are activated in response to hypoxia. Both HIF-1? and STAT3 regulate various aspects of cancer biology such as cell survival, proliferation, angiogenesis etc. and are constitutively expressed in a wide range of human cancers. In the last decade, over expression of HIF-1? and STAT3 has been demonstrated in many common human cancers, thereby emerging as highly compelling anticancer targets for drug discovery. We herein report the design and synthesis of new imidazopyridine based potent dual inhibitors of HIF-1? and STAT3 pathways. The lead compound of this series P3971 has been identified as a potent inhibitor of HIF-1? (200 nM) and STAT3 (350 nM) with significant antiproliferative activity against various cancer cell lines. Moreover, P3971 was also found to be orally efficacious in HCT116 (colon cancer) and H460 (lung cancer) xenograft mice models. PMID:24102269

Godse, Pallavi; Kumar, Pramod; Yewalkar, Nilambari; Deore, Vijaykumar; Lohar, Manoj; Mundada, Ramswaroop; Padgaonkar, Amol; Manohar, Sonal; Joshi, Asavari; Bhatia, Dimple; Desai, Nikesh; Damre, Anagha; Bhonde, Mandar; Joshi, Kalpana; Sharma, Rajiv; Kumar, Sanjay

2013-11-01

189

The JAK2/STAT3 and mitochondrial pathways are essential for quercetin nanoliposome-induced C6 glioma cell death  

PubMed Central

The formulation of quercetin nanoliposomes (QUE-NLs) has been shown to enhance QUE antitumor activity in C6 glioma cells. At high concentrations, QUE-NLs induce necrotic cell death. In this study, we probed the molecular mechanisms of QUE-NL-induced C6 glioma cell death and examined whether QUE-NL-induced programmed cell death involved Bcl-2 family and mitochondrial pathway through STAT3 signal transduction pathway. Downregulation of Bcl-2 and the overexpression of Bax by QUE-NL supported the involvement of Bcl-2 family proteins upstream of C6 glioma cell death. In addition, the activation of JAK2 and STAT3 were altered following exposure to QUE-NLs in C6 glioma cells, suggesting that QUE-NLs downregulated Bcl-2 mRNAs expression and enhanced the expression of mitochondrial mRNAs through STAT3-mediated signaling pathways either via direct or indirect mechanisms. There are several components such as ROS, mitochondrial, and Bcl-2 family shared by the necrotic and apoptotic pathways. Our studies indicate that the signaling cross point of the mitochondrial pathway and the JAK2/STAT3 signaling pathway in C6 glioma cell death is modulated by QUE-NLs. In conclusion, regulation of JAK2/STAT3 and ROS-mediated mitochondrial pathway agonists alone or in combination with treatment by QUE-NLs could be a more effective method of treating chemical-resistant glioma.

Wang, G; Wang, J J; Chen, X L; Du, S M; Li, D S; Pei, Z J; Lan, H; Wu, L B

2013-01-01

190

Hepatocyte IKK?/NF-?B inhibits tumor promotion and progression by preventing oxidative stress driven STAT3 activation  

PubMed Central

SUMMARY The NF-?B activating kinase IKK? suppresses early chemically-induced liver tumorigenesis by inhibiting hepatocyte death and compensatory proliferation. To study IKK?’s role in late tumor promotion and progression, we developed a transplant system that allows initiated mouse hepatocytes to form hepatocellular carcinomas (HCC) in host liver after a long latency. Deletion of IKK? long after initiation accelerated HCC development and enhanced proliferation of tumor initiating cells. These effects of IKK?/NF-?B were cell autonomous and correlated with increased accumulation of reactive oxygen species (ROS) that led to JNK and STAT3 activation. Hepatocyte-specific STAT3 ablation prevented HCC development. The negative crosstalk between NF-?B and STAT3, which is also evident in human HCC, is a critical regulator of liver cancer development and progression.

He, Guobin; Yu, Guann-Yi; Temkin, Vladislav; Ogata, Hisanobu; Kuntzen, Christian; Sakurai, Toshiharu; Sieghart, Wolfgang; Peck-Radosavljevic, Markus; Leffert, Hyam L.; Karin, Michael

2010-01-01

191

STAT3 Mutations in the Hyper-IgE Syndrome  

Microsoft Academic Search

Methods We collected longitudinal clinical data on patients with the hyper-IgE syndrome and their families and assayed the levels of cytokines secreted by stimulated leuko- cytes and the gene expression in resting and stimulated cells. These data impli- cated the signal transducer and activator of transcription 3 gene (STAT3) as a candi- date gene, which we then sequenced. Results We

Steven M. Holland; Frank R. DeLeo; Houda Z. Elloumi; Amy P. Hsu; Nina Brodsky; Alexandra F. Freeman; Andrew Demidowich; Joie Davis; Maria L. Turner; Victoria L. Anderson; Dirk N. Darnell; Pamela A. Welch; Douglas B. Kuhns; David M. Frucht; Harry L. Malech; John I. Gallin; Scott D. Kobayashi; Adeline R. Whitney; Jovanka M. Voyich; James M. Musser; Cristina Woellner; Alejandro A. Schäffer; Jennifer M. Puck; Bodo Grimbacher

2010-01-01

192

Protein Inhibitor of Activated STAT-3 Expression in Lung Cancer  

PubMed Central

Protein Inhibitor of Activated Signal Transducer and Activators of Transcription 3 (PIAS3) is an endogenous inhibitor of STAT3 transcriptional activity. We have previously demonstrated the concentration-dependent negative regulatory effect of PIAS3 on STAT3 signaling and its capacity to decrease lung cancer proliferation and synergize with epidermal growth factor inhibition. We now investigate PIAS3 expression in both non-small cell lung cancer (NSCLC) cell lines and human resected NSCLC specimens. We also investigated the mechanism by which some lung cancers have significantly decreased PIAS3 expression. Expression of PIAS3 is variable in lung cancer cells lines with 2 of 3 squamous cell carcinoma (SCC) cell lines having no or little PIAS3 protein expression. Similarly, the majority of human SCCs of the lung lack PIAS3 expression by immunohistochemistry; this despite the finding that SCCs have significantly higher levels of PIAS3 mRNA compared to adenocarcinomas. High PIAS3 expression generally correlates with decreased phosphorylated STAT3 in both SCC cell lines and human specimens compatible with the negative regulatory effect of this protein on STAT3 signaling. To investigate this variable expression of PIAS3 we first performed sequencing of the PIAS3 gene that demonstrated single nucleotide polymorphisms but no mutations. Exposure of lung cancer cells to 5-azacytidine and trichostatin A results in a significant increase in PIAS3 mRNA and protein expression. However, methylation-specific PCR demonstrates a lack of CpG island methylation in the promoter region of PIAS3. Exposure of cells to an agent blocking proteosomal degradation results in a significant increase in PIAS3. Our data thus shows that SCC of the lung commonly lacks PIAS3 protein expression and that post-translational modifications may explain this finding in some cases. PIAS3 is a potential therapeutic molecule to target STAT3 pathway in lung cancer.

Kluge, Amy; Dabir, Snehal; Vlassenbroeck, Ilse; Eisenberg, Rosana; Dowlati, Afshin

2011-01-01

193

Absolute requirement for STAT3 function in small-intestine crypt stem cell survival  

PubMed Central

The transcription factor signal transducer and activator of transcription 3 (STAT3) is frequently activated in human cancers. Interestingly, STAT3 also maintains the pluripotency and self-renewal of murine embryonic stem cells, and several tissue stem cell types. To investigate whether STAT3 also maintains the small-intestine crypt stem cell, we conditionally inactivated a Floxed Stat3 allele (Stat3fl) in murine small-intestine crypt stem cells. Following Cre recombinase expression, apoptosis increased in Stat3fl/? experimental crypts relative to Stat3wt/? controls before declining. Control Stat3wt/? mice carrying a Flox-STOP LacZ reporter transgene stably expressed LacZ after Cre induction. In contrast, Stat3fl/? intestine LacZ expression initially increased modestly, before declining to background levels. Quantitative PCRs revealed a similar transient in recombined Stat3fl allele levels. Long-term bromodeoxyuridine labelling directly demonstrated that functional STAT3 is required for +4 to +6 region label-retaining small-intestine stem cell survival. Rapid clearance of recombined Stat3fl/? cells involves apoptosis potentially induced by elevated c-Myc in non-recombined cells and involves elevated p53 expression and caspase 3 activation. Intriguingly, Stat3fl/? intestine recombination triggered dramatically upregulated polycomb transcriptional repressor Bmi1 – potentially accelerating recombined crypt repopulation. In summary, STAT3 activity is absolutely required for small-intestine crypt stem cell survival at both the +4 to +6 label-retaining and crypt base columnar cell locations.

Matthews, J R; Sansom, O J; Clarke, A R

2011-01-01

194

Induction of p21WAF1\\/CIP1 and cyclin D1 expression by the Src oncoprotein in mouse fibroblasts: role of activated STAT3 signaling  

Microsoft Academic Search

While the activated viral Src oncoprotein, v-Src, induces uncontrolled cell growth, the mechanisms underlying cell cycle deregulation by v-Src have not been fully defined. Previous studies demonstrated that v-Src induces constitutively active STAT3 signaling that is required for cell transformation and recent data have implicated STAT3 in the transcriptional control of critical cell cycle regulators. Here we show in mouse

Dominic Sinibaldi; Walker Wharton; James Turkson; Tammy Bowman; Warren J Pledger; Richard Jove

2000-01-01

195

Cytoplasmic Polyadenylation Element Binding Protein Deficiency Stimulates PTEN and Stat3 mRNA Translation and Induces Hepatic Insulin Resistance  

PubMed Central

The cytoplasmic polyadenylation element binding protein CPEB1 (CPEB) regulates germ cell development, synaptic plasticity, and cellular senescence. A microarray analysis of mRNAs regulated by CPEB unexpectedly showed that several encoded proteins are involved in insulin signaling. An investigation of Cpeb1 knockout mice revealed that the expression of two particular negative regulators of insulin action, PTEN and Stat3, were aberrantly increased. Insulin signaling to Akt was attenuated in livers of CPEB–deficient mice, suggesting that they might be defective in regulating glucose homeostasis. Indeed, when the Cpeb1 knockout mice were fed a high-fat diet, their livers became insulin-resistant. Analysis of HepG2 cells, a human liver cell line, depleted of CPEB demonstrated that this protein directly regulates the translation of PTEN and Stat3 mRNAs. Our results show that CPEB regulated translation is a key process involved in insulin signaling.

Jung, Dae Young; Friedline, Randall; Ko, Hwi Jin; Xu, Mei; O'Sullivan-Murphy, Bryan; Bortell, Rita; Huang, Yen-Tsung; Urano, Fumihiko; Kim, Jason K.; Richter, Joel D.

2012-01-01

196

Cloning, molecular characterization, and expression analysis of the signal transducer and activator of transcription 3 (STAT3) gene from grass carp (Ctenopharyngodon idellus).  

PubMed

Signal transducer and activator of transcription 3 (STAT3) binds to Janus kinase 2 (JAK2) to initiate the JAK2/STAT3 signal transduction pathway, which plays an important role in cancer cell proliferation, immune regulation, reproduction, lipid metabolism, and other physiological processes of the organism. In this study, the cDNA sequence of the STAT3 gene from grass carp was cloned using RACE (rapid-amplification of cDNA ends). Twelve characteristics of the STAT3 gene and its encoded protein sequence were predicted and analyzed using bioinformatics methods; these features included the general physical and chemical properties, the hydrophobicity, the secondary structure and the three-dimensional structure of the protein. Quantitative real-time PCR was employed to detect grass carp STAT3 expression pattern in different tissues. The results showed that the full-length STAT3 gene from grass carp is 2739-bp long and contains a 216-bp 5'UTR, a 300-bp 3'UTR, and a 2223-bp open reading frame (ORF) that encodes a 740-amino acid peptide. The deduced protein exhibited 99%?94% homology to the STAT3 protein of zebra?sh (Danio rerio), medaka (Oryzias latipes), turbot (Scophthalmus maximus), white-spotted char (Salvelinus leucomaenis), mandarin fish (Siniperca chuatsi), rainbow trout (Oncorhynchus mykiss), and green pufferfish (Tetraodon ?uviatilis). The deduced grass carp STAT3 protein contains a protein interaction domain, an alpha domain, a DNA binding domain, and an SH2 domain. The STAT3 protein of grass carp is a hydrophilic and non-secretory protein, and its molecular mass and isoeletronic point were found to be 98,5412.1 Da and 6.39, respectively. The structural elements of STAT3 included ?-helixes, ?-sheets, and loops. The grass carp STAT3 is expressed in all of the six tissues tested, which were the liver, spleen, gill, muscle, heart, and brain. The highest expression level was found in the liver (P < 0.05), whereas a significantly lower expression level was found in the spleen, gills, brain, and muscle (P < 0.05), and the lowest expression level was found in the heart (P < 0.05). This study provides a basis for further structural and functional exploration of the STAT3 from grass carp, including its deduced protein and its signal transduction function. PMID:24055509

Guo, Ting; Leng, Xiang-Jun; Wu, Xiao-Feng; Li, Jia-Le; Gao, Jian-Zhong; Li, Xiao-Qin; Gan, Tian; Wei, Jing

2013-09-18

197

Heme Mediated STAT3 Activation in Severe Malaria  

Microsoft Academic Search

BackgroundThe mortality of severe malaria [cerebral malaria (CM), severe malaria anemia (SMA), acute lung injury (ALI) and acute respiratory distress syndrome (ARDS)] remains high despite the availability associated with adequate treatments. Recent studies in our laboratory and others have revealed a hitherto unknown correlation between chemokine CXCL10\\/CXCR3, Heme\\/HO-1 and STAT3 and cerebral malaria severity and mortality. Although Heme\\/HO-1 and CXCL10\\/CXCR3

Mingli Liu; Audu S. Amodu; Sidney Pitts; John Patrickson; Jacqueline M. Hibbert; Monica Battle; Solomon F. Ofori-Acquah; Jonathan K. Stiles

2012-01-01

198

Physical and functional interactions between STAT3 and KAP1  

Microsoft Academic Search

Signal transducers and activators of transcription (STATs) mediate cell proliferation, differentiation and survival in immune responses, hematopoiesis, neurogenesis and other biological processes. For example, STAT3 has been reported to be constitutively activated in numerous cancer cells. To clarify the molecular mechanisms underlying the STAT activation, we performed yeast two-hybrid screening and identified KAP1\\/TIF1? as a novel STAT-binding partner. KAP1 is

R Tsuruma; N Ohbayashi; S Kamitani; O Ikeda; N Sato; R Muromoto; Y Sekine; K Oritani; T Matsuda

2008-01-01

199

Ethanolamine is a novel STAT3 dependent cardioprotective agent  

Microsoft Academic Search

Ethanolamine is a biogenic amine found naturally in the body as part of membrane lipids and as a metabolite of the cardioprotective\\u000a substances, sphingosine-1-phosphate (S1P) and anandamide. In the brain, ethanolamine, formed from the breakdown of anandamide\\u000a protects against ischaemic apoptosis. However, the effects of ethanolamine in the heart are unknown. Signal transducer and\\u000a activator of transcription 3 (STAT-3) is

Roisin F. KellyKim; Kim T. Lamont; Sarin Somers; Damian Hacking; Lydia Lacerda; Paul Thomas; Lionel H. Opie; Sandrine Lecour

2010-01-01

200

RBP-J kappa repression activity is mediated by a co-repressor and antagonized by the Epstein-Barr virus transcription factor EBNA2.  

PubMed Central

The Epstein-Barr virus (EBV) protein EBNA2 is a transcriptional activator that can be targeted to its DNA responsive elements by direct interaction with the cellular protein RBP-J kappa. RBP-J kappa is a ubiquitous factor, highly conserved between man, mouse and Drosophila, whose function in mammalian cells is largely unknown. Here we provide evidence that RBP-J kappa is a transcriptional repressor and, more importantly, that RBP-J kappa repression is mediated by a co-repressor. The function of the co-repressor could be counterbalanced by making a fusion protein (RBP-VP16) between RBP-J kappa and the VP16 activation domain. This RBP-VP16-mediated activation could be strongly increased by an EBNA2 protein deprived of its activation domain, but not by an EBNA2 protein incapable of making physical contact with RBP-J kappa. Our results suggest that EBNA2 activates transcription by both interfering with the function of a co-repressor recruited by RBP-J kappa and providing an activation domain. Images

Waltzer, L; Bourillot, P Y; Sergeant, A; Manet, E

1995-01-01

201

JAK2/STAT3 activation by melatonin attenuates the mitochondrial oxidative damage induced by myocardial ischemia/reperfusion injury.  

PubMed

Ischemia/reperfusion injury (IRI) is harmful to the cardiovascular system and causes mitochondrial oxidative stress. Numerous data indicate that the JAK2/STAT3 signaling pathway is specifically involved in preventing myocardial IRI. Melatonin has potent activity against IRI and may regulate JAK2/STAT3 signaling. This study investigated the protective effect of melatonin pretreatment on myocardial IRI and elucidated its potential mechanism. Perfused isolated rat hearts and cultured neonatal rat cardiomyocytes were exposed to melatonin in the absence or presence of the JAK2/STAT3 inhibitor AG490 or JAK2 siRNA and then subjected to IR. Melatonin conferred a cardio-protective effect, as shown by improved postischemic cardiac function, decreased infarct size, reduced apoptotic index, diminished lactate dehydrogenase release, up-regulation of the anti-apoptotic protein Bcl2, and down-regulation of the pro-apoptotic protein Bax. AG490 or JAK2 siRNA blocked melatonin-mediated cardio-protection by inhibiting JAK2/STAT3 signaling. Melatonin exposure also resulted in a well-preserved mitochondrial redox potential, significantly elevated mitochondrial superoxide dismutase (SOD) activity, and decreased formation of mitochondrial hydrogen peroxide (H2 O2 ) and malondialdehyde (MDA), which indicates that the IR-induced mitochondrial oxidative damage was significantly attenuated. However, this melatonin-induced effect on mitochondrial function was reversed by AG490 or JAK2 siRNA treatment. In summary, our results demonstrate that melatonin pretreatment can attenuate IRI by reducing IR-induced mitochondrial oxidative damage via the activation of the JAK2/STAT3 signaling pathway. PMID:23796350

Yang, Yang; Duan, Weixun; Jin, Zhenxiao; Yi, Wei; Yan, Juanjuan; Zhang, Song; Wang, Ning; Liang, Zhenxing; Li, Yue; Chen, Wensheng; Yi, Dinghua; Yu, Shiqiang

2013-06-25

202

The JAK2 Inhibitor, AZD1480, Potently Blocks Stat3 Signaling and Oncogenesis in Solid Tumors  

PubMed Central

Summary Persistent activation of Stat3 is oncogenic and is prevalent in a wide variety of human cancers. Chronic cytokine stimulation is associated with Stat3 activation in some tumors, implicating cytokine receptor-associated Jak family kinases. Using Jak2 inhibitors, we demonstrate a central role of Jaks in modulating basal and cytokine-induced Stat3 activation in human solid tumor cell lines. Inhibition of Jak2 activity is associated with abrogation of Stat3 nuclear translocation and tumorigenesis. The Jak2 inhibitor, AZD1480, suppresses the growth of human solid tumor xenografts harboring persistent Stat3 activity. We demonstrate the essential role of Stat3 downstream of Jaks by inhibition of tumor growth using shRNA targeting Stat3. Our data support a key role of Jak kinase activity in Stat3-dependent tumorigenesis.

Hedvat, Michael; Huszar, Dennis; Herrmann, Andreas; Gozgit, Joseph M.; Schroeder, Anne; Sheehy, Adam; Buettner, Ralf; Proia, David; Kowolik, Claudia M.; Xin, Hong; Armstrong, Brian; Bebernitz, Geraldine; Weng, Shaobu; Wang, Lin; Ye, Minwei; McEachern, Kristen; Chen, Huawei; Morosini, Deborah; Bell, Kirsten; Alimzhanov, Marat; Ioannidis, Stephanos; McCoon, Patricia; Cao, Zhu A.; Yu, Hua; Jove, Richard; Zinda, Michael

2009-01-01

203

The JAK2 inhibitor AZD1480 potently blocks Stat3 signaling and oncogenesis in solid tumors.  

PubMed

Persistent activation of Stat3 is oncogenic and is prevalent in a wide variety of human cancers. Chronic cytokine stimulation is associated with Stat3 activation in some tumors, implicating cytokine receptor-associated Jak family kinases. Using Jak2 inhibitors, we demonstrate a central role of Jaks in modulating basal and cytokine-induced Stat3 activation in human solid tumor cell lines. Inhibition of Jak2 activity is associated with abrogation of Stat3 nuclear translocation and tumorigenesis. The Jak2 inhibitor AZD1480 suppresses the growth of human solid tumor xenografts harboring persistent Stat3 activity. We demonstrate the essential role of Stat3 downstream of Jaks by inhibition of tumor growth using short hairpin RNA targeting Stat3. Our data support a key role of Jak kinase activity in Stat3-dependent tumorigenesis. PMID:19962667

Hedvat, Michael; Huszar, Dennis; Herrmann, Andreas; Gozgit, Joseph M; Schroeder, Anne; Sheehy, Adam; Buettner, Ralf; Proia, David; Kowolik, Claudia M; Xin, Hong; Armstrong, Brian; Bebernitz, Geraldine; Weng, Shaobu; Wang, Lin; Ye, Minwei; McEachern, Kristen; Chen, Huawei; Morosini, Deborah; Bell, Kirsten; Alimzhanov, Marat; Ioannidis, Stephanos; McCoon, Patricia; Cao, Zhu A; Yu, Hua; Jove, Richard; Zinda, Michael

2009-12-01

204

STAT3 controls the neutrophil migratory response to CXCR2 ligands by direct activation of G-CSF-induced CXCR2 expression and via modulation of CXCR2 signal transduction  

PubMed Central

Neutrophil mobilization, the release of neutrophils from the bone marrow reserve into circulating blood, is important to increase peripheral neutrophil amounts during bacterial infections. Granulocyte colony-stimulating factor (G-CSF) and chemokines, such as macrophage-inflammatory protein-2 (MIP-2; CXCL2), can induce neutrophil mobilization, but the mechanism(s) they use remain unclear. Signal transducers and activator of transcription 3 (STAT3) is the principal intracellular signaling molecule activated upon G-CSF ligation of its receptor. Using a murine model with conditional STAT3 deletion in bone marrow, we demonstrated previously that STAT3 regulates acute G-CSF–responsive neutrophil mobilization and MIP-2–dependent neutrophil chemotaxis. In this study, we show STAT3 is also necessary for MIP-2–elicited neutrophil mobilization. STAT3 appears to function by controlling extracellular signal-regulated kinase (ERK) activation, which is important for MIP-2–mediated chemotaxis. In addition, we demonstrate that G-CSF stimulates the expression of the MIP-2 receptor via STAT3-dependent transcriptional activation of Il8rb. G-CSF treatment also induces STAT3-dependent changes in bone marrow chemokine expression levels which may further affect neutrophil retention and release. Taken together, our study demonstrates that STAT3 regulates multiple aspects of chemokine and chemokine receptor expression and function within the bone marrow, indicating a central role in the neutrophil mobilization response.

Nguyen-Jackson, Hoainam; Panopoulos, Athanasia D.; Zhang, Huiyuan; Li, Haiyan S.

2010-01-01

205

Stat3 Activation Is Required for Cellular Transformation by v-src  

Microsoft Academic Search

Stat3 activation has been associated with cytokine-induced proliferation, anti-apoptosis, and transforma- tion. Constitutively activated Stat3 has been found in many human tumors as well as v-abl- and v-src- transformed cell lines. Because of these correlations, we examined directly the relationship of activated Stat3 to cellular transformation and found that wild-type Stat3 enhances the transforming potential of v-src while three dominant

JACQUELINE F. BROMBERG; CURT M. HORVATH; DANIEL BESSER; WYNDHAM W. LATHEM

1998-01-01

206

Structure-Based Design of Conformationally Constrained, Cell-Permeable STAT3 Inhibitors  

PubMed Central

We report herein the structure-based design of a class of conformationally constrained, potent, cell-permeable small-molecule inhibitors to target the SH2 domain in STAT3. Compound 11 (CJ-1383) binds to STAT3 with a Ki value of 0.95 µM, dose-dependently inhibits cellular STAT3 signaling and cancer cell growth, and induces apoptosis in the MDA-MB-468 cancer cell line with constitutively activated STAT3.

Chen, Jianyong; Bai, Longchuan; Bernard, Denzil; Nikolovska-Coleska, Zaneta; Gomez, Cindy; Zhang, Jian; Yi, Han; Wang, Shaomeng

2010-01-01

207

Pancreatic STAT3 protects mice against caerulein-induced pancreatitis via PAP1 induction.  

PubMed

The signal transducer and activator of transcription 3 (STAT3) is a transcription factor that controls expressions of several genes involved in cell survival, proliferation and differentiation, and tissue inflammation. However, the significance of pancreatic STAT3 in acute pancreatitis remains unclear. We generated conditional STAT3 knockout (stat3(?/?)) mice by crossing stat3(flox/flox) mice with Pdx1-promoter Cre transgenic mice. Caerulein administration activated pancreatic STAT3 and induced acute pancreatitis as early as 3 hours in wild-type mice, and full recovery from the induced pancreatic injury was observed within 7 days. The levels of serum amylase and lipase and histologic scores of pancreatic necrosis and inflammatory cell infiltration were significantly higher at 3 hours in stat3(?/?) mice than in stat3(flox/flox) mice. Pancreatic recovery after pancreatitis was significantly delayed in stat3(?/?) mice compared with stat3(flox/flox) mice. Although stat3(flox/flox) mice had marked production in the pancreas of pancreatitis-associated protein 1 (PAP1), a serum acute phase protein, this induction was completely abrogated in stat3(?/?) mice. Enforced production of PAP1 by a hydrodynamic procedure in the liver significantly suppressed pancreatic necrosis and inflammation and also promoted pancreatic regeneration and recovery in stat3(?/?) mice to levels similar to those observed in stat3(flox/flox) mice. In conclusion, pancreatic STAT3 is indispensable for PAP1 production, and this STAT3/PAP1 pathway plays a protective role in caerulein-induced pancreatitis. PMID:23064197

Shigekawa, Minoru; Hikita, Hayato; Kodama, Takahiro; Shimizu, Satoshi; Li, Wei; Uemura, Akio; Miyagi, Takuya; Hosui, Atsushi; Kanto, Tatsuya; Hiramatsu, Naoki; Tatsumi, Tomohide; Takeda, Kiyoshi; Akira, Shizuo; Takehara, Tetsuo

2012-10-10

208

Identification of Purine-Scaffold Small-Molecule Inhibitors of Stat3 Activation by QSAR Studies  

PubMed Central

To facilitate the discovery of clinically useful Stat3 inhibitors, computational analysis of the binding to Stat3 of the existing Stat3 dimerization disruptors and quantitative structure?activity relationships (QSAR) were pursued, by which a pharmacophore model was derived for predicting optimized Stat3 dimerization inhibitors. The 2,6,9-trisubstituted-purine scaffold was functionalized in order to access the three subpockets of the Stat3 SH2 domain surface and to derive potent Stat3-binding inhibitors. Select purine scaffolds showed good affinities (KD, 0.8?12 ?M) for purified, nonphosphorylated Stat3 and inhibited Stat3 DNA-binding activity in vitro and intracellular phosphorylation at 20?60 ?M. Furthermore, agents selectively suppressed viability of human prostate, breast and pancreatic cancer cells, and v-Src-transformed mouse fibroblasts that harbor aberrant Stat3 activity. Studies herein identified novel small-molecule trisubstituted purines as effective inhibitors of constitutively active Stat3 and of the viability of Stat3-dependent tumor cells, and are the first to validate the use of purine bases as templates for building novel Stat3 inhibitors.

2010-01-01

209

Mitochondrial Localized STAT3 Is Involved in NGF Induced Neurite Outgrowth  

PubMed Central

Background Signal transducer and activator of transcription 3 (STAT3) plays critical roles in neural development and is increasingly recognized as a major mediator of injury response in the nervous system. Cytokines and growth factors are known to phosphorylate STAT3 at tyrosine705 with or without the concomitant phosphorylation at serine727, resulting in the nuclear localization of STAT3 and subsequent transcriptional activation of genes. Recent evidence suggests that STAT3 may control cell function via alternative mechanisms independent of its transcriptional activity. Currently, the involvement of STAT3 mono-phosphorylated at residue serine727 (P-Ser-STAT3) in neurite outgrowth and the underlying mechanism is largely unknown. Principal Findings In this study, we investigated the role of nerve growth factor (NGF) induced P-Ser-STAT3 in mediating neurite outgrowth. NGF induced the phosphorylation of residue serine727 but not tyrosine705 of STAT3 in PC12 and primary cortical neuronal cells. In PC12 cells, serine but not tyrosine dominant negative mutant of STAT3 was found to impair NGF induced neurite outgrowth. Unexpectedly, NGF induced P-Ser-STAT3 was localized to the mitochondria but not in the nucleus. Mitochondrial STAT3 was further found to be intimately involved in NGF induced neurite outgrowth and the production of reactive oxygen species (ROS). Conclusion Taken together, the findings herein demonstrated a hitherto unrecognized novel transcription independent mechanism whereby the mitochondria localized P-Ser-STAT3 is involved in NGF induced neurite outgrowth.

Zhou, Lihan; Too, Heng-Phon

2011-01-01

210

STAT3 Regulation of Skeletal Muscle Wasting in Cancer Cachexia  

Microsoft Academic Search

Cachexia is a highly complex syndrome identified by metabolic, hormonal and cytokine-related abnormalities, but can be shortly characterized as accelerated skeletal muscle and adipose tissue loss in the context of a chronic inflammatory response. Cachexia is a debilitating complication of several diseases such as AIDS, sepsis, diabetes, renal failure, burn injury and cancer. Cachexia is responsible for 25-30% of cancer

Tufan Aydogdu

2010-01-01

211

ephrinB1 signals from the cell surface to the nucleus by recruitment of STAT3  

PubMed Central

The Eph (erythropoietin-producing hepatoma) family of receptor tyrosine kinases and their membrane-bound ligands, the ephrins, have been implicated in regulating cell adhesion and migration during development by mediating cell-to-cell signaling events. The transmembrane ephrinB (Eph receptor interactor B) protein is a bidirectional signaling molecule that sends a forward signal through the activation of its cognate receptor tyrosine kinase, residing on another cell. A reverse signal can be transduced into the ephrinB-expressing cell via tyrosine phosphorylation of its conserved C-terminal cytoplasmic domain. Although some insight has been gained regarding how ephrinB may send signals affecting cytoskeletal components, little is known about how ephrinB1 reverse signaling affects transcriptional processes. Here we report that signal transducer and activator of transcription 3 (STAT3) can interact with ephrinB1 in a phosphorylation-dependent manner that leads to enhanced activation of STAT3 transcriptional activity. This activity depends on the tyrosine kinase Jak2, and two tyrosines within the intracellular domain of ephrinB1 are critical for the association with STAT3 and its activation. The recruitment of STAT3 to ephrinB1, and its resulting Jak2-dependent activation and transcription of reporter targets, reveals a signaling pathway from ephrinB1 to the nucleus.

Bong, Yong-Sik; Lee, Hyun-Shik; Carim-Todd, Laura; Mood, Kathleen; Nishanian, Tagvor G.; Tessarollo, Lino; Daar, Ira O.

2007-01-01

212

TMF/ARA160 is a BC-box-containing protein that mediates the degradation of Stat3.  

PubMed

TMF/ARA160 is a Golgi resident protein whose cellular functions have not been conclusively revealed. Herein we show that TMF/ARA160 can direct the proteasomal degradation of the key cell growth regulator - Stat3. TMF/ARA160 was dispersed in the cytoplasm of myogenic C2C12 cells that were grown under low-serum conditions. The cytoplasmic distribution of TMF/ARA160 was accompanied by its transient association with the tyrosine kinase Fer and with Stat3, which underwent proteasomal degradation under those conditions. Moreover, serum deprivation induced the association of ubiquitinated proteins, with the TMF/ARA160 complex. However, TMF/ARA160 did not bind Stat1, whose cellular levels were increased in serum-starved C2C12 cells. Amino-acid sequence analysis identified a BC-box element in TMF/ARA160 that mediated the binding of this protein to elongin C. Ectopic expression of TMF/ARA160 in serum-starved C2C12 cells drove the ubiquitination and proteasomal degradation of Stat3, an effect that was not caused by TMF/ARA160 devoid of the BC-box motif. Thus, the Golgi apparatus harbors a novel BC-box-containing protein that can direct Stat3 to proteasomal degradation. Interestingly, the level of TMF/ARA160 was significantly decreased in malignant brain tumors, implying a suppressive role of that protein in tumor progression. PMID:15467733

Perry, Erez; Tsruya, Rachel; Levitsky, Pavel; Pomp, Oz; Taller, Michal; Weisberg, Shira; Parris, Wendy; Kulkarni, Sarang; Malovani, Hana; Pawson, Tony; Shpungin, Sally; Nir, Uri

2004-11-25

213

Loss of STAT5 causes liver fibrosis and cancer development through increased TGF-? and STAT3 activation  

PubMed Central

The molecular mechanisms underlying the development of hepatocellular carcinoma are not fully understood. Liver-specific signal transducer and activator of transcription (STAT) 5A/B–null mice (STAT5-LKO) were treated with carbon tetrachloride (CCl4), and histological analyses revealed liver fibrosis and tumors. Transforming growth factor (TGF)–? levels and STAT3 activity were elevated in liver tissue from STAT5-LKO mice upon CCl4 treatment. To define the molecular link between STAT5 silencing and TGF-? up-regulation, as well as STAT3 activation, we examined STAT5-null mouse embryonic fibroblasts and primary hepatocytes. These cells displayed elevated TGF-? protein levels, whereas messenger RNA levels remained almost unchanged. Protease inhibitor studies revealed that STAT5 deficiency enhanced the stability of mature TGF-?. Immunoprecipitation and immunohistochemistry analyses demonstrated that STAT5, through its N-terminal sequences, could bind to TGF-? and that retroviral-mediated overexpression of STAT5 decreased TGF-? levels. To confirm the in vivo significance of the N-terminal domain of STAT5, we treated mice that expressed STAT5 lacking the N terminus (STAT5-?N) with CCl4. STAT5-?N mice developed CCl4-induced liver fibrosis but no tumors. In conclusion, loss of STAT5 results in elevated TGF-? levels and enhanced growth hormone–induced STAT3 activity. We propose that a deregulated STAT5–TGF-?–STAT3 network contributes to the development of chronic liver disease.

Kimura, Akiko; Yamaji, Daisuke; Zhu, Bing-mei; Na, Risu; Hennighausen, Lothar

2009-01-01

214

A point mutation, E95D, in the mumps virus V protein disengages STAT3 targeting from STAT1 targeting.  

PubMed

Mumps virus, like other paramyxoviruses in the Rubulavirus genus, encodes a V protein that can assemble a ubiquitin ligase complex from cellular components, leading to the destruction of cellular signal transducer and activator of transcription (STAT) proteins. While many V proteins target the interferon-activated STAT1 or STAT2 protein, mumps virus V protein is unique in its ability to also target STAT3 for ubiquitin modification and proteasome-mediated degradation. Here we report that a single amino acid substitution in the mumps virus V protein, E95D, results in defective STAT3 targeting while maintaining the ability to target STAT1. Results indicate that the E95D mutation disrupts the ability of the V protein to associate with STAT3. A recombinant mumps virus carrying the E95D mutation in its P and V proteins replicates normally in cultured cells but fails to induce targeting of STAT3. Infection with the recombinant virus results in the differential regulation of a number of cellular genes compared to wild-type mumps virus and increases cell death in infected cells, producing a large-plaque phenotype. PMID:19386700

Puri, Mamta; Lemon, Ken; Duprex, W Paul; Rima, Bertus K; Horvath, Curt M

2009-04-22

215

STAT3 and STAT1 mediate IL-11-dependent and inflammation-associated gastric tumorigenesis in gp130 receptor mutant mice  

PubMed Central

Deregulated activation of STAT3 is frequently associated with many human hematological and epithelial malignancies, including gastric cancer. While exaggerated STAT3 signaling facilitates an antiapoptotic, proangiogenic, and proproliferative environment for neoplastic cells, the molecular mechanisms leading to STAT3 hyperactivation remain poorly understood. Using the gp130Y757F/Y757F mouse model of gastric cancer, which carries a mutated gp130 cytokine receptor signaling subunit that cannot bind the negative regulator of cytokine signaling SOCS3 and is characterized by hyperactivation of the signaling molecules STAT1 and STAT3, we have provided genetic evidence that IL-11 promotes chronic gastric inflammation and associated tumorigenesis. Expression of IL-11 was increased in gastric tumors in gp130Y757F/Y757F mice, when compared with unaffected gastric tissue in wild-type mice, while gp130Y757F/Y757F mice lacking the IL-11 ligand–binding receptor subunit (IL-11R?) showed normal gastric STAT3 activation and IL-11 expression and failed to develop gastric tumors. Furthermore, reducing STAT3 activity in gp130Y757F/Y757F mice, either genetically or by therapeutic administration of STAT3 antisense oligonucleotides, normalized gastric IL-11 expression and alleviated gastric tumor burden. Surprisingly, the genetic reduction of STAT1 expression also reduced gastric tumorigenesis in gp130Y757F/Y757F mice and coincided with reduced gastric inflammation and IL-11 expression. Collectively, our data have identified IL-11 as a crucial cytokine promoting chronic gastric inflammation and associated tumorigenesis mediated by excessive activation of STAT3 and STAT1.

Ernst, Matthias; Najdovska, Meri; Grail, Dianne; Lundgren-May, Therese; Buchert, Michael; Tye, Hazel; Matthews, Vance B.; Armes, Jane; Bhathal, Prithi S.; Hughes, Norman R.; Marcusson, Eric G.; Karras, James G.; Na, Songqing; Sedgwick, Jonathon D.; Hertzog, Paul J.; Jenkins, Brendan J.

2008-01-01

216

Interferon induces miR-21 through a STAT3-dependent pathway as a suppressive negative feedback on interferon-induced apoptosis  

PubMed Central

The microRNA miR-21 is overexpressed in many human cancers where accumulating evidence indicate it functions as an oncogene. Here we report that the cytokine; rapidly induces miR-21 expression in human and mouse cells. STAT3 was implicated in this pathway based on the lack of an effect of IFN on miR-21 expression in prostate cancer cells with a deletion in the STAT3 gene. STAT3 ablation abrogated IFN induction of miR-21, confirming the important role of STAT3 in regulating miR-21. Chromatin immunoprecipitation analysis showed that STAT3 directly bound the miR-21 promoter in response to IFN. Experiments in mouse embryo fibroblasts with a genetic deletion of the p65 NF-?B subunit showed that IFN-induced miR-21 expression was also dependent on NF-?B. STAT3 silencing blocked both IFN-induced p65 binding to the miR-21 promoter and p65 nuclear translocation. Thus, IFN-induced miR-21 expression is co-regulated by STAT3 and NF-?B at the level of the miR-21 promoter. Several cell death regulators were identified as downstream targets of miR-21, including PTEN and Akt. Functional experiments in prostate cancer cells demonstrated directly that miR-21 plays a critical role in suppressing IFN-induced apoptosis. Our results identify miR-21 as a novel IFN target gene that functions as a key feedback regulator of IFN-induced apoptosis.

Yang, Chuan He; Yue, Junming; Fan, Meiyun; Pfeffer, Lawrence M.

2010-01-01

217

H11 kinase/heat shock protein 22 deletion impairs both nuclear and mitochondrial functions of STAT3 and accelerates the transition into heart failure on cardiac overload  

PubMed Central

Background Cardiac overload, a major cause of heart failure, induces the expression of the heat shock protein H11 kinase/Hsp22 (Hsp22). Methods and Results To determine the specific function of Hsp22 in that context, a knockout (KO) mouse model of Hsp22 deletion was generated. Although comparable to wild type mice in basal conditions, KO mice exposed to pressure overload developed less hypertrophy, and showed ventricular dilation, impaired contractile function, increased myocyte length and accumulation of interstitial collagen, faster transition into heart failure and increased mortality. Microarrays revealed that hearts from KO mice failed to transactivate genes regulated by the transcription factor STAT3. Accordingly, nuclear STAT3 tyrosine phosphorylation was decreased in KO. Silencing and over-expression experiments in isolated neonatal rat cardiomyocytes showed that Hsp22 activates STAT3 via production of interleukin-6 by the transcription factor NF-?B. In addition to its transcriptional function, STAT3 also translocates to the mitochondria where it increases oxidative phosphorylation. Both mitochondrial STAT3 translocation and respiration were significantly decreased in KO mice as well. Conclusions Hsp22 represents a previously undescribed activator of both nuclear and mitochondrial functions of STAT3, and its deletion in a context of pressure overload in vivo accelerates the transition into heart failure and increases mortality.

Qiu, Hongyu; Lizano, Paulo; Laure, Lydie; Sui, Xiangzhen; Rashed, Eman; Park, Ji Yeon; Hong, Chull; Gao, Shumin; Holle, Eric; Morin, Didier; Dhar, Sunil K.; Wagner, Thomas E.; Berdeaux, Alain; Tian, Bin; Vatner, Stephen F.; Depre, Christophe

2011-01-01

218

Impaired JAK2-induced activation of STAT3 in failing human myocytes.  

PubMed

Although angiotensin (Ang)II-induced Janus-activated kinase (JAK)2 phosphorylation was reported to be enhanced in failing human cardiomyocytes, the downstream balance between cardio-protective (signal transducer and activator of transcription-STAT3) and the pro-inflammatory (STAT2 and STAT5) response remains unexplored. Therefore STATs phosphorylation and putative genes overexpression following JAK2 activation were investigated in isolated cardiomyocytes obtained from failing human hearts (n = 16), and from non-failing(NF) hearts of humans (putative donors, n = 6) or adult rats. In NF myocytes Ang II-induced JAK2 activation was followed by STAT3 phosphorylation (186 ± 45% at 30 min), with no STAT2 or STAT5 response. The associated B cell lymphoma (Bcl)-xL overexpression (1.05 ± 0.39 fold) was abolished by both JAK2 and extracellular signal-regulated kinase (ERK)1/2 inhibitors (AG490, 10 ?M, and PD98059, 30 ?M, respectively), whereas Fas ligand (Fas-L) response (0.91 ± 0.21 fold) was inhibited only by p38MAPK antagonism (SB203580, 10 ?M). In failing myocytes Ang II-induced JAK2 activation was followed by STAT2 (237 ± 38%) and STAT5 (222 ± 31%) phosphorylation, with no STAT3 response. No changes in Bcl-xL expression were observed, and the associated Fas-L gene overexpression (1.14 ± 0.27 fold) being abolished by p38 mitogen-activated protein kinase (MAPK) antagonism. The altered JAK2 induced STATs response in human failing cardiomyocytes may be of relevance for the progression of cardiac dysfunction in heart failure. PMID:22735740

Cambi, Giulia Elisa; Lucchese, Gianluca; Djeokeng, Mah Mc Harol; Modesti, Alessandra; Fiaschi, Tania; Faggian, Giuseppe; Sani, Guido; Modesti, Pietro Amedeo

2012-06-26

219

Inhibition of a novel specific neuroglial integrin signaling pathway increases STAT3-mediated CNTF expression  

PubMed Central

Background Ciliary neurotrophic factor (CNTF) expression is repressed in astrocytes by neuronal contact in the CNS and is rapidly induced by injury. Here, we defined an inhibitory integrin signaling pathway. Results The integrin substrates laminin, fibronectin and vitronectin, but not collagen, thrombospondin or fibrinogen, reduced CNTF expression in C6 astroglioma cells. Antibodies against ?v and ?5, but not ?6 or ?1, integrin induced CNTF. Together, the ligand and antibody specificity suggests that CNTF is repressed by ?v?5 integrin. Antibodies against Thy1, an abundant neuronal surface protein whose function is unclear, induced CNTF in neuron-astrocyte co-cultures indicating that it is a neuroglial CNTF repressor. Inhibition of the integrin signaling molecule Focal Adhesion Kinase (FAK) or the downstream c-Jun N-terminal kinase (JNK), but not extracellular regulated kinase (ERK) or p38 MAPK, greatly induced CNTF mRNA and protein expression within 4 hours. This selective inhibitory pathway phosphorylated STAT3 on its inhibitory ser-727 residue interfering with activity of the pro-transcription Tyr-705 residue. STAT3 can activate CNTF transcription because it bound to its promoter and FAK antagonist-induced CNTF was reduced by blocking STAT3. Microinjection of FAK inhibitor directly into the brain or spinal cord in adult mice rapidly induced CNTF mRNA and protein expression. Importantly, systemic treatment with FAK inhibitors over 3 days induced CNTF in the subventricular zone and increased neurogenesis. Conclusions Neuron-astroglia contact mediated by integrins serves as a sensor to enable rapid neurotrophic responses and provides a new pharmacological avenue to exploit the neuroprotective properties of endogenous CNTF.

2013-01-01

220

STAT3 inhibition is a therapeutic strategy for ABC-like diffuse large B cell lymphoma  

PubMed Central

Persistent STAT3 signaling contributes to malignant progression in many diverse types of human cancer. STAT3 is constitutively active in activated B cell (ABC)-like diffuse large B cell lymphomas (DLBCL), a class of non-germinal center derived DLBCL cells for which existing therapy is weakly effective. In this report, we provide a preclinical proof of concept that STAT3 is an effective molecular target for ABC-like DLBCL therapy. Direct inhibition of STAT3 with shRNA suppressed the growth of human ABC-like DLBCL in mouse models in a manner associated with apoptosis, repression of STAT3 target genes and inhibition of a tumor-promoting microenvironment. Together, these results suggest that STAT3 is essential to maintain the pathophysiology of ABC-like DLBCL and therefore that STAT3 inhibition may offer a promising approach in its therapy.

Scuto, Anna; Kujawski, Maciej; Kowolik, Claudia; Krymskaya, Ludmila; Wang, Lin; Weiss, Lawrence M.; DiGiusto, David; Yu, Hua; Forman, Stephen; Jove, Richard

2011-01-01

221

Identification of a Stat3-dependent transcription regulatory network involved in metastatic progression  

PubMed Central

High levels of activated Stat3 are often found in human breast cancers and can correlate with poor patient outcome. We employed an activated-ErbB2 mouse model of breast cancer to investigate the in vivo role of Stat3 in mammary tumor progression and found that Stat3 does not alter mammary tumor initiation but dramatically affects metastatic progression. Four-fold fewer animals exhibited lung metastases in the absence of Stat3 and a 12-fold reduction in the number of lung lesions was observed in the Stat3-null tumors when compared to tumors from the wild type cohort. The decreased malignancy in Stat3-deficient tumors is attributed to a reduction in both angiogenic and inflammatory responses associated with a Stat3-dependent transcriptional cascade involving C/EBP?.

Ranger, Jill J.; Levy, David E.; Shahalizadeh, Solmaz; Hallett, Michael; Muller, William J.

2010-01-01

222

Calreticulin-STAT3 Signaling Pathway Modulates Mitochondrial Function in a Rat Model of Furazolidone-Induced Dilated Cardiomyopathy  

PubMed Central

Background Calreticulin is a Ca2+-binding chaperone of the endoplasmic reticulum which regulates the signal transducer and activator of transcription 3 (STAT3). The effects of the calreticulin-STAT3 signaling pathway on cardiac mitochondria and on the progress of dilated cardiomyopathy (DCM) are still unclear. Methods and Results The DCM model was generated in rats by the daily oral administration of furazolidone. Echocardiographic and hemodynamic studies demonstrated enlarged LV dimensions and reduced systolic and diastolic functions at thirty weeks after the first furazolidone administration. Morphometric analysis showed significant myocardial degeneration, interstitial fibrosis, and mitochondrial swelling with fractured or dissolved cristae in the model group. Compared with the control group, the mitochondrial membrane potential (MMP) level of the freshly isolated cardiac mitochondria and the enzyme activities of cytochrome c oxidase and succinate dehydrogenase in the model group were significantly decreased (P<0.05). Real-time PCR and western-blot revealed the increased expression of calreticulin associated with decreased activity of STAT3 in the model group. When cultured neonatal rat cardiomyocytes were exposed to furazolidone, a dose-dependent decrease in cell viability and MMP, and the increase of apoptosis rate were observed. The mRNA and protein expression of CRT gradually increased with the increase of furazolidone concentration, associated with a gradual decrease of the STAT3 phosphorylation level both in the whole cell and mitochondrial fraction. When calreticulin was knocked down with siRNA in cardiomyocytes, these changes of cardiomyocytes and mitochondria induced by furazolidone were significantly attenuated. Conclusions A rat model of DCM induced by furazolidone is successfully established. The calreticulin-STAT3 signaling pathway is involved in cardiac mitochondrial injury and the progress of furazolidone induced DCM.

Zhang, Ming; Wei, Jin; Shan, Hu; Wang, Hao; Zhu, Yanhe; Xue, Jiahong; Lin, Lin; Yan, Rui

2013-01-01

223

Lipopolysaccharide-squamous cell carcinoma-monocyte interactions induce cancer-supporting factors leading to rapid STAT3 activation.  

PubMed

Oral and oro-pharyngeal squamous cell carcinomas (OSCC) exhibit surface breach, and recent studies have demonstrated bacterial contamination of primary and metastatic OSCC. Increasing concentrations of inflammatory products, such as interleukin (IL)-6 and vascular endothelial growth factor (VEGF), correlate with, and contribute to, cancer progression, but their regulation in OSCC is poorly understood. We hypothesized that monocyte-lineage cells and bacterial contamination may contribute important inflammatory products that can support OSCC progression. We found that relative to non-specific chronic mucositis, oral carcinoma-in-situ/superficially-invasive OSCC contained more monocyte-lineage cells. In vitro, we used lipopolysaccharide (LPS) to model bacterial contamination, and evaluated the effects of oral and oropharyngeal (O)SCC-monocyte interactions and of LPS on OSCC cells and on the production of IL-6 and VEGF. OSCC cell lines varied in constitutive cytokine and chemokine production, and OSCC-monocyte interactions in the absence of LPS stimulated IL-6 and VEGF occasionally, while LPS-OSCC-monocyte interactions were always strongly stimulatory. Importantly, LPS independently stimulated some OSCC lines to secrete monocyte-dendritic cell chemoattractants CCL2 and/or CCL20, as well as IL-6 and/or VEGF. While very little constitutive Y705-STAT3 phosphorylation (pY705-STAT3) was detectable in HNSCC lines, IL-6 rapidly induced pY705-STAT3 in OSCC lines that produced little IL-6 constitutively. Supernatants from LPS-OSCC-monocyte co-cultures always rapidly and strongly activated STAT3, which was partly due to IL-6. We conclude that monocytes and microbial contamination have the potential to contribute to OSCC progression, as STAT3 activation in OSCC cells depends on soluble factors, which are consistently available through LPS-OSCC-monocyte interactions. PMID:19603082

Kurago, Zoya B; Lam-ubol, Aroonwan; Stetsenko, Anton; De La Mater, Chris; Chen, Yiyi; Dawson, Deborah V

2008-03-01

224

IL-17 induces AKT-dependent IL-6/JAK2/STAT3 activation and tumor progression in hepatocellular carcinoma  

PubMed Central

Background The Th17 subset and IL-17 have been found in increased frequencies within certain tumors. However, their relevance in cancer biology remains controversial. This study aimed to clarify the biological action of IL-17 on hepatocellular carcinoma (HCC). Methods Effects and underlying molecular mechanisms of IL-17 on human HCC were explored in vitro using exogenous IL-17 stimulation and in nude mice by implanting IL-17 overexpressed HCC cells. The clinical significance of IL-17 was investigated in tissue microarrays containing HCC tissues from 323 patients following hepatectomy using immunohistochemistry. Results Although exogenous IL-17 showed no direct effect on the growth rate of HCC cells in vitro, PCR and ELISA showed that IL-17 selectively augmented the secretion of diverse proinvasive factors and transwell showed a direct promotion of invasion of HCC cells by IL-17. Furthermore, transfection of IL-17 into HCC cells significantly promoted neoangiogenesis, neutrophil recruitment and tumor growth in vivo. Using siRNA mediated knockdown of AKT and STAT3, we suggested that the effects of IL-17 were operated through activation of the AKT signaling in HCC, which resulted in IL-6 production. Then, IL-6 in turn activated JAK2/STAT3 signaling and subsequently up-regulated its downstream targets IL-8, MMP2, and VEGF. Supporting these findings, in human HCC tissues, immunostaining indicated that IL-17 expression was significantly and positively associated with STAT3 phosphorylation, neutrophil infiltration and increased tumor vascularity. The clinical significance of IL-17 was authenticated by revealing that the combination of intratumoral IL-17+ cells and phospho-STAT3 served as a better prognosticator for postoperative tumor recurrence than either marker alone. Conclusions IL-17 mediated tumor-promoting role involves a direct effect on HCC cells through IL-6/JAK2/STAT3 induction by activating the AKT pathway.

2011-01-01

225

Interleukin-6 Induces S100A9 Expression in Colonic Epithelial Cells through STAT3 Activation in Experimental Ulcerative Colitis  

PubMed Central

Background Intestinal epithelium is essential for maintaining normal intestinal homeostasis; its breakdown leads to chronic inflammatory pathologies, such as inflammatory bowel diseases (IBDs). Although high concentrations of S100A9 protein and interleukin-6 (IL-6) are found in patients with IBD, the expression mechanism of S100A9 in colonic epithelial cells (CECs) remains elusive. We investigated the role of IL-6 in S100A9 expression in CECs using a colitis model. Methods IL-6 and S100A9 expression, signal transducer and activator of transcription 3 (STAT3) phosphorylation, and infiltration of immune cells were analyzed in mice with dextran sulfate sodium (DSS)-induced colitis. The effects of soluble gp130-Fc protein (sgp130Fc) and S100A9 small interfering (si) RNA (si-S100A9) on DSS-induced colitis were evaluated. The molecular mechanism of S100A9 expression was investigated in an IL-6-treated Caco-2 cell line using chromatin immunoprecipitation assays. Results IL-6 concentrations increased significantly in the colon tissues of DSS-treated mice. sgp130Fc or si-S100A9 administration to DSS-treated mice reduced granulocyte infiltration in CECs and induced the down-regulation of S100A9 and colitis disease activity. Treatment with STAT3 inhibitors upon IL-6 stimulation in the Caco-2 cell line demonstrated that IL-6 mediated S100A9 expression through STAT3 activation. Moreover, we found that phospho-STAT3 binds directly to the S100A9 promoter. S100A9 may recruit immune cells into inflamed colon tissues. Conclusions Elevated S100A9 expression in CECs mediated by an IL-6/STAT3 signaling cascade may play an important role in the development of colitis.

Choi, Ji Won; Lee, Chang-Seok; Sim, Ji Hyun; Cho, Chung-Hyun; Lee, Kwang-Ho; Cho, Ik-Hyun; Chung, Myung-Hee; Kim, Hang-Rae; Ye, Sang-Kyu

2012-01-01

226

CCR1-mediated STAT3 tyrosine phosphorylation and CXCL8 expression in THP-1 macrophage-like cells involve pertussis toxin-insensitive G?(14/16) signaling and IL-6 release.  

PubMed

Agonists of CCR1 contribute to hypersensitivity reactions and atherosclerotic lesions, possibly via the regulation of the transcription factor STAT3. CCR1 was demonstrated to use pertussis toxin-insensitive G?(14/16) to stimulate phospholipase C? and NF-?B, whereas both G?(14) and G?(16) are also capable of activating STAT3. The coexpression of CCR1 and G?(14/16) in human THP-1 macrophage-like cells suggests that CCR1 may use G?(14/16) to induce STAT3 activation. In this study, we demonstrated that a CCR1 agonist, leukotactin-1 (CCL15), could indeed stimulate STAT3 Tyr(705) and Ser(727) phosphorylation via pertussis toxin-insensitive G proteins in PMA-differentiated THP-1 cells, human erythroleukemia cells, and HEK293 cells overexpressing CCR1 and G?(14/16). The STAT3 Tyr(705) and Ser(727) phosphorylations were independent of each other and temporally distinct. Subcellular fractionation and confocal microscopy illustrated that Tyr(705)-phosphorylated STAT3 translocated to the nucleus, whereas Ser(727)-phosphorylated STAT3 was retained in the cytosol after CCR1/G?(14) activation. CCL15 was capable of inducing IL-6 and IL-8 (CXCL8) production in both THP-1 macrophage-like cells and HEK293 cells overexpressing CCR1 and G?(14/16). Neutralizing Ab to IL-6 inhibited CCL15-mediated STAT3 Tyr(705) phosphorylation, whereas inhibition of STAT3 activity abolished CCL15-activated CXCL8 release. The ability of CCR1 to signal through G?(14/16) provides a linkage for CCL15 to regulate IL-6/STAT3-signaling cascades, leading to expression of CXCL8, a cytokine that is involved in inflammation and the rupture of atherosclerotic plaque. PMID:23125416

Lee, Maggie M K; Chui, Ricky K S; Tam, Issan Y S; Lau, Alaster H Y; Wong, Yung H

2012-11-02

227

JAK1 activates STAT3 activity in non-small-cell lung cancer cells and IL-6 neutralizing antibodies can suppress JAK1-STAT3 signaling.  

PubMed

Members of the signal transducer and activator of transcription (STAT) family of transcription factors are potential targets for the treatment and prevention of cancers including non-small-cell lung cancer. STAT proteins can be phosphorylated and activated by diverse upstream kinases including cytokine receptors and tyrosine kinases. We examined STAT protein activation in lung cancer cell lines including those with activating mutations in the EGFR and examined upstream kinases responsible for STAT3 phosphorylation and activation using small molecules, antibodies, and RNA interference. We found more pronounced STAT3 activation in cells with activating EGFR mutations, yet inhibition of EGFR activity had no effect on STAT3 activation. Inhibition of JAK1 with small molecules or RNA interference resulted in loss of STAT3 tyrosine phosphorylation and inhibition of cell growth. An interleukin-6 neutralizing antibody, siltuximab (CNTO 328) could inhibit STAT3 tyrosine phosphorylation in a cell-dependent manner. Siltuximab could completely inhibit STAT3 tyrosine phosphorylation in H1650 cells, and this resulted in inhibition of lung cancer cell growth in vivo. Combined EGFR inhibition with erlotinib and siltuximab resulted in dual inhibition of both tyrosine and serine STAT3 phosphorylation, more pronounced inhibition of STAT3 transcriptional activity, and translated into combined effects on lung cancer growth in a mouse model. Our results suggest that JAK1 is responsible for STAT3 activation in lung cancer cells and that indirect attacks on JAK1-STAT3 using an IL-6 neutralizing antibody with or without EGFR inhibition can inhibit lung cancer growth in lung cancer subsets. PMID:21216930

Song, Lanxi; Rawal, Bhupendra; Nemeth, Jeffrey A; Haura, Eric B

2011-01-07

228

Neural Differentiation Potentiated by the Leukaemia Inhibitory Factor through STAT3 Signalling in Mouse Embryonal Carcinoma Cells  

Microsoft Academic Search

LIF is a cytokine playing a key role in the regulation of self-renewal and maintenance of undif- ferentiated state in mouse ES cells. The response of pluripotent cells to LIF is mediated mainly by the STAT3 and ERK signalling pathways. Recently, we have shown that LIF potentiated retinoic acid-in- duced neural differentiation of pluripotent mouse embryonal carcinoma P19 cells. Here

J. PACHERNÍK; V. HORVÁTH; L. KUBALA; P. DVO?ÁK; A. KOZUBÍK; A. HAMPL

229

Expression of p53\\/hgf\\/c-met\\/STAT3 signal in fetuses with neural tube defects  

Microsoft Academic Search

Neural tube defects (NTD) are morphogenetic alterations due to a defective closure of neural tube. Hepatocyte growth factor\\u000a (HGF)\\/c-met system plays a role in morphogenesis of nervous system, lung, and kidney. HGF\\/c-met morphogenetic effects are\\u000a mediated by signal transducers and activators of transcription (STAT)3 and both HGF and c-met genes are regulated from p53.\\u000a The aim of our study was

Maria Trovato; Maria D’Armiento; Luca Lavra; Alessandra Ulivieri; Roberto Dominici; Enrica Vitarelli; Maddalena Grosso; Raffaella Vecchione; Gaetano Barresi; Salvatore Sciacchitano

2007-01-01

230

STAT3? interacts with nuclear GSK3beta and cytoplasmic RISK pathway and stabilizes rhythm in the anoxic-reoxygenated embryonic heart.  

PubMed

Activation of the Janus Kinase 2/Signal Transducer and Activator of Transcription 3 (JAK2/STAT3) pathway is known to play a key role in cardiogenesis and to afford cardioprotection against ischemia-reperfusion in adult. However, involvement of JAK2/STAT3 pathway and its interaction with other signaling pathways in developing heart transiently submitted to anoxia remains to be explored. Hearts isolated from 4-day-old chick embryos were submitted to anoxia (30 min) and reoxygenation (80 min) with or without the antioxidant MPG, the JAK2/STAT3 inhibitor AG490 or the PhosphoInositide-3-Kinase (PI3K)/Akt inhibitor LY-294002. Time course of phosphorylation of STAT3?(tyrosine705) and Reperfusion Injury Salvage Kinase (RISK) proteins [PI3K, Akt, Glycogen Synthase Kinase 3beta (GSK3beta), Extracellular signal-Regulated Kinase 2 (ERK2)] was determined in homogenate and in enriched nuclear and cytoplasmic fractions of the ventricle. STAT3 DNA-binding was determined. The chrono-, dromo- and inotropic disturbances were also investigated by electrocardiogram and mechanical recordings. Phosphorylation of STAT3?(tyr705) was increased by reoxygenation, reduced (~50%) by MPG or AG490 but not affected by LY-294002. STAT3 and GSK3beta were detected both in nuclear and cytoplasmic fractions while PI3K, Akt and ERK2 were restricted to cytoplasm. Reoxygenation led to nuclear accumulation of STAT3 but unexpectedly without DNA-binding. AG490 decreased the reoxygenation-induced phosphorylation of Akt and ERK2 and phosphorylation/inhibition of GSK3beta in the nucleus, exclusively. Inhibition of JAK2/STAT3 delayed recovery of atrial rate, worsened variability of cardiac cycle length and prolonged arrhythmias as compared to control hearts. Thus, besides its nuclear translocation without transcriptional activity, oxyradicals-activated STAT3? can rapidly interact with RISK proteins present in nucleus and cytoplasm, without dual interaction, and reduce the anoxia-reoxygenation-induced arrhythmias in the embryonic heart. PMID:21279516

Pedretti, Sarah; Raddatz, Eric

2011-01-29

231

Antiangiogenic effects of ganetespib in colorectal cancer mediated through inhibition of HIF-1? and STAT-3.  

PubMed

Hypoxia-inducible factors (HIFs) and STAT-3 play essential roles in angiogenesis. HIF-1? and STAT-3 are clients of the heat shock protein 90 (HSP90). We hypothesized that ganetespib, a potent HSP90 inhibitor, would disrupt angiogenesis in colorectal cancer (CRC) through inhibition of HIF-1? and STAT-3. CRC cell lines (HCT116 and HT29) were used in all the experiments. Egg CAM and HUVEC assays revealed decreased angiogenesis in ganetespib treated cell lines. Ganetespib inhibited matrigel plug vascularization and tumor growth of xenografts. Significant inhibition of PDGFA, FGF2, Ang-1, Ang-2, TGF?1, VEGF, HIF-1? and STAT-3 expression was observed in both cell lines treated ganetespib. HIF-1? overexpression resulted in the increase VEGF and STAT-3 expression and this was inhibited by ganetespib. HIF-1? knockdown inhibited VEGF and STAT-3 expression. STAT-3 knockdown inhibited VEGF but not HIF-1? expression. HSP90, STAT-3 and VEGF expression was significantly higher in CRC compared to adjacent normal tissue. Significant downregulation of PDGFA, FGF2, Ang-1, Ang-2, TGF?1, VEGF, STAT-3 and HIF-1? mRNA was observed in the post ganetespib treatment tumor samples from patients with rectal cancer. These results collectively suggest that inhibition of HSP90 is a promising antiangiogenic strategy in CRC. HSP90 angiogenic effects are mediated through HIF-1? and STAT-3. PMID:23838996

Ganji, Purnachandra Nagaraju; Park, Wungki; Wen, Jing; Mahaseth, Hemchandra; Landry, Jerome; Farris, Alton B; Willingham, Field; Sullivan, Patrick S; Proia, David A; El-Hariry, Iman; Taliaferro-Smith, Latonia; Diaz, Roberto; El-Rayes, Bassel F

2013-07-10

232

The role of STAT3 activation in modulating the immune microenvironment of GBM  

PubMed Central

Glioblastoma multiforme (GBM) modulates the immune system to engance its malignant potential. Signal transducer and activator of transcription 3 (STAT3) activation is a regulatory node in modulating the immune microenvironment in several human tumors, including GBM. To investigate whether STAT3 inhibition might enhance anti-tumor responses, we inhibited STAT3 signaling using small interfering RNA against STAT3. We tested the human GBM cell lines U87, U251, and HS683, which are known to constitutively express high levels of phospho-STAT3. STAT3 inhibition resulted in enhanced expression of several proinflammatory cytokines and chemokines and supernatants from STAT3-silenced human GBM cell lines increased lipopolysaccharide-induced dendritic cell activation in vitro. We obtained comparable results when STAT3 activity was suppressed with specific small molecule inhibitors. Our results support the hypothesis that activated STAT3 contributes to the immunosuppressive microenvironment in GBM and support previous studies implicating STAT3 as a potential target for immunotherapy.

See, Alfred P.; Han, James E.; Phallen, Jillian; Binder, Zev; Gallia, Gary; Pan, Fan; Jinasena, Dilini; Jackson, Christopher; Belcaid, Zineb; Jeong, Sung Jin; Gottschalk, Chelsea; Zeng, Jing; Ruzevick, Jacob; Nicholas, Sarah; Kim, Young; Albesiano, Emilia; Pardoll, Drew M.; Lim, Michael

2013-01-01

233

Loss of STAT3 in CD4+ T cells prevents development of experimental autoimmune diseases.  

PubMed

Th17 cells are implicated in CNS autoimmune diseases. We show that mice with targeted-deletion of Stat3 in CD4(+) T cells (CD4(Stat3)(-/-)) do not develop experimental autoimmune uveoretinitis (EAU) or experimental autoimmune encephalomyelitis. Defective Th17 differentiation noted in CD4(Stat3)(-/-) mice is compensated by exaggerated increases in Foxp3-, IL-10-, IL-4-, and IFN-gamma-expressing T cells, suggesting critical roles of STAT3 in shaping Ag-specific CD4(+) T cell repertoire. In mice with EAU, a high percentage of IL-17-expressing T cells in their peripheral lymphoid organs also secrete IFN-gamma while these double-expressors are absent in CD4(Stat3)(-/-) and wild-type mice without EAU, raising the intriguing possibility that uveitis maybe mediated by Th17 and IL-17-expressing Th1 cells. Resistance of Stat3-deficient mice to EAU derives in part from an inability of uveitogenic Th17 and Th1 cells to enter eyes or brain of the CD4(Stat3)(-/-) mouse because of the reduction in the expression of activated alpha4/beta1 integrins on CD4(Stat3)(-/-) T cells. Adoptive transfer of activated interphotoreceptor retinoid-binding protein-specific uveitogenic T cells induced in CD4(Stat3)(-/-) mice a severe EAU characterized by development of retinal folds, infiltration of inflammatory cells into the retina, and destruction of retinal architecture, underscoring our contention that the loss of STAT3 in CD4(+) T cells results in an intrinsic developmental defect that renders CD4(Stat3)(-/-) resistant to CNS inflammatory diseases. STAT3 requirement for IL-17 production by Th17, generation of double positive T cells expressing IL-17 and IFN-gamma, and for T cell trafficking into CNS tissues suggests that STAT3 may be a therapeutic target for modulating uveitis, sceritis, or multiple sclerosis. PMID:18424728

Liu, Xuebin; Lee, Yun Sang; Yu, Cheng-Rong; Egwuagu, Charles E

2008-05-01

234

Loss of STAT3 in CD4+ T cells prevents development of experimental autoimmune diseases  

PubMed Central

Th17 cells are implicated in CNS autoimmune diseases. We show that mice with targeted-deletion of STAT3 in CD4+ T-cells (CD4Stat3?/?) do not develop experimental autoimmune uveoretinitis (EAU) or experimental autoimmune encephalomyelitis (EAE). Defective Th17 differentiation noted in CD4Stat3?/? mice is compensated by exaggerated increases in Foxp3-, IL-10-, IL-4- and IFN-?-expressing T-cells, suggesting critical roles of STAT3 in shaping Ag-specific CD4+ T-cell repertoire. In mice with EAU, a high percentage of IL-17-expressing-T-cells in their peripheral lymphoid organs also secretes IFN-? while these double-expressors are absent in CD4Stat3?/? and WT mice without EAU, raising intriguing possibility that uveitis maybe mediated by Th17 and IL-17-expressing Th1 cells. Resistance of STAT3-deficient mice to EAU derives in part from an inability of uveitogenic Th17 and Th1 cells to enter eyes or brain of the CD4Stat3?/? mouse because of the reduction in the expression of activated ?4/?1 integrins on CD4Stat3?/? T cells. Adoptive transfer of activated IRBP-specific uveitogenic T cells induced in CD4Stat3?/? mice a severe EAU characterized by development of retinal folds, infiltration of inflammatory cells into the retina and destruction of retinal architecture, underscoring our contention that the loss of STAT3 in CD4+ T cells results in an intrinsic developmental defect that renders CD4Stat3?/? resistant to CNS inflammatory diseases. STAT3 requirement for IL-17 production by Th17, generation of double positive T cells expressing IL-17 and IFN-? and for T-cell trafficking into CNS tissues, suggests that STAT3 may be a therapeutic target for modulating uveitis, sceritis or multiple sclerosis.

Liu, Xuebin; Lee, Yun sang; Yu, Cheng-Rong; Egwuagu, Charles E.

2008-01-01

235

Inhibition of STAT3 with orally active JAK inhibitor, AZD1480, decreases tumor growth in Neuroblastoma and Pediatric Sarcomas In vitro and In vivo.  

PubMed

The IL-6/JAK/STAT pathway is a key signal transduction pathway implicated in the pathogenesis of many human cancers, suggesting that kinase inhibitors targeting JAK/STAT3 may have a broad spectrum of antitumor activity. AZD1480, a pharmacological JAK1/2 inhibitor, exhibits anti-tumor potency in multiple adult malignancies. To evaluate the efficacy of inhibition of JAK/STAT3 signal transduction pathway we assessed the activity of AZD1480 in pediatric malignancies using preclinical models of three highly malignant pediatric solid tumors: neuroblastoma (NB), rhabdomyosarcoma (RMS) and the Ewing Sarcoma Family Tumors (ESFT). In this study, we employed panels of biomedical and biological experiments to evaluate the in vitro and in vivo activity of AZD1480 in NB, RMS and ESFT. Our data indicate that AZD1480 blocks endogenous as well as IL-6 induced STAT3 activation. AZD1480 decreases cell viability in 7/7NB, 7/7RMS and 2/2 ESFT cell lines (median EC50 is 1.5 ?M, ranging from 0.36-5.37 ?M). AZD1480 induces cell growth inhibition and caspase-dependent apoptosis in vitro and decreases expression of STAT3 target genes, including cell cycle regulators CyclinD1, 3 and CDC25A, anti-apoptotic genes Bcl-2 and survivin, the metastasis-related factor TIMP-1 and c-Myc. In vivo studies showed AZD1480 significantly decreased tumor growth and prolonged overall survival in tumor-bearing mice. Tumors from AZD1480-treated mice showed inhibition of activated STAT3 as well as decreased expression of STAT3 downstream targets. Our study provides strong evidence of the anti-tumor growth potency of JAK inhibitor AZD1480 in pediatric solid tumors, providing proof-of principle that inhibition of the JAK/STAT3 signal transduction could be a promising therapeutic target for high-risk pediatric solid tumors. PMID:23531921

Yan, Shuang; Li, Zhijie; Thiele, Carol J

2013-03-01

236

Overexpression of P-glycoprotein, STAT3, phospho-STAT3 and KIT in spontaneous canine cutaneous mast cell tumours before and after prednisolone treatment.  

PubMed

Prednisolone is a glucocorticoid (GC) commonly used in the treatment of canine mast cell tumours (MCTs); however, resistance to GCs develops in many MCTs following repeated treatment. P-glycoprotein (P-gp), signal transducer and activator of transcription 3 (STAT3) and KIT (CD117) are involved in GC resistance. The aim of this study was to evaluate the response to prednisolone treatment in canine cutaneous MCTs and to investigate the levels of P-gp, STAT3, phospho-STAT3 (pSTAT3) and KIT proteins in MCTs with or without prednisolone treatment. Immunohistochemistry was performed on tumour samples from 41 dogs with cutaneous MCTs. The overall objective response rate (including complete and partial responses) was 51.8% for dogs treated with prednisolone; poorly differentiated or higher stage MCTs had a lower response rate. The median time-span of tumours to reach maximal tumour regression was 14 d (range 3-77 d); 22 (81.5%) reached maximal regression at 21 d. The majority of MCTs overexpressed both P-gp and STAT3 before and after prednisolone treatment. Reduced expression of pSTAT3 and alterations in the KIT expression pattern were observed in MCTs post-treatment. Prednisolone treatment that caused a marked reduction in tumour volume was correlated with reduced pSTAT3 expression. A cytoplasmic KIT staining pattern was correlated with a lower tumour response rate to prednisolone treatment. PMID:22398132

Teng, Shr-Ping; Hsu, Wei-Li; Chiu, Cheng-Yang; Wong, Min-Liang; Chang, Shih-Chieh

2012-03-06

237

Baicalin promotes neuronal differentiation of neural stem/progenitor cells through modulating p-stat3 and bHLH family protein expression.  

PubMed

Signal transducer and activator of transcription 3 (stat3) and basic helix-loop-helix (bHLH) gene family are important cellular signal molecules for the regulation of cell fate decision and neuronal differentiation of neural stem/progenitor cells (NPCs). In the present study, we investigated the effects of baicalin, a flavonoid compound isolated from Scutellaria baicalensis G, on regulating phosphorylation of stat3 and expression of bHLH family proteins and promoting neuronal differentiation of NPCs. Embryonic NPCs from the cortex of E15-16 rats were treated with baicalin (2, 20 ?M) for 2h and 7 days. Neuronal and glial differentiations were identified with mature neuronal marker microtubule associated protein (MAP-2) and glial marker Glial fibrillary acidic protein (GFAP) immunostaining fluorescent microscopy respectively. Phosphorylation of stat3 (p-stat3) and expressions of bHLH family genes including Mash1, Hes1 and NeuroD1 were detected with immunofluorescent microscopy and Western blot analysis. The results revealed that baicalin treatment increased the percentages of MAP-2 positive staining cells and decreased GFAP staining cells. Meanwhile, baicalin treatment down-regulated the expression of p-stat3 and Hes1, but up-regulated the expressions of NeuroD1 and Mash1. Those results indicate that baicalin can promote the neural differentiation but inhibit glial formation and its neurogenesis-promoting effects are associated with the modulations of stat3 and bHLH genes in neural stem/progenitor cells. PMID:22088824

Li, Yue; Zhuang, Pengwei; Shen, Bingrui; Zhang, Yanjun; Shen, Jiangang

2011-10-20

238

The IL-6 family of cytokines modulates STAT3 activation by desumoylation of PML through SENP1 induction  

SciTech Connect

Post-translational modification by small ubiquitin-like modifier (SUMO) plays an important role in the regulation of different signaling pathways and is involved in the formation of promyelocytic leukemia (PML) protein nuclear bodies following sumoylation of PML. In the present study, we found that IL-6 induces desumoylation of PML and dissociation between PML and SUMO1 in hepatoma cells. We also found that IL-6 induces mRNA expression of SENP1, a member of the SUMO-specific protease family. Furthermore, wild-type SENP1 but not an inactive SENP1 mutant restored the PML-mediated suppression of STAT3 activation. These results indicate that the IL-6 family of cytokines modulates STAT3 activation by desumoylation and inactivation PML through SENP1 induction.

Ohbayashi, Norihiko; Kawakami, Shiho; Muromoto, Ryuta; Togi, Sumihito; Ikeda, Osamu; Kamitani, Shinya; Sekine, Yuichi [Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-Ku Kita 12 Nishi 6, Sapporo 060-0812 (Japan); Honjoh, Tsutomu [Morinaga Institute of Biological Sciences, Inc., 2-1-16, Sachiura, Kanazawa-ku, Yokohama 236-0003 (Japan); Matsuda, Tadashi [Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-Ku Kita 12 Nishi 6, Sapporo 060-0812 (Japan)], E-mail: tmatsuda@pharm.hokudai.ac.jp

2008-07-11

239

STAT3 Signaling Induces the Differentiation of Human ICOS+ CD4 T Cells Helping B lymphocytes  

PubMed Central

The generation of high-affinity antibodies and the development of B cell memory are dependent on the help provided by CD4 T cells. Mouse studies indicate that STAT3 signaling in CD4 T cells promotes the acquisition of the B cell help function. However, the role of STAT3 in humans has been controversial. In this study, we show that IL-6 and other STAT3 activating cytokines (IL-21 and IL-27) induce the differentiation of CD4 T cells promoting antibody production by B cells. The acquisition of B cell stimulating properties by naive cord blood CD4 T cells required the STAT3-dependent expression of ICOS and IL-21. Gene reporter and ChIP experiments unambiguously demonstrated that upon IL-6 stimulation, STAT3 induces the transcription of the ICOS gene through direct recruitment to the proximal promoter region indicating that STAT3 acts in part through the direct activation of the ICOS gene.

Delmarcelle, Yves; Nguyen, Muriel; Leo, Oberdan; Goriely, Stanislas; Marchant, Arnaud

2013-01-01

240

An activated JAK/STAT3 pathway and CD45 expression are associated with sensitivity to Hsp90 inhibitors in multiple myeloma.  

PubMed

The molecular chaperone Hsp90 is required to maintain the activity of many signaling proteins, including members of the JAK/STAT and the PI3K pathways. Inhibitors of Hsp90 (Hsp90-Is) demonstrated varying activity against multiple myeloma (MM) in clinical trials. We aimed to determine which signaling pathways that account for the differential sensitivity to the Hsp90-I 17DMAG on a panel of MM cell lines and freshly obtained MM cells. Three CD45(+) cell lines with an activated JAK/STAT3 pathway were sensitive to 17DMAG and underwent prominent apoptosis upon treatment, while the majority of CD45(-) cell lines, that were dependent on the activated PI3K pathway, were more resistant to the drug. Culturing the most resistant cell line, LP1, in the presence of IL-6 resulted in up-regulation of CD45 and pSTAT3, and sensitized to 17DMAG-induced apoptosis, primarily in the induced CD45(+) sub-population of cells. The high CD45 expressers among primary myeloma cells also expressed significantly higher levels of pSTAT3, as compared to the low CD45 expressers. Ex vivo treatment of primary myeloma cells with 17DMAG resulted in a stronger caspase3 activation in tumor samples with the prevalence of high CD45 expressers. STAT3 activity was efficiently inhibited by Hsp90-Is in both cell lines and primary cells suggesting an importance of STAT3 inactivation for the pro-apoptotic effects of HSP90-Is. Indeed, over-expression of STAT3C, a variant with an increased DNA binding activity, in U266 cells protected them from 17DMAG-induced cell death. The down-regulation of the STAT3 target gene Mcl-1 at both the mRNA and protein levels following 17DMAG treatment was significantly attenuated in STAT3C-expressing cells, and transient over-expression of Mcl-1 protected U266 cells from 17DMAG-induced cell death. The finding that CD45(+) MM cells with an IL-6-activated JAK/STAT3 pathway are particularly sensitive to Hsp90-Is as compared to the low CD45 expressers may provide a rational basis for selection of MM patients amenable to Hsp90-I treatment. PMID:23246572

Lin, Huiqiong; Kolosenko, Iryna; Björklund, Ann-Charlotte; Protsyuk, Darya; Österborg, Anders; Grandér, Dan; Tamm, Katja Pokrovskaja

2012-12-13

241

Common STAT3 Variants Are Not Associated With Obesity or Insulin Resistance in Female Twins  

Microsoft Academic Search

In animal models, STAT3 action in the hypothalamus and liver appears essential for normal body weight and glucose homeostasis in response to insulin. We hypothesized that variation in the STAT3 gene may be associated with body fat and\\/or insulin resistance in the general population. Five tagging SNPs spanning the STAT3 gene, rs8074524, rs2293152, rs2306580, rs6503695, and rs7211777 were genotyped in

Yalda Jamshidi; Theodosios Kyriakou; Sakina B. Gooljar; Laura J. Collins; Harold Snieder; Xiaoling Wang; Tim D. Spector; Sandra D. O’Dell

2007-01-01

242

Hyperactivation of Stat3 in gp130 mutant mice promotes gastric hyperproliferation and desensitizes TGF-? signaling  

Microsoft Academic Search

The latent transcription factor Stat3 is activated by gp130, the common receptor for the interleukin (IL)-6 cytokine family and other growth factor and cytokine receptors. Ligand-induced dimerization of gp130 leads to activation of the Stat1, Stat3 and Shp2-Ras-Erk signaling pathways. Here we assess genetically the contribution of exaggerated Stat3 activation to the phenotype of gp130Y757F\\/Y757F mice, in which a knock-in

Brendan J Jenkins; Dianne Grail; Thao Nheu; Meri Najdovska; Bo Wang; Paul Waring; Melissa Inglese; Rachel M McLoughlin; Simon A Jones; Nicholas Topley; Heinz Baumann; Louise M Judd; Andrew S Giraud; Alex Boussioutas; Hong-Jian Zhu; Matthias Ernst

2005-01-01

243

Cucurbitacin Q: a selective STAT3 activation inhibitor with potent antitumor activity  

Microsoft Academic Search

Constitutive activation of the JAK\\/STAT3 pathway is a major contributor to oncogenesis. In the present study, structure–activity relationship (SAR) studies with five cucurbitacin (Cuc) analogs, A, B, E, I, and Q, led to the discovery of Cuc Q, which inhibits the activation of STAT3 but not JAK2; Cuc A which inhibits JAK2 but not STAT3 activation; and Cuc B, E,

Jiazhi Sun; Michelle A Blaskovich; Richard Jove; Sandra K Livingston; Domenico Coppola; Saïd M Sebti

2005-01-01

244

LIGHT, a member of the TNF superfamily, activates Stat3 mediated by NIK pathway  

SciTech Connect

Stat3, a member of the signal transducers and activators of transcription (STAT) family, is a key signal transduction protein activated by numerous cytokines, growth factors, and oncoproteins that controls cell proliferation, differentiation, development, survival, and inflammation. Constitutive activation of Stat3 has been found frequently in a wide variety of human tumors and induces cellular transformation and tumor formation. In this study, we demonstrated that LIGHT, a member of tumor necrosis factor superfamily, activates Stat3 in cancer cells. LIGHT induces dose-dependent activation of Stat3 by phosphorylation at both the tyrosine 705 and serine 727 residues. The activation of Stat3 by LIGHT appears to be mediated by NIK phosphorylation. Expression of a kinase-inactive NIK mutant abolished LIGHT induced Stat3 activation. Overexpression of an active NIK induces Stat3 activation by phosphorylation at the both tyrosine 705 and serine 727 residues. Activation of Stat3 by NIK requires NIK kinase activity as showed by kinase assays. In addition, LIGHT increases the expression of Stat3 target genes including cyclin D1, survivin, and Bcl-xL, and stimulates human LNCaP prostate cancer cell growth in vitro which can be blocked by expression of a dominant-negative Stat3 mutant. Taken together, these results indicate that in addition to activating NF-{kappa}B/p52, LIGHT also activates Stat3. Activation of Stat3 together with activating non-canonical NF-{kappa}B/p52 signaling by LIGHT may maximize its effects on cellular proliferation, survival, and inflammation.

Nadiminty, Nagalakshmi [Departments of Medicine, Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263 (United States); Chun, Jae Yeon [Departments of Medicine, Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263 (United States); Hu, Yan [Departments of Medicine, Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263 (United States); Dutt, Smitha [Departments of Medicine, Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263 (United States); Lin, Xin [Department of Molecular Oncology, MD Anderson Cancer Center, Houston, TX 77030 (United States); Gao, Allen C. [Departments of Medicine, Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263 (United States)]. E-mail: allen.gao@roswellpark.org

2007-07-27

245

Mechanism of the inhibition of the STAT3 signaling pathway by EGCG.  

PubMed

Signal transducer and activator of transcription 3 (STAT3) is an oncogene that promotes cell survival, proliferation, and motility. In the present study, we explored the mechanism involved in the inhibition by epigallocatechin-3-gallate (EGCG) of STAT3 signaling as detected by surface plasmon resonance (SPR)-binding assays and in silico docking. Stat3?binding assay indicated that EGCG significantly interrupted Stat3 peptide binding at micromolar concentrations, and the docking experiments indicated that EGCG had a strong interaction with Arg-609, one of the key residues in the STAT3 SH2 domain that contributes greatly to Stat3 and phosphorylated peptide binding. Following treatment of the hepatocellular carcinoma cell lines BEL-7402 and QGY-7703 with EGCG, in vitro, EGCG significantly suppressed cell proliferation as detected by MTT assay, induced apoptosis as detected by flow cytometry, dramatically lowered the expression levels of phosphorylated Stat3 proteins (p-Stat3) as determined by immunoblot detection, and inhibited the expression of multiple genes including Bcl-xL, c-Myc, VEGF and cyclin D1 as demonstrated by RT-PCR analysis. In conclusion, our research data indicate that the anticancer function of green tea results from the inhibition of the STAT3 signaling pathway by EGCG. PMID:24065300

Wang, Yang; Ren, Xuequn; Deng, Chaoyang; Yang, Lu; Yan, Erfu; Guo, Tao; Li, Yanmin; Xu, Marvin Xuejun

2013-09-20

246

Luteolin Induces Carcinoma Cell Apoptosis through Binding Hsp90 to Suppress Constitutive Activation of STAT3  

PubMed Central

Background Abnormal activity of STAT3 is associated with a number of human malignancies. Hsp90 plays a central role in stabilizing newly synthesized proteins and participates in maintaining the functional competency of a number of signaling transducers involved in cell growth, survival and oncogenesis, such as STAT3. Hsp90 interacts with STAT3 and stabilizes Tyr-phosphorylated STAT3. It has been reported that luteolin possesses anticancer activity through degradation of Tyr705-phosphorylated STAT3. Methodology/Principal Findings We found that overexpression of Hsp90 inhibited luteolin-induced degradation of Tyr705-phosphorylated STAT3 and luteolin also reduced the levels of some other Hsp90 interacting proteins. Results from co-immunoprecipitation and immunoblot analysis demonstrated that luteolin prevented the association between Hsp90 and STAT3 and induced both Tyr705- and Ser727-phosphorylated STAT3 degradation through proteasome-dependent pathway. The molecular modeling analysis with CHARMm–Discovery Studio 2.1(DS 2.1) indicated that luteolin could bind to the ATP-binding pocket of Hsp90. SPR technology-based binding assay confirmed the association between luteolin and Hsp90. ATP-sepharose binding assay displayed that luteolin inhibited Hsp90-ATP binding. Conclusions/Significance Luteolin promoted the degradation of Tyr705- and Ser727-phosphorylated STAT3 through interacting with Hsp90 and induced apoptosis of cancer cells. This study indicated that luteolin may act as a potent HSP90 inhibitor in antitumor strategies.

Zhao, Bo; Zhao, Zhihui; Zhou, Jiahong; Xu, Yimiao; Xin, Yinqiang; Liu, Chang; Luo, Lan; Yin, Zhimin

2012-01-01

247

STAT3 nuclear import is independent of tyrosine phosphorylation and mediated by importin-?3  

PubMed Central

Signal transducer and activator of transcription (STAT)3 is a member of a family of DNA-binding factors that function to induce expression of responsive genes. STAT3 can act as an oncogene, and its function has been shown to be critical for cellular transformation by a number of oncogenic tyrosine kinases. The role of STAT3 as a DNA-binding transcription factor naturally depends on its ability to gain entrance to the nucleus. In this study, we provide evidence that STAT3 is distinct from previously characterized STAT molecules in that it dynamically shuttles between cytoplasmic and nuclear compartments and maintains prominent nuclear presence. Although tyrosine phosphorylation is required for STAT3 to bind to specific DNA target sites, nuclear import takes place constitutively and independently of tyrosine phosphorylation. We identify a region within the coiled-coil domain of the STAT3 molecule that is necessary for nuclear import and demonstrate that this region is critical for its recognition by specific import carrier importin-?3. RNA interference studies were used to verify the role and specificity of importin-?3 in STAT3 nuclear translocation. These results distinguish STAT3 cellular localization from other STAT molecules and identify a feature that may be targeted in the clinical intervention of STAT3-dependent neoplasia.

Liu, Ling; McBride, Kevin M.; Reich, Nancy C.

2005-01-01

248

Critical role of STAT3 in IL-6-mediated drug resistance in human neuroblastoma.  

PubMed

Drug resistance is a major cause of treatment failure in cancer. Here, we have evaluated the role of STAT3 in environment-mediated drug resistance (EMDR) in human neuroblastoma. We determined that STAT3 was not constitutively active in most neuroblastoma cell lines but was rapidly activated upon treatment with interleukin (IL)-6 alone and in combination with the soluble IL-6 receptor (sIL-6R). Treatment of neuroblastoma cells with IL-6 protected them from drug-induced apoptosis in a STAT3-dependent manner because the protective effect of IL-6 was abrogated in the presence of a STAT3 inhibitor and upon STAT3 knockdown. STAT3 was necessary for the upregulation of several survival factors such as survivin (BIRC5) and Bcl-xL (BCL2L1) when cells were exposed to IL-6. Importantly, IL-6-mediated STAT3 activation was enhanced by sIL-6R produced by human monocytes, pointing to an important function of monocytes in promoting IL-6-mediated EMDR. Our data also point to the presence of reciprocal activation of STAT3 between tumor cells and bone marrow stromal cells including not only monocytes but also regulatory T cells (Treg) and nonmyeloid stromal cells. Thus, the data identify an IL-6/sIL-6R/STAT3 interactive pathway between neuroblastoma cells and their microenvironment that contributes to drug resistance. PMID:23633489

Ara, Tasnim; Nakata, Rie; Sheard, Michael A; Shimada, Hiroyuki; Buettner, Ralf; Groshen, Susan G; Ji, Lingyun; Yu, Hua; Jove, Richard; Seeger, Robert C; DeClerck, Yves A

2013-04-30

249

Mechanisms of chronic JAK-STAT3-SOCS3 signaling in obesity  

PubMed Central

Janus kinase (JAK)-signal transducers and activators of transcription (STAT) signaling pathways are critical for the maintenance of homeostatic and developmental processes; however, deregulation and chronic activation of JAK-STAT3 results in numerous diseases. Among others, obesity is currently being intensively studied. In obesity, chronic JAK-STAT3 is activated by the CNS by increased circulating leptin levels leading to the development of leptin resistance, whereas in the peripheral organs chronic IL-6-induced JAK-STAT3 impairs insulin action. We report the consequences of chronic JAK-STAT3 induced signaling as present under obese conditions in the main metabolic organs.

Wunderlich, Claudia M.; Hovelmeyer, Nadine; Wunderlich, F. Thomas

2013-01-01

250

Metastasis suppressor Nm23-H1 inhibits STAT3 signaling via a negative feedback mechanism.  

PubMed

Persistent STAT3 activation is a critical event in tumorigenesis and metastatic progression. Recent studies have found higher levels of STAT3 in metastatic tissues than in primary tumor tissues. We speculated that such increased STAT3 activity might be attributed to a loss of function or reduction in expression of metastasis inhibitory protein during cancer progression, and we therefore examined the role of tumor metastasis-suppressor nm23-H1 in the activation of STAT3 in the A549 lung cancer cell line. We found that IL-6-dependent induction of tyrosine phosphorylation and activation of STAT3 were influenced by nm23-H1 inhibition. IL-6-induced STAT3(Tyr705) phosphorylation was significantly enhanced in A549 cells transfected with siRNA specific for nm23-H1, and the effect of nm23-H1 depletion on IL-6-induced STAT3(Tyr705) phosphorylation was reversed by ectopic expression of shRNA-resistant nm23-H1 protein. Moreover, STAT3 directly bound to the STAT3 binding site on the nm23-H1 promoter and activated its expression. Thus, we have identified a new feedback mechanism that might provide insight into an in-built metastasis-suppression function in tumor cells and which could be a logical new target for treatment of early metastatic disease. PMID:23583378

Gong, Lei; Wu, Zhihao; Guo, Lili; Li, Lin; Zhao, Rongzhi; Zhu, Daxing; Zhou, Qinghua

2013-04-10

251

S1PR1 is an effective target to block STAT3 signaling in activated B cell-like diffuse large B-cell lymphoma  

PubMed Central

STAT3 plays a crucial role in promoting progression of human cancers, including several types of B-cell lymphoma. However, as a transcription factor lacking its own enzymatic activity, STAT3 remains difficult to target with small-molecule drugs in the clinic. Here we demonstrate that persistent activated STAT3 colocalizes with elevated expression of S1PR1, a G-protein–coupled receptor for sphingosine-1-phosphate (S1P), in the tumor cells of the activated B cell–like subtype of diffuse large B-cell lymphoma patient specimens. Inhibition of S1PR1 expression by shRNA in the lymphoma cells validates that blocking S1PR1 affects expression of STAT3 downstream genes critically involved in tumor cell survival, proliferation, tumor invasion, and/or immunosuppression. Using S1PR1 shRNA, or FTY720, an antagonist of S1P that is in the clinic for other indications, we show that inhibiting S1PR1 expression down-regulates STAT3 activity and causes growth inhibition of the lymphoma tumor cells in vitro and in vivo. Our results suggest that targeting S1P/S1PR1 using a clinically relevant and available drug or other approaches is potentially an effective new therapeutic modality for treating the activated B cell–like subtype of diffuse large B-cell lymphoma, a subset of lymphoma that is less responsive to current available therapies.

Liu, Yong; Deng, Jiehui; Wang, Lin; Lee, Heehyoung; Armstrong, Brian; Scuto, Anna; Kowolik, Claudia; Weiss, Lawrence M.; Forman, Stephen

2012-01-01

252

Functional graphene oxide as a plasmid-based Stat3 siRNA carrier inhibits mouse malignant melanoma growth in vivo  

NASA Astrophysics Data System (ADS)

Graphene oxide (GO) has attracted intensive interest in the biomedical field in recent years. We investigate whether the use of functional graphene oxide as an efficient delivery system for delivering specific molecular antitumor therapeutics in vivo could achieve a more excellent antitumor effect. Constitutive activation of signal transducer and activator of transcription 3 (Stat3) promotes survival in a wide spectrum of human cancers. In this paper, we study the in vivo behavior of graphene oxide chemically functionalized with polyethylenimine and polyethylene glycol (GO-PEI-PEG) as a plasmid-based Stat3-specific small interfering RNA (siRNA) carrier in mouse malignant melanoma. The in vivo results indicate significant regression in tumor growth and tumor weight after plasmid-based Stat3 siRNA delivered by GO-PEI-PEG treatment. Moreover, there was no significant side effect from GO-PEI-PEG treatment according to histological examination and blood chemistry analysis in mice. Thus, our work is the first success of using GO-PEI-PEG as a promising carrier for plasmid Stat3 siRNA delivery and down-regulation of Stat3 by a polymer-mediated vehicle and suggests the great promise of graphene in biomedical applications such as cancer treatment.

Yin, Di; Li, Yang; Lin, Hang; Guo, Baofeng; Du, Yanwei; Li, Xin; Jia, Huijie; Zhao, Xuejian; Tang, Jun; Zhang, Ling

2013-03-01

253

Upregulation of Tissue Factor by Activated Stat3 Contributes to Malignant Pleural Effusion Generation via Enhancing Tumor Metastasis and Vascular Permeability in Lung Adenocarcinoma  

PubMed Central

Malignant pleural effusion (MPE) is a poor prognostic sign for patients with lung cancer. Tissue factor (TF) is a coagulation factor that participates in angiogenesis and vascular permeability and is abundant in MPE. We previously demonstrated that autocrine IL-6-activated Stat3 contributes to tumor metastasis and upregulation of VEGF, resulting in the generation of MPE in lung adenocarcinoma. In this study, we found IL-6-triggered Stat3 activation also induces TF expression. By using pharmacologic inhibitors, it was shown that JAK2 kinase, but not Src kinase, contributed to autocrine IL-6-induced TF expression. Inhibition of Stat3 activation by dominant negative Stat3 (S3D) in lung adenocarcinoma suppressed TF-induced coagulation, anchorage-independent growth in vitro, and tumor growth in vivo. Consistently, knockdown of TF expression by siRNA resulted in a reduction of anchorage-independent growth of lung adenocarcinoma cells. Inhibition of TF expression also decreased the adhesion ability of cancer cells in normal lung tissues. In the nude mouse model, both lung metastasis and MPE generation were decreased when PC14PE6/AS2-siTF cells (TF expression was silenced) were intravenously injected. PC14PE6/AS2-siTF cells also produced less malignant ascites through inhibition of vascular permeability. In summary, we showed that TF expression plays a pivotal role in the pathogenesis of MPE generation via regulating of tumor metastasis and vascular permeability in lung adenocarcinoma bearing activated Stat3.

Yeh, Hsuan-Heng; Chang, Wen-Tsan; Lu, Kuang-Chu; Lai, Wu-Wei; Liu, Hsiao-Sheng; Su, Wu-Chou

2013-01-01

254

Jolkinolide B from Euphorbia fischeriana Steud induces in human leukemic cells apoptosis via JAK2/STAT3 pathways.  

PubMed

Jolkinolide B from the roots of Euphorbia fischeriana Steud exhibits significant antitumor activities against several tumor lines. Previous study has shown that Jolkinolide B could induce apoptosis in human leukemia cells. However, the exact mechanism and signaling pathway involved in Jolkinolide B-induced apoptosis have not been fully elucidated. In the present study, we found that Jolkinolide B reduced cell viability and induced apoptosis in dose- and time-dependent manner in human leukemic HL-60 and THP-1 cells. The induction of apoptosis was accompanied by the downregulation of JAK2/STAT3. Our results also suggest that expression of Bcl-2 and mitochondrial cytochrome c was dosedependently reduced following Jolkinolide B-treated THP-1 and HL-60 cells, whereas Jolkinolide B up-regulated the expression of Bax and cytosolic cytochrome c. Moreover, we observed that Jolkinolide B treatment resulted in activation of caspase-3, -8, and -9. JSI-124, a STAT-3 inhibitor, was able to block the negative effect of Jolkinolide B on cell apoptosis. Taken together, our study for the first time suggests that Jolkinolide B is able to enhance apoptosis of human leukemic HL-60 and THP-1 cells, at least in part, through downregulation of JAK2/STAT3 and bcl-2, and upregulation of Bax and cytosolic cytochrome c. Moreover, the triggering of caspase-3, -8, and -9 activation mediated apoptotic induction. PMID:23253949

Wang, Jia-He; Zhang, Ke; Niu, Hui-Yan; Shu, Lin-Hua; Yue, Dong-Mei; Li, Dong- Yang; He, Ping

2013-03-01

255

Upregulation of STAT3 Marks Burkitt Lymphoma Cells Refractory to Epstein-Barr Virus Lytic Cycle Induction by HDAC Inhibitors?  

PubMed Central

A fundamental problem in studying the latent-to-lytic switch of Epstein-Barr virus (EBV) and the viral lytic cycle itself is the lack of a culture system fully permissive to lytic cycle induction. Strategies to target EBV-positive tumors by inducing the viral lytic cycle with chemical agents are hindered by inefficient responses to stimuli. In vitro, even in the most susceptible cell lines, more than 50% of cells latently infected with EBV are refractory to induction of the lytic cycle. The mechanisms underlying the refractory state are not understood. We separated lytic from refractory Burkitt lymphoma-derived HH514-16 cells after treatment with an HDAC inhibitor, sodium butyrate. Both refractory- and lytic-cell populations responded to the inducing stimulus by hyperacetylation of histone H3. However, analysis of host cell gene expression showed that specific cellular transcripts Stat3, Fos, and interleukin-8 (IL-8) were preferentially upregulated in the refractory-cell population, while IL-6 was upregulated in the lytic population. STAT3 protein levels were also substantially increased in refractory cells relative to untreated or lytic cells. This increase in de novo expression resulted primarily in unphosphorylated STAT3. Examination of single cells revealed that high levels of STAT3 were strongly associated with the refractory state. The refractory state is manifest in a unique subpopulation of cells that exhibits different cellular responses than do lytic cells exposed to the same stimulus. Identifying characteristics of cells refractory to lytic induction relative to cells that undergo lytic activation will be an important step in developing a better understanding of the regulation of the EBV latent to lytic switch.

Daigle, Derek; Megyola, Cynthia; El-Guindy, Ayman; Gradoville, Lyn; Tuck, David; Miller, George; Bhaduri-McIntosh, Sumita

2010-01-01

256

Loss of STAT5 causes liver fibrosis and cancer development through increased TGF-{beta} and STAT3 activation.  

PubMed

The molecular mechanisms underlying the development of hepatocellular carcinoma are not fully understood. Liver-specific signal transducer and activator of transcription (STAT) 5A/B-null mice (STAT5-LKO) were treated with carbon tetrachloride (CCl(4)), and histological analyses revealed liver fibrosis and tumors. Transforming growth factor (TGF)-beta levels and STAT3 activity were elevated in liver tissue from STAT5-LKO mice upon CCl(4) treatment. To define the molecular link between STAT5 silencing and TGF-beta up-regulation, as well as STAT3 activation, we examined STAT5-null mouse embryonic fibroblasts and primary hepatocytes. These cells displayed elevated TGF-beta protein levels, whereas messenger RNA levels remained almost unchanged. Protease inhibitor studies revealed that STAT5 deficiency enhanced the stability of mature TGF-beta. Immunoprecipitation and immunohistochemistry analyses demonstrated that STAT5, through its N-terminal sequences, could bind to TGF-beta and that retroviral-mediated overexpression of STAT5 decreased TGF-beta levels. To confirm the in vivo significance of the N-terminal domain of STAT5, we treated mice that expressed STAT5 lacking the N terminus (STAT5-DeltaN) with CCl(4). STAT5-DeltaN mice developed CCl(4)-induced liver fibrosis but no tumors. In conclusion, loss of STAT5 results in elevated TGF-beta levels and enhanced growth hormone-induced STAT3 activity. We propose that a deregulated STAT5-TGF-beta-STAT3 network contributes to the development of chronic liver disease. PMID:19332876

Hosui, Atsushi; Kimura, Akiko; Yamaji, Daisuke; Zhu, Bing-mei; Na, Risu; Hennighausen, Lothar

2009-03-30

257

Thyroid Hormone Promotes Neuronal Differentiation of Embryonic Neural Stem Cells by Inhibiting STAT3 Signaling Through TR?1  

PubMed Central

A deficiency of maternal thyroid hormones (THs) during pregnancy may have severe impacts on fetal brain development. However, the cellular targets of THs and their underlying mechanisms are still unclear. In this study, we found that maternal hypothyroidism during pregnancy in mice inhibited neurogenesis in the embryonic telencephalon and caused learning and memory impairment in the offspring. To explore the underlying mechanisms, we treated cultured mouse embryonic neural stem cells (eNSCs) with a physiological level of 3, 5, 3?-triiodo-L-thyronine (T3). We found that T3 promoted the neuronal differentiation of eNSCs, while inhibiting astrocytic differentiation. In addition, the proliferation and maintenance of eNSCs were inhibited by T3. Furthermore, the TH receptor alpha 1 (TR?1) was detected in the eNSCs both in vivo and in vitro. Silencing TR?1 protein expression with specific siRNA eliminated the effects of T3 on eNSCs. We also found that T3 decreased STAT3 phosphorylation and STAT3-DNA binding activity through TR?1. The over expression of STAT3 attenuated the promotive effects of T3 on neuronal differentiation of eNSCs. Taken together, these results suggest that T3 promotes the neuronal differentiation of eNSCs by inhibiting STAT3 signaling activity through TR?1 and contributes to early neurogenesis in the embryonic telencephalon. Our studies reveal the physiological effects of TH in regulating eNSCs differentiation and suggest that eNSCs are one of the major cellular targets in the central nervous system by which TH influences early brain development. These findings also provide new insights into the mechanisms of neurological deficits caused by TH deficiency during embryogenesis.

Chen, Chunhai; Zhou, Zhou; Zhong, Min; Zhang, Yanwen; Li, Maoquan; Zhang, Lei; Qu, Mingyue; Yang, Ju; Wang, Yuan

2012-01-01

258

Early Activation of Rat Skeletal Muscle IL-6/STAT1/STAT3 Dependent Gene Expression in Resistance Exercise Linked to Hypertrophy  

PubMed Central

Cytokine interleukin-6 (IL-6) is an essential regulator of satellite cell-mediated hypertrophic muscle growth through the transcription factor signal transducer and activator of transcription 3 (STAT3). The importance of this pathway linked to the modulation of myogenic regulatory factors expression in rat skeletal muscle undergoing hypertrophy following resistance exercise, has not been investigated. In this study, the phosphorylation and nuclear localization of STAT3, together with IL-6/STAT3-responsive gene expression, were measured after both a single bout of resistance exercise and 10 weeks of training. Flexor Digitorum Profundus muscle samples from Wistar rats were obtained 2 and 6 hours after a single bout of resistance exercise and 72 h after the last bout of either 2, 4, or 10 weeks of resistance training. We observed an increase in IL-6 and SOCS3 mRNAs concomitant with phosphorylation of STAT1 and STAT3 after 2 and 6 hours of a single bout of exercise (p<0.05). STAT3-dependent early responsive genes such as CyclinD1 and cMyc were also upregulated whereas MyoD and Myf5 mRNAs were downregulated (p<0.05). BrdU-positive satellite cells increased at 2 and 6 hours after exercise (p<0.05). Muscle fiber hypertrophy reached up to 100% after 10 weeks of training and the mRNA expression of Myf5, c-Myc and Cyclin-D1 decreased, whereas IL-6 mRNA remained upregulated. We conclude that the IL-6/STAT1/STAT3 signaling pathway and its responsive genes after a single bout of resistance exercise are an important event regulating the SC pool and behavior involved in muscle hypertrophy after ten weeks of training in rat skeletal muscle.

Begue, Gwenaelle; Douillard, Aymeric; Galbes, Olivier; Rossano, Bernadette; Vernus, Barbara; Candau, Robin; Py, Guillaume

2013-01-01

259

Transcriptional activation of signal transducer and activator of transcription (STAT) 3 and STAT5B partially mediate homeobox A1-stimulated oncogenic transformation of the immortalized human mammary epithelial cell.  

PubMed

We have previously demonstrated that the p44/42 MAPK pathway is one pathway involved in homeobox (HOX) A1-stimulated oncogenesis. However, inhibition of MAPK kinase 1 does not completely prevent HOXA1-stimulated oncogenic transformation, suggesting the involvement of additional signal transduction pathways. Here, we report that forced expression of HOXA1 in immortalized human mammary epithelial cells significantly increased levels of signal transducer and activator of transcription (STAT) 3, 5A, and 5B mRNA by transcriptional up-regulation. The protein levels of STAT3 and 5B, but not STAT5A, and protein phosphorylation levels of STAT3 and 5B were significantly increased by forced expression of HOXA1. Forced expression of STAT3 or STAT5B was sufficient to transform oncogenically an immortalized human mammary epithelial cell line. Accordingly, inhibition of STAT3 or STAT5B activity with dominant negative STAT3 or STAT5B abrogated the ability of HOXA1 to stimulate cell proliferation, survival, oncogenic transformation, and generation of large disorganized multiacinar structures in three-dimensional culture. These results suggest that HOXA1 partially mediates oncogenic transformation of the immortalized human mammary epithelial cell through modulation of the STAT3 and STAT5B pathways. PMID:18276758

Mohankumar, Kumarasamypet M; Perry, Jo K; Kannan, Nagarajan; Kohno, Kimitoshi; Gluckman, Peter D; Emerald, B Starling; Lobie, Peter E

2008-02-14

260

Cytoplasmic and Nuclear STAT3 in GH-Stimulated Fibroblasts of Children with Idiopathic Short Stature  

Microsoft Academic Search

Background: STAT5, which plays an important role in GH signal transduction, has been studied extensively in children with growth retardation, but there is scarce information regarding STAT3. Aim: We determined total and phosphorylated STAT3 after GH stimulation in fibroblasts from children with idiopathic short stature (ISS) and control children with normal stature. Subjects and Methods: We studied 15 prepubertal children

Jonathan Martínez Pinto; Teresa Salazar; Paula Ocaranza; Ariel Fuentes; Rossana Román; Fernando Cassorla

2010-01-01

261

Roles of activated Src and Stat3 signaling in melanoma tumor cell growth  

Microsoft Academic Search

Activation of protein tyrosine kinases is prevalent in human cancers and previous studies have demonstrated that Stat3 signaling is a point of convergence for many of these tyrosine kinases. Moreover, a critical role for constitutive activation of Stat3 in tumor cell proliferation and survival has been established in diverse cancers. However, the oncogenic signaling pathways in melanoma cells remain to

Guilian Niu; Tammy Bowman; Mei Huang; Steve Shivers; Douglas Reintgen; Adil Daud; Alfred Chang; Alan Kraker; Richard Jove; Hua Yu

2002-01-01

262

IL-9 Induces CCL11 Expression via STAT3 Signalling in Human Airway Smooth Muscle Cells  

PubMed Central

Background Previous findings support the concept that IL-9 may play a significant role in mediating both pro-inflammatory and changes in airway responsiveness that characterizes the atopic asthmatic state. We previously demonstrated that human airway smooth muscle (ASM) cells express a functional IL-9R that mediate CCL11 expression. However, the signaling pathway governing this effect is not well understood. Methodology/Principal Findings In this study, we showed that IL-9 mediated CCL11 expression in ASM cells does not rely on STAT6 or STAT5 but on STAT3 pathway. IL-9 induced rapid STAT3 activation in primary ASM cells that was not observed in case of STAT6 or STAT5. STAT3 binding to CCL11 promoter was also observed in vivo upon IL-9 stimulation of ASM cells. Disruption of STAT3 activity with SH2 domain binding inhibitory peptide results in significant reduction of IL-9 mediated CCL11 promoter activity. DN STAT3? over-expression in ASM cells, but not Ser 727 STAT3 or STAT6 DN, abolishes IL-9 mediated CCL11 promoter activity. Finally, STAT3 but not STAT6 silenced ASM cells showed significant reduction in IL-9 mediated CCL11 promoter activity and mRNA expression. Conclusion/Significance Taken together, our results indicate that IL-9 mediated CCL11 via STAT3 signalling pathway may play a crucial role in airway inflammatory responses.

Koussih, Latifa; Muro, Shigeo; Halayko, Andrew J.; Gounni, Abdelilah S.

2010-01-01

263

Small-molecule STAT3 signaling pathway modulators from Polygonum cuspidatum.  

PubMed

Constitutively activated STAT3 plays a pivotal role in oncogenesis and metastasis in many human cancers, and STAT3 has been validated as a novel anticancer drug target. Thus, the identification of small molecules that modulate STAT3 activity could be of great therapeutic importance. The aim of this study was to isolate novel modulators of the STAT3 signaling pathway from the roots of Polygonum cuspidatum by bioassay-guided fractionation using a STAT3 reporter gene assay. 2-Methoxystypandrone (1), as well as three anthraquinones (2-4), were identified as major active components of P. cuspidatum. Compound 1 demonstrated a potent inhibitory effect on STAT3 activation and significantly inhibited cell proliferation of human breast cancer cells, especially those with constitutively activated STAT3 (IC???=?2.7-3.1?µM). The SAR analysis of quinone analogues suggested that the phenolic and carbonyl groups are the key structures contributing to their inhibitory activities against the STAT3 signaling. PMID:22855270

Liu, Jiawei; Zhang, Qing; Chen, Kaotang; Liu, Jingli; Kuang, Shan; Chen, Weiwen; Yu, Qiang

2012-08-01

264

Characterization of STAT3 activation and expression in canine and human osteosarcoma  

Microsoft Academic Search

BACKGROUND: Dysregulation of signal transducer and activator of transcription 3 (STAT3) has been implicated as a key participant in tumor cell survival, proliferation, and metastasis and is often correlated with a more malignant tumor phenotype. STAT3 phosphorylation has been demonstrated in a subset of human osteosarcoma (OSA) tissues and cell lines. OSA in the canine population is known to exhibit

Stacey L Fossey; Albert T Liao; Jennifer K McCleese; Misty D Bear; Jiayuh Lin; Pui-Kai Li; William C Kisseberth; Cheryl A London

2009-01-01

265

Hepatocyte growth factor induces delayed STAT3 phosphorylation through interleukin-6 expression.  

PubMed

Met receptor tyrosine kinase mediates pleiotropic cellular responses following its activation by hepatocyte growth factor or scatter factor (HGF/SF). STAT3 was reported to be one of direct downstream molecules in HGF/SF-Met signaling. In the present study, however, we observed that Tyr705 of STAT3 was phosphorylated from 2 h or 6 h in NIH3T3 and Chang liver cells, respectively, after HGF/SF treatment. Blocking of the phosphorylation by cycloheximide or actinomycin D and the rapid STAT3 phosphorylation with the conditioned medium from HGF/SF-treated NIH3T3 cells suggested that a newly synthesized secretory protein was responsible for the delayed STAT3 phosphorylation. Among the known mediators to induce STAT3 phosphorylation, interleukin-6 (IL-6) mRNA and protein were induced by HGF/SF, and the released IL-6 was accumulated in the conditioned medium after HGF/SF treatment. Furthermore, the neutralizing IL-6 antibody abolished the STAT3 phosphorylation. Treatment with LY294002, a PI3 kinase inhibitor, but not with other signal inhibitors, resulted in the loss of delayed STAT3 phosphorylation by HGF/SF, showing the involvement of PI3 kinase pathway. Collectively, these results demonstrate that HGF/SF-Met signal cascade stimulates IL-6 production via PI3 kinase pathway, leading to STAT3 phosphorylation as a secondary effect. PMID:19071214

Lee, Bok-Soon; Park, Minseon; Cha, Hyun-Young; Lee, Jae-Ho

2008-11-30

266

Activation of STAT3 induced by cerebral ischemia in rat hippocampus and its possible mechanisms.  

PubMed

It has been demonstrated that signal transducer and activator of transcription-3 (STAT3) is activated after cerebral ischemia/reperfusion (I/R) in cortex and striatum. In this study, we investigated whether STAT3 was rapidly activated in hippocampus by cerebral ischemia without reperfusion in four-vessel occlusion (4-VO) model of Sprague-Dawley (SD) rats. The results showed that tyrosine phosphorylation and DNA binding activity of STAT3 was rapidly increased by ischemia. The p-STAT3 level in cytoplasm increased 5 min after occlusion and reached a peak at 10 min following ischemia (1.7 folds vs sham) by means of immunoblotting (IB). P-STAT3 in nucleus was gradually enhanced with its peak activity occurring at 30 min of ischemia (2.3 folds vs sham). Electrophoretic mobility shift assay (EMSA) with STAT3 probe demonstrated that DNA binding activity of STAT3 in nuclear extracts increased from 5 min and peaked at 30 min of ischemia (3.2 folds vs sham). These changes were prevented by genistein (a protein tyrosine kinase inhibitor) and antioxidant N-acetyl-L-cysteine (NAC), but promoted by sodium orthovanadate (a protein phosphatase inhibitor), which were administered to the SD rats 20 min before ischemia. These results indicate that the activation of STAT3 following cerebral ischemia may be modulated by PTK/PTP, and that this pathway may be of benefit to the adaptation of the hippocampal neurons to oxidative stress. PMID:12817299

Li, Hong-Chun; Zhang, Guang-Yi

2003-06-25

267

A novel nuclear zinc finger protein EZI enhances nuclear retention and transactivation of STAT3  

PubMed Central

A novel cDNA EZI isolated as an oncostatin M- inducible gene encoded a protein containing 12 C2H2-type zinc fingers. EZI was found to transactivate the promoters that are also responsive to STAT3 and activated the acute phase response element (APRE) synergistically with STAT3. Co-immunoprecipitation demonstrated the association of EZI with STAT3, which was mediated by the N-terminal region (1–183) of EZI. The EZI mutant lacking this region showed reduced transcriptional activity, indicating that EZI and STAT3 function cooperatively through physical interaction. While EZI predominantly localized in the nucleus and enhanced the nuclear localization of STAT3, the EZI mutant lacking 11 zinc finger motifs failed to translocate into the nucleus and also inhibited nuclear localization of STAT3 as well as STAT3-mediated transactivation. These results indicate that EZI is a novel nuclear zinc finger protein that augments STAT3 activity by keeping it in the nucleus.

Nakayama, Koh; Kim, Kyung-Woon; Miyajima, Atsushi

2002-01-01

268

PDGF receptor tyrosine kinase inhibitor suppresses mesangial cell proliferation involving STAT3 activation  

PubMed Central

Proliferation of mesangial cells is a hallmark of glomerular disease, and understanding the regulatory mechanisms is critically important. The purpose of this study was to examine the relationship between mesangial cell proliferation and phosphorylated signal transducer and activator of transcription (STAT) 3 and to determine whether the PDGF receptor tyrosine kinase inhibitor STI 571 inhibited mesangial cell proliferation via modulation of STAT3. In this study, we investigated for the first time, the glomerular expression of phosphorylated STAT3 in paraffin sections from animals with experimental mesangial proliferative glomeronephritis. Phosphorylated STAT3 colocalized with many proliferating mesangial cells. We also demonstrated that treatment with STI 571 reduced mesangial cell proliferation and phosphorylated STAT3 signalling both in vitro and in vivo. In vivo, STI 571 treatment reduced the number of glomerular mesangial cells positive for both phosphorylated STAT3 and proliferating cell nuclear antigen. In summary, phosphorylated STAT3 is strongly expressed during mesangial cell proliferation and STI 571 induced suppression of mesangial cell proliferation involves inhibition of phosphorylated STAT3 signalling.

Hirai, T; Masaki, T; Kuratsune, M; Yorioka, N; Kohno, N

2006-01-01

269

Targeted Disruption of the Mouse Stat3 Gene Leads to Early Embryonic Lethality  

Microsoft Academic Search

Signal transducer and activator of transcription (STAT) proteins have been shown to mediate biological actions in response to cytokines. Stat3, a member of the STAT family, is activated by a variety of cytokines, including the interleukin 6 family of cytokines, leptin, granulocyte colony-stimulating factor, and epidermal growth factor. To address the biological function of Stat3, we generated mice deficient in

Kiyoshi Takeda; Koichi Noguchi; Wei Shi; Takashi Tanaka; Makoto Matsumoto; Nobuaki Yoshida; Tadamitsu Kishimoto; Shizuo Akira

1997-01-01

270

Stat3 inhibition activates tumor macrophages and abrogates glioma growth in mice.  

PubMed

As the main effector-cell population of the central nervous system, microglia (MG) are considered to play an important immunoregulatory function in a number of pathological conditions such as inflammation, trauma, degenerative disease, and brain tumors. Recent studies, however, have suggested that the anti-neoplastic function of MG may be suppressed in malignant brain tumors. Considering the proposed suppressive role of signal transducers and activators of transcription 3 (Stat3) in antitumor immunity, we evaluated the role of Stat3 inhibition on MG and macrophage (MP) activation and tumor growth in a murine glioma model. N9 MG cells were exposed to GL261 glioma conditioned medium (GL261-CM) and evaluated for Stat3 activity and cytokine expression. Furthermore, the role of Stat3 inhibition on MG and MP activation was studied both in vitro and in vivo. Finally, the effect of Stat3 inhibition on tumor growth was assessed in intracranial GL261 gliomas. GL261-CM increased Stat3 activity in N9 cells in vitro and resulted in overexpression of IL-10 and IL-6, and downregulation of IL1-beta, a pro-inflammatory cytokine. Inhibition of Stat3 by CPA-7 or siRNA reversed glioma-induced cytokine expression profile in N9 cells. Furthermore, inactivation of Stat3 in intracranial GL261 tumors by siRNA resulted in MG/MP activation and tumor growth inhibition. Glioma-induced MG and MP suppression may be mediated thorough Stat3. Inhibition of Stat3 function in tumor MG/MP may result in their activation and can potentially be used as an adjunct immunotherapy approach for gliomas. PMID:19306372

Zhang, Leying; Alizadeh, Darya; Van Handel, Michelle; Kortylewski, Marcin; Yu, Hua; Badie, Behnam

2009-10-01

271

Novel small molecular inhibitors disrupt the JAK/STAT3 and FAK signaling pathways and exhibit a potent antitumor activity in glioma cells.  

PubMed

JAK (Janus kinase)/STAT (signal transducers and activators of transcription) signaling is involved in the regulation of cell growth, differentiation and apoptosis. Constitutive activation of STATs, in particular STAT3, is observed in a large number of human tumors, including gliomas and may contribute to oncogenesis by stimulating cell proliferation and preventing apoptosis, thus it emerges as a promising target for anti-cancer therapy. To investigate the therapeutic potential of blocking STAT3 in glioma cells a set of small synthetic molecules - caffeic acid derivatives, structurally related to AG490 was screened for its ability to inhibit STAT3. Inhibitor 2 (E)-2-cyano-N-[(S)-1-phenylethyl]-3-(pyridin-2-yl)acrylamide was the most effective in inhibition of JAK/STAT3 signaling and at doses ? 25 ?M significantly reduced the level of phosphorylated JAK1, JAK2 and STAT3 (at Tyr705) and downregulated the expression of known STAT3 targets. In treated cells we observed rapid detachment and rounding of cells associated with reduction of focal adhesion kinase phosphorylation and activity, followed by upregulation of phosphorylated p38, JNK and ERK1/2 levels. Accumulation of cells with fragmented DNA, increases of the cleaved caspase 3 and fragmented PARP levels were detected 24 h after the treatment suggesting ongoing apoptotic cell death. Three human malignant glioblastoma cell lines defective in tumor suppressors TP53 and/or PTEN were susceptible to inhibitor 2 that induced the programmed cell death. Global gene expression profiling revealed modulation of numerous genes in cells treated with inhibitor 2 revealing novel, potential JAK/STAT targets. Our study demonstrates that suitably modified caffeic acid molecules exhibit significant cytotoxic potential toward glioma cells. PMID:22555804

Swiatek-Machado, Karolina; Mieczkowski, Jakub; Ellert-Miklaszewska, Aleksandra; Swierk, Piotr; Fokt, Izabela; Szymanski, Slawomir; Skora, Stanislaw; Szeja, Wies?aw; Grynkiewicz, Grzegorz; Lesyng, Bogdan; Priebe, Waldemar; Kaminska, Bozena

2012-06-01

272

The cooperative induction of hypoxia-inducible factor-1 alpha and STAT3 during hypoxia induced an impairment of tumor susceptibility to CTL-mediated cell lysis.  

PubMed

Hypoxia is an essential component of tumor microenvironment. In this study, we investigated the influence of hypoxia (1% PO(2)) on CTL-mediated tumor cell lysis. We demonstrate that exposure of target tumor cells to hypoxia has an inhibitory effect on the CTL clone (Heu171)-induced autologous target cell lysis. Such inhibition correlates with hypoxia-inducible factor-1alpha (HIF-1alpha) induction but is not associated with an alteration of CTL reactivity as revealed by granzyme B polarization or morphological change. Western blot analysis indicates that although hypoxia had no effect on p53 accumulation, it induced the phosphorylation of STAT3 in tumor cells by a mechanism at least in part involving vascular endothelial growth factor secretion. We additionally show that a simultaneous nuclear translocation of HIF-1alpha and phospho-STAT3 was observed. Interestingly, gene silencing of STAT3 by small interfering RNA resulted in HIF-1alpha inhibition and a significant restoration of target cell susceptibility to CTL-induced killing under hypoxic conditions by a mechanism involving at least in part down-regulation of AKT phosphorylation. Moreover, knockdown of HIF-1alpha resulted in the restoration of target cell lysis under hypoxic conditions. This was further supported by DNA microarray analysis where STAT3 inhibition resulted in a partly reversal of the hypoxia-induced gene expression profile. The present study demonstrates that the concomitant hypoxic induction of phospho-STAT3 and HIF-1alpha are functionally linked to the alteration of non-small cell lung carcinoma target susceptibility to CTL-mediated killing. Considering the eminent functions of STAT3 and HIF-1alpha in the tumor microenvironment, their targeting may represent novel strategies for immunotherapeutic intervention. PMID:19265129

Noman, Muhammad Zaeem; Buart, Stéphanie; Van Pelt, Jos; Richon, Catherine; Hasmim, Meriem; Leleu, Nathalie; Suchorska, Wictoria Maria; Jalil, Abdelali; Lecluse, Yann; El Hage, Faten; Giuliani, Massimo; Pichon, Christophe; Azzarone, Bruno; Mazure, Nathalie; Romero, Pedro; Mami-Chouaib, Fathia; Chouaib, Salem

2009-03-15

273

Purvalanol A induces apoptosis and downregulation of antiapoptotic proteins through abrogation of phosphorylation of JAK2/STAT3 and RNA polymerase II.  

PubMed

To clarify the mechanisms of purvalanol A in the induction of apoptosis, we investigated whether purvalanol A influenced the RNA synthesis and expression of RNA polymerase II and signal transducer and activator of transcription 3 (STAT3). When MKN45 cells were treated with 30 micromol/l purvalanol A, mitochondrial dysfunction occurred before the induction of the apoptosis and the expression of antiapoptotic proteins survivin, Bcl-XL, and Bcl-2 was reduced. The treatment with parvalanol A was also shown to reduce not only mRNA for these proteins but also global RNA synthesis. The phosphorylation of the carboxy-terminal domain of RNA polymerase II, which was involved in transcriptional regulation, was strongly inhibited by purvalanol A, followed by the partial inhibition of the expression of RNA polymerase II. Furthermore, the phosphorylation at Tyr705 of STAT3, which is known to be a phosphorylation site for Janus kinase 2 (JAK2), was completely inhibited by purvalanol A early (3 h) after drug treatment, although the phosphorylation of STAT3 at Ser727, which is a phosphorylation site for Ras/Raf/MEK and extracellular signal-regulated protein kinase 1/2, was still detectable until late (12 h) after treatment. In addition, the tyrosine phosphorylation of JAK2 was efficiently inhibited by purvalanol A. These results suggest that the inhibition of JAK2/STAT3 and RNA polymerase II is crucial in the downregulation of antiapoptotic proteins leading to the apoptotic cell death induced by parvalanol A. PMID:18525315

Iizuka, Daisuke; Ogura, Aki; Kuwabara, Mikinori; Inanami, Osamu

2008-07-01

274

Stem cell-specific expression of Dax1 is conferred by STAT3 and Oct3/4 in embryonic stem cells  

SciTech Connect

Embryonic stem (ES) cells are pluripotent cells derived from inner cell mass of blastocysts. An orphan nuclear receptor, Dax1, is specifically expressed in undifferentiated ES cells and plays an important role in their self-renewal. The regulatory mechanism of Dax1 expression in ES cells, however, remains unknown. In this study, we found that STAT3 and Oct3/4, essential transcription factors for ES cell self-renewal, are involved in the regulation of Dax1 expression. Suppression of either STAT3 or Oct3/4 resulted in down-regulation of Dax1. Reporter assay identified putative binding sites for these factors in the promoter/enhancer region of the Dax1 gene. Chromatin immunoprecipitation analysis suggested the in vivo association of STAT3 and Oct3/4 with the putative sites. Furthermore, gel shift assay indicated that these transcription factors directly bind to their putative binding sites. These results suggest that STAT3 and Oct3/4 control the expression of Dax1 to maintain the self-renewal of ES cells.

Sun Chuanhai [Department of Stem Cell Biology, Graduate School of Medical Science, Kanazawa University, Ishikawa 920-8640 (Japan); Nakatake, Yuhki [Laboratory for Pluripotent Cell Studies, RIKEN Center for Developmental Biology, Kobe 650-0047 (Japan); Ura, Hiroki; Akagi, Tadayuki [Department of Stem Cell Biology, Graduate School of Medical Science, Kanazawa University, Ishikawa 920-8640 (Japan); Niwa, Hitoshi [Laboratory for Pluripotent Cell Studies, RIKEN Center for Developmental Biology, Kobe 650-0047 (Japan); Koide, Hiroshi [Department of Stem Cell Biology, Graduate School of Medical Science, Kanazawa University, Ishikawa 920-8640 (Japan)], E-mail: hkoide@med.kanazawa-u.ac.jp; Yokota, Takashi [Department of Stem Cell Biology, Graduate School of Medical Science, Kanazawa University, Ishikawa 920-8640 (Japan)

2008-07-18

275

Elevated inflammatory response in caveolin-1-deficient mice with Pseudomonas aeruginosa infection is mediated by STAT3 protein and nuclear factor kappaB (NF-kappaB).  

PubMed

Caveolin-1 (Cav-1), an important composition protein within the flask-shaped membrane invaginations termed caveolae, may play a role in host defense against infections. However, the phenotype in Pseudomonas aeruginosa-infected cav1 knock-out (KO) mice is still unresolved, and the mechanism involved is almost entirely unknown. Using a respiratory infection model, we confirmed a crucial role played by Cav-1 in host defense against this pathogen because Cav-1 KO mice showed increased mortality, severe lung injury, and systemic dissemination as compared with wild-type (WT) littermates. In addition, cav1 KO mice exhibited elevated inflammatory cytokines (IL-6, TNF-?, and IL-12a), decreased phagocytic ability of macrophages, and increased superoxide release in the lung, liver, and kidney. We further studied relevant cellular signaling processes and found that STAT3 and NF-?B are markedly activated. Our data revealed that the Cav-1/STAT3/NF-?B axis is responsible for a dysregulated cytokine response, which contributes to increased mortality and disease progression. Moreover, down-regulating Cav-1 in cell culture with a dominant negative strategy demonstrated that STAT3 activation was essential for the translocation of NF-?B into the nucleus, confirming the observations from cav1 KO mice. Collectively, our studies indicate that Cav-1 is critical for inflammatory responses regulating the STAT3/NF-?B pathway and thereby impacting P. aeruginosa infection. PMID:21515682

Yuan, Kefei; Huang, Canhua; Fox, John; Gaid, Madeleine; Weaver, Andrew; Li, Guoping; Singh, Brij B; Gao, Hongwei; Wu, Min

2011-04-22

276

Targeting the androgen receptor with siRNA promotes prostate cancer metastasis through enhanced macrophage recruitment via CCL2/CCR2-induced STAT3 activation  

PubMed Central

Increased CCL2 expression in prostate cancer (PCa) cells enhanced metastasis via macrophage recruitment. However, its linkage to androgen receptor (AR)-mediated PCa progression remains unclear. Here, we identified a previously unrecognized regulation: targeting AR with siRNA in PCa cells increased macrophage recruitment via CCL2 up-regulation, which might then result in enhancing PCa invasiveness. Molecular mechanism dissection revealed that targeting PCa AR with siRNA promoted PCa cell migration/invasion via CCL2-dependent STAT3 activation and epithelial–mesenchymal transition (EMT) pathways. Importantly, pharmacologic interruption of the CCL2/CCR2-STAT3 axis suppressed EMT and PCa cell migration, providing a new mechanism linking CCL2 and EMT. Simultaneously targeting PCa AR with siRNA and the CCL2/CCR2-STAT3 axis resulted in better suppression of PCa growth and metastasis in a xenograft PCa mouse model. Human PCa tissue microarray analysis suggests that increased CCL2 expression may be potentially associated with poor prognosis of PCa patients. Together, these results may provide a novel therapeutic approach to better battle PCa progression and metastasis at the castration resistant stage via the combination of targeting AR with siRNA and anti-CCL2/CCR2-STAT3 signalling.

Izumi, Kouji; Fang, Lei-Ya; Mizokami, Atsushi; Namiki, Mikio; Li, Lei; Lin, Wen-Jye; Chang, Chawnshang

2013-01-01

277

Stat3 Activation Is Limiting for Reprogramming to Ground State Pluripotency  

PubMed Central

Summary The cytokine leukemia inhibitory factor (Lif) sustains self-renewal of mouse embryonic and induced pluripotent stem cells by activating Jak kinase and the transcription factor Stat3. Here we investigate whether Jak/Stat3 may also contribute to induction of pluripotency. EpiSCs derived from postimplantation embryos express low levels of Lif receptor and Stat3. We introduced into EpiSCs a Jak/Stat3 activating receptor (GY118F) responsive to granulocyte colony stimulating factor (Gcsf). On transfer to ground state culture, in which MAPK signaling and glycogen synthase kinase are inhibited, Gcsf induced transcriptional resetting and functional reprogramming. Activation of a tamoxifen-regulatable fusion, Stat3ERT2, also converted EpiSCs into chimera-competent iPSCs. We exploited GY118F to increase Jak/Stat3 activity during somatic cell reprogramming. Incompletely reprogrammed cells derived from neural stem cells or fibroblasts responded to Gcsf with elevated frequencies of progression to ground state pluripotency. These findings indicate that Jak/Stat3 participate directly in molecular reprogramming and that activation of this pathway is a limiting component.

Yang, Jian; van Oosten, Anouk L.; Theunissen, Thorold W.; Guo, Ge; Silva, Jose C.R.; Smith, Austin

2010-01-01

278

S100B Attenuates Microglia Activation in Gliomas: Possible Role of STAT3 Pathway  

PubMed Central

Despite significant infiltration into tumors, the effector function of macrophages (MPs) and microglia (MG) appears to be suppressed in gliomas. Although STAT3 pathway is thought to play a role in this process, the exact mechanism by which gliomas induce STAT3 activation in MPs and MG is not known. Because activation of receptor for advanced glycation end products (RAGE) can induce STAT3, and because gliomas express high levels of S100B, a RAGE ligand, we hypothesized that MP/MG STAT3 activity may be modulated through S100B-RAGE interaction. Exposure of N9 MG and bone marrow-derived monocytes (BMM) to GL261 glioma condition medium (GCM) and low (nM) levels of S100B increased RAGE expression, induced STAT3 and suppressed MG function in vitro. Furthermore, neutralization of S100B in GCM, partially reversed IL-1? suppression in BMM, suggesting that the inhibitory effect of GCM to be in part due to S100B. Finally, blockage of S100B-RAGE interaction inhibited STAT3 activation in N9 MG and in glioma MG/MP in vivo. These findings suggest that the RAGE pathway may play an important role in STAT3 induction in glioma-associated MG/MPs, and that this process may be mediated through S100B.

Zhang, Leying; Liu, Wei; Alizadeh, Darya; Zhao, Dongchang; Farrukh, Omar; Lin, Jeffrey; Badie, Sam A.; Badie, Behnam

2010-01-01

279

Development and utilization of activated STAT3 detection assays for screening a library of secreted proteins.  

PubMed

Interleukin-6 (IL-6) family of cytokines are multifunctional proteins that play an important role in host defenses, acute phase reactions, immune responses, hematopoiesis, and tumorigenesis. The cytokines are produced by various lymphoid and nonlymphoid cells and mediate their biological activity through initial low-affinity binding to cell surface receptors, which are specific for their respective ligands. Ligand-specific receptor binding results in the receptor heterodimerization with ubiquitously expressed signal-transducing transmembrane component gp130 followed by activation of the gp130-associated Janus kinase, which, in turn, phosphorylates signal transducer and activator of transcription 3 (STAT3). Phosphorylated STAT3 (pSTAT3) dimerizes and translocates to the nucleus, where it activates gene transcription. Activation of STAT3 is essential to IL-6 family-associated physiological effects. Therefore, the ability to assess STAT3 phosphorylation is important for drug discovery efforts targeting IL-6 family cytokines. Various reagents and technologies are available to detect the effect of IL-6 type cytokines in treated cells. The present study describes the development of two pSTAT3 detection assays: the high-throughput screening assay based on Meso-Scale Discovery technology, which utilizes electrochemoluminescent signal measurements for the detection of pSTAT3 in treated cell extracts, and the secondary characterization assay based on fluorescent imaging analysis, which monitors pSTAT3 nuclear translocation in cells after activation. We have successfully utilized these assays to screen a small library of secreted proteins and identified inducers of STAT3 phosphorylation. The results obtained in this study demonstrate that both assays are robust, reliable, and amenable to high-throughput screening applications. PMID:21294636

Fursov, Natalie; Gates, Irina V; Panavas, Tadas; Giles-Komar, Jill; Powers, Gordon

2011-02-06

280

Intronic microRNA suppresses endothelial nitric oxide synthase expression and endothelial cell proliferation via inhibition of STAT3 signaling  

Microsoft Academic Search

Intronic microRNA (miRNAs) suppressed the expression of endothelial nitric oxide synthase (eNOS) gene in endothelial cells\\u000a (ECs). This study was to investigate the role of signal transducer and activator of transcription 3 (STAT3) in the regulation\\u000a of eNOS expression and vascular EC proliferation by the intronic 27-nucleotide (nt) miRNA derived from the 27-base pair repeats\\u000a in intron 4 of eNOS

Limei Yan; Hong Hao; Terry S. Elton; Zhenguo Liu; Hesheng Ou

281

STAT3 promotes corticospinal remodelling and functional recovery after spinal cord injury.  

PubMed

If and how neurons remodel their connections after CNS injury critically influences recovery of function. Here, we investigate the role of the growth-initiating transcription factor STAT3 during remodelling of the injured corticospinal tract (CST). Endogenous STAT3 expression in lesioned cortical projection neurons is transient but can be sustained by viral gene transfer. Sustained activation of STAT3 enhances remodelling of lesioned CST fibres and induces de novo formation of collaterals from unlesioned CST fibres. In a unilateral pyramidotomy paradigm, this recruitment of unlesioned fibres leads to the formation of midline crossing circuits that establish ipsilateral forelimb activation and functional recovery. PMID:23928811

Lang, Claudia; Bradley, Peter M; Jacobi, Anne; Kerschensteiner, Martin; Bareyre, Florence M

2013-08-09

282

Intrinsic apoptosis in mechanically ventilated human diaphragm: linkage to a novel Fos/FoxO1/Stat3-Bim axis  

PubMed Central

Mechanical ventilation (MV) is a life-saving measure in many critically ill patients. However, prolonged MV results in diaphragm dysfunction that contributes to the frequent difficulty in weaning patients from the ventilator. The molecular mechanisms underlying ventilator-induced diaphragm dysfunction (VIDD) remain poorly understood. We report here that MV induces myonuclear DNA fragmentation (3-fold increase; P<0.01) and selective activation of caspase 9 (P<0.05) and Bcl2-interacting mediator of cell death (Bim; 2- to 7-fold increase; P<0.05) in human diaphragm. MV also statistically significantly down-regulates mitochondrial gene expression and induces oxidative stress. In cultured muscle cells, we show that oxidative stress activates each of the catabolic pathways thought to underlie VIDD: apoptotic (P<0.05), proteasomal (P<0.05), and autophagic (P<0.01). Further, silencing Bim expression blocks (P<0.05) oxidative stress-induced apoptosis. Overlapping the gene expression profiles of MV human diaphragm and H2O2-treated muscle cells, we identify Fos, FoxO1, and Stat3 as regulators of Bim expression as well as of expression of the catabolic markers atrogin and LC3. We thus identify a novel Fos/FoxO1/Stat3-Bim intrinsic apoptotic pathway and establish the centrality of oxidative stress in the development of VIDD. This information may help in the design of specific drugs to prevent this condition.—Tang, H., Lee, M., Budak, M. T., Pietras, N., Hittinger, S., Vu, M., Khuong, A., Hoang, C. D., Hussain, S. N. A., Levine, S., Shrager, J. B. Intrinsic apoptosis in mechanically ventilated human diaphragm: linkage to a novel Fos/FoxO1/Stat3-Bim axis.

Tang, Huibin; Lee, Myung; Budak, Murat T.; Pietras, Nicole; Hittinger, Scott; Vu, Michael; Khuong, Andy; Hoang, Chuong D.; Hussain, Sabah N. A.; Levine, Sanford; Shrager, Joseph B.

2011-01-01

283

SOCS3 Expression Correlates with Severity of Inflammation, Expression of Proinflammatory Cytokines, and Activation of STAT3 and p38 MAPK in LPS-Induced Inflammation In Vivo  

PubMed Central

SOCS3 is an inducible endogenous negative regulator of JAK/STAT pathway, which is relevant in inflammatory conditions. We used a model of LPS-induced periodontal disease in rats to correlate SOCS3 expression with the inflammatory status. In vitro we used a murine macrophage cell line to assess the physical interaction between SOCS3 and STAT3 by coimmunoprecipitation. 30?ug of LPS from Escherichia coli were injected in the gingival tissues on the palatal aspect of first molars of the animals 3x/week for up to 4 weeks. Control animals were injected with the vehicle (PBS). The rats were sacrificed at 7, 15, and 30 days. Inflammation and gene expression were assessed by stereometric analysis, immunohistochemistry, RT-qPCR, and western blot. LPS injections increased inflammation, paralleled by an upregulation of SOCS3, of the proinflammatory cytokines IL-1?, IL-6, and TNF-? and increased phosphorylation of STAT3 and p38 MAPK. SOCS3 expression accompanied the severity of inflammation and the expression of proinflammatory cytokines, as well as the activation status of STAT3 and p38 MAPK. LPS stimulation in a macrophage cell line in vitro induced transient STAT3 activation, which was inversely correlated with a dynamic physical interaction with SOCS3, suggesting that this may be a mechanism for SOCS3 regulatory function.

Chaves de Souza, Joao Antonio; Nogueira, Andressa Vilas Boas; Chaves de Souza, Pedro Paulo; Kim, Yeon Jung; Silva Lobo, Caroline; Pimentel Lopes de Oliveira, Guilherme Jose; Cirelli, Joni Augusto; Garlet, Gustavo Pompermaier; Rossa, Carlos

2013-01-01

284

Neuroprotection by leptin in a rat model of permanent cerebral ischemia: effects on STAT3 phosphorylation in discrete cells of the brain  

PubMed Central

In addition to its effects in the hypothalamus to control body weight, leptin is involved in the regulation of neuronal function, development and survival. Recent findings have highlighted the neuroprotective effects of leptin against ischemic brain injury; however, to date, little is known about the role performed by the signal transducer and activator of transcription (STAT)-3, a major mediator of leptin receptor transduction pathway in the brain, in the beneficial effects of the hormone. Our data demonstrate that systemic acute administration of leptin produces neuroprotection in rats subjected to permanent middle cerebral artery occlusion (MCAo), as revealed by a significant reduction of the brain infarct volume and neurological deficit up to 7 days after the induction of ischemia. By combining a subcellular fractionation approach with immunohistofluorescence, we observe that neuroprotection is associated with a cell type-specific modulation of STAT3 phosphorylation in the ischemic cortex. The early enhancement of nuclear phospho-STAT3 induced by leptin in the astrocytes of the ischemic penumbra may contribute to a beneficial effect of these cells on the evolution of tissue damage. In addition, the elevation of phospho-STAT3 induced by leptin in the neurons after 24?h MCAo is associated with an increased expression of tissue inhibitor of matrix metalloproteinases-1 in the cortex, suggesting its possible involvement to the neuroprotection produced by the adipokine.

Amantea, D; Tassorelli, C; Russo, R; Petrelli, F; Morrone, L A; Bagetta, G; Corasaniti, M T

2011-01-01

285

miR-337-3p and Its Targets STAT3 and RAP1A Modulate Taxane Sensitivity in Non-Small Cell Lung Cancers  

PubMed Central

NSCLC (non-small cell lung cancer) often exhibits resistance to paclitaxel treatment. Identifying the elements regulating paclitaxel response will advance efforts to overcome such resistance in NSCLC therapy. Using in vitro approaches, we demonstrated that over-expression of the microRNA miR-337-3p sensitizes NCI-H1155 cells to paclitaxel, and that miR-337-3p mimic has a general effect on paclitaxel response in NSCLC cell lines, which may provide a novel adjuvant strategy to paclitaxel in the treatment of lung cancer. By combining in vitro and in silico approaches, we identified STAT3 and RAP1A as direct targets that mediate the effect of miR-337-3p on paclitaxel sensitivity. Further investigation showed that miR-337-3p mimic also sensitizes cells to docetaxel, another member of the taxane family, and that STAT3 levels are significantly correlated with taxane resistance in lung cancer cell lines, suggesting that endogenous STAT3 expression is a determinant of intrinsic taxane resistance in lung cancer. The identification of a miR-337-3p as a modulator of cellular response to taxanes, and STAT3 and RAP1A as regulatory targets which mediate that response, defines a novel regulatory pathway modulating paclitaxel sensitivity in lung cancer cells, which may provide novel adjuvant strategies along with paclitaxel in the treatment of lung cancer and may also provide biomarkers for predicting paclitaxel response in NSCLC.

Du, Liqin; Subauste, Maria C.; DeSevo, Christopher; Zhao, Zhenze; Baker, Michael; Borkowski, Robert; Schageman, Jeoffrey J.; Greer, Rachel; Yang, Chin-Rang; Suraokar, Milind; Wistuba, Ignacio I.; Gazdar, Adi F.; Minna, John D.; Pertsemlidis, Alexander

2012-01-01

286

Leptin-induced Growth Stimulation of Breast Cancer Cells Involves Recruitment of Histone Acetyltransferases and Mediator Complex to CYCLIN D1 Promoter via Activation of Stat3*  

PubMed Central

Numerous epidemiological studies documented that obesity is a risk factor for breast cancer development in postmenopausal women. Leptin, the key player in the regulation of energy balance and body weight control also acts as a growth factor on certain organs in both normal and disease state. In this study, we analyzed the role of leptin and the molecular mechanism(s) underlying its action in breast cancer cells that express both short and long isoforms of leptin receptor. Leptin increased MCF7 cell population in the S-phase of the cell cycle along with a robust increase in CYCLIN D1 expression. Also, leptin induced Stat3-phosphorylation-dependent proliferation of MCF7 cells as blocking Stat3 phosphorylation with a specific inhibitor, AG490, abolished leptin-induced proliferation. Using deletion constructs of CYCLIN D1 promoter and chromatin immunoprecipitation assay, we show that leptin induced increase in CYCLIN D1 promoter activity is mediated through binding of activated Stat3 at the Stat binding sites and changes in histone acetylation and methylation. We also show specific involvement of coactivator molecules, histone acetyltransferase SRC1, and mediator complex in leptin-mediated regulation of CYCLIN D1 promoter. Importantly, silencing of SRC1 and Med1 abolished the leptin induced increase in CYCLIN D1 expression and MCF7 cell proliferation. Intriguingly, recruitment of both SRC1 and Med1 was dependent on phosphorylated Stat3 as AG490 treatment inhibited leptin-induced recruitment of these coactivators to CYCLIN D1 promoter. Our data suggest that CYCLIN D1 may be a target gene for leptin mediated growth stimulation of breast cancer cells and molecular mechanisms involve activated Stat3-mediated recruitment of distinct coactivator complexes.

Saxena, Neeraj K.; Vertino, Paula M.; Anania, Frank A.; Sharma, Dipali

2010-01-01

287

Oncostatin M promotes STAT3 activation, VEGF production, and invasion in osteosarcoma cell lines  

Microsoft Academic Search

Background  We have previously demonstrated that both canine and human OSA cell lines, as well as 8 fresh canine OSA tumor samples, exhibit\\u000a constitutive phosphorylation of STAT3, and that this correlates with enhanced expression of matrix metalloproteinase-2 (MMP2).\\u000a While multiple signal transduction pathways can result in phosphorylation of STAT3, stimulation of the cytokine receptor gp130\\u000a through either IL-6 or Oncostatin M

Stacey L Fossey; Misty D Bear; William C Kisseberth; Michael Pennell; Cheryl A London

2011-01-01

288

Hepatocyte growth factor induces delayed STAT3 phosphorylation through interleukin-6 expression  

Microsoft Academic Search

Met receptor tyrosine kinase mediates pleiotropic cellular responses following its activation by hepatocyte growth factor or scatter factor (HGF\\/SF). STAT3 was reported to be one of direct downstream molecules in HGF\\/SF-Met signaling. In the present study, however, we observed that Tyr705 of STAT3 was phosphorylated from 2 h or 6 h in NIH3T3 and Chang liver cells, respectively, after HGF\\/SF treatment. Blocking

Bok-Soon Lee; Hyun-Young Cha; Jae-Ho Lee

2009-01-01

289

Overexpression of STAT3 in HPV-mediated cervical cancer in a north Indian population.  

PubMed

The constitutively activated STAT family members, particularly STAT3, have been shown to possess transforming properties, and are strongly correlated with tumor development and progression. STAT3 transmits signals from many cytokines and growth factors to target genes in the nucleus through the Jak/Stat signaling pathway. HPV is the main etiological factor in the development of cervical cancer. In the current study, the expression of STAT3 was analyzed in various stages of HPV-mediated cervical carcinogenesis. Tissue biopsies from 100 patients with cervical cancer of different stages and normal tissues from patients undergoing hysterectomy were selected for studying the HPV status and STAT3 expression. HPV status of each corresponding biopsy was analyzed by PCR and typing. The mRNA expression was analyzed by reverse-transcriptase polymerase chain reaction (RT-PCR). HPV infection was detected in majority of cases: 75% (9/12) in precancer, 85% (34/40) stage I & II, and 95% (36/38) in stage III & IV of cervical cancer cases by L1 PCR. Further sub typing revealed HPV16 in 100% (9/9) of L1 positives in precancerous & 90% (63/70) in different stages of cancer. Significant level of STAT3 mRNA expression was predominantly found in cervical cancer cases as compared to normal controls (P = 0.001). We also found a significant correlation of STAT3 expression in cases infected with HPV (P = 0.001). Our results indicate a potentially interactive effect between HPV 16/18 and transcriptional activation of STAT3 gene in cervical carcinogenesis. To our knowledge, this is the first such study to be reported from India. Further investigations are needed to determine the influence of STAT3 expression on cervical carcinogenesis and its possible interaction with HPV infection status. PMID:19421717

Sobti, R C; Singh, Neha; Hussain, Showket; Suri, Vanita; Bharti, A C; Das, B C

2009-05-07

290

Functional STAT3 deficiency compromises the generation of human T follicular helper cells  

PubMed Central

T follicular helper (Tfh) cells are critical for providing the necessary signals to induce differentiation of B cells into memory and Ab-secreting cells. Accordingly, it is important to identify the molecular requirements for Tfh cell development and function. We previously found that IL-12 mediates the differentiation of human CD4+ T cells to the Tfh lineage, because IL-12 induces naive human CD4+ T cells to acquire expression of IL-21, BCL6, ICOS, and CXCR5, which typify Tfh cells. We have now examined CD4+ T cells from patients deficient in IL-12R?1, TYK2, STAT1, and STAT3 to further explore the pathways involved in human Tfh cell differentiation. Although STAT1 was dispensable, mutations in IL12RB1, TYK2, or STAT3 compromised IL-12–induced expression of IL-21 by human CD4+ T cells. Defective expression of IL-21 by STAT3-deficient CD4+ T cells resulted in diminished B-cell helper activity in vitro. Importantly, mutations in STAT3, but not IL12RB1 or TYK2, also reduced Tfh cell generation in vivo, evidenced by decreased circulating CD4+CXCR5+ T cells. These results highlight the nonredundant role of STAT3 in human Tfh cell differentiation and suggest that defective Tfh cell development and/or function contributes to the humoral defects observed in STAT3-deficient patients.

Avery, Danielle T.; Chan, Anna; Batten, Marcel; Bustamante, Jacinta; Boisson-Dupuis, Stephanie; Arkwright, Peter D.; Kreins, Alexandra Y.; Averbuch, Diana; Engelhard, Dan; Magdorf, Klaus; Kilic, Sara S.; Minegishi, Yoshiyuki; Nonoyama, Shigeaki; French, Martyn A.; Choo, Sharon; Smart, Joanne M.; Peake, Jane; Wong, Melanie; Gray, Paul; Cook, Matthew C.; Fulcher, David A.; Casanova, Jean-Laurent; Deenick, Elissa K.

2012-01-01

291

Inhibition of STAT3 by niclosamide synergizes with erlotinib against head and neck cancer.  

PubMed

Epidermal growth factor receptor (EGFR) is extensively expressed in head and neck cancer. However, EGFR-targeted therapy has only modest efficacy in head and neck cancer, through mechanisms that are not fully understood. Here, we found that inhibition of EGFR by erlotinib stimulated phosphorylation and activation of STAT3 leading to increased Bcl2/Bcl-XL expression in head and neck cancer cells, which may dampen the therapeutic efficacy of erlotinib against head and neck cancer. Erlotinib-enhanced STAT3 phosphorylation results, at least in part, from suppression of its physiological phosphatase, PTPMeg2. Specific knockdown of STAT3 by RNA interference significantly sensitized head and neck cancer cells to erlotinib treatment. Pharmacological inhibition of STAT3 by niclosamide not only blocked erlotinib-stimulated STAT3 phosphorylation but also synergistically repressed head and neck cancer growth in vitro and in vivo. Combined inhibition of EGFR and STAT3 by erlotinib and niclosamide more effectively induced apoptosis in tumor tissues without toxicity for normal tissues. Based on our findings, treatment with erlotinib combined with niclosamide may offer an effective therapeutic approach to improve the prognosis of head and neck cancer. PMID:24019973

Li, Rui; You, Shuo; Hu, Zhongliang; Chen, Zhuo G; Sica, Gabriel L; Khuri, Fadlo R; Curran, Walter J; Shin, Dong M; Deng, Xingming

2013-09-03

292

JNK-Dependent Stat3 Phosphorylation Contributes to Akt Activation in Response to Arsenic Exposure  

PubMed Central

Environmental exposure to arsenic, especially the trivalent inorganic form (As3+), has been linked to human cancers in addition to a number of other diseases including skin lesions, cardiovascular disorders, neuropathy, and internal organ injury. In the present study, we describe a novel signaling axis of the c-Jun NH2 kinase (JNK) and signal transducer and activator of transcription 3 (Stat3) and its involvement in As3+-induced Akt activation in human bronchial epithelial cells. As3+ activates JNK and induces phosphorylation of the Stat3 at serine 727 (S727) in a dose- and time-dependent manner, which occurred concomitantly with Akt activation. Disruption of the JNK signaling pathway by treatment with the JNK inhibitor SP600125, siRNA knockdown of JNK, or genetic deficiency of the JNK1 or JNK2 gene abrogated As3+-induced S727 phosphorylation of Stat3, Akt activation, and the consequent release of vascular endothelial growth factor (VEGF) and migration of the cells. Similarly, pretreatment of the cells with Stat3 inhibitor or Stat3 siRNA prevented Akt activation and VEGF release from the cells in response to As3+ treatment. Taken together, these data revealed a new signaling mechanism that might be pivotal in As3+-induced malignant transformation of the cells by linking the key stress signaling pathway, JNK, to the activation of Stat3 and the carcinogenic kinase, Akt.

Chen, Fei

2012-01-01

293

Radiation enhances the invasion abilities of pulmonary adenocarcinoma cells via STAT3.  

PubMed

In the present study, the effect of radiation on the invasion of the pulmonary adenocarcinoma cell line, A549, was investigated. Invasion of A549 cells irradiated with 2 and 4 Gy doses of ??ray was detected using the transwell Matrigel invasion assay. Levels of matrix metalloproteinase 2 (MMP?2) and phosphorylated signal transducer and activator of transcription 3 (STAT3) were detected by reverse transcription PCR (RT-PCR) and/or immunoblotting. The enzyme activity of MMP?2 was examined by gelatin zymography. Results demonstrated that the invasion of A549 cells was significantly enhanced by ??ray radiation at doses of 2 or 4 Gy. In addition, exposure to radiation was found to promote transcriptional expression of MMP?2 and increase MMP?2 enzyme activity. Irradiation activated the phosphorylation of STAT3 and promoted the nuclear localization of STAT3. The blockage of STAT3 phosphorylation using a specific inhibitor (AG490) suppressed the irradiation?induced elevation of MMP?2 expression, enzyme activity and invasion of A549 cells. Finally, the expression of vascular endothelial growth factor (VEGF) was found to be upregulated by radiation, which was associated with the activation of STAT3. Results of the current study indicate that irradiation leads to activation of STAT3 and translocation to the nucleus, leading to activation of VEGF and MMP?2 transcription, resulting in the increased invasion of A549 cells. PMID:23620191

Li, Fengsheng; Gao, Ling; Jiang, Qisheng; Wang, Zhidong; Dong, Bo; Yan, Tao; Chen, Xiaohua

2013-04-25

294

Functional STAT3 deficiency compromises the generation of human T follicular helper cells.  

PubMed

T follicular helper (Tfh) cells are critical for providing the necessary signals to induce differentiation of B cells into memory and Ab-secreting cells. Accordingly, it is important to identify the molecular requirements for Tfh cell development and function. We previously found that IL-12 mediates the differentiation of human CD4(+) T cells to the Tfh lineage, because IL-12 induces naive human CD4(+) T cells to acquire expression of IL-21, BCL6, ICOS, and CXCR5, which typify Tfh cells. We have now examined CD4(+) T cells from patients deficient in IL-12R?1, TYK2, STAT1, and STAT3 to further explore the pathways involved in human Tfh cell differentiation. Although STAT1 was dispensable, mutations in IL12RB1, TYK2, or STAT3 compromised IL-12-induced expression of IL-21 by human CD4(+) T cells. Defective expression of IL-21 by STAT3-deficient CD4(+) T cells resulted in diminished B-cell helper activity in vitro. Importantly, mutations in STAT3, but not IL12RB1 or TYK2, also reduced Tfh cell generation in vivo, evidenced by decreased circulating CD4(+)CXCR5(+) T cells. These results highlight the nonredundant role of STAT3 in human Tfh cell differentiation and suggest that defective Tfh cell development and/or function contributes to the humoral defects observed in STAT3-deficient patients. PMID:22403255

Ma, Cindy S; Avery, Danielle T; Chan, Anna; Batten, Marcel; Bustamante, Jacinta; Boisson-Dupuis, Stephanie; Arkwright, Peter D; Kreins, Alexandra Y; Averbuch, Diana; Engelhard, Dan; Magdorf, Klaus; Kilic, Sara S; Minegishi, Yoshiyuki; Nonoyama, Shigeaki; French, Martyn A; Choo, Sharon; Smart, Joanne M; Peake, Jane; Wong, Melanie; Gray, Paul; Cook, Matthew C; Fulcher, David A; Casanova, Jean-Laurent; Deenick, Elissa K; Tangye, Stuart G

2012-03-08

295

STAT3 signaling induces the differentiation of human ICOS(+) CD4 T cells helping B lymphocytes.  

PubMed

The generation of high-affinity antibodies and the development of B cell memory are dependent on the help provided by CD4 T cells. Mouse studies indicate that STAT3 signaling in CD4 T cells promotes the acquisition of the B cell help function. However, the role of STAT3 in humans has been controversial. In this study, we show that IL-6 and other STAT3 activating cytokines (IL-21 and IL-27) induce the differentiation of CD4 T cells promoting antibody production by B cells. The acquisition of B cell stimulating properties by naive cord blood CD4 T cells required the STAT3-dependent expression of ICOS and IL-21. Gene reporter and ChIP experiments unambiguously demonstrated that upon IL-6 stimulation, STAT3 induces the transcription of the ICOS gene through direct recruitment to the proximal promoter region indicating that STAT3 acts in part through the direct activation of the ICOS gene. PMID:23923047

Ysebrant de Lendonck, Laure; Eddahri, Fouad; Delmarcelle, Yves; Nguyen, Muriel; Leo, Oberdan; Goriely, Stanislas; Marchant, Arnaud

2013-07-26

296

Inhibition of STAT3 by Niclosamide Synergizes with Erlotinib against Head and Neck Cancer  

PubMed Central

Epidermal growth factor receptor (EGFR) is extensively expressed in head and neck cancer. However, EGFR-targeted therapy has only modest efficacy in head and neck cancer, through mechanisms that are not fully understood. Here, we found that inhibition of EGFR by erlotinib stimulated phosphorylation and activation of STAT3 leading to increased Bcl2/Bcl-XL expression in head and neck cancer cells, which may dampen the therapeutic efficacy of erlotinib against head and neck cancer. Erlotinib-enhanced STAT3 phosphorylation results, at least in part, from suppression of its physiological phosphatase, PTPMeg2. Specific knockdown of STAT3 by RNA interference significantly sensitized head and neck cancer cells to erlotinib treatment. Pharmacological inhibition of STAT3 by niclosamide not only blocked erlotinib-stimulated STAT3 phosphorylation but also synergistically repressed head and neck cancer growth in vitro and in vivo. Combined inhibition of EGFR and STAT3 by erlotinib and niclosamide more effectively induced apoptosis in tumor tissues without toxicity for normal tissues. Based on our findings, treatment with erlotinib combined with niclosamide may offer an effective therapeutic approach to improve the prognosis of head and neck cancer.

Li, Rui; You, Shuo; Hu, Zhongliang; Chen, Zhuo G.; Sica, Gabriel L.; Khuri, Fadlo R.; Curran, Walter J.; Shin, Dong M.; Deng, Xingming

2013-01-01

297

Stable expression of constitutively-activated STAT3 in benign prostatic epithelial cells changes their phenotype to that resembling malignant cells  

PubMed Central

Background Signal transducers and activators of transcription (STATs) are involved in growth regulation of cells. They are usually activated by phosphorylation at specific tyrosine residues. In neoplastic cells, constitutive activation of STATs accompanies growth dysregulation and resistance to apoptosis through changes in gene expression, such as enhanced anti-apoptotic gene expression or reduced pro-apoptotic gene expression. Activated STAT3 is thought to play an important role in prostate cancer (PCA) progression. Because we are interested in how persistently-activated STAT3 changes the cellular phenotype to a malignant one in prostate cancer, we used expression vectors containing a gene for constitutively-activated STAT3, called S3c, into NRP-152 rat and BPH-1 human benign prostatic epithelial cells. Results We observed that prostatic cell lines stably expressing S3c required STAT3 expression for survival, because they became sensitive to antisense oligonucleotide for STAT3. However, S3c-transfected cells were not sensitive to the effects of JAK inhibitors, meaning that STAT3 was constitutively-activated in these transfected cell lines. NRP-152 prostatic epithelial cells lost the requirement for exogenous growth factors. Furthermore, we observed that NRP-152 expressing S3c had enhanced mRNA levels of retinoic acid receptor (RAR)-?, reduced mRNA levels of RAR-? and -?, while BPH-1 cells transfected with S3c became insensitive to the effects of androgen, and also to the effects of a testosterone antagonist. Both S3c-transfected cell lines grew in soft agar after stable transfection with S3c, however neither S3c-transfected cell line was tumorigenic in severe-combined immunodeficient mice. Conclusions We conclude, based on our findings, that persistently-activated STAT3 is an important molecular marker of prostate cancer, which develops in formerly benign prostate cells and changes their phenotype to one more closely resembling transformed prostate cells. That the S3c-transfected cell lines require the continued expression of S3c demonstrates that a significant phenotypic change occurred in the cells. These conclusions are based on our data with respect to loss of growth factor requirement, loss of androgen response, gain of growth in soft agar, and changes in RAR subunit expression, all of which are consistent with a malignant phenotype in prostate cancer. However, an additional genetic change may be required for S3c-transfected prostate cells to become tumorigenic.

Huang, Hosea F; Murphy, Thomas F; Shu, Ping; Barton, Arnold B; Barton, Beverly E

2005-01-01

298

Hepatitis B virus X protein modulates apoptosis in human renal proximal tubular epithelial cells by activating the JAK2/STAT3 signaling pathway  

PubMed Central

Hepatitis B virus X protein (HBx) is a multifunctional protein, and it activates multiple signal transduction pathways in multiple types of cells and regulates the process of cell apoptosis. In the present study, we mainly investigated the correlation between HBx and renal tubular epithelial cell apoptosis in hepatitis B virus-associated glomerulonephritis (HBVGN) and the possible signaling mechanism. Cell apoptosis in nephridial tissues of patients with HBVGN were determined by the TUNEL method. HBx, p-STAT3 and STAT3 levels in nephridial tissues were determined by immunohistochemical assay, and a correlation analysis between HBx expression levels and apoptosis index in nephridial tissues was conducted. The activation of the JAK2/STAT3 signaling pathway in HK-2 cells and the expression of the apoptosis-related proteins Bax and Bcl-2 were determined by western blot analysis following transfection with the HBx eukaryotic expression vector. Cellular proliferation activity was determined by the CCK-8 method, and cell apoptosis was determined with HO33342 staining using transmission electron microscopy and Annexin V/PI double staining flow cytometry. The results revealed that the apoptosis index in nephridial tissues of patients with HBVGN was significantly higher when compared to that of the control group, and p-STAT3 expression levels in HBVGN nephridial tissues were significantly increased. In the control group, no HBx expression was observed in the nephridial tissues, whereas HBx expression was found in the nephridial tissues of 86% of the patients with HBVGN. The HBx expression levels had a linear correlation with the apoptosis index in the nephridial tissues. After target gene HBx infection, expression levels of both p-JAK2 and p-STAT3 in human proximal HK-2 cells were significantly increased, and the Bax/Bcl-2 ratio was also significantly increased. At the same time, cellular proliferation of HK-2 cells was significantly inhibited, and the rate of apoptosis was increased. After incubation with AG490, the JAK2/STAT3 signaling pathway was partially blocked, which caused a decrease in the Bax/Bcl-2 ratio and reduced cell apoptosis caused by HBx. In conclusion, HBx upregulates the Bax/Bcl-2 ratio by activating the JAK2/STAT3 signaling pathway to cause renal tubular epithelial cell apoptosis, and it is possibly involved in the pathogenic mechanism of nephridial tissue damage caused by HBV.

HE, PING; ZHANG, DAN; LI, HONG; YANG, XU; LI, DETIAN; ZHAI, YONGZHEN; MA, LI; FENG, GUOHE

2013-01-01

299

NVP-BKM120, a novel PI3K inhibitor, shows synergism with a STAT3 inhibitor in human gastric cancer cells harboring KRAS mutations.  

PubMed

Aberrations of Phosphoinositide 3-kinase (PI3K)/AKT signaling are frequently observed in many types of cancer, promoting its emergence as a promising target for cancer treatment. PI3K can become activated by various pathways, one of which includes RAS. RAS can not only directly activate the PI3K/AKT pathway via binding to p110 of PI3K, but also regulates mTOR via ERK or RSK independently of the PI3K/AKT pathway. Thus, actively mutated RAS can constitutively activate PI3K signaling. Additionally, in RAS tumorigenic transformation, signal transducer and activator of transcription 3 (STAT3) has been known also to be required. In this study, we examined the efficacy of NVP-BKM120, a pan-class I PI3K inhibitor in human gastric cancer cells and hypothesized that the combined inhibition of PI3K and STAT3 would be synergistic in KRAS mutant gastric cancer cells. NVP-BKM120 demonstrated anti-proliferative activity in 11 human gastric cancer cell lines by decreasing mTOR downstream signaling. But NVP-BKM120 treatment increased p-AKT by subsequent abrogation of feedback inhibition by stabilizing insulin receptor substrate-1. In KRAS mutant gastric cancer cells, either p-ERK or p-STAT3 was also increased upon treatment of NVP-BKM120. The synergistic efficacy study demonstrated that dual PI3K and STAT3 blockade showed a synergism in cells harboring mutated KRAS by inducing apoptosis. The synergistic effect was not seen in KRAS wild-type cells. Together, these findings suggest for the first time that the dual inhibition of PI3K and STAT3 signaling may be an effective therapeutic strategy for KRAS mutant gastric cancer patients. PMID:22159814

Park, Eunju; Park, Jinah; Han, Sae-Won; Im, Seock-Ah; Kim, Tae-You; Oh, Do-Youn; Bang, Yung-Jue

2011-12-08

300

NVP-BKM120, a novel PI3K inhibitor, shows synergism with a STAT3 inhibitor in human gastric cancer cells harboring KRAS mutations  

PubMed Central

Aberrations of Phosphoinositide 3-kinase (PI3K)/AKT signaling are frequently observed in many types of cancer, promoting its emergence as a promising target for cancer treatment. PI3K can become activated by various pathways, one of which includes RAS. RAS can not only directly activate the PI3K/AKT pathway via binding to p110 of PI3K, but also regulates mTOR via ERK or RSK independently of the PI3K/AKT pathway. Thus, actively mutated RAS can constitutively activate PI3K signaling. Additionally, in RAS tumorigenic transformation, signal transducer and activator of transcription 3 (STAT3) has been known also to be required. In this study, we examined the efficacy of NVP-BKM120, a pan-class I PI3K inhibitor in human gastric cancer cells and hypothesized that the combined inhibition of PI3K and STAT3 would be synergistic in KRAS mutant gastric cancer cells. NVP-BKM120 demonstrated anti-proliferative activity in 11 human gastric cancer cell lines by decreasing mTOR downstream signaling. But NVP-BKM120 treatment increased p-AKT by subsequent abrogation of feedback inhibition by stabilizing insulin receptor substrate-1. In KRAS mutant gastric cancer cells, either p-ERK or p-STAT3 was also increased upon treatment of NVP-BKM120. The synergistic efficacy study demonstrated that dual PI3K and STAT3 blockade showed a synergism in cells harboring mutated KRAS by inducing apoptosis. The synergistic effect was not seen in KRAS wild-type cells. Together, these findings suggest for the first time that the dual inhibition of PI3K and STAT3 signaling may be an effective therapeutic strategy for KRAS mutant gastric cancer patients.

PARK, EUNJU; PARK, JINAH; HAN, SAE-WON; IM, SEOCK-AH; KIM, TAE-YOU; OH, DO-YOUN; BANG, YUNG-JUE

2012-01-01

301

Novel synthetic derivatives of the natural product berbamine inhibit Jak2/Stat3 signaling and induce apoptosis of human melanoma cells  

PubMed Central

Persistent Jak/Stat3 signal transduction plays a crucial role in tumorigenesis and immune development. Activated Jak/Stat3 signaling has been validated as a promising molecular target for cancer therapeutics discovery and development. Berbamine (BBM), a natural bis-benzylisoquinoline alkaloid, was identified from the traditional Chinese herbal medicine Berberis amurensis used for treatment of cancer patients. While BBM has been shown to have potent antitumor activities with low toxicity in various cancer types, the molecular mechanism of action of BBM remains largely unknown. Here, we determine the antitumor activities of thirteen synthetic berbamine derivatives (BBMDs) against human solid tumor cells. BBMD3, which is the most potent in this series of novel BBMDs, exhibits over 6-fold increase in biological activity compared to natural BBM. Moreover, BBMD3, directly inhibits Jak2 autophosphorylation kinase activity in vitro with IC50 = 0.69 ?M. Autophosphorylation of Jak2 kinase at Tyr1007/1008 sites also was strongly inhibited in the range of 1 ?M to 5 ?M of BBMD3 in human melanoma cells at 4 h after treatment. Following inhibition of autophosphorylation of Jak2, BBMD3 blocked constitutive activation of downstream Stat3 signaling in melanoma cells. BBMD3 also down-regulated expression of the Stat3 target proteins Mcl-1 and Bcl-xL, associated with induction of apoptosis. In sum, our findings demonstrate that the novel berbamine derivative BBMD3 is an inhibitor of the Jak2/Stat3 signaling pathway, providing evidence for a molecular mechanism whereby BBMD3 exerts at least in part the apoptosis of human melanoma cells. In addition, BBMD3 represents a promising lead compound for development of new therapeutics for cancer treatment.

Nam, Sangkil; Xie, Jun; Perkins, Angela; Ma, Yuelong; Yang, Fan; Wu, Jun; Wang, Yan; Xu, Rong-zhen; Huang, Wendong; Horne, David A.; Jove, Richard

2012-01-01

302

Novel synthetic derivatives of the natural product berbamine inhibit Jak2/Stat3 signaling and induce apoptosis of human melanoma cells.  

PubMed

Persistent Jak/Stat3 signal transduction plays a crucial role in tumorigenesis and immune development. Activated Jak/Stat3 signaling has been validated as a promising molecular target for cancer therapeutics discovery and development. Berbamine (BBM), a natural bis-benzylisoquinoline alkaloid, was identified from the traditional Chinese herbal medicine Berberis amurensis used for treatment of cancer patients. While BBM has been shown to have potent antitumor activities with low toxicity in various cancer types, the molecular mechanism of action of BBM remains largely unknown. Here, we determine the antitumor activities of 13 synthetic berbamine derivatives (BBMDs) against human solid tumor cells. BBMD3, which is the most potent in this series of novel BBMDs, exhibits over 6-fold increase in biological activity compared to natural BBM. Moreover, BBMD3, directly inhibits Jak2 autophosphorylation kinase activity in vitro with IC(50)0.69 ?M. Autophosphorylation of Jak2 kinase at Tyr1007/1008 sites also was strongly inhibited in the range of 15 ?M of BBMD3 in human melanoma cells at 4h after treatment. Following inhibition of autophosphorylation of Jak2, BBMD3 blocked constitutive activation of downstream Stat3 signaling in melanoma cells. BBMD3 also down-regulated expression of the Stat3 target proteins Mcl-1and Bcl-x(L), associated with induction of apoptosis. In sum, our findings demonstrate that the novel berbamine derivative BBMD3 is an inhibitor of the Jak2/Stat3 signaling pathway, providing evidence for a molecular mechanism whereby BBMD3 exerts at least in part the apoptosis of human melanoma cells. In addition, BBMD3 represents a promising lead compound for development of new therapeutics for cancer treatment. PMID:22717603

Nam, Sangkil; Xie, Jun; Perkins, Angela; Ma, Yuelong; Yang, Fan; Wu, Jun; Wang, Yan; Xu, Rong-Zhen; Huang, Wendong; Horne, David A; Jove, Richard

2012-06-02

303

Curcumin: A Novel Stat 3 Pathway Inhibitor for Chemoprevention of Lung Cancer  

PubMed Central

Objective Multiple studies from independent groups find evidence for Stat3 activation in nearly 50% of lung cancers suggesting a functional role for this target in subsets of lung cancer. Based on the existing evidence we hypothesized that bioavailable curcuminoid complex may modulate lung carcinogenesis, primarily by inhibiting Stat3 activation. With the safety of this botanical well established, the objective of these studies is to test our hypothesis in vitro and in vivo in an effort to inform the design of a phase II chemoprevention trial in former smokers. Methods We treated non-tumor derived, normal (but immortalized) human bronchial epithelial cells (AALE) and lung adenocarcinoma derived cells (H441) with bioactive Curcumin C3 Complex. Asynchronous cells in each case were treated with curcumin for 24 hrs, followed by immunoblotting for Stat3 and activated Stat3-P, prior signal of which was used for normalization. We also completed a preclinical trial in which 12 mice were randomly divided into three groups and subjected to 3 days or 9 days of curcumin i.p. injections, followed by analysis of lung tissues for Stat3-P changes and growth suppressive effects of the curcumin. The growth suppressive effects were measured using Cyclin D1 and the replicative helicase subunit, Mcm2, as surrogates for the proliferative capacity of the tissues. Results in vitro studies with curcuminoid complex demonstrated that the activity of Stat3 in both normal bronchoepithelial cells and lung cancer derived cells is sensitive to curcumin exposure. In a dose-dependent manner, curcumin treatment resulted in significant suppression of Stat3 phosphorylation and reduction in the proliferative capacity of both cell types. In the preclinical trial with rodent models, curcumin reduced Stat3-P and the proliferative markers CycD1 and Mcm2 in mice lung tissues in vivo. Conclusion These culture and preclinical studies indicate that the activity of the Stat3 pathway can be suppressed by curcumin treatment, concomitant with a reduction in cell proliferation, supporting our hypothesis that inhibition of the Stat3 pathway represents at least one important mechanism by which curcumin elicits its effects on the bronchoepithelium. These data provide a rationale for the use of curcumin as a promising chemopreventive agent in high risk populations such as former smokers.

Alexandrow, Mark G.; Song, Lanxi J.; Altiok, Soner; Gray, Jhanelle; Haura, Eric B.; Kumar, Nagi B.

2011-01-01

304

Age exaggerates proinflammatory cytokine signaling and truncates STAT3 signaling following ischemic stroke in the rat  

PubMed Central

Neuroinflammation is associated with glial activation following a variety of brain injuries, including stroke. While activation of perilesional astrocytes and microglia following ischemic brain injury is well documented, the influence of age on these cellular responses after stroke is unclear. This study investigated the influence of advanced age on neuronal degeneration, neuroinflammation, and glial activation in female Sprague-Dawley rats after reversible embolic occlusion of the middle cerebral artery (MCAO). Results indicate that in comparison to young adult rats (3 months), aged rats (18 months) showed enhanced neuronal degeneration, altered microglial response, and a markedly increased expression of proinflammatory cytokines/chemokines following MCAO. In addition, the time-course for activation of STAT3, the signaling mechanism that regulates astrocyte reactivity, was truncated in the aged rats after MCAO. Moreover, the expression of SOCS3, which is associated with termination of astrogliosis, was enhanced as a function of age after MCAO. These findings are suggestive of an enhanced proinflammatory response and a truncated astroglial response as a function of advanced age following MCAO. These data provide further evidence of the prominent role played by age in the molecular and cellular responses to ischemic stroke and suggest that astrocytes may represent targets for future therapies aimed at improving stroke outcome.

DiNapoli, V.A.; Benkovic, S.A.; Li, X.; Kelly, K.A.; Miller, D.B.; Rosen, C.L.; Huber, J.D.; O'Callaghan, J.P.

2010-01-01

305

Fibroblast growth factor inhibits interferon ?-STAT1 and interleukin 6-STAT3 signaling in chondrocytes  

PubMed Central

Activation of fibroblast growth factor receptor 3 (FGFR3) leads to attenuation of cartilage growth. The members of the STAT family of transcription factors are believed to participate in FGFR3 signaling in cartilage, however the molecular mechanism of this action is poorly understood. Here, we demonstrate that a chronic FGF stimulus leads to accumulation of STAT1, 3, 5 and 6, evident in both in vitro chondrocyte model and murine limb explant cultures. Despite the accumulation, both endogenous and cytokine-induced activation of STAT1 and STAT3 is impaired by FGF, as demonstrated by imaging of active STAT nuclear translocation and analyses of STAT activatory phosphorylation and transcriptional activation. Further, we demonstrate that FGF induces expression of CIS, SOCS1 and SOCS3 inhibitors of gp130, a common receptor for the IL6-family of cytokines. Since cytokine-gp130 signaling represents an important positive regulator of cartilage, its inhibition may contribute to the growth-inhibitory effect of FGFR3 in cartilage.

Krejci, Pavel; Prochazkova, Jirina; Bryja, Vitezslav; Jelinkova, Petra; Pejchalova, Katerina; Kozubik, Alois; Thompson, Leslie Michels; Wilcox, William R.

2008-01-01

306

Prevention of Trauma and Hemorrhagic Shock-Mediated Liver Apoptosis by Activation of Stat3?  

PubMed Central

Trauma is a major cause of mortality in the United States. Death among those surviving the initial insult is caused by multiple organ failure (MOF) with the liver among the organs most frequently affected. We previously demonstrated in rodents that trauma complicated by hemorrhagic shock (trauma/HS) results in liver injury that can be prevented by IL-6 administration at the start of resuscitation; however, the contribution of the severity of HS to the extent of liver injury, whether or not resuscitation is required and the mechanism for the IL-6 protective effect have not been reported. In the experiments reported here, we demonstrated that the extent of liver apoptosis induced by trauma/HS depends on the duration of hypotension and requires resuscitation. We established that IL-6 administration at the start of resuscitation is capable of completely reversing liver apoptosis and is associated with increased Stat3 activation. Microarray analysis of the livers showed that the main effect of IL-6 was to normalize the trauma/HS-induced apoptosis transcriptome. Pharmacological inhibition of Stat3 activity within the liver blocked the ability of IL-6 to prevent liver apoptosis and to normalize the trauma/HS- induced liver apoptosis transcriptome. Genetic deletion of a Stat3?, a naturally occurring, dominant-negative isoform of the Stat3, attenuated trauma/HS-induced liver apoptosis, confirming a role for Stat3, especially Stat3?, in preventing trauma/HS-mediated liver apoptosis. Thus, trauma/HS-induced liver apoptosis depends on the duration of hypotension and requires resuscitation. IL-6 administration at the start of resuscitation reverses HS-induced liver apoptosis, through activation of Stat3?, which normalizes the trauma/HS-induced liver apoptosis transcriptome.

Moran, Ana; Akcan Arikan, Ayse; Mastrangelo, Mary-Ann A.; Wu, Yong; Yu, Bi; Poli, Valeria; Tweardy, David J.

2008-01-01

307

Stat3: linking inflammation to epithelial cancer - more than a "gut" feeling?  

PubMed Central

Inflammation is an important environmental factor that promotes tumourigenesis and the progression of established cancerous lesions, and recent studies have started to dissect the mechanisms linking the two pathologies. These inflammatory and infectious conditions trigger immune and stromal cell release of soluble mediators which facilitate survival and proliferation of tumour cells in a paracrine manner. In addition, (epi-)genetic mutations affecting oncogenes, tumour-suppressor genes, chromosomal rearrangements and amplifications trigger the release of inflammatory mediators within the tumour microenvironment to promote neoplastic growth in an autocrine manner. These two pathways converge in tumour cells and result in activation of the latent signal transducer and activator of transcription 3 (Stat3) which mediates a transcriptional response favouring survival, proliferation and angiogenesis. The abundance of cytokines that activate Stat3 within the tumour microenvironment, which comprises of members of the interleukin (IL) IL6, IL10 and IL17/23 families, underpins a signaling network that simultaneously promotes the growth of neoplastic epithelium, fuels inflammation and suppresses the host's anti-tumour immune response. Accordingly, aberrant and persistent Stat3 activation is a frequent observation in human cancers of epithelial origin and is often associated with poor outcome. Here we summarize insights gained from mice harbouring mutations in components of the Stat3 signaling cascade and in particular of gp130, the shared receptor for the IL6 family of cytokines. We focus on the various feed-back and feed-forward loops in which Stat3 provides the signaling node in cells of the tumour and its microenvironment thereby functionally linking excessive inflammation to neoplastic growth. Although these observations are particularly pertinent to gastrointestinal tumours, we suggest that the tumour's addiction to persistent Stat3 activation is likely to also impact on other epithelial cell-derived cancers. These insights provide clues to the judicious interference of the gp130/Stat3 signaling cascade in therapeutically targeting cancer.

2010-01-01

308

Neuronal STAT3 activation is essential for CNTF- and inflammatory stimulation-induced CNS axon regeneration  

PubMed Central

CNS neurons, such as retinal ganglion cells (RGCs), do not normally regenerate injured axons, but instead undergo apoptotic cell death. Regenerative failure is due to inhibitory factors in the myelin and forming glial scar as well as due to an insufficient intrinsic capability of mature neurons to regrow axons. Nevertheless, RGCs can be transformed into an active regenerative state upon inflammatory stimulation (IS) in the inner eye, for instance by lens injury, enabling these RGCs to survive axotomy and to regenerate axons into the lesioned optic nerve. The beneficial effects of IS are mediated by various factors, including CNTF, LIF and IL-6. Consistently, IS activates various signaling pathways, such as JAK/STAT3 and PI3K/AKT/mTOR, in several retinal cell types. Using a conditional knockdown approach to specifically delete STAT3 in adult RGCs, we investigated the role of STAT3 in IS-induced neuroprotection and axon regeneration. Conditional STAT3 knockdown in RGCs did not affect the survival of RGCs after optic nerve injury compared with controls, but significantly reduced the neuroprotective effects of IS. STAT3 depletion significantly compromised CNTF-stimulated neurite growth in culture and IS-induced transformation of RGCs into an active regenerative state in vivo. As a consequence, IS-mediated axonal regeneration into the injured optic nerve was almost completely abolished in mice with STAT3 depleted in RGCs. In conclusion, STAT3 activation in RGCs is involved in neuroprotection and is a necessary prerequisite for optic nerve regeneration upon IS.

Leibinger, M; Andreadaki, A; Diekmann, H; Fischer, D

2013-01-01

309

The study of c-Src kinase and pStat3 protein expression in retinoblastoma.  

PubMed

We examine the immunoreactivity of the non-receptor tyrosine kinase, c-Src kinase and its downstream molecule, signal transducer and activator of transcription 3 (pStat3) in retinoblastoma (RB), and correlation with invasiveness and differentiation. Tumor samples from 40 patients with RB were available for the study. There were 18 tumors in group 1 (non-invasive) and 22 tumors in group 2 (invasive). The immunoreactivity of c-Src kinase and pStat3 was compared in the two groups of tumors. Group 1 (non-invasive) RB showed intermediate c-Src kinase immunoreactivity (Allred score 4-5) in 14/18 tumors and low immunoreactivity (Allred score 2-3) in 4/18 tumors. pStat3 was intermediate (Allred score 4-5) in 6/18 tumors and negative (Allred score 0) in 12/18 tumors. Group 2 (invasive) RB showed high c-Src kinase immunoreactivity (Allred score 6-8) in 22/22 tumors and high pStat3 (Allred score 6-8) in 19/22 tumors. The expression of c-Src kinase (P<0.001) and pStat3 (P<0.001) was significantly higher in group 2 RB. Src kinase expression (P<0.05) and pStat3 expression (P<0.05) was higher in the poorly differentiated tumors compared to moderately- and well-differentiated tumors. The increased expression of c-Src kinase and pStat3 expression could play a role in the invasiveness of group 2 tumors. Further characterization of the pathways involved in the pathogenesis of RB will shed light on fundamental mechanisms of tumorigenesis. PMID:16716300

Mohan, Adithi; Mallikarjuna, Kandalam; Venkatesan, Nalini; Abhyankar, Dhiraj; Parikh, Purvish M; Krishnakumar, Subramanian

2006-05-22

310

IL-6-Mediated Activation of Stat3? Prevents Trauma/Hemorrhagic Shock-Induced Liver Inflammation  

PubMed Central

Trauma complicated by hemorrhagic shock (T/HS) is the leading cause of morbidity and mortality in the United States for individuals under the age of 44 years. Initial survivors are susceptible to developing multiple organ failure (MOF), which is thought to be caused, at least in part, by excessive or maladaptive activation of inflammatory pathways. We previously demonstrated in rodents that T/HS results in liver injury that can be prevented by IL-6 administration at the start of resuscitation; however, the contribution of the severity of HS to the extent of liver injury, whether or not resuscitation is required, and the mechanism(s) for the IL-6 protective effect have not been reported. In the experiments described here, we demonstrated that the extent of liver inflammation induced by T/HS depends on the duration of hypotension and requires resuscitation. We established that IL-6 administration at the start of resuscitation is capable of completely reversing liver inflammation and is associated with increased Stat3 activation. Global assessment of the livers showed that the main effect of IL-6 was to normalize the T/HS-induced inflammation transcriptome. Pharmacological inhibition of Stat3 activity within the liver blocked the ability of IL-6 to prevent liver inflammation and to normalize the T/HS-induced liver inflammation transcriptome. Genetic deletion of a Stat3?, a naturally occurring, dominant-negative isoform of the Stat3, attenuated T/HS-induced liver inflammation, confirming a role for Stat3, especially Stat3?, in preventing T/HS-mediated liver inflammation. Thus, T/HS-induced liver inflammation depends on the duration of hypotension and requires resuscitation; IL-6 administration at the start of resuscitation reverses T/HS-induced liver inflammation, through activation of Stat3?, which normalized the T/HS-induced liver inflammation transcriptome.

Moran, Ana; Thacker, Stephen A.; Arikan, Ayse Akcan; Mastrangelo, Mary-Ann A.; Wu, Yong; Yu, Bi; Tweardy, David J.

2011-01-01

311

STAT3 signal transduction through interleukin-22 in oral squamous cell carcinoma.  

PubMed

Interleukin (IL)-22 is a member of the IL-10 family. Its main targets are epithelial cells, not immune cells. We examined IL-22 signal transduction in oral squamous cell carcinoma (OSCC) cells. Immunohistochemical staining revealed that IL-22R was expressed more highly in OSCC compared to normal regions. An IL-22R signal was also observed in metastatic OSCC cells in the lymph node. RT-PCR showed that the human OSCC cell lines MISK81-5, HSC-3, HSC-4, SAS and SQUU-B expressed IL-22 receptor chains. Immunoblotting showed that IL-22 induced a transient tyrosine phosphorylation of STAT3 (pY705-STAT3) in MISK81-5 cells. The change in the serine phosphorylation of STAT3 was subtle during the examination periods. Simultaneously, pY705-STAT3 activation in HSC-3 cells was undetectable after IL-22 stimulation. Immunocytochemistry demonstrated that IL-22 induced the translocation of phosphorylated STAT3 into the nucleus of MISK81-5 cells. IL-22 temporarily upregulated the expression of anti-apoptotic and mitogenic genes such as Bcl-x, survivin and c-Myc, as well as SOCS3. IL-22 transiently activated ERK1/2 and induced a delayed phosphorylation of p38 MAP kinase, but negligibly involved the activation of NF-?B in MISK81-5 cells. MISK81-5 and SQUU-B cells treated with IL-22 showed mild cellular proliferation. MISK81-5, HSC-4 and SAS cells treated with IL-22 downregulated the keratinocyte differentiation-related genes compared with unstimulated cells. Conversely, STAT3 suppression by STAT3 siRNA strongly disrupted the downregulation of these genes by IL-22, but it did not significantly affect the activation of ERK1/2 by IL-22. The OSCC cells used in this study upregulated the expression of SERPINB3/4 (SCCA1/2), well-known SCC markers, following treatment with IL-22. These results indicate that IL-22 differentially activates the STAT3 signaling system depending on the type of OSCC. IL-22 may therefore play a role in tumor growth, cell differentiation and progression through STAT3-dependent and -independent pathways. PMID:22922995

Naher, Lutfun; Kiyoshima, Tamotsu; Kobayashi, Ieyoshi; Wada, Hiroko; Nagata, Kengo; Fujiwara, Hiroaki; Ookuma, Yukiko F; Ozeki, Satoru; Nakamura, Seiji; Sakai, Hidetaka

2012-08-21

312

Alternative implication of CXCR4 in JAK2/STAT3 activation in small cell lung cancer  

PubMed Central

Small cell lung cancer (SCLC) is an aggressive, rapidly metastasising tumour. Previously, we demonstrated the influence of CXCL12–CXCR4 interaction on processes involved in metastasis and chemoresistance in SCLC. We show here that STAT3 is expressed in both primary SCLC tumour tissues and SCLC cell lines. We investigated the function of STAT3 upon CXCL12 stimulation in SCLC cell lines. Small cell lung cancer cell lines present constitutive phosphorylation of STAT3, and in the reference cell lines NCI-H69 and NCI-H82 constitutive phosphorylation was further increased by CXCL12 stimulation. Further investigating this signalling cascade, we showed that it involves interactions between CXCR4 and JAK2 in both cell lines. However CXCL12-induced adhesion to VCAM-1 could be completely inhibited by the JAK2 inhibitor AG490 only in NCI-H82. Furthermore, CXCR4 antagonist but not AG490 inhibited cell adhesion whereas both antagonisms were shown to inhibit growth of the cells in soft agar, indicating the central involvement of this signalling in anchorage-independent growth of SCLC cells. Most interestingly, while using primary tumour material, we observed that in contrast to non-small-cell lung cancer samples from primary tumour tissues, all analysed samples from SCLC were strongly positive for tyrosine-phosphorylated STAT3. Taken together, these data indicate that STAT3 is constitutively phosphorylated in SCLC and is important in SCLC growth and spreading thus presenting an interesting target for therapy.

Pfeiffer, M; Hartmann, T N; Leick, M; Catusse, J; Schmitt-Graeff, A; Burger, M

2009-01-01

313

STAT3 single-nucleotide polymorphisms and STAT3 mutations associated with hyper-IgE syndrome are not responsible for increased serum IgE serum levels in asthma families  

Microsoft Academic Search

Mutations in STAT3 (signal transducer and activator of transcription 3) have recently been found to cause the hyper-IgE syndrome (HIES) – a rare immunodeficiency syndrome including complex somatic features. We now tested whether STAT3 mutations or single-nucleotide polymorphisms (SNPs) within STAT3 may be responsible for increased IgE levels in asthmatic children. We genotyped DNA samples from 918 individuals of 217

Matthias Wjst; Peter Lichtner; Thomas Meitinger; Bodo Grimbacher

2009-01-01

314

Kansuinine A and Kansuinine B from Euphorbia kansui L. inhibit IL-6-induced Stat3 activation.  

PubMed

The current study was performed to examine the mechanisms underlying the potential effects of E. KANSUI on IL-6-induced cellular signaling in human hepatoma cells. We found that two diterpenoids, kansuinine A and B, from E. KANSUI have an inhibitory effect on IL-6-induced Stat3 activation by activating ERK1/2. Inhibition of MEK significantly blocked the effects of kansuinine A and B on IL-6-induced Stat3 activation and tyrosine phosphorylation. These results suggest that blocking of IL-6-induced signal transduction is partially due to the sustained activation of ERK1/2 by kansuinine A and B, which in turn results in an increase of Stat3 serine phosphorylation and SOCS-3 expression. Treatment with kansuinine A and B represents a novel method to block these IL-6-induced effects. PMID:20379953

Chang, Jong Sun; Lee, Seung Woong; Park, Mi Hye; Kim, Myo Sun; Hudson, Barry I; Park, Su-Jin; Lee, Woo Song; Rho, Mun-Chual

2010-04-08

315

STAT3 as a therapeutic target for Epstein-Barr virus (EBV): associated nasopharyngeal carcinoma.  

PubMed

Nasopharyngeal carcinoma (NPC), an endemic head and neck cancer found in Southeast Asia, is etiologically associated with the infection of an oncogenic virus, the Epstein-Barr virus (EBV). Here, we review literature findings on the potential/putative role of STAT3 signaling in its pathogenesis and discuss anti-STAT3 targeting as a therapeutic and possibly prevention strategy for NPC. Lastly, the potential involvement of STAT3 in other oncovirus-associated (e.g. the human papillomavirus) head and neck cancers have not been investigated and we hope that findings in EBV-associated NPC can prompt future investigations in these cancers, which are of increasing impact in the Western countries. PMID:23220625

Ho, Yeung; Tsao, Sai-Wah; Zeng, Musheng; Lui, Vivian Wai Yan

2012-12-06

316

FER kinase activation of Stat3 is determined by the N-terminal sequence.  

PubMed

p94(fer) and p51(ferT) are two tyrosine kinases that share identical SH2 and kinase domains but differ in their N-terminal regions. To further explore the cellular functions of these two highly related tyrosine kinases, their subcellular distribution profiles and in vivo phosphorylation activity were followed using double immunofluorescence assay. When combined with immunoprecipitation analysis, this assay showed that p94(fer) can lead to the tyrosine phosphorylation and activation of Stat3 but not of Stat1 or Stat2. Native p94(fer) exerted this activity when residing in the cytoplasm. However, modified forms of p94(fer), which are constitutively nuclear, could also lead to the phosphorylation of Stat3. Endogenous Stat3 and p94(fer) co-immunoprecipitated with each other, thus proving the interaction of these two proteins in vivo. Unlike p94(fer), p51(ferT) did not induce the phosphorylation of Stat3 but led to the phosphorylation of other nuclear proteins. Replacing the unique 43-amino acid-long N-terminal tail of p51(ferT) with a parallel segment from the N-terminal tail of p94(fer) did not change the subcellular localization of p51(ferT) but enabled it to activate Stat3. Thus the different N-terminal sequences of p94(fer) and p51(ferT) can affect their ability to induce phosphorylation of Stat3 and most probably direct their different cellular functions. PMID:10878010

Priel-Halachmi, S; Ben-Dor, I; Shpungin, S; Tennenbaum, T; Molavani, H; Bachrach, M; Salzberg, S; Nir, U

2000-09-15

317

STAT3 and SOCS3 Expression Patterns During Murine Placenta Development  

PubMed Central

Signal transducers and activators of transcription 3 (STAT3) has been identified as an important signal transducer in the invasive phenotype of the trophoblasts cells in in vitro studies. However, the in situ distribution and patterns of expression of this molecule in trophoblast cells during the development of the placenta are still under-elucidated. Mice uteri of gestational ages between 7 and 14 days of pregnancy (dop) were fixed in methacarn and processed with immunoperoxidase techniques for detection of STAT3 and its phosphorylation at serine (p-ser727) residues, as well as the suppressor of cytokine signaling 3 (SOCS3) expression. STAT3 was observed at 7 through 9 dop in both the antimesometrial and mesometrial deciduas, while continued immunoreactivity between 10 and 13 dop was seen only in the mesometrial decidua. In the placenta, STAT3 was detected in the cytotrophoblast cells of labyrinth and giant trophoblast cells between 10 and 14 dop. Immunoreactivity for STAT3 was also seen in trophoblast cells surrounding the maternal blood vessels. On days 10 and 11 of pregnancy, p-ser727 was detectable in the mesometrial decidua and in giant trophoblasts, while during 12-14 dop in the spongiotrophoblast region. In addition, SOCS3 was immunodetected in maternal and placental tissues, principally in the giant trophoblast cells during the whole period of the study. The present in situ study shows the distribution of STAT3, its serine activation and SOCS3 in different maternal and fetal compartments during murine placental development, thus further supporting the idea that they play a role during physiological placentation in mice.

San Martin, S.; Fitzgerald, J.S.; Weber, M.; Parraga, M.; Saez, T.; Zorn, T.M.; Markert, U.R.

2013-01-01

318

Anti-Angiogenic Activity of a Small Molecule STAT3 Inhibitor LLL12  

PubMed Central

Background Recent data indicate the Signal Transducer and Activator of Transcription 3 (STAT3) pathway is required for VEGF production and angiogenesis in various types of cancers. STAT3 inhibitors have been shown to reduce tumor microvessel density in tumors but a direct anti-angiogenic activity has not been described. Methodology/Principal Findings We investigated the direct action of a small molecule inhibitor of STAT3 (LLL12) in human umbilical cord vascular endothelial cells (HUVECs) in vitro, in a Matrigel model for angiogenesis in vivo, and its antitumor activity in a xenograft model of osteosarcoma. LLL12 (100 nM) significantly inhibited VEGF-stimulated STAT3 phosphorylation in HUVECs, reduced their proliferation/migration and inhibited VEGF-induced tube formation. Morphologic analysis of LLL12 treated HUVECs demonstrated marked changes in actin/tubulin distribution and bundling. In scid mice, LLL12 reduced microvessel invasion into VEGF-infused Matrigel plugs by ?90% at a dose of 5 mg/kg daily. Following a period of tumor progression (2 weeks), LLL12 completely suppressed further growth of established OS-1 osteosarcoma xenografts. Pharmacodynamic studies showed robust phosphorylated STAT3 in control tumors, whereas phospho-STAT3 was not detected in LLL12-treated OS-1 tumors. Treated tumors demonstrated decreased proliferation (Ki67 staining), and decreased microvessel density (CD34 staining), but no significant increase in apoptosis (TUNEL staining), relative to controls. Assay of angiogenic factors, using an antibody array, showed VEGF, MMP-9, Angiopoietin1/2, Tissue Factor and FGF-1 expression were dramatically reduced in LLL12-treated tumors compared to control tumors. Conclusions These findings provide the first evidence that LLL12 effectively inhibits tumor angiogenesis both in vitro and in vivo.

Bid, Hemant K.; Oswald, Duane; Li, Chenglong; London, Cheryl A.; Lin, Jiayuh; Houghton, Peter J.

2012-01-01

319

STAT subtype specificity and ischemic preconditioning in mice: is STAT-3 enough?  

PubMed Central

The role of other STAT subtypes in conferring ischemic tolerance is unclear. We hypothesized that in STAT-3 deletion alternative STAT subtypes would protect myocardial function against ischemia-reperfusion injury. Wild-type (WT) male C57BL/6 mice or mice with cardiomyocyte STAT-3 knockout (KO) underwent baseline echocardiography. Langendorff-perfused hearts underwent ischemic preconditioning (IPC) or no IPC before ischemia-reperfusion. Following ex vivo perfusion, hearts were analyzed for STAT-5 and -6 phosphorylation by Western blot analysis of nuclear fractions. Echocardiography and postequilibration cardiac performance revealed no differences in cardiac function between WT and KO hearts. Phosphorylated STAT-5 and -6 expression was similar in WT and KO hearts before perfusion. Contractile function in WT and KO hearts was significantly impaired following ischemia-reperfusion in the absence of IPC. In WT hearts, IPC significantly improved the recovery of the maximum first derivative of developed pressure (+dP/dtmax) compared with that in hearts without IPC. IPC more effectively improved end-reperfusion dP/dtmax in WT hearts compared with KO hearts. Preconditioned and nonpreconditioned KO hearts exhibited increased phosphorylated STAT-5 and -6 expression compared with WT hearts. The increased subtype activation did not improve the efficacy of IPC in KO hearts. In conclusion, baseline cardiac performance is preserved in hearts with cardiac-restricted STAT-3 deletion. STAT-3 deletion attenuates preconditioning and is not associated with a compensatory upregulation of STAT-5 and -6 subtypes. The activation of STAT-5 and -6 in KO hearts following ischemic challenge does not provide functional compensation for the loss of STAT-3. JAK-STAT signaling via STAT-3 is essential for effective IPC.

Goodman, Michael D.; Koch, Sheryl E.; Afzal, Muhammad R.

2011-01-01

320

Hydrazinocurcumin Encapsuled nanoparticles "re-educate" tumor-associated macrophages and exhibit anti-tumor effects on breast cancer following STAT3 suppression.  

PubMed

Tumor-associated macrophages (TAMs) are essential cellular components within tumor microenvironment (TME). TAMs are educated by TME to transform to M2 polarized population, showing a M2-like phenotype, IL-10(high), IL-12(low), TGF-?(high). STAT3 signaling triggers crosstalk between tumor cells and TAMs, and is crucial for the regulation of malignant progression. In our study, legumain-targeting liposomal nanoparticles (NPs) encapsulating HC were employed to suppress STAT3 activity and "re-educate" TAMs, and to investigate the effects of suppression of tumor progression in vivo. The results showed that TAMs treated by HC encapsuled NPs could switch to M1-like phenotype, IL-10(low), IL-12(high), TGF-?(low), and the "re-educated" macrophages (M1-like macrophages) considerably demonstrated opposite effect of M2-like macrophages, especially the induction of 4T1 cells migration and invasion in vitro, and suppression of tumor growth, angiogenesis and metastasis in vivo. These data indicated that inhibition of STAT3 activity of TAMs by HC-NPs was able to reverse their phenotype and could regulate their crosstalk between tumor cells and TAMs in order to suppress tumor progression. PMID:23825527

Zhang, Xiwen; Tian, Wenxia; Cai, Xiaozhong; Wang, Xiaofei; Dang, Weiqi; Tang, Hao; Cao, Hong; Wang, Lin; Chen, Tingmei

2013-06-25

321

Requirement of histone deacetylase1 (HDAC1) in signal transducer and activator of transcription 3 (STAT3) nucleocytoplasmic distribution  

PubMed Central

Signal Transducer and Activator of Transcription 3 (STAT3) is a transcription factor that plays a crucial role in interleukin-6 (IL-6) signaling, mediating the acute-phase induction of the human Angiotensinogen (hAGT) gene in hepatocytes. We showed earlier that IL-6 induces acetylation of the STAT3 NH2-terminus by the recruitment of the p300 coactivator. We had also observed a physical interaction of STAT3 and Histone Deacetylase1 (HDAC1) in an IL-6-dependent manner that leads to transcriptional repression. In this study, we sought to elucidate the mechanism by which HDAC1 controls STAT3 transcriptional activity. Here, we mapped the interacting domains of both STAT3 and HDAC1 and found that the COOH-terminal domain of HDAC1 is necessary for IL-6-induced STAT3 transcriptional repression, whereas the NH2-terminal acetylation domain of STAT3 is required for HDAC1 binding. Interestingly, over expression of HDAC1 in HepG2 cells leads to significantly reduced amounts of nuclear STAT3 after IL-6 induction, whereas silencing of HDAC1 resulted in accumulation of total and acetylated STAT3 in the nucleus. We have found that HDAC1 knockdown also interferes with the responsiveness of the STAT3-dependent MCP1 target gene expression to IL-6, as confirmed by real-time RT–PCR analysis. Together, our study reveals the novel functional consequences of IL-6-induced STAT3-HDAC1 interaction on nucleocytoplasmic distribution of STAT3.

Ray, Sutapa; Lee, Chang; Hou, Tieying; Boldogh, Istvan; Brasier, Allan R.

2008-01-01

322

Identification of a novel Stat3 recruitment and activation motif within the granulocyte colony-stimulating factor receptor.  

PubMed

Stat3 is essential for early embryonic development and for myeloid differentiation induced by the cytokines granulocyte colony-stimulating factor (G-CSF) and interleukin-6 (IL-6). Two isoforms of Stat3 have been identified, (p92) and beta (p83), which have distinct transcriptional and biological functions. Activation of both Stat3 and Stat3beta requires the distal cytoplasmic domain of the G-CSFR, which contains four Tyr at positions 704, 729, 744, and 764. The studies reported here were undertaken to determine which, if any, of these tyrosine residues participated in Stat3/beta recruitment and activation. We showed that Stat3 and Stat3beta were affinity purified using phosphopeptides containing Y704 and Y744 but not by nonphosphorylated peptide analogues or by phosphopeptides containing Y729 and Y764. Complementary results were obtained in studies examining the ability of these peptides to destabilize and inhibit DNA binding of activated Stat3. Both Y704 and Y744 contributed to optimal activation of Stat3/beta in M1 murine myeloid leukemia cells containing wild-type and Y-to-F mutant G-CSFR constructs. Carboxy-terminal to Y704 at the +3 position is Gln; YXXQ represents a consensus Stat3 recruitment and activation motif. Y744 is followed at the +3 position by Cys (C); YXXC, represents a novel motif implicated in the recruitment and activation of Stat3. Modeling of the SH2 domain of Stat3 based on homologous SH2 domains of known structure revealed polar residues whose side chains contact the +3 position. This substitution may confer specificity for the Y704- and Y744-based ligands by allowing H-bond formation between the binding surface and the Gln or Cys found at the respective +3 position. PMID:9864141

Chakraborty, A; Dyer, K F; Cascio, M; Mietzner, T A; Tweardy, D J

1999-01-01

323

The Expression of p-STAT3 in Stage IV Melanoma: Risk of CNS Metastasis and Survival  

PubMed Central

Purpose The signal transducer and activator of transcription 3 (STAT3) is a key molecular hub of tumorigenesis and immune suppression. The expression of phosphorylated STAT3 (p-STAT3) has been shown to be higher in melanoma metastasis to the central nervous system (CNS) relative to distant metastasis in the rest of the body (systemic). We sought to determine whether the increased expression of p-STAT3 in non-CNS systemic melanoma metastasis is associated with an increased risk of developing CNS metastasis and is a negative prognostic factor for overall survival time. Methods We retrospectively identified 299 patients with stage IV melanoma. In a tissue microarray of systemic non-CNS metastasis specimens from these patients, we used immunohistochemical analysis to measure the percentage of cells with p-STAT3 expression and Kaplan–Meier survival estimates to analyze the association of p-STAT3 expression with median survival time, time to first CNS metastasis, and development of CNS metastasis. Results Lung metastases exhibited the highest level of p-STAT3 expression while spleen lesions had the lowest. The p-STAT3 expression was not associated with an increased risk of developing CNS metastasis or time to CNS metastasis. However, p-STAT3 expression was a negative prognostic factor for overall survival time in patients that did not develop CNS metastasis. Conclusions Stage IV melanoma patients without CNS metastasis treated with p-STAT3 inhibitors in efficacy studies should be stratified based on tumor expression of p-STAT3; however since p-STAT3 expression is not associated with the risk of CNS disease, increased MRI surveillance of the brain is not likely necessary.

Bassett, Roland; Kong, Ling-Yuan; Schacherer, Christopher W.; Gershenwald, Jeffrey E.; Grimm, Elizabeth A.; Fuller, Gregory N.; Heimberger, Amy B.

2012-01-01

324

Oct 4 is Critical for Survival/Antiapoptosis of Murine Embryonic Stem Cells Subjected to Stress. Effects Associated with STAT3/Survivin  

PubMed Central

Understanding survival/anti-apoptosis of murine embryonic stem (ES) cells may enhance their clinical potential. We hypothesized that Oct-4 might be involved in survival of undifferentiated ES cells under stress. Oct-4 tetracycline conditional knockout cell line ZHBtc4 was used to test this possibility and apoptosis was induced by either etoposide, heat shock or UV exposure. Apoptosis in Oct-4 knocked-down ES cells was significantly increased in response to all stress situations compared to parental cells. Oct-4 knockdown was not associated with changes in morphology, or expression of nanog, SSEA-1, KLF-4, or Sox2 within the time-frame and culture conditions used, suggesting that enhanced sensitivity of these cells to apoptosis was not due to an overtly differentiated state of the cells. To address potential intracellular mediators, we focused on IAP family member Survivin, an anti-apoptosis protein. The Survivin promoter was transfected into ES cells after knock-down of Oct-4. Survivin promoter activity was dramatically decreased in the Oct-4 knock-down cells. Western blots substantiated that Oct-4 knockdown ES cells had decreased Survivin protein expression. Since the Survivin promoter does not have binding sites for Oct-4, this suggested an indirect effect of Oct-4 on expression of Survivin. LIF-induced STAT3 is responsible for ES cell survival, and STAT3 regulates Survivin expression in breast cancer cells. Western Blot analysis showed that down regulated Oct-4 was associated with decreased phosphorylation of STAT3. Our results suggest that Oct-4 is essential for anti-apoptosis of ES cells in response to stress, effects that may be mediated through the STAT3/Survivin pathway.

Guo, Ying; Mantel, Charlie; Hromas, Robert A.; Broxmeyer, Hal E.

2010-01-01

325

The macrophage response towards LPS and its control through the p38(MAPK)-STAT3 axis.  

PubMed

In macrophages detection of gram-negative bacteria particularly involves binding of the outer-wall component lipopolysaccharide (LPS) to its cognate receptor complex, comprising Toll like receptor 4 (TLR4), CD14 and MD2. LPS-induced formation of the LPS receptor complex elicits a signaling network, including intra-cellular signal-transduction directly activated by the TLR4 receptor complex as well as successional induction of indirect autocrine and paracrine signaling events. All these different pathways are integrated into the macrophage response towards an inflammatory stimulus by a highly complex cross-talk of the pathways engaged. This also includes a tight control by several intra- and inter-cellular feedback loops warranting an inflammatory response sufficient to battle invading pathogens and to avoid non-essential tissue damage caused by an overwhelming inflammatory response. Several evidences indicate that the reciprocal cr