Regulation of kinetochore recruitment of two essential mitotic spindle checkpoint proteins by Mps1 phosphorylation.

PubMed

Xu, Quanbin; Zhu, Songcheng; Wang, Wei; Zhang, Xiaojuan; Old, William; Ahn, Natalie; Liu, Xuedong

2009-01-01

Mps1 is a protein kinase that plays essential roles in spindle checkpoint signaling. Unattached kinetochores or lack of tension triggers recruitment of several key spindle checkpoint proteins to the kinetochore, which delays anaphase onset until proper attachment or tension is reestablished. Mps1 acts upstream in the spindle checkpoint signaling cascade, and kinetochore targeting of Mps1 is required for subsequent recruitment of Mad1 and Mad2 to the kinetochore. The mechanisms that govern recruitment of Mps1 or other checkpoint proteins to the kinetochore upon spindle checkpoint activation are incompletely understood. Here, we demonstrate that phosphorylation of Mps1 at T12 and S15 is required for Mps1 recruitment to the kinetochore. Mps1 kinetochore recruitment requires its kinase activity and autophosphorylation at T12 and S15. Mutation of T12 and S15 severely impairs its kinetochore association and markedly reduces recruitment of Mad2 to the kinetochore. Our studies underscore the importance of Mps1 autophosphorylation in kinetochore targeting and spindle checkpoint signaling.

Deconstructing Ras Signaling in the Thymus

PubMed Central

Kortum, Robert L.; Sommers, Connie L.; Pinski, John M.; Alexander, Clayton P.; Merrill, Robert K.; Li, Wenmei; Love, Paul E.

2012-01-01

Thymocytes must transit at least two distinct developmental checkpoints, governed by signals that emanate from either the pre-T cell receptor (pre-TCR) or the TCR to the small G protein Ras before emerging as functional T lymphocytes. Recent studies have shown a role for the Ras guanine exchange factor (RasGEF) Sos1 at the pre-TCR checkpoint. At the second checkpoint, the quality of signaling through the TCR is interrogated to ensure the production of an appropriate T cell repertoire. Although RasGRP1 is the only confirmed RasGEF required at the TCR checkpoint, current models suggest that the intensity and character of Ras activation, facilitated by both Sos and RasGRP1, will govern the boundary between survival (positive selection) and death (negative selection) at this stage. Using mouse models, we have assessed the independent and combined roles for the RasGEFs Sos1, Sos2, and RasGRP1 during thymocyte development. Although Sos1 was the dominant RasGEF at the pre-TCR checkpoint, combined Sos1/RasGRP1 deletion was required to effectively block development at this stage. Conversely, while RasGRP1 deletion efficiently blocked positive selection, combined RasGRP1/Sos1 deletion was required to block negative selection. This functional redundancy in RasGEFs during negative selection may act as a failsafe mechanism ensuring appropriate central tolerance. PMID:22586275

Mechanism-based screen for G1/S checkpoint activators identifies a selective activator of EIF2AK3/PERK signalling.

PubMed

Stockwell, Simon R; Platt, Georgina; Barrie, S Elaine; Zoumpoulidou, Georgia; Te Poele, Robert H; Aherne, G Wynne; Wilson, Stuart C; Sheldrake, Peter; McDonald, Edward; Venet, Mathilde; Soudy, Christelle; Elustondo, Frédéric; Rigoreau, Laurent; Blagg, Julian; Workman, Paul; Garrett, Michelle D; Mittnacht, Sibylle

2012-01-01

Human cancers often contain genetic alterations that disable G1/S checkpoint control and loss of this checkpoint is thought to critically contribute to cancer generation by permitting inappropriate proliferation and distorting fate-driven cell cycle exit. The identification of cell permeable small molecules that activate the G1/S checkpoint may therefore represent a broadly applicable and clinically effective strategy for the treatment of cancer. Here we describe the identification of several novel small molecules that trigger G1/S checkpoint activation and characterise the mechanism of action for one, CCT020312, in detail. Transcriptional profiling by cDNA microarray combined with reverse genetics revealed phosphorylation of the eukaryotic initiation factor 2-alpha (EIF2A) through the eukaryotic translation initiation factor 2-alpha kinase 3 (EIF2AK3/PERK) as the mechanism of action of this compound. While EIF2AK3/PERK activation classically follows endoplasmic reticulum (ER) stress signalling that sets off a range of different cellular responses, CCT020312 does not trigger these other cellular responses but instead selectively elicits EIF2AK3/PERK signalling. Phosphorylation of EIF2A by EIF2A kinases is a known means to block protein translation and hence restriction point transit in G1, but further supports apoptosis in specific contexts. Significantly, EIF2AK3/PERK signalling has previously been linked to the resistance of cancer cells to multiple anticancer chemotherapeutic agents, including drugs that target the ubiquitin/proteasome pathway and taxanes. Consistent with such findings CCT020312 sensitizes cancer cells with defective taxane-induced EIF2A phosphorylation to paclitaxel treatment. Our work therefore identifies CCT020312 as a novel small molecule chemical tool for the selective activation of EIF2A-mediated translation control with utility for proof-of-concept applications in EIF2A-centered therapeutic approaches, and as a chemical starting point for

Induction of a G1-S checkpoint in fission yeast.

PubMed

Bøe, Cathrine A; Krohn, Marit; Rødland, Gro Elise; Capiaghi, Christoph; Maillard, Olivier; Thoma, Fritz; Boye, Erik; Grallert, Beáta

2012-06-19

Entry into S phase is carefully regulated and, in most organisms, under the control of a G(1)-S checkpoint. We have previously described a G(1)-S checkpoint in fission yeast that delays formation of the prereplicative complex at chromosomal replication origins after exposure to UV light (UVC). This checkpoint absolutely depends on the Gcn2 kinase. Here, we explore the signal for activation of the Gcn2-dependent G(1)-S checkpoint in fission yeast. If some form of DNA damage can activate the checkpoint, deficient DNA repair should affect the length of the checkpoint-induced delay. We find that the cell-cycle delay differs in repair-deficient mutants from that in wild-type cells. However, the duration of the delay depends not only on the repair capacity of the cells, but also on the nature of the repair deficiency. First, the delay is abolished in cells that are deficient in the early steps of repair. Second, the delay is prolonged in repair mutants that fail to complete repair after the incision stage. We conclude that the G(1)-S delay depends on damage to the DNA and that the activating signal derives not from the initial DNA damage, but from a repair intermediate(s). Surprisingly, we find that activation of Gcn2 does not depend on the processing of DNA damage and that activated Gcn2 alone is not sufficient to delay entry into S phase in UVC-irradiated cells. Thus, the G(1)-S delay depends on at least two different inputs.

RAD18 Activates the G2/M Checkpoint through DNA Damage Signaling to Maintain Genome Integrity after Ionizing Radiation Exposure

PubMed Central

Sasatani, Megumi; Xu, Yanbin; Kawai, Hidehiko; Cao, Lili; Tateishi, Satoshi; Shimura, Tsutomu; Li, Jianxiang; Iizuka, Daisuke; Noda, Asao; Hamasaki, Kanya; Kusunoki, Yoichiro; Kamiya, Kenji

2015-01-01

The ubiquitin ligase RAD18 is involved in post replication repair pathways via its recruitment to stalled replication forks, and its role in the ubiquitylation of proliferating cell nuclear antigen (PCNA). Recently, it has been reported that RAD18 is also recruited to DNA double strand break (DSB) sites, where it plays novel functions in the DNA damage response induced by ionizing radiation (IR). This new role is independent of PCNA ubiquitylation, but little is known about how RAD18 functions after IR exposure. Here, we describe a role for RAD18 in the IR-induced DNA damage signaling pathway at G2/M phase in the cell cycle. Depleting cells of RAD18 reduced the recruitment of the DNA damage signaling factors ATM, γH2AX, and 53BP1 to foci in cells at the G2/M phase after IR exposure, and attenuated activation of the G2/M checkpoint. Furthermore, depletion of RAD18 increased micronuclei formation and cell death following IR exposure, both in vitro and in vivo. Our data suggest that RAD18 can function as a mediator for DNA damage response signals to activate the G2/M checkpoint in order to maintain genome integrity and cell survival after IR exposure. PMID:25675240

An origin-deficient yeast artificial chromosome triggers a cell cycle checkpoint.

PubMed

van Brabant, A J; Buchanan, C D; Charboneau, E; Fangman, W L; Brewer, B J

2001-04-01

Checkpoint controls coordinate entry into mitosis with the completion of DNA replication. Depletion of nucleotide precursors by treatment with the drug hydroxyurea triggers such a checkpoint response. However, it is not clear whether the signal for this hydroxyurea-induced checkpoint pathway is the presence of unreplicated DNA, or rather the persistence of single-stranded or damaged DNA. In a yeast artificial chromosome (YAC) we have engineered an approximately 170 kb region lacking efficient replication origins that allows us to explore the specific effects of unreplicated DNA on cell cycle progression. Replication of this YAC extends the length of S phase and causes cells to engage an S/M checkpoint. In the absence of Rad9 the YAC becomes unstable, undergoing deletions within the origin-free region.

The human intra-S checkpoint response to UVC-induced DNA damage.

PubMed

Kaufmann, William K

2010-05-01

The intra-S checkpoint response to 254 nm light (UVC)-induced DNA damage appears to have dual functions to slow the rate of DNA synthesis and stabilize replication forks that become stalled at sites of UVC-induced photoproducts in DNA. These functions should provide more time for repair of damaged DNA before its replication and thereby reduce the frequencies of mutations and chromosomal aberrations in surviving cells. This review tries to summarize the history of discovery of the checkpoint, the current state of understanding of the biological features of intra-S checkpoint signaling and its mechanisms of action with a focus primarily on intra-S checkpoint responses in human cells. The differences in the intra-S checkpoint responses to UVC and ionizing radiation-induced DNA damage are emphasized. Evidence that [6-4]pyrimidine-pyrimidone photoproducts in DNA trigger the response is discussed and the relationships between cellular responses to UVC and the molecular dose of UVC-induced DNA damage are briefly summarized. The role of the intra-S checkpoint response in protecting against solar radiation carcinogenesis remains to be determined.

Determining the Effectiveness Of Flexible Checkpoints

DOT National Transportation Integrated Search

2017-05-01

Flexible checkpoints are sometimes referred to as phantom checkpoints, public awareness checkpoints, mobile awareness patrols, and mock checkpoints. This checkpoint strategy involves staging a checkpoint, but not actually staf...

Toward an optimal online checkpoint solution under a two-level HPC checkpoint model

DOE PAGES

Di, Sheng; Robert, Yves; Vivien, Frederic; ...

2016-03-29

The traditional single-level checkpointing method suffers from significant overhead on large-scale platforms. Hence, multilevel checkpointing protocols have been studied extensively in recent years. The multilevel checkpoint approach allows different levels of checkpoints to be set (each with different checkpoint overheads and recovery abilities), in order to further improve the fault tolerance performance of extreme-scale HPC applications. How to optimize the checkpoint intervals for each level, however, is an extremely difficult problem. In this paper, we construct an easy-to-use two-level checkpoint model. Checkpoint level 1 deals with errors with low checkpoint/recovery overheads such as transient memory errors, while checkpoint level 2more » deals with hardware crashes such as node failures. Compared with previous optimization work, our new optimal checkpoint solution offers two improvements: (1) it is an online solution without requiring knowledge of the job length in advance, and (2) it shows that periodic patterns are optimal and determines the best pattern. We evaluate the proposed solution and compare it with the most up-to-date related approaches on an extreme-scale simulation testbed constructed based on a real HPC application execution. Simulation results show that our proposed solution outperforms other optimized solutions and can improve the performance significantly in some cases. Specifically, with the new solution the wall-clock time can be reduced by up to 25.3% over that of other state-of-the-art approaches. Lastly, a brute-force comparison with all possible patterns shows that our solution is always within 1% of the best pattern in the experiments.« less

The Interaction between Checkpoint Kinase 1 (Chk1) and the Minichromosome Maintenance (MCM) Complex Is Required for DNA Damage-induced Chk1 Phosphorylation*

PubMed Central

Han, Xiangzi; Aslanian, Aaron; Fu, Kang; Tsuji, Toshiya; Zhang, Youwei

2014-01-01

Chk1 is an essential mediator of the DNA damage response and cell cycle checkpoint. However, how exactly Chk1 transduces the checkpoint signaling is not fully understood. Here we report the identification of the heterohexamic minichromosome maintenance (MCM) complex that interacts with Chk1 by mass spectrometry. The interaction between Chk1 and the MCM complex was reduced by DNA damage treatment. We show that the MCM complex, at least partially, contributes to the chromatin association of Chk1, allowing for immediate phosphorylation of Chk1 by ataxia telangiectasia mutated and Rad3-related (ATR) in the presence of DNA damage. Further, phosphorylation of Chk1 at ATR sites reduces the interaction between Chk1 and the MCM complex, facilitating chromatin release of phosphorylated Chk1, a critical step in the initiation and amplification of cell cycle checkpoint. Together, these data provide novel insights into the activation of Chk1 in response to DNA damage. PMID:25049228

Checkpoint inhibitors in advanced melanoma: effect on the field of immunotherapy.

PubMed

O'reilly, Aine; Larkin, James

2017-07-01

The success of the immune checkpoint inhibitors in melanoma has reinvigorated the field of immunotherapy. Immune checkpoint inhibitors are now the standard of care in multiple cancer types including lung cancer, head and neck cancer, urothelial cancer and renal cell cancer. The field of immunotherapy is currently expanding rapidly and will be a focus of research and development for decades to come. Areas covered: This review covers the early development of immune checkpoint inhibitors and the changes that occurred in the drug development paradigm to facilitate the development of immunotherapy. The review will summarise the areas into which immune checkpoint inhibitors have been adopted and will review the data that supported this. Furthermore, we will discuss future developments in immunotherapy and the current landscape regarding maximising the potential of immunotherapy in clinical practice. Expert commentary: In the author's opinion, the potential of immunotherapy is vast. To date immune checkpoint inhibition has already delivered durable responses in a proportion of patients with cancer types which were previously universally lethal. The future of immunotherapy will rely upon the intelligent application of translational research to clinical practice, such that immunotherapy can be effective for a wider population and maintain its current growth.

Compiler-assisted static checkpoint insertion

NASA Technical Reports Server (NTRS)

Long, Junsheng; Fuchs, W. K.; Abraham, Jacob A.

1992-01-01

This paper describes a compiler-assisted approach for static checkpoint insertion. Instead of fixing the checkpoint location before program execution, a compiler enhanced polling mechanism is utilized to maintain both the desired checkpoint intervals and reproducible checkpoint 1ocations. The technique has been implemented in a GNU CC compiler for Sun 3 and Sun 4 (Sparc) processors. Experiments demonstrate that the approach provides for stable checkpoint intervals and reproducible checkpoint placements with performance overhead comparable to a previously presented compiler assisted dynamic scheme (CATCH) utilizing the system clock.

Human cytomegalovirus inhibits a DNA damage response by mislocalizing checkpoint proteins

NASA Astrophysics Data System (ADS)

Gaspar, Miguel; Shenk, Thomas

2006-02-01

The DNA damage checkpoint pathway responds to DNA damage and induces a cell cycle arrest to allow time for DNA repair. Several viruses are known to activate or modulate this cellular response. Here we show that the ataxia-telangiectasia mutated checkpoint pathway, which responds to double-strand breaks in DNA, is activated in response to human cytomegalovirus DNA replication. However, this activation does not propagate through the pathway; it is blocked at the level of the effector kinase, checkpoint kinase 2 (Chk2). Late after infection, several checkpoint proteins, including ataxia-telangiectasia mutated and Chk2, are mislocalized to a cytoplasmic virus assembly zone, where they are colocalized with virion structural proteins. This colocalization was confirmed by immunoprecipitation of virion proteins with an antibody that recognizes Chk2. Virus replication was resistant to ionizing radiation, which causes double-strand breaks in DNA. We propose that human CMV DNA replication activates the checkpoint response to DNA double-strand breaks, and the virus responds by altering the localization of checkpoint proteins to the cytoplasm and thereby inhibiting the signaling pathway. ionizing radiation | ataxia-telangiectasia mutated pathway

Immune checkpoint inhibitors in small cell lung cancer.

PubMed

Pakkala, Suchita; Owonikoko, Taofeek K

2018-02-01

Small cell lung cancer (SCLC) is a rapidly progressive cancer that often debilitates patients within months of detection and quickly becomes refractory to the limited options of therapy. While SCLC is not generally considered an immunogenic tumor, clinical experience suggests that patients with robust immune response manifesting as paraneoplastic syndrome are more likely to present with limited stage of the disease and tend to have a better prognosis. Monoclonal antibodies targeting critical negative regulators of immune response, so called immune checkpoints, such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed death 1 (PD-1) have expanded the application of immune-based therapies to increasing number of advanced stage cancers. These agents overcome the inhibitory immune signals leading to a heightened immune response against cancer cells. These immune checkpoint inhibitors have established efficacy leading to regulatory approval for their use in many cancer types including non-small cell lung cancer (NSCLC). Evaluation of the CTLA-4 inhibitor, ipilimumab and PD-1 inhibitors, nivolumab and pembrolizumab in SCLC have shown encouraging signal but definitive studies are still ongoing. In this review, we discuss the rationale behind the use of checkpoint inhibitors in SCLC, contextualize the results of early trials of immunotherapy agents in SCLC and project the future evolution of this strategy.

Epithelial-mesenchymal transition is associated with a distinct tumor microenvironment including elevation of inflammatory signals and multiple immune checkpoints in lung adenocarcinoma

PubMed Central

Lou, Yanyan; Diao, Lixia; Cuentas, Edwin Roger Parra; Denning, Warren L.; Chen, Limo; Fan, Youhong; Byers, Lauren A.; Wang, Jing; Papadimitrakopoulou, Vassiliki; Behrens, Carmen; Rodriguez, Jaime Canales; Hwu, Patrick; Wistuba, Ignacio I.; Heymach, John V.; Gibbons, Don L.

2016-01-01

Purpose Promising results in the treatment of NSCLC have been seen with agents targeting immune checkpoints, such as PD-1 or PD-L1. However, only a select group of patients respond to these interventions. The identification of biomarkers that predict clinical benefit to immune checkpoint blockade is critical to successful clinical translation of these agents. Methods We conducted an integrated analysis of three independent large datasets, including The Cancer Genome Atlas (TCGA) of lung adenocarcinoma and two datasets from MD Anderson Cancer Center, Profiling of Resistance patterns and Oncogenic Signaling Pathways in Evaluation of Cancers of the Thorax (named PROSPECT) and Biomarker-integrated Approaches of Targeted Therapy for Lung Cancer Elimination (named BATTLE-1). Comprehensive analysis of mRNA gene expression, reverse phase protein array (RPPA), immunohistochemistry and correlation with clinical data were performed. Results Epithelial-mesenchymal transition (EMT) is highly associated with an inflammatory tumor microenvironment in lung adenocarcinoma, independent of tumor mutational burden. We found immune activation co-existent with elevation of multiple targetable immune checkpoint molecules, including PD-L1, PD-L2, PD-1, TIM-3, B7-H3, BTLA and CTLA-4, along with increases in tumor infiltration by CD4+Foxp3+ regulatory T cells in lung adenocarcinomas that displayed an EMT phenotype. Furthermore, we identify B7-H3 as a prognostic marker for NSCLC. Conclusions The strong association between EMT status and an inflammatory tumor microenvironment with elevation of multiple targetable immune checkpoint molecules warrants further investigation of using EMT as a predictive biomarker for immune checkpoint blockade agents and other immunotherapies in NSCLC and possibly a broad range of other cancers. PMID:26851185

Chk1 and Cds1: linchpins of the DNA damage and replication checkpoint pathways

PubMed Central

Rhind, Nicholas; Russell, Paul

2010-01-01

SUMMARY Recent work on the mechanisms of DNA damage and replication cell cycle checkpoints has revealed great similarity between the checkpoint pathways of organisms as diverse as yeasts, flies and humans. However, there are differences in the ways these organisms regulate their cell cycles. To connect the conserved checkpoint pathways with various cell cycle targets requires an adaptable link that can target different cell cycle components in different organisms. The Chk1 and Cds1 protein kinases, downstream effectors in the checkpoint pathways, seem to play just such roles. Perhaps more surprisingly, the two kinases not only have different targets in different organisms but also seem to respond to different signals in different organisms. So, whereas in fission yeast Chk1 is required for the DNA damage checkpoint and Cds1 is specifically involved in the replication checkpoint, their roles seem to be shuffled in metazoans. PMID:11058076

Leucine facilitates insulin signaling through a Gαi protein-dependent signaling pathway in hepatocytes.

PubMed

Yang, Xuefeng; Mei, Shuang; Wang, Xiaolei; Li, Xiang; Liu, Rui; Ma, Yan; Hao, Liping; Yao, Ping; Liu, Liegang; Sun, Xiufa; Gu, Haihua; Liu, Zhenqi; Cao, Wenhong

2013-03-29

In this study, we addressed the direct effect of leucine on insulin signaling. In investigating the associated mechanisms, we found that leucine itself does not activate the classical Akt- or ERK1/2 MAP kinase-dependent signaling pathways but can facilitate the insulin-induced phosphorylations of Akt(473) and ERK1/2 in a time- and dose-dependent manner in cultured hepatocytes. The leucine-facilitated insulin-induced phosphorylation of Akt at residue 473 was not affected by knocking down the key component of mTORC1 or -2 complexes but was blocked by inhibition of c-Src (PP2), PI3K (LY294002), Gαi protein (pertussis toxin or siRNA against Gαi1 gene, or β-arrestin 2 (siRNA)). Similarly, the leucine-facilitated insulin activation of ERK1/2 was also blunted by pertussis toxin. We further show that leucine facilitated the insulin-mediated suppression of glucose production and expression of key gluconeogenic genes in a Gαi1 protein-dependent manner in cultured primary hepatocytes. Together, these results show that leucine can directly facilitate insulin signaling through a Gαi protein-dependent intracellular signaling pathway. This is the first evidence showing that macronutrients like amino acid leucine can facilitate insulin signaling through G proteins directly.

Leucine Facilitates Insulin Signaling through a Gαi Protein-dependent Signaling Pathway in Hepatocytes*

PubMed Central

Yang, Xuefeng; Mei, Shuang; Wang, Xiaolei; Li, Xiang; Liu, Rui; Ma, Yan; Hao, Liping; Yao, Ping; Liu, Liegang; Sun, Xiufa; Gu, Haihua; Liu, Zhenqi; Cao, Wenhong

2013-01-01

In this study, we addressed the direct effect of leucine on insulin signaling. In investigating the associated mechanisms, we found that leucine itself does not activate the classical Akt- or ERK1/2 MAP kinase-dependent signaling pathways but can facilitate the insulin-induced phosphorylations of Akt473 and ERK1/2 in a time- and dose-dependent manner in cultured hepatocytes. The leucine-facilitated insulin-induced phosphorylation of Akt at residue 473 was not affected by knocking down the key component of mTORC1 or -2 complexes but was blocked by inhibition of c-Src (PP2), PI3K (LY294002), Gαi protein (pertussis toxin or siRNA against Gαi1 gene, or β-arrestin 2 (siRNA)). Similarly, the leucine-facilitated insulin activation of ERK1/2 was also blunted by pertussis toxin. We further show that leucine facilitated the insulin-mediated suppression of glucose production and expression of key gluconeogenic genes in a Gαi1 protein-dependent manner in cultured primary hepatocytes. Together, these results show that leucine can directly facilitate insulin signaling through a Gαi protein-dependent intracellular signaling pathway. This is the first evidence showing that macronutrients like amino acid leucine can facilitate insulin signaling through G proteins directly. PMID:23404499

Aurora B potentiates Mps1 activation to ensure rapid checkpoint establishment at the onset of mitosis.

PubMed

Saurin, Adrian T; van der Waal, Maike S; Medema, René H; Lens, Susanne M A; Kops, Geert J P L

2011-01-01

The mitotic checkpoint prevents mitotic exit until all chromosomes are attached to spindle microtubules. Aurora B kinase indirectly invokes this checkpoint by destabilizing incorrect attachments; however, a more direct role remains controversial. In contrast, activity of the kinase Mps1 is indispensible for the mitotic checkpoint. Here we show that Aurora B and Hec1 are needed for efficient Mps1 recruitment to unattached kinetochores, allowing rapid Mps1 activation at the onset of mitosis. Live monitoring of cyclin B degradation reveals that this is essential to establish the mitotic checkpoint quickly at the start of mitosis. Delayed Mps1 activation and checkpoint establishment upon Aurora B inhibition or Hec1 depletion are rescued by tethering Mps1 to kinetochores, demonstrating that Mps1 recruitment is the primary role of Aurora B and Hec1 in mitotic checkpoint signalling. These data demonstrate a direct role for Aurora B in initiating the mitotic checkpoint rapidly at the onset of mitosis.

Cid1, a Fission Yeast Protein Required for S-M Checkpoint Control when DNA Polymerase δ or ɛ Is Inactivated

PubMed Central

Wang, Shao-Win; Toda, Takashi; MacCallum, Robert; Harris, Adrian L.; Norbury, Chris

2000-01-01

The S-M checkpoint is an intracellular signaling pathway that ensures that mitosis is not initiated in cells undergoing DNA replication. We identified cid1, a novel fission yeast gene, through its ability when overexpressed to confer specific resistance to a combination of hydroxyurea, which inhibits DNA replication, and caffeine, which overrides the S-M checkpoint. Cid1 overexpression also partially suppressed the hydroxyurea sensitivity characteristic of DNA polymerase δ mutants and mutants defective in the “checkpoint Rad” pathway. Cid1 is a member of a family of putative nucleotidyltransferases including budding yeast Trf4 and Trf5, and mutation of amino acid residues predicted to be essential for this activity resulted in loss of Cid1 function in vivo. Two additional Cid1-like proteins play similar but nonredundant checkpoint-signaling roles in fission yeast. Cells lacking Cid1 were found to be viable but specifically sensitive to the combination of hydroxyurea and caffeine and to be S-M checkpoint defective in the absence of Cds1. Genetic data suggest that Cid1 acts in association with Crb2/Rhp9 and through the checkpoint-signaling kinase Chk1 to inhibit unscheduled mitosis specifically when DNA polymerase δ or ɛ is inhibited. PMID:10757807

Loss of BubR1 acetylation causes defects in spindle assembly checkpoint signaling and promotes tumor formation

PubMed Central

Park, Inai; Lee, Hae-ock; Choi, Eunhee; Lee, Yoo-Kyung; Kwon, Mi-Sun; Min, Jaewon; Park, Pil-Gu; Lee, Seonju; Kong, Young-Yun; Gong, Gyungyub

2013-01-01

BubR1 acetylation is essential in mitosis. Mice heterozygous for the acetylation-deficient BubR1 allele (K243R/+) spontaneously developed tumors with massive chromosome missegregations. K243R/+ mouse embryonic fibroblasts (MEFs) exhibited a weakened spindle assembly checkpoint (SAC) with shortened mitotic timing. The generation of the SAC signal was intact, as Mad2 localization to the unattached kinetochore (KT) was unaltered; however, because of the premature degradation of K243R-BubR1, the mitotic checkpoint complex disassociated prematurely in the nocodazole-treated condition, suggesting that maintenance of the SAC is compromised. BubR1 acetylation was also required to counteract excessive Aurora B activity at the KT for stable chromosome–spindle attachments. The association of acetylation-deficient BubR1 with PP2A-B56α phosphatase was reduced, and the phosphorylated Ndc80 at the KT was elevated in K243R/+ MEFs. In relation, there was a marked increase of micronuclei and p53 mutation was frequently detected in primary tumors of K243R/+ mice. Collectively, the combined effects of failure in chromosome–spindle attachment and weakened SAC cause genetic instability and cancer in K243R/+ mice. PMID:23878276

Suspended animation in C. elegans requires the spindle checkpoint.

PubMed

Nystul, Todd G; Goldmark, Jesse P; Padilla, Pamela A; Roth, Mark B

2003-11-07

In response to environmental signals such as anoxia, many organisms enter a state of suspended animation, an extreme form of quiescence in which microscopically visible movement ceases. We have identified a gene, san-1, that is required for suspended animation in Caenorhabditis elegans embryos. We show that san-1 functions as a spindle checkpoint component in C. elegans. During anoxia-induced suspended animation, embryos lacking functional SAN-1 or a second spindle checkpoint component, MDF-2, failed to arrest the cell cycle, exhibited chromosome missegregation, and showed reduced viability. These data provide a model for how a dynamic biological process is arrested in suspended animation.

Keeping Tumors in Check: A Mechanistic Review of Clinical Response and Resistance to Immune Checkpoint Blockade in Cancer.

PubMed

Borcherding, Nicholas; Kolb, Ryan; Gullicksrud, Jodi; Vikas, Praveen; Zhu, Yuwen; Zhang, Weizhou

2018-07-06

Immune checkpoints are a diverse set of inhibitory signals to the immune system that play a functional role in adaptive immune response and self-tolerance. Dysregulation of these pathways is a vital mechanism in the avoidance of immune destruction by tumor cells. Immune checkpoint blockade (ICB) refers to targeted strategies to disrupt the tumor co-opted immune suppression to enhance anti-tumor immunity. Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death 1 (PD-1) are two immune checkpoints that have the widest range of antibody-based therapies. These therapies have gone from promising approaches to Food and Drug Administration-approved first- and second-line agents for a number of immunogenic cancers. The burgeoning investigations of ICB efficacy in blood and solid cancers have underscored the importance of identifying the predictors of response and resistance to ICB. Identification of response correlates is made complicated by the observations of mixed reactions, or different responses in multiple lesions from the same patient, and delayed responses that can occur over a year after the induction therapy. Factors that can influence response and resistance in ICB can illuminate underlying molecular mechanisms of immune activation and suppression. These same response predictors can guide the identification of patients who would benefit from ICB, reduce off-target immune-relate adverse events, and facilitate the use of combinatorial therapies to increase efficacy. Here we review the underlying principles of immune checkpoint therapy and results of single-agent ICB clinical trials, and summarize the predictors of response and resistance. Copyright © 2018 Elsevier Ltd. All rights reserved.

Checkpointing for a hybrid computing node

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cher, Chen-Yong

2016-03-08

According to an aspect, a method for checkpointing in a hybrid computing node includes executing a task in a processing accelerator of the hybrid computing node. A checkpoint is created in a local memory of the processing accelerator. The checkpoint includes state data to restart execution of the task in the processing accelerator upon a restart operation. Execution of the task is resumed in the processing accelerator after creating the checkpoint. The state data of the checkpoint are transferred from the processing accelerator to a main processor of the hybrid computing node while the processing accelerator is executing the task.

Reducing space overhead for independendent checkpointing

NASA Technical Reports Server (NTRS)

Wang, Yi-Min; Chung, Pi-Yu; Lin, In-Jen; Fuchs, W. Kent

1992-01-01

The main disadvantages of independent checkpointing are the possible domino effect and the associated storage space overhead for maintaining multiple checkpoints. In most previous work, it has been assumed that only the checkpoints older than the current global recovery line can be discarded. Here, we generalize a notion of recovery line to potential recovery line. Only the checkpoints belonging to at least one of the potential recovery lines cannot be discarded. By using the model of maximum-sized antichains on a partially ordered set, an efficient algorithm is developed for finding all non-discardable checkpoints, and we show that the number of non-discardable checkpoints cannot exceed N(N+1)/2, where N is the number of processors. Communication trace driven simulation for several hypercube programs is performed to show the benefit of the proposed algorithm for real applications.

Lazy checkpoint coordination for bounding rollback propagation

NASA Technical Reports Server (NTRS)

Wang, Yi-Min; Fuchs, W. Kent

1992-01-01

Independent checkpointing allows maximum process autonomy but suffers from potential domino effects. Coordinated checkpointing eliminates the domino effect by sacrificing a certain degree of process autonomy. In this paper, we propose the technique of lazy checkpoint coordination which preserves process autonomy while employing communication-induced checkpoint coordination for bounding rollback propagation. The introduction of the notion of laziness allows a flexible trade-off between the cost for checkpoint coordination and the average rollback distance. Worst-case overhead analysis provides a means for estimating the extra checkpoint overhead. Communication trace-driven simulation for several parallel programs is used to evaluate the benefits of the proposed scheme for real applications.

Pontin is required for pre-TCR signaling at the β-selection checkpoint in T cell development.

PubMed

Boo, Kyungjin; Baek, Sung Hee; Lee, Ho

2014-04-25

Pontin is a chromatin remodeling factor that possesses both ATPase and DNA helicase activities. Based on high expression in lymphoid tissues, we examined whether Pontin has a T cell-specific function. We generated Pontin(f/f);Lck-Cre mice, in which Pontin can be conditionally deleted in T cells and then explored T cell-specific function of Pontin in vivo. Here, we show that specific abrogation of Pontin expression in T cells almost completely blocked development of αβ T cells at the β-selection checkpoint by inducing cell apoptosis indicating that Pontin is essential for early T cell development. Pontin-deficient thymocytes show a comparable expression level of T cell receptor (TCR)β chain, but have enhanced activation of p53 and Notch signaling compared to wild-type thymocytes. Intriguingly, the developmental block of αβ T cells can be partially rescued by loss of p53. Together, our data demonstrate a novel role of Pontin as a crucial regulator in pre-TCR signaling during T cell development. Copyright © 2014 Elsevier Inc. All rights reserved.

Checkpointing in speculative versioning caches

DOEpatents

Eichenberger, Alexandre E; Gara, Alan; Gschwind, Michael K; Ohmacht, Martin

2013-08-27

Mechanisms for generating checkpoints in a speculative versioning cache of a data processing system are provided. The mechanisms execute code within the data processing system, wherein the code accesses cache lines in the speculative versioning cache. The mechanisms further determine whether a first condition occurs indicating a need to generate a checkpoint in the speculative versioning cache. The checkpoint is a speculative cache line which is made non-speculative in response to a second condition occurring that requires a roll-back of changes to a cache line corresponding to the speculative cache line. The mechanisms also generate the checkpoint in the speculative versioning cache in response to a determination that the first condition has occurred.

Epigenetic modifiers in immunotherapy: a focus on checkpoint inhibitors.

PubMed

Terranova-Barberio, Manuela; Thomas, Scott; Munster, Pamela N

2016-06-01

Immune surveillance should be directed to suppress tumor development and progression, involving a balance of coinhibitory and costimulatory signals that amplify immune response without overwhelming the host. Immunotherapy confers durable clinical benefit in 'immunogenic tumors', whereas in other tumors the responses are modest. Thus, immune checkpoint inhibitors may need to be combined with strategies to boost immune response or increase the tumor immune profile. Epigenetic aberrations contribute significantly to carcinogenesis. Recent findings suggest that epigenetic drugs prime the immune response by increasing expression of tumor-associated antigens and immune-related genes, as well as modulating chemokines and cytokines involved in immune system activation. This review describes our current understanding regarding epigenetic and immunotherapy combination, focusing on immune response priming to checkpoint blockade.

Interprofessional Collaboration with Immune Checkpoint Inhibitor Therapy: the Roles of Gastroenterology, Endocrinology and Neurology.

PubMed

Seery, Virginia

2017-11-01

To discuss immune checkpoint inhibitor therapy and identify opportunities for interprofessional collaboration in the management of toxicities in the areas of gastroenterology, endocrinology, and neurology. Published research and education articles in oncology, nursing, and various specialties. The use of immune checkpoint inhibitors is expanding; timely management of toxicity is critical for positive patient outcomes. There are many opportunities for interprofessional collaboration in the diagnosis and treatment of immune-related adverse events. Nurses play key roles in recognizing immune-related adverse events, providing patient education, and helping to facilitate interprofessional collaboration. Copyright © 2017 Elsevier Inc. All rights reserved.

Identification of three signaling molecules required for calcineurin-dependent monopolar growth induced by the DNA replication checkpoint in fission yeast.

PubMed

Kume, Kazunori; Hashimoto, Tomoyo; Suzuki, Masashi; Mizunuma, Masaki; Toda, Takashi; Hirata, Dai

2017-09-30

Cell polarity is coordinately regulated with the cell cycle. Growth polarity of the fission yeast Schizosaccharomyces pombe transits from monopolar to bipolar during G2 phase, termed NETO (new end take off). Upon perturbation of DNA replication, the checkpoint kinase Cds1/CHK2 induces NETO delay through activation of Ca 2+ /calmodulin-dependent protein phosphatase calcineurin (CN). CN in turn regulates its downstream targets including the microtubule (MT) plus-end tracking CLIP170 homologue Tip1 and the Casein kinase 1γ Cki3. However, whether and which Ca 2+ signaling molecules are involved in the NETO delay remains elusive. Here we show that 3 genes (trp1322, vcx1 and SPAC6c3.06c encoding TRP channel, antiporter and P-type ATPase, respectively) play vital roles in the NETO delay. Upon perturbation of DNA replication, these 3 genes are required for not only the NETO delay but also for the maintenance of cell viability. Trp1322 and Vcx1 act downstream of Cds1 and upstream of CN for the NETO delay, whereas SPAC6c3.06c acts downstream of CN. Consistently, Trp1322 and Vcx1, but not SPAC6c3.06c, are essential for activation of CN. Interestingly, we have found that elevated extracellular Ca 2+ per se induces a NETO delay, which depends on CN and its downstream target genes. These findings imply that Ca 2+ -CN signaling plays a central role in cell polarity control by checkpoint activation. Copyright © 2017 Elsevier Inc. All rights reserved.

DNA replication checkpoint promotes G1-S transcription by inactivating the MBF repressor Nrm1

PubMed Central

de Bruin, R. A. M.; Kalashnikova, T. I.; Aslanian, A.; Wohlschlegel, J.; Chahwan, C.; Yates, J. R.; Russell, P.; Wittenberg, C.

2008-01-01

The cell cycle transcriptional program imposes order on events of the cell-cycle and is a target for signals that regulate cell-cycle progression, including checkpoints required to maintain genome integrity. Neither the mechanism nor functional significance of checkpoint regulation of the cell-cycle transcription program are established. We show that Nrm1, an MBF-specific transcriptional repressor acting at the transition from G1 to S phase of the cell cycle, is at the nexus between the cell cycle transcriptional program and the DNA replication checkpoint in fission yeast. Phosphorylation of Nrm1 by the Cds1 (Chk2) checkpoint protein kinase, which is activated in response to DNA replication stress, promotes its dissociation from the MBF transcription factor. This leads to the expression of genes encoding components that function in DNA replication and repair pathways important for cell survival in response to arrested DNA replication. PMID:18682565

Evaluation of Charlottesville checkpoint operations

DOT National Transportation Integrated Search

1985-05-01

Under a grant from the Virginia Office of Highway Safety, the Charlottesville Police Department implemented a Driver's License and Sobriety Checkpoint Program from December 30, 1983 to December 31, 1984. During the period, 94 checkpoint operations we...

Checkpoint Blockade Cancer Immunotherapy Targets Tumour-Specific Mutant Antigens

PubMed Central

Gubin, Matthew M.; Zhang, Xiuli; Schuster, Heiko; Caron, Etienne; Ward, Jeffrey P.; Noguchi, Takuro; Ivanova, Yulia; Hundal, Jasreet; Arthur, Cora D.; Krebber, Willem-Jan; Mulder, Gwenn E.; Toebes, Mireille; Vesely, Matthew D.; Lam, Samuel S.K.; Korman, Alan J.; Allison, James P.; Freeman, Gordon J.; Sharpe, Arlene H.; Pearce, Erika L.; Schumacher, Ton N.; Aebersold, Ruedi; Rammensee, Hans-Georg; Melief, Cornelis J. M.; Mardis, Elaine R.; Gillanders, William E.; Artyomov, Maxim N.; Schreiber, Robert D.

2014-01-01

The immune system plays key roles in determining the fate of developing cancers by not only functioning as a tumour promoter facilitating cellular transformation, promoting tumour growth and sculpting tumour cell immunogenicity1–6, but also as an extrinsic tumour suppressor that either destroys developing tumours or restrains their expansion1,2,7. Yet clinically apparent cancers still arise in immunocompetent individuals in part as a consequence of cancer induced immunosuppression. In many individuals, immunosuppression is mediated by Cytotoxic T-Lymphocyte Associated Antigen-4 (CTLA-4) and Programmed Death-1 (PD-1), two immunomodulatory receptors expressed on T cells8,9. Monoclonal antibody (mAb) based therapies targeting CTLA-4 and/or PD-1 (checkpoint blockade) have yielded significant clinical benefits—including durable responses—to patients with different malignancies10–13. However, little is known about the identity of the tumour antigens that function as the targets of T cells activated by checkpoint blockade immunotherapy and whether these antigens can be used to generate vaccines that are highly tumour-specific. Herein, we use genomics and bioinformatics approaches to identify tumour-specific mutant proteins as a major class of T cell rejection antigens following αPD-1 and/or αCTLA-4 therapy of mice bearing progressively growing sarcomas and show that therapeutic synthetic long peptide (SLP) vaccines incorporating these mutant epitopes induce tumour rejection comparably to checkpoint blockade immunotherapy. Whereas, mutant tumour antigen-specific T cells are present in progressively growing tumours, they are reactivated following treatment with αPD-1- and/or αCTLA-4 and display some overlapping but mostly treatment-specific transcriptional profiles rendering them capable of mediating tumour rejection. These results reveal that tumour-specific mutant antigens (TSMA) are not only important targets of checkpoint blockade therapy but also can be

The Scalable Checkpoint/Restart Library

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moody, A.

The Scalable Checkpoint/Restart (SCR) library provides an interface that codes may use to worite our and read in application-level checkpoints in a scalable fashion. In the current implementation, checkpoint files are cached in local storage (hard disk or RAM disk) on the compute nodes. This technique provides scalable aggregate bandwidth and uses storage resources that are fully dedicated to the job. This approach addresses the two common drawbacks of checkpointing a large-scale application to a shared parallel file system, namely, limited bandwidth and file system contention. In fact, on current platforms, SCR scales linearly with the number of compute nodes.more » It has been benchmarked as high as 720GB/s on 1094 nodes of Atlas, which is nearly two orders of magnitude faster thanthe parallel file system.« less

Natural Loss of Mps1 Kinase in Nematodes Uncovers a Role for Polo-like Kinase 1 in Spindle Checkpoint Initiation.

PubMed

Espeut, Julien; Lara-Gonzalez, Pablo; Sassine, Mélanie; Shiau, Andrew K; Desai, Arshad; Abrieu, Ariane

2015-07-07

The spindle checkpoint safeguards against chromosome loss during cell division by preventing anaphase onset until all chromosomes are attached to spindle microtubules. Checkpoint signal is generated at kinetochores, the primary attachment site on chromosomes for spindle microtubules. Mps1 kinase initiates checkpoint signaling by phosphorylating the kinetochore-localized scaffold protein Knl1 to create phospho-docking sites for Bub1/Bub3. Mps1 is widely conserved but is surprisingly absent in many nematode species. Here, we show that PLK-1, which targets a substrate motif similar to that of Mps1, functionally substitutes for Mps1 in C. elegans by phosphorylating KNL-1 to direct BUB-1/BUB-3 kinetochore recruitment. This finding led us to re-examine checkpoint initiation in human cells, where we found that Plk1 co-inhibition significantly reduced Knl1 phosphorylation and Bub1 kinetochore recruitment relative to Mps1 inhibition alone. Thus, the finding that PLK-1 functionally substitutes for Mps1 in checkpoint initiation in C. elegans uncovered a role for Plk1 in species that have Mps1. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

A new look at NHTSA's evaluation of the 1984 Charlottesville Sobriety Checkpoint Program: implications for current checkpoint issues.

PubMed

Voas, Robert B

2008-03-01

Currently, the implementation of sobriety checkpoint programs, which have been demonstrated to be effective in reducing alcohol-related crashes, is limited by the belief that they require large consignments of police officers and result in few arrests. However, one of the earliest evaluations of a checkpoint program in Charlottesville, Virginia, demonstrated that effective checkpoints could be mounted in which police officers made as many arrests as officers on regular patrols. That study was printed by the NHTSA but was not published in a peer-reviewed journal. Because of its significance to current issues in the staffing of and procedures for checkpoint operations, this article reanalyzes the results of that study and describes the procedures implemented in checkpoints. A before-and-after control design was used to measure the change in nighttime crashes from three baseline years to the program year. Two analyses were conducted: the first on the percentage of all crashes occurring at night in the test city--Charlottesville--and the second on the percentage of all nighttime crashes in the state of Virginia that occurred in the test city. In addition, three waves of random-digit-dialing telephone surveys were conducted: one before and two during the checkpoint program in the test city, and the comparison city, Blacksburg. Finally, the number of impaired-driving arrests per officer hour at the checkpoints was compared with the number of arrests per hour by officers on regular patrol and the effect on arrests of the use of passive sensors was determined. The monthly percentage of nighttime crashes in Charlottesville was reduced by 17% (p = 000) in relation to the baseline level. The percentage of nighttime crashes in the state of Virginia that occurred in Charlottesville was reduced by 11% (p = .013) from baseline levels. Drivers arrested at checkpoints had lower BACs than those arrested by the regular patrols; however, the conviction rates were the same. The arrest

Multiple Duties for Spindle Assembly Checkpoint Kinases in Meiosis

PubMed Central

Marston, Adele L.; Wassmann, Katja

2017-01-01

Cell division in mitosis and meiosis is governed by evolutionary highly conserved protein kinases and phosphatases, controlling the timely execution of key events such as nuclear envelope breakdown, spindle assembly, chromosome attachment to the spindle and chromosome segregation, and cell cycle exit. In mitosis, the spindle assembly checkpoint (SAC) controls the proper attachment to and alignment of chromosomes on the spindle. The SAC detects errors and induces a cell cycle arrest in metaphase, preventing chromatid separation. Once all chromosomes are properly attached, the SAC-dependent arrest is relieved and chromatids separate evenly into daughter cells. The signaling cascade leading to checkpoint arrest depends on several protein kinases that are conserved from yeast to man. In meiosis, haploid cells containing new genetic combinations are generated from a diploid cell through two specialized cell divisions. Though apparently less robust, SAC control also exists in meiosis. Recently, it has emerged that SAC kinases have additional roles in executing accurate chromosome segregation during the meiotic divisions. Here, we summarize the main differences between mitotic and meiotic cell divisions, and explain why meiotic divisions pose special challenges for correct chromosome segregation. The less-known meiotic roles of the SAC kinases are described, with a focus on two model systems: yeast and mouse oocytes. The meiotic roles of the canonical checkpoint kinases Bub1, Mps1, the pseudokinase BubR1 (Mad3), and Aurora B and C (Ipl1) will be discussed. Insights into the molecular signaling pathways that bring about the special chromosome segregation pattern during meiosis will help us understand why human oocytes are so frequently aneuploid. PMID:29322045

Immune checkpoint therapy in liver cancer.

PubMed

Xu, Feng; Jin, Tianqiang; Zhu, Yuwen; Dai, Chaoliu

2018-05-29

Immune checkpoints include stimulatory and inhibitory checkpoint molecules. In recent years, inhibitory checkpoints, including cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), programmed cell death protein-1 (PD-1), and programmed cell death ligand 1 (PD-L1), have been identified to suppress anti-tumor immune responses in solid tumors. Novel drugs targeting immune checkpoints have succeeded in cancer treatment. Specific PD-1 blockades were approved for treatment of melanoma in 2014 and for treatment of non-small-cell lung cancer in 2015 in the United States, European Union, and Japan. Preclinical and clinical studies show immune checkpoint therapy provides survival benefit for greater numbers of patients with liver cancer, including hepatocellular carcinoma and cholangiocarcinoma, two main primary liver cancers. The combination of anti-PD-1/PD-L1 with anti-CTLA-4 antibodies is being evaluated in phase 1, 2 or 3 trials, and the results suggest that an anti-PD-1 antibody combined with locoregional therapy or other molecular targeted agents is an effective treatment strategy for HCC. In addition, studies on activating co-stimulatory receptors to enhance anti-tumor immune responses have increased our understanding regarding this immunotherapy in liver cancer. Epigenetic modulations of checkpoints for improving the tumor microenvironment also expand our knowledge of potential therapeutic targets in improving the tumor microenvironment and restoring immune recognition and immunogenicity. In this review, we summarize current knowledge and recent developments in immune checkpoint-based therapies for the treatment of hepatocellular carcinoma and cholangiocarcinoma and attempt to clarify the mechanisms underlying its effects.

Requirement of the Mre11 complex and exonuclease 1 for activation of the Mec1 signaling pathway.

PubMed

Nakada, Daisuke; Hirano, Yukinori; Sugimoto, Katsunori

2004-11-01

The large protein kinases, ataxia-telangiectasia mutated (ATM) and ATM-Rad3-related (ATR), orchestrate DNA damage checkpoint pathways. In budding yeast, ATM and ATR homologs are encoded by TEL1 and MEC1, respectively. The Mre11 complex consists of two highly related proteins, Mre11 and Rad50, and a third protein, Xrs2 in budding yeast or Nbs1 in mammals. The Mre11 complex controls the ATM/Tel1 signaling pathway in response to double-strand break (DSB) induction. We show here that the Mre11 complex functions together with exonuclease 1 (Exo1) in activation of the Mec1 signaling pathway after DNA damage and replication block. Mec1 controls the checkpoint responses following UV irradiation as well as DSB induction. Correspondingly, the Mre11 complex and Exo1 play an overlapping role in activation of DSB- and UV-induced checkpoints. The Mre11 complex and Exo1 collaborate in producing long single-stranded DNA (ssDNA) tails at DSB ends and promote Mec1 association with the DSBs. The Ddc1-Mec3-Rad17 complex associates with sites of DNA damage and modulates the Mec1 signaling pathway. However, Ddc1 association with DSBs does not require the function of the Mre11 complex and Exo1. Mec1 controls checkpoint responses to stalled DNA replication as well. Accordingly, the Mre11 complex and Exo1 contribute to activation of the replication checkpoint pathway. Our results provide a model in which the Mre11 complex and Exo1 cooperate in generating long ssDNA tracts and thereby facilitate Mec1 association with sites of DNA damage or replication block.

Experimental evaluation of sobriety checkpoint programs

DOT National Transportation Integrated Search

1995-06-01

Six California communities were selected to participate in the study on the basis of comparability and isolation from each other. Four of the communities' police departments implemented programs of sobriety checkpoints; the checkpoint configurations ...

A novel ATM-dependent checkpoint defect distinct from loss of function mutation promotes genomic instability in melanoma.

PubMed

Spoerri, Loredana; Brooks, Kelly; Chia, KeeMing; Grossman, Gavriel; Ellis, Jonathan J; Dahmer-Heath, Mareike; Škalamera, Dubravka; Pavey, Sandra; Burmeister, Bryan; Gabrielli, Brian

2016-05-01

Melanomas have high levels of genomic instability that can contribute to poor disease prognosis. Here, we report a novel defect of the ATM-dependent cell cycle checkpoint in melanoma cell lines that promotes genomic instability. In defective cells, ATM signalling to CHK2 is intact, but the cells are unable to maintain the cell cycle arrest due to elevated PLK1 driving recovery from the arrest. Reducing PLK1 activity recovered the ATM-dependent checkpoint arrest, and over-expressing PLK1 was sufficient to overcome the checkpoint arrest and increase genomic instability. Loss of the ATM-dependent checkpoint did not affect sensitivity to ionizing radiation demonstrating that this defect is distinct from ATM loss of function mutations. The checkpoint defective melanoma cell lines over-express PLK1, and a significant proportion of melanomas have high levels of PLK1 over-expression suggesting this defect is a common feature of melanomas. The inability of ATM to impose a cell cycle arrest in response to DNA damage increases genomic instability. This work also suggests that the ATM-dependent checkpoint arrest is likely to be defective in a higher proportion of cancers than previously expected. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Jab1 Mediates Protein Degradation of Rad9/Rad1/Hus1 Checkpoint Complex

PubMed Central

Huang, Jin; Yuan, Honglin; Lu, Chongyuan; Liu, Ximeng; Cao, Xu; Wan, Mei

2009-01-01

Summary The Rad1-Rad9-Hus1 (9-1-1) complex serves a dual role as a DNA-damage sensor in checkpoint signaling and as a mediator in DNA repair pathway. However, the intercellular mechanisms that regulate 9-1-1 complex are poorly understood. Jab1, the fifth component of the COP9 signalosome complex, plays a central role in the degradation of multiple proteins and is emerging as an important regulator in cancer development. Here, we tested the hypothesis that Jab1 controls the protein stability of the 9-1-1 complex via the proteosome pathway. We provide evidence that Jab1 physically associates with the 9-1-1 complex. This association is mediated through direct interaction between Jab1 and Rad1, one of the subunits of 9-1-1 complex. Importantly, Jab1 causes the translocation of the 9-1-1 complex from the nucleus to the cytoplasm, mediating rapid degradation of the 9-1-1 complex via 26S proteasome. Furthermore, Jab1 significantly suppresses checkpoint signaling activation, DNA synthesis recovery from blockage and cell viability after replication stresses such as UV exposure, γ radiation and hydroxyurea treatment. These results suggest that Jab1 is an important regulator for 9-1-1 protein stability control in cells, which may provide novel information on the involvement of Jab1 in checkpoint and DNA repair signaling in response to DNA damage. PMID:17583730

Advances of Immune Checkpoint Inhibitors in Tumor Immunotherapy

NASA Astrophysics Data System (ADS)

Guo, Qiao

2018-01-01

Immune checkpoints are cell surface molecules that can fine-tune the immune responses, they are crucial for modulating the duration and amplitude of immune reactions while maintaining self-tolerance in order to minimize autoimmune responses. Numerous studies have demonstrated that tumors cells can directly express immune-checkpoint molecules, or induce many inhibitory molecules expression in the tumor microenvironment to inhibit the anti-tumor immunity. Releasing these brakes has emerged as an exciting strategy to cure cancer. In the past few years, clinical trials with therapeutic antibodies targeting to the checkpoint molecules CTLA-4 and PD-1 have rekindled the hope for cancer immunotherapy. In contrast to the conventional treatment, checkpoint inhibitors induce broad and durable antitumor responses. In the future, treatment may involve combination therapy to target different checkpoint molecules and stages of the adaptive immune responses. In this review, we summarized the recent advances of the study and development of other checkpoint molecules in tumor immunotherapy.

Efficient Checkpointing of Virtual Machines using Virtual Machine Introspection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aderholdt, Ferrol; Han, Fang; Scott, Stephen L

Cloud Computing environments rely heavily on system-level virtualization. This is due to the inherent benefits of virtualization including fault tolerance through checkpoint/restart (C/R) mechanisms. Because clouds are the abstraction of large data centers and large data centers have a higher potential for failure, it is imperative that a C/R mechanism for such an environment provide minimal latency as well as a small checkpoint file size. Recently, there has been much research into C/R with respect to virtual machines (VM) providing excellent solutions to reduce either checkpoint latency or checkpoint file size. However, these approaches do not provide both. This papermore » presents a method of checkpointing VMs by utilizing virtual machine introspection (VMI). Through the usage of VMI, we are able to determine which pages of memory within the guest are used or free and are better able to reduce the amount of pages written to disk during a checkpoint. We have validated this work by using various benchmarks to measure the latency along with the checkpoint size. With respect to checkpoint file size, our approach results in file sizes within 24% or less of the actual used memory within the guest. Additionally, the checkpoint latency of our approach is up to 52% faster than KVM s default method.« less

Checkpointing and Recovery in Distributed and Database Systems

ERIC Educational Resources Information Center

Wu, Jiang

2011-01-01

A transaction-consistent global checkpoint of a database records a state of the database which reflects the effect of only completed transactions and not the results of any partially executed transactions. This thesis establishes the necessary and sufficient conditions for a checkpoint of a data item (or the checkpoints of a set of data items) to…

The Use of Sobriety Checkpoints for Impaired Driving Enforcement

DOT National Transportation Integrated Search

1990-11-01

Sobriety checkpoints have been a valuable tool for law enforcement's continuing fight to remove impaired drivers from the road. The purpose of the checkpoint is twofold; to apprehend impaired drivers at the physical location of the checkpoint; and se...

Affinity-aware checkpoint restart

DOE PAGES

Saini, Ajay; Rezaei, Arash; Mueller, Frank; ...

2014-12-08

Current checkpointing techniques employed to overcome faults for HPC applications result in inferior application performance after restart from a checkpoint for a number of applications. This is due to a lack of page and core affinity awareness of the checkpoint/restart (C/R) mechanism, i.e., application tasks originally pinned to cores may be restarted on different cores, and in case of non-uniform memory architectures (NUMA), quite common today, memory pages associated with tasks on a NUMA node may be associated with a different NUMA node after restart. Here, this work contributes a novel design technique for C/R mechanisms to preserve task-to-core mapsmore » and NUMA node specific page affinities across restarts. Experimental results with BLCR, a C/R mechanism, enhanced with affinity awareness demonstrate significant performance benefits of 37%-73% for the NAS Parallel Benchmark codes and 6-12% for NAMD with negligible overheads instead of up to nearly four times longer an execution times without affinity-aware restarts on 16 cores.« less

Affinity-aware checkpoint restart

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saini, Ajay; Rezaei, Arash; Mueller, Frank

Current checkpointing techniques employed to overcome faults for HPC applications result in inferior application performance after restart from a checkpoint for a number of applications. This is due to a lack of page and core affinity awareness of the checkpoint/restart (C/R) mechanism, i.e., application tasks originally pinned to cores may be restarted on different cores, and in case of non-uniform memory architectures (NUMA), quite common today, memory pages associated with tasks on a NUMA node may be associated with a different NUMA node after restart. Here, this work contributes a novel design technique for C/R mechanisms to preserve task-to-core mapsmore » and NUMA node specific page affinities across restarts. Experimental results with BLCR, a C/R mechanism, enhanced with affinity awareness demonstrate significant performance benefits of 37%-73% for the NAS Parallel Benchmark codes and 6-12% for NAMD with negligible overheads instead of up to nearly four times longer an execution times without affinity-aware restarts on 16 cores.« less

In Vitro Analysis of the Role of Replication Protein A (RPA) and RPA Phosphorylation in ATR-mediated Checkpoint Signaling*

PubMed Central

Lindsey-Boltz, Laura A.; Reardon, Joyce T.; Wold, Marc S.; Sancar, Aziz

2012-01-01

Replication protein A (RPA) plays essential roles in DNA metabolism, including replication, checkpoint, and repair. Recently, we described an in vitro system in which the phosphorylation of human Chk1 kinase by ATR (ataxia telangiectasia mutated and Rad3-related) is dependent on RPA bound to single-stranded DNA. Here, we report that phosphorylation of other ATR targets, p53 and Rad17, has the same requirements and that RPA is also phosphorylated in this system. At high p53 or Rad17 concentrations, RPA phosphorylation is inhibited and, in this system, RPA with phosphomimetic mutations cannot support ATR kinase function, whereas a non-phosphorylatable RPA mutant exhibits full activity. Phosphorylation of these ATR substrates depends on the recruitment of ATR and the substrates by RPA to the RPA-ssDNA complex. Finally, mutant RPAs lacking checkpoint function exhibit essentially normal activity in nucleotide excision repair, revealing RPA separation of function for checkpoint and excision repair. PMID:22948311

In vitro analysis of the role of replication protein A (RPA) and RPA phosphorylation in ATR-mediated checkpoint signaling.

PubMed

Lindsey-Boltz, Laura A; Reardon, Joyce T; Wold, Marc S; Sancar, Aziz

2012-10-19

Replication protein A (RPA) plays essential roles in DNA metabolism, including replication, checkpoint, and repair. Recently, we described an in vitro system in which the phosphorylation of human Chk1 kinase by ATR (ataxia telangiectasia mutated and Rad3-related) is dependent on RPA bound to single-stranded DNA. Here, we report that phosphorylation of other ATR targets, p53 and Rad17, has the same requirements and that RPA is also phosphorylated in this system. At high p53 or Rad17 concentrations, RPA phosphorylation is inhibited and, in this system, RPA with phosphomimetic mutations cannot support ATR kinase function, whereas a non-phosphorylatable RPA mutant exhibits full activity. Phosphorylation of these ATR substrates depends on the recruitment of ATR and the substrates by RPA to the RPA-ssDNA complex. Finally, mutant RPAs lacking checkpoint function exhibit essentially normal activity in nucleotide excision repair, revealing RPA separation of function for checkpoint and excision repair.

Phosphorylation of Minichromosome Maintenance 3 (MCM3) by Checkpoint Kinase 1 (Chk1) Negatively Regulates DNA Replication and Checkpoint Activation.

PubMed

Han, Xiangzi; Mayca Pozo, Franklin; Wisotsky, Jacob N; Wang, Benlian; Jacobberger, James W; Zhang, Youwei

2015-05-08

Mechanisms controlling DNA replication and replication checkpoint are critical for the maintenance of genome stability and the prevention or treatment of human cancers. Checkpoint kinase 1 (Chk1) is a key effector protein kinase that regulates the DNA damage response and replication checkpoint. The heterohexameric minichromosome maintenance (MCM) complex is the core component of mammalian DNA helicase and has been implicated in replication checkpoint activation. Here we report that Chk1 phosphorylates the MCM3 subunit of the MCM complex at Ser-205 under normal growth conditions. Mutating the Ser-205 of MCM3 to Ala increased the length of DNA replication track and shortened the S phase duration, indicating that Ser-205 phosphorylation negatively controls normal DNA replication. Upon replicative stress treatment, the inhibitory phosphorylation of MCM3 at Ser-205 was reduced, and this reduction was accompanied with the generation of single strand DNA, the key platform for ataxia telangiectasia mutated and Rad3-related (ATR) activation. As a result, the replication checkpoint is activated. Together, these data provide significant insights into the regulation of both normal DNA replication and replication checkpoint activation through the novel phosphorylation of MCM3 by Chk1. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Pseudoprogression and hyperprogression after checkpoint blockade.

PubMed

Wang, Qiaohong; Gao, Jingze; Wu, Xia

2018-05-01

Immune checkpoint inhibitors appear to be one of the most promising immunotherapies with significant clinical benefits and durable responses in multiple tumor types. A heterogeneity of responses appears in patients receiving checkpoint blockade, including pseudoprogression where the tumor burden or number of tumor lesions increases initially before decreasing. Another special response observed after checkpoint blockade is hyperprogression, a phenomenon reflecting a very rapid tumor progression following immunotherapy, suggesting that checkpoint blockade could impact detrimentally on a small subset of patients. As immunotherapeutics, especially anti-PD-1/PD-L1 agents, become more widely available, evaluating the efficacy of these novel drugs poses a major challenge to clinicians, who aim to avoid either premature withdrawal of the treatment or prolonging ineffective treatment. Although the mechanism and recognition of pseudoprogression have gradually come to light, the incidence, basis, identification and predictive biomarkers of hyperprogression have been largely unknown, and this review documents the existing research findings and points out the areas where further studies are badly needed. Copyright © 2018 Elsevier B.V. All rights reserved.

Checkpoint triggering in a computer system

DOEpatents

Cher, Chen-Yong

2016-09-06

According to an aspect, a method for triggering creation of a checkpoint in a computer system includes executing a task in a processing node of the computer system and determining whether it is time to read a monitor associated with a metric of the task. The monitor is read to determine a value of the metric based on determining that it is time to read the monitor. A threshold for triggering creation of the checkpoint is determined based on the value of the metric. Based on determining that the value of the metric has crossed the threshold, the checkpoint including state data of the task is created to enable restarting execution of the task upon a restart operation.

Hallmarks of response to immune checkpoint blockade

PubMed Central

Cogdill, Alexandria P; Andrews, Miles C; Wargo, Jennifer A

2017-01-01

Unprecedented advances have been made in the treatment of cancer through the use of immune checkpoint blockade, with approval of several checkpoint blockade regimens spanning multiple cancer types. However, responses to this form of therapy are not universal, and insights are clearly needed to identify optimal biomarkers of response and to combat mechanisms of therapeutic resistance. A working knowledge of the hallmarks of cancer yields insight into responses to immune checkpoint blockade, although the focus of this is rather tumour-centric and additional factors are pertinent, including host immunity and environmental influences. Herein, we describe the foundation for pillars and hallmarks of response to immune checkpoint blockade, with a discussion of their relevance to immune monitoring and mechanisms of resistance. Evolution of this understanding will ultimately help guide treatment strategies to enhance therapeutic responses. PMID:28524159

Plk1 and Mps1 Cooperatively Regulate the Spindle Assembly Checkpoint in Human Cells.

PubMed

von Schubert, Conrad; Cubizolles, Fabien; Bracher, Jasmine M; Sliedrecht, Tale; Kops, Geert J P L; Nigg, Erich A

2015-07-07

Equal mitotic chromosome segregation is critical for genome integrity and is monitored by the spindle assembly checkpoint (SAC). We have previously shown that the consensus phosphorylation motif of the essential SAC kinase Monopolar spindle 1 (Mps1) is very similar to that of Polo-like kinase 1 (Plk1). This prompted us to ask whether human Plk1 cooperates with Mps1 in SAC signaling. Here, we demonstrate that Plk1 promotes checkpoint signaling at kinetochores through the phosphorylation of at least two Mps1 substrates, including KNL-1 and Mps1 itself. As a result, Plk1 activity enhances Mps1 catalytic activity as well as the recruitment of the SAC components Mad1:C-Mad2 and Bub3:BubR1 to kinetochores. We conclude that Plk1 strengthens the robustness of SAC establishment at the onset of mitosis and supports SAC maintenance during prolonged mitotic arrest. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Checkpoint independence of most DNA replication origins in fission yeast

PubMed Central

Mickle, Katie L; Ramanathan, Sunita; Rosebrock, Adam; Oliva, Anna; Chaudari, Amna; Yompakdee, Chulee; Scott, Donna; Leatherwood, Janet; Huberman, Joel A

2007-01-01

Background In budding yeast, the replication checkpoint slows progress through S phase by inhibiting replication origin firing. In mammals, the replication checkpoint inhibits both origin firing and replication fork movement. To find out which strategy is employed in the fission yeast, Schizosaccharomyces pombe, we used microarrays to investigate the use of origins by wild-type and checkpoint-mutant strains in the presence of hydroxyurea (HU), which limits the pool of deoxyribonucleoside triphosphates (dNTPs) and activates the replication checkpoint. The checkpoint-mutant cells carried deletions either of rad3 (which encodes the fission yeast homologue of ATR) or cds1 (which encodes the fission yeast homologue of Chk2). Results Our microarray results proved to be largely consistent with those independently obtained and recently published by three other laboratories. However, we were able to reconcile differences between the previous studies regarding the extent to which fission yeast replication origins are affected by the replication checkpoint. We found (consistent with the three previous studies after appropriate interpretation) that, in surprising contrast to budding yeast, most fission yeast origins, including both early- and late-firing origins, are not significantly affected by checkpoint mutations during replication in the presence of HU. A few origins (~3%) behaved like those in budding yeast: they replicated earlier in the checkpoint mutants than in wild type. These were located primarily in the heterochromatic subtelomeric regions of chromosomes 1 and 2. Indeed, the subtelomeric regions defined by the strongest checkpoint restraint correspond precisely to previously mapped subtelomeric heterochromatin. This observation implies that subtelomeric heterochromatin in fission yeast differs from heterochromatin at centromeres, in the mating type region, and in ribosomal DNA, since these regions replicated at least as efficiently in wild-type cells as in

Enhancing Immune Checkpoint Inhibitor Therapy In Kidney Cancer

DTIC Science & Technology

2016-10-01

AWARD NUMBER: W81XWH-15-1-0141 TITLE: Enhancing Immune Checkpoint Inhibitor therapy in Kidney Cancer PRINCIPAL INVESTIGATOR: Hans-Joerg Hammers...Immune Checkpoint Inhibitor therapy in Kidney Cancer 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH- 15-1-0141 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...to develop strategies to enhance immune checkpoint inhibition in kidney cancer. The work is designed to test different strategies to induce or

Enhancing Immune Checkpoint Inhibitor Therapy in Kidney Cancer

DTIC Science & Technology

2017-10-01

AWARD NUMBER: W81XWH-15-1-0141 TITLE: Enhancing Immune Checkpoint Inhibitor therapy in Kidney Cancer PRINCIPAL INVESTIGATOR: Hans-Joerg Hammers...SUBTITLE Enhancing Immune Checkpoint Inhibitor therapy in Kidney Cancer 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH- 15-1-0141 5c. PROGRAM ELEMENT NUMBER...immune checkpoint inhibition in kidney cancer . The work is designed to test different strategies to induce or enhance the abscopal in a kidney cancer

Immune checkpoint inhibitors: basics and challenges.

PubMed

Li, Bin; Chan, Ho Lam; Chen, Pingping

2017-08-04

Cancer is one of the most deadly diseases in modern world. The last decade has witnessed dramatic advances in the cancer treatment through immunotherapy. One extremely promising means to achieve anti-caner immunity is to block the immune checkpoint pathways, which mechanism was adopted by cancer cells to disguise themselves as regular components of human body. While checkpoint blockade is universally effective against a broad spectrum of cancer types and mostly unrestricted by certain gene mutation status, only a minority of patients achieved a complete response to such treatment. In this review we summarize the basic principles of immune checkpoint inhibitors and discuss potential mechanisms of resistance. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

The checkpoint ordering problem

PubMed Central

Hungerländer, P.

2017-01-01

Abstract We suggest a new variant of a row layout problem: Find an ordering of n departments with given lengths such that the total weighted sum of their distances to a given checkpoint is minimized. The Checkpoint Ordering Problem (COP) is both of theoretical and practical interest. It has several applications and is conceptually related to some well-studied combinatorial optimization problems, namely the Single-Row Facility Layout Problem, the Linear Ordering Problem and a variant of parallel machine scheduling. In this paper we study the complexity of the (COP) and its special cases. The general version of the (COP) with an arbitrary but fixed number of checkpoints is NP-hard in the weak sense. We propose both a dynamic programming algorithm and an integer linear programming approach for the (COP) . Our computational experiments indicate that the (COP) is hard to solve in practice. While the run time of the dynamic programming algorithm strongly depends on the length of the departments, the integer linear programming approach is able to solve instances with up to 25 departments to optimality. PMID:29170574

DNA replication checkpoint signaling depends on a Rad53-Dbf4 N-terminal interaction in Saccharomyces cerevisiae.

PubMed

Chen, Ying-Chou; Kenworthy, Jessica; Gabrielse, Carrie; Hänni, Christine; Zegerman, Philip; Weinreich, Michael

2013-06-01

Dbf4-dependent kinase (DDK) and cyclin-dependent kinase (CDK) are essential to initiate DNA replication at individual origins. During replication stress, the S-phase checkpoint inhibits the DDK- and CDK-dependent activation of late replication origins. Rad53 kinase is a central effector of the replication checkpoint and both binds to and phosphorylates Dbf4 to prevent late-origin firing. The molecular basis for the Rad53-Dbf4 physical interaction is not clear but occurs through the Dbf4 N terminus. Here we found that both Rad53 FHA1 and FHA2 domains, which specifically recognize phospho-threonine (pT), interacted with Dbf4 through an N-terminal sequence and an adjacent BRCT domain. Purified Rad53 FHA1 domain (but not FHA2) bound to a pT Dbf4 peptide in vitro, suggesting a possible phospho-threonine-dependent interaction between FHA1 and Dbf4. The Dbf4-Rad53 interaction is governed by multiple contacts that are separable from the Cdc5- and Msa1-binding sites in the Dbf4 N terminus. Importantly, abrogation of the Rad53-Dbf4 physical interaction blocked Dbf4 phosphorylation and allowed late-origin firing during replication checkpoint activation. This indicated that Rad53 must stably bind to Dbf4 to regulate its activity.

Template based parallel checkpointing in a massively parallel computer system

DOEpatents

Archer, Charles Jens [Rochester, MN; Inglett, Todd Alan [Rochester, MN

2009-01-13

A method and apparatus for a template based parallel checkpoint save for a massively parallel super computer system using a parallel variation of the rsync protocol, and network broadcast. In preferred embodiments, the checkpoint data for each node is compared to a template checkpoint file that resides in the storage and that was previously produced. Embodiments herein greatly decrease the amount of data that must be transmitted and stored for faster checkpointing and increased efficiency of the computer system. Embodiments are directed to a parallel computer system with nodes arranged in a cluster with a high speed interconnect that can perform broadcast communication. The checkpoint contains a set of actual small data blocks with their corresponding checksums from all nodes in the system. The data blocks may be compressed using conventional non-lossy data compression algorithms to further reduce the overall checkpoint size.

Modeling the temporal evolution of the spindle assembly checkpoint and role of Aurora B kinase

PubMed Central

Mistry, Hitesh B.; MacCallum, David E.; Jackson, Robert C.; Chaplain, Mark A. J.; Davidson, Fordyce A.

2008-01-01

Faithful separation of chromosomes prior to cell division at mitosis is a highly regulated process. One family of serine/threonine kinases that plays a central role in regulation is the Aurora family. Aurora B plays a role in the spindle assembly checkpoint, in part, by destabilizing the localization of BubR1 and Mad2 at centrosomes and responds to changes in tension caused by aberrant microtubule kinetochore attachments. Aurora B is overexpressed in a subset of cancers and is required for mitosis, making it an attractive anticancer target. Here, we use mathematical modeling to extend a current model of the spindle assembly checkpoint to incorporate all signaling kinetochores within a cell rather than just one and the role of Aurora B within the resulting model. We find that the current model of the spindle assembly checkpoint is robust to variation in its key diffusion-limited parameters. Furthermore, when Aurora B inhibition is considered within the model, for a certain range of inhibitor concentrations, a prolonged prometaphase/metaphase is observed. This level of inhibitor concentrations has not yet been studied experimentally, to the authors' best knowledge. Therefore, experimental verification of the results discussed here could provide a deeper understanding of how kinetochores and Aurora B cooperate in the spindle assembly checkpoint. PMID:19091947

Centromeric DNA replication reconstitution reveals DNA loops and ATR checkpoint suppression.

PubMed

Aze, Antoine; Sannino, Vincenzo; Soffientini, Paolo; Bachi, Angela; Costanzo, Vincenzo

2016-06-01

Half of the human genome is made up of repetitive DNA. However, mechanisms underlying replication of chromosome regions containing repetitive DNA are poorly understood. We reconstituted replication of defined human chromosome segments using bacterial artificial chromosomes in Xenopus laevis egg extract. Using this approach we characterized the chromatin assembly and replication dynamics of centromeric alpha-satellite DNA. Proteomic analysis of centromeric chromatin revealed replication-dependent enrichment of a network of DNA repair factors including the MSH2-6 complex, which was required for efficient centromeric DNA replication. However, contrary to expectations, the ATR-dependent checkpoint monitoring DNA replication fork arrest could not be activated on highly repetitive DNA due to the inability of the single-stranded DNA binding protein RPA to accumulate on chromatin. Electron microscopy of centromeric DNA and supercoil mapping revealed the presence of topoisomerase I-dependent DNA loops embedded in a protein matrix enriched for SMC2-4 proteins. This arrangement suppressed ATR signalling by preventing RPA hyper-loading, facilitating replication of centromeric DNA. These findings have important implications for our understanding of repetitive DNA metabolism and centromere organization under normal and stressful conditions.

Centromeric DNA replication reconstitution reveals DNA loops and ATR checkpoint suppression

PubMed Central

Aze, Antoine; Sannino, Vincenzo; Soffientini, Paolo; Bachi, Angela; Costanzo, Vincenzo

2016-01-01

Half of human genome is made of repetitive DNA. However, mechanisms underlying replication of chromosome regions containing repetitive DNA are poorly understood. We reconstituted replication of defined human chromosome segments using Bacterial Artificial Chromosomes (BACs) in Xenopus laevis egg extract. Using this approach we characterized chromatin assembly and replication dynamics of centromeric alpha-satellite DNA. Proteomic analysis of centromeric chromatin revealed replication dependent enrichment of a network of DNA repair factors among which the MSH2-6 complex, which was required for efficient centromeric DNA replication. However, contrary to expectations, the ATR dependent checkpoint monitoring DNA replication fork arrest could not be activated on highly repetitive DNA due to inability of single stranded DNA binding protein RPA to accumulate on chromatin. Electron microscopy of centromeric DNA and supercoil mapping revealed the presence of Topoisomerase I dependent DNA loops embedded in a protein matrix enriched for SMC2-4 proteins. This arrangement suppressed ATR signalling by preventing RPA hyper-loading, facilitating replication of centromeric DNA. These findings have important implications on our understanding of repetitive DNA metabolism and centromere organization under normal and stressful conditions. PMID:27111843

McrEngine: A Scalable Checkpointing System Using Data-Aware Aggregation and Compression

DOE PAGES

Islam, Tanzima Zerin; Mohror, Kathryn; Bagchi, Saurabh; ...

2013-01-01

High performance computing (HPC) systems use checkpoint-restart to tolerate failures. Typically, applications store their states in checkpoints on a parallel file system (PFS). As applications scale up, checkpoint-restart incurs high overheads due to contention for PFS resources. The high overheads force large-scale applications to reduce checkpoint frequency, which means more compute time is lost in the event of failure. We alleviate this problem through a scalable checkpoint-restart system, mcrEngine. McrEngine aggregates checkpoints from multiple application processes with knowledge of the data semantics available through widely-used I/O libraries, e.g., HDF5 and netCDF, and compresses them. Our novel scheme improves compressibility ofmore » checkpoints up to 115% over simple concatenation and compression. Our evaluation with large-scale application checkpoints show that mcrEngine reduces checkpointing overhead by up to 87% and restart overhead by up to 62% over a baseline with no aggregation or compression.« less

Sobriety checkpoints reduce crash deaths on Tennessee roads

DOT National Transportation Integrated Search

1999-06-19

Sobriety checkpoints are known to be effective in getting alcohol-impaired drivers off the roads. The National Highway Traffic Safety Administration funded equipment and conducted an evaluation of Tennessee's two-year statewide checkpoint demonstrati...

Mammalian Homologs of Yeast Checkpoint Genes

DTIC Science & Technology

2002-07-01

pathway is sensitive to various forms of DNA damage Developmental Biology throughout the cell cycle . The DNA replication check- Yale University point...components would be ordered into pathways for mammalian checkpoint function, with emphasis on p53 regulation, cell cycle regulation, and complementation...structurally related to the human tumor suppressor ATM. MEC1 and RAD53, two essential genes, play a central role in DNA damage checkpoints at all cell cycle

Viral-induced Modulation of Multiple Checkpoint Proteins in Cancers.

PubMed

Nuovo, Gerard J; Folcik, Virginia A; Magro, Cynthia

2017-07-01

Therapy with checkpoint inhibitors represents a major advance in cancer treatment. The purpose of this study was to examine the expression patterns of the checkpoint proteins programmed death ligand 1 (PD L1), PD L2, indoleamine 2,3-dioxygenase 1 (IDO1), and cytotoxic T-lymphocyte antigen 4 (CTLA4) in cancers including those associated with viral infections. Normal, noninflamed tissues rarely express checkpoint proteins with exceptions including the placenta and stomach. Expression of PD L1 was noted in 30%, PD L2 in 18%, IDO1 in 13%, and CTLA4 in 14% of 333 nonviral malignancies including endometrial, ovarian, lung, and breast cancers. The expression of each checkpoint protein was significantly higher among 166 cases of viral-related (mostly human papillomavirus) cancers where expression of PD L1 was noted in 84%, PD L2 in 67%, IDO1 in 61%, and CTLA4 in 37% (each P value <0.001); 97% of the viral-related cancers showed expression of at least 1 checkpoint protein. In addition, over 90% of the CD8 cells in the viral-associated cancers were quiescent based on low coexpression of Ki-67 as well as pSTAT1. It is concluded that viral infection in cancers is associated with the increased expression of key checkpoint proteins. This indicates that cancers with productive viral infection may be better targets for checkpoint inhibitor therapy.

Determining the Effectiveness of Flexible Checkpoints : Traffic Tech

DOT National Transportation Integrated Search

2017-05-01

Checkpoint operations are highly visible and are often used for Driving While Intoxicated (DWI) countermeasure enforcement efforts. However, checkpoints can be resource-intensive, so it is often difficult to generate as much use of that tactic as is ...

Berkeley lab checkpoint/restart (BLCR) for Linux clusters

DOE PAGES

Hargrove, Paul H.; Duell, Jason C.

2006-09-01

This article describes the motivation, design and implementation of Berkeley Lab Checkpoint/Restart (BLCR), a system-level checkpoint/restart implementation for Linux clusters that targets the space of typical High Performance Computing applications, including MPI. Application-level solutions, including both checkpointing and fault-tolerant algorithms, are recognized as more time and space efficient than system-level checkpoints, which cannot make use of any application-specific knowledge. However, system-level checkpointing allows for preemption, making it suitable for responding to fault precursors (for instance, elevated error rates from ECC memory or network CRCs, or elevated temperature from sensors). Preemption can also increase the efficiency of batch scheduling; for instancemore » reducing idle cycles (by allowing for shutdown without any queue draining period or reallocation of resources to eliminate idle nodes when better fitting jobs are queued), and reducing the average queued time (by limiting large jobs to running during off-peak hours, without the need to limit the length of such jobs). Each of these potential uses makes BLCR a valuable tool for efficient resource management in Linux clusters. © 2006 IOP Publishing Ltd.« less

Intellectual property issues of immune checkpoint inhibitors

PubMed Central

Storz, Ulrich

2016-01-01

Immune checkpoint inhibitors are drugs that interfere with tumor escape responses. Some members of this class are already approved, and expected to be blockbusters in the future. Many companies have developed patent activities in this field. This article focuses on the patent landscape, and discusses key players and cases related to immune checkpoint inhibitors. PMID:26466763

The deterrent capability of sobriety checkpoints : summary of the American literature

DOT National Transportation Integrated Search

1992-03-01

This report reviews and evaluates the scientific literature on sobriety checkpoints in the United States. Concerns about the constitutionality of checkpoint procedures initially limited the number of checkpoint programs in this country as well as con...

TAM receptor tyrosine kinases as emerging targets of innate immune checkpoint blockade for cancer therapy.

PubMed

Akalu, Yemsratch T; Rothlin, Carla V; Ghosh, Sourav

2017-03-01

Cancer immunotherapy utilizing T-cell checkpoint inhibitors has shown tremendous clinical success. Yet, this mode of treatment is effective in only a subset of patients. Unresponsive patients tend to have non-T-cell-inflamed tumors that lack markers associated with the activation of adaptive anti-tumor immune responses. Notably, elimination of cancer cells by T cells is critically dependent on the optimal activity of innate immune cells. Therefore, identifying new targets that regulate innate immune cell function and promote the engagement of adaptive tumoricidal responses is likely to lead to the development of improved therapies against cancer. Here, we review the TAM receptor tyrosine kinases-TYRO3, AXL, and MERTK-as an emerging class of innate immune checkpoints that participate in key steps of anti-tumoral immunity. Namely, TAM-mediated efferocytosis, negative regulation of dendritic cell activity, and dysregulated production of chemokines collectively favor the escape of malignant cells. Hence, disabling TAM signaling may promote engagement of adaptive immunity and complement T-cell checkpoint blockade. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

The DNA Replication Checkpoint Directly Regulates MBF-Dependent G1/S Transcription▿

PubMed Central

Dutta, Chaitali; Patel, Prasanta K.; Rosebrock, Adam; Oliva, Anna; Leatherwood, Janet; Rhind, Nicholas

2008-01-01

The DNA replication checkpoint transcriptionally upregulates genes that allow cells to adapt to and survive replication stress. Our results show that, in the fission yeast Schizosaccharomyces pombe, the replication checkpoint regulates the entire G1/S transcriptional program by directly regulating MBF, the G1/S transcription factor. Instead of initiating a checkpoint-specific transcriptional program, the replication checkpoint targets MBF to maintain the normal G1/S transcriptional program during replication stress. We propose a mechanism for this regulation, based on in vitro phosphorylation of the Cdc10 subunit of MBF by the Cds1 replication-checkpoint kinase. Replacement of two potential phosphorylation sites with phosphomimetic amino acids suffices to promote the checkpoint transcriptional program, suggesting that Cds1 phosphorylation directly regulates MBF-dependent transcription. The conservation of MBF between fission and budding yeast, and recent results implicating MBF as a target of the budding yeast replication checkpoint, suggests that checkpoint regulation of the MBF transcription factor is a conserved strategy for coping with replication stress. Furthermore, the structural and regulatory similarity between MBF and E2F, the metazoan G1/S transcription factor, suggests that this checkpoint mechanism may be broadly conserved among eukaryotes. PMID:18662996

DNA Replication Checkpoint Signaling Depends on a Rad53–Dbf4 N-Terminal Interaction in Saccharomyces cerevisiae

PubMed Central

Chen, Ying-Chou; Kenworthy, Jessica; Gabrielse, Carrie; Hänni, Christine; Zegerman, Philip; Weinreich, Michael

2013-01-01

Dbf4-dependent kinase (DDK) and cyclin-dependent kinase (CDK) are essential to initiate DNA replication at individual origins. During replication stress, the S-phase checkpoint inhibits the DDK- and CDK-dependent activation of late replication origins. Rad53 kinase is a central effector of the replication checkpoint and both binds to and phosphorylates Dbf4 to prevent late-origin firing. The molecular basis for the Rad53–Dbf4 physical interaction is not clear but occurs through the Dbf4 N terminus. Here we found that both Rad53 FHA1 and FHA2 domains, which specifically recognize phospho-threonine (pT), interacted with Dbf4 through an N-terminal sequence and an adjacent BRCT domain. Purified Rad53 FHA1 domain (but not FHA2) bound to a pT Dbf4 peptide in vitro, suggesting a possible phospho-threonine-dependent interaction between FHA1 and Dbf4. The Dbf4–Rad53 interaction is governed by multiple contacts that are separable from the Cdc5- and Msa1-binding sites in the Dbf4 N terminus. Importantly, abrogation of the Rad53–Dbf4 physical interaction blocked Dbf4 phosphorylation and allowed late-origin firing during replication checkpoint activation. This indicated that Rad53 must stably bind to Dbf4 to regulate its activity. PMID:23564203

Assays for the spindle assembly checkpoint in cell culture.

PubMed

Marcozzi, Chiara; Pines, Jonathon

2018-01-01

The spindle assembly checkpoint (SAC) is crucial to maintain genomic stability since it prevents premature separation of sister chromatids in mitosis and ensures the fidelity of chromosome segregation. The SAC arrests cells in mitosis and is not satisfied until all kinetochores are stably attached to the mitotic spindle. Improperly attached kinetochores activate the SAC and catalyze the formation of the mitotic checkpoint complex (MCC), containing Mad2, Cdc20, BubR1, and Bub3 proteins. The MCC binds and thereby inhibits the APC/C E3 ubiquitin ligase until the last kinetochore has attached to microtubules. Once the SAC is satisfied, the APC/C promptly activates and targets cyclin B1 and securin for degradation, thus allowing sister chromatids to separate and the cell to exit mitosis. Our understanding of SAC signaling has increased thanks to the development of new genetic, biochemical, molecular, and structural biology techniques. Here, we describe how live-cell imaging microscopy in combination with gene-targeting strategies and biochemical assays can be exploited to investigate the intrinsic properties of the SAC in mammalian cultured cells. © 2018 Elsevier Inc. All rights reserved.

Immune checkpoint failures in inflammatory myopathies: An overview.

PubMed

Herbelet, Sandrine; De Bleecker, Jan L

2018-06-06

Dermatomyositis (DM), polymyositis (PM), inclusion body myositis (IBM), immune mediated necrotizing myopathy (IMNM) and overlap myositis (OM) are classified as inflammatory myopathies (IM) with involvement of autoimmune features such as autoreactive lymphocytes and autoantibodies. Autoimmunity can be defined as a loss in self-tolerance and attack of autoantigens by the immune system. Self-tolerance is achieved by a group of immune mechanisms occurring in central and periphal lymphoid organs and tissues, called immune checkpoints, that work in synergy to protect the body from harmful immune reactions. Autoimmune disorders appear when immune checkpoints fail. In this review, the different immune checkpoint failures are discussed in DM, PM, IBM and IMNM. Exploring research contribution in each of these immune checkpoints might help to highlight research perspectives in the field and obtain a more complete picture of IM disease pathology. Copyright © 2018 Elsevier B.V. All rights reserved.

Comparative Analysis of Immune Checkpoint Molecules and Their Potential Role in the Transmissible Tasmanian Devil Facial Tumor Disease

PubMed Central

Flies, Andrew S.; Blackburn, Nicholas B.; Lyons, Alan Bruce; Hayball, John D.; Woods, Gregory M.

2017-01-01

Immune checkpoint molecules function as a system of checks and balances that enhance or inhibit immune responses to infectious agents, foreign tissues, and cancerous cells. Immunotherapies that target immune checkpoint molecules, particularly the inhibitory molecules programmed cell death 1 and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), have revolutionized human oncology in recent years, yet little is known about these key immune signaling molecules in species other than primates and rodents. The Tasmanian devil facial tumor disease is caused by transmissible cancers that have resulted in a massive decline in the wild Tasmanian devil population. We have recently demonstrated that the inhibitory checkpoint molecule PD-L1 is upregulated on Tasmanian devil (Sarcophilus harrisii) facial tumor cells in response to the interferon-gamma cytokine. As this could play a role in immune evasion by tumor cells, we performed a thorough comparative analysis of checkpoint molecule protein sequences among Tasmanian devils and eight other species. We report that many of the key signaling motifs and ligand-binding sites in the checkpoint molecules are highly conserved across the estimated 162 million years of evolution since the last common ancestor of placental and non-placental mammals. Specifically, we discovered that the CTLA-4 (MYPPPY) ligand-binding motif and the CTLA-4 (GVYVKM) inhibitory domain are completely conserved across all nine species used in our comparative analysis, suggesting that the function of CTLA-4 is likely conserved in these species. We also found that cysteine residues for intra- and intermolecular disulfide bonds were also highly conserved. For instance, all 20 cysteine residues involved in disulfide bonds in the human 4-1BB molecule were also present in devil 4-1BB. Although many key sequences were conserved, we have also identified immunoreceptor tyrosine-based inhibitory motifs (ITIMs) and immunoreceptor tyrosine-based switch motifs (ITSMs

Immune mediated neuropathy following checkpoint immunotherapy.

PubMed

Gu, Yufan; Menzies, Alexander M; Long, Georgina V; Fernando, S L; Herkes, G

2017-11-01

Checkpoint immunotherapy has revolutionised cancer therapy and is now standard treatment for many malignancies including metastatic melanoma. Acute inflammatory neuropathies, often labelled as Guillain-Barre syndrome, are an uncommon but potentially severe complication of checkpoint immunotherapy with individual cases described but never characterised as a group. We describe a case of acute sensorimotor and autonomic neuropathy following a single dose of combination ipilimumab and nivolumab for metastatic melanoma. A literature search was performed, identifying 14 other cases of acute neuropathy following checkpoint immunotherapy, with the clinical, electrophysiological and laboratory features summarised. Most cases described an acute sensorimotor neuropathy (92%) with hyporeflexia (92%) that could occur from induction up till many weeks after the final dose of therapy. In contrast to Guillain-Barre syndrome, the cerebrospinal fluid (CSF) analysis often shows a lymphocytic picture (50%) and the electrophysiology showed an axonal pattern (55%). Treatment was variable and often in combination. 11 cases received steroid therapy with only 1 death within this group, whereas of the 4 patients who did not receive steroid therapy there were 3 deaths. In conclusion checkpoint immunotherapy - induced acute neuropathies are distinct from and progress differently to Guillain-Barre syndrome. As with other immunotherapy related adverse events corticosteroid therapy should be initiated in addition to usual therapy. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synaptonemal Complex Components Are Required for Meiotic Checkpoint Function in Caenorhabditis elegans

PubMed Central

Bohr, Tisha; Ashley, Guinevere; Eggleston, Evan; Firestone, Kyra; Bhalla, Needhi

2016-01-01

Synapsis involves the assembly of a proteinaceous structure, the synaptonemal complex (SC), between paired homologous chromosomes, and is essential for proper meiotic chromosome segregation. In Caenorhabditis elegans, the synapsis checkpoint selectively removes nuclei with unsynapsed chromosomes by inducing apoptosis. This checkpoint depends on pairing centers (PCs), cis-acting sites that promote pairing and synapsis. We have hypothesized that the stability of homolog pairing at PCs is monitored by this checkpoint. Here, we report that SC components SYP-3, HTP-3, HIM-3, and HTP-1 are required for a functional synapsis checkpoint. Mutation of these components does not abolish PC function, demonstrating they are bona fide checkpoint components. Further, we identify mutant backgrounds in which the instability of homolog pairing at PCs does not correlate with the synapsis checkpoint response. Altogether, these data suggest that, in addition to homolog pairing, SC assembly may be monitored by the synapsis checkpoint. PMID:27605049

Endocrinological side-effects of immune checkpoint inhibitors.

PubMed

Torino, Francesco; Corsello, Salvatore M; Salvatori, Roberto

2016-07-01

Three mAbs targeting immune checkpoint proteins are available for the treatment of patients with melanoma, lung, and kidney cancer, and their use will likely expand in the future to additional tumor types. We here update the literature on the incidence and pathophysiology of endocrine toxicities induced by these agents, and discuss management guidance. Immune checkpoint inhibition may trigger autoimmune syndromes involving different organs, including several endocrine glands (pituitary, thyroid, adrenals, and endocrine pancreas). Hypophysitis is more frequently associated with ipilimumab, whereas the incidence of thyroid dysfunction is higher with nivolumab/pembrolizumab. Primary adrenal insufficiency can rarely occur with either treatment. Autoimmune diabetes is very rare. As hypophysitis and adrenalitis may be life-threatening, endocrinological evaluation is essential particularly in patients developing fatigue and other symptoms consistent with adrenal insufficiency. Corticosteroids should be promptly used when hypophysitis-induced adrenal insufficiency or adrenalitis are diagnosed, but not in thyroiditis or diabetes. No impact of corticosteroids on the efficacy/activity of immune checkpoint-inhibiting drugs is reported. Hormonal deficiencies are often permanent. In absence of predicting factors, accurate information to patients provided by the oncology care team is essential for early diagnosis and to limit the consequences of checkpoint inhibition-related endocrine toxicity.

Low-manpower checkpoints: can they provide effective DUI enforcement in small communities?

PubMed

Lacey, John H; Ferguson, Susan A; Kelley-Baker, Tara; Rider, Raamses P

2006-09-01

Sobriety checkpoints can be effective in reducing alcohol-impaired driving. Checkpoints are underutilized, however, partially because police believe a large number of officers are required. This study evaluated the feasibility and impact of conducting small-scale checkpoints in rural communities. Law enforcement agencies in two counties agreed to conduct weekly checkpoints for one year. Two nonadjacent counties did not undertake additional checkpoints. Evaluation included public-awareness surveys and roadside surveys (including blood alcohol concentration [BAC] measurements) of weekend nighttime drivers. Relative to drivers in the comparison counties, the proportion of drivers in the experimental counties with BACs >0.05% was 70% lower. Drivers surveyed at driver's license offices in the experimental counties after program implementation were more likely to report seeing or passing through a checkpoint and were more aware of publicity on driving under the influence (DUI) enforcement. Small rural communities can safely and effectively conduct low-staff sobriety checkpoints on a weekly basis. Such programs can be expected to result in large reductions in drivers operating at higher BACs.

Orchestration of DNA Damage Checkpoint Dynamics across the Human Cell Cycle.

PubMed

Chao, Hui Xiao; Poovey, Cere E; Privette, Ashley A; Grant, Gavin D; Chao, Hui Yan; Cook, Jeanette G; Purvis, Jeremy E

2017-11-22

Although molecular mechanisms that prompt cell-cycle arrest in response to DNA damage have been elucidated, the systems-level properties of DNA damage checkpoints are not understood. Here, using time-lapse microscopy and simulations that model the cell cycle as a series of Poisson processes, we characterize DNA damage checkpoints in individual, asynchronously proliferating cells. We demonstrate that, within early G1 and G2, checkpoints are stringent: DNA damage triggers an abrupt, all-or-none cell-cycle arrest. The duration of this arrest correlates with the severity of DNA damage. After the cell passes commitment points within G1 and G2, checkpoint stringency is relaxed. By contrast, all of S phase is comparatively insensitive to DNA damage. This checkpoint is graded: instead of halting the cell cycle, increasing DNA damage leads to slower S phase progression. In sum, we show that a cell's response to DNA damage depends on its exact cell-cycle position and that checkpoints are phase-dependent, stringent or relaxed, and graded or all-or-none. Copyright © 2017 Elsevier Inc. All rights reserved.

The problem of suspended and revoked drivers who avoid detection at checkpoints.

PubMed

Parrish, Kelly E; Masten, Scott V

2015-01-01

Although driver license suspension and revocation have been shown to improve traffic safety, suspended or revoked (SR) drivers who continue to drive-which appears to be the majority-are about 3 times more likely to be involved in crashes and to cause a fatal crash. In California and many other U.S. states, drivers are typically mailed notices requesting that they surrender their licenses when they are SR for reasons other than driving under the influence of alcohol or drugs (DUI), yet they frequently do not comply. Typical procedures at DUI checkpoints in California and other U.S. states include inspecting driver licenses and checking for signs of intoxication during brief contacts with law enforcement officers. Hence, these checkpoints are in fact DUI/license checkpoints in California and many other states. The purpose of this study was to estimate the extent to which SR drivers avoid being detected at DUI/license checkpoints for SR driving, because they illegally retained possession of their license cards. Law enforcement officers used electronic license card readers at DUI/license checkpoints in Sacramento, California, to record data for 13,705 drivers. The SR status of all contacted drivers was determined after the checkpoints and compared to law enforcement citation records from the checkpoints. Although only 3% of the drivers contacted at the checkpoints were SR, about 41% of SR drivers were able to pass through undetected because they presented license cards that they illegally retained. Drivers SR for DUI-related reasons were more likely to be detected, whereas those SR for failure to provide proof of financial responsibility (insurance) were less likely to be detected. The fact that many SR drivers are able to pass through DUI/license checkpoints undetected weakens both the specific and general impacts of checkpoints for deterring SR driving and may diminish the effectiveness of suspension and revocation actions for reducing the crash risk posed by problem

Space Reclamation for Uncoordinated Checkpointing in Message-Passing Systems. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Wang, Yi-Min

1993-01-01

Checkpointing and rollback recovery are techniques that can provide efficient recovery from transient process failures. In a message-passing system, the rollback of a message sender may cause the rollback of the corresponding receiver, and the system needs to roll back to a consistent set of checkpoints called recovery line. If the processes are allowed to take uncoordinated checkpoints, the above rollback propagation may result in the domino effect which prevents recovery line progression. Traditionally, only obsolete checkpoints before the global recovery line can be discarded, and the necessary and sufficient condition for identifying all garbage checkpoints has remained an open problem. A necessary and sufficient condition for achieving optimal garbage collection is derived and it is proved that the number of useful checkpoints is bounded by N(N+1)/2, where N is the number of processes. The approach is based on the maximum-sized antichain model of consistent global checkpoints and the technique of recovery line transformation and decomposition. It is also shown that, for systems requiring message logging to record in-transit messages, the same approach can be used to achieve optimal message log reclamation. As a final topic, a unifying framework is described by considering checkpoint coordination and exploiting piecewise determinism as mechanisms for bounding rollback propagation, and the applicability of the optimal garbage collection algorithm to domino-free recovery protocols is demonstrated.

Expression of checkpoint molecules on myeloid-derived suppressor cells.

PubMed

Ballbach, Marlene; Dannert, Angelika; Singh, Anurag; Siegmund, Darina M; Handgretinger, Rupert; Piali, Luca; Rieber, Nikolaus; Hartl, Dominik

2017-12-01

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous cell population expanded in cancer, infection and autoimmunity capable of suppressing T-cell functions. Checkpoint inhibitors have emerged as a key therapeutic strategy in immune-oncology. While checkpoint molecules were initially associated with T cell functions, recent evidence suggests a broader expression and function in innate myeloid cells. Previous studies provided first evidence for a potential role for checkpoints on MDSCs, yet the human relevance remained poorly understood. Therefore, we investigated the expression and functional relevance of checkpoint molecules in human MDSC-T-cell interactions. Our studies demonstrate that programmed death-ligand 1 (PD-L1) is expressed on granulocytic MDSCs upon co-culture with T cells. Transwell experiments showed that cell-to-cell contact was required for MDSC-T-cell interactions and antibody blocking studies showed that targeting PD-L1 partially impaired MDSC-mediated T-cell suppression. Collectively, these studies suggest a role for PD-L1 in human MDSC function and thereby expand the functionality of this checkpoint beyond T cells, which could pave the way for further understanding and therapeutic targeting of PD-1/PD-L1 in innate immune-mediated diseases. Copyright © 2017 European Federation of Immunological Societies. Published by Elsevier B.V. All rights reserved.

Message Efficient Checkpointing and Rollback Recovery in Heterogeneous Mobile Networks

NASA Astrophysics Data System (ADS)

Jaggi, Parmeet Kaur; Singh, Awadhesh Kumar

2016-06-01

Heterogeneous networks provide an appealing way of expanding the computing capability of mobile networks by combining infrastructure-less mobile ad-hoc networks with the infrastructure-based cellular mobile networks. The nodes in such a network range from low-power nodes to macro base stations and thus, vary greatly in their capabilities such as computation power and battery power. The nodes are susceptible to different types of transient and permanent failures and therefore, the algorithms designed for such networks need to be fault-tolerant. The article presents a checkpointing algorithm for the rollback recovery of mobile hosts in a heterogeneous mobile network. Checkpointing is a well established approach to provide fault tolerance in static and cellular mobile distributed systems. However, the use of checkpointing for fault tolerance in a heterogeneous environment remains to be explored. The proposed protocol is based on the results of zigzag paths and zigzag cycles by Netzer-Xu. Considering the heterogeneity prevalent in the network, an uncoordinated checkpointing technique is employed. Yet, useless checkpoints are avoided without causing a high message overhead.

Sobriety checkpoints in Thailand: a review of effectiveness and developments over time.

PubMed

Ditsuwan, Vallop; Veerman, J Lennert; Bertram, Melanie; Vos, Theo

2015-03-01

This review describes the legal basis for and implementation of sobriety checkpoints in Thailand and identifies factors that influenced their historical development and effectiveness. The first alcohol and traffic injury control law in Thailand was implemented in 1934. The 0.05 g/100 mL blood alcohol concentration limit was set in 1994. Currently, 3 types of sobriety checkpoints are used: general police checkpoints, selective breath testing, and special event sobriety checkpoints. The authors found few reports on the strategies, frequencies, and outcomes for any of these types of checkpoints, despite Thailand having devoted many resources to their implementation. In Thailand and other low-middle income countries, it is necessary to address the country-specific barriers to successful enforcement (including political and logistical issues, lack of equipment, and absence of other supportive alcohol harm reduction measures) before sobriety checkpoints can be expected to be as effective as reported in high-income countries. © 2011 APJPH.

Disease severity in a mouse model of ataxia telangiectasia is modulated by the DNA damage checkpoint gene Hus1

PubMed Central

Balmus, Gabriel; Zhu, Min; Mukherjee, Sucheta; Lyndaker, Amy M.; Hume, Kelly R.; Lee, Jaesung; Riccio, Mark L.; Reeves, Anthony P.; Sutter, Nathan B.; Noden, Drew M.; Peters, Rachel M.; Weiss, Robert S.

2012-01-01

The human genomic instability syndrome ataxia telangiectasia (A-T), caused by mutations in the gene encoding the DNA damage checkpoint kinase ATM, is characterized by multisystem defects including neurodegeneration, immunodeficiency and increased cancer predisposition. ATM is central to a pathway that responds to double-strand DNA breaks, whereas the related kinase ATR leads a parallel signaling cascade that is activated by replication stress. To dissect the physiological relationship between the ATM and ATR pathways, we generated mice defective for both. Because complete ATR pathway inactivation causes embryonic lethality, we weakened the ATR mechanism to different degrees by impairing HUS1, a member of the 911 complex that is required for efficient ATR signaling. Notably, simultaneous ATM and HUS1 defects caused synthetic lethality. Atm/Hus1 double-mutant embryos showed widespread apoptosis and died mid-gestationally. Despite the underlying DNA damage checkpoint defects, increased DNA damage signaling was observed, as evidenced by H2AX phosphorylation and p53 accumulation. A less severe Hus1 defect together with Atm loss resulted in partial embryonic lethality, with the surviving double-mutant mice showing synergistic increases in genomic instability and specific developmental defects, including dwarfism, craniofacial abnormalities and brachymesophalangy, phenotypes that are observed in several human genomic instability disorders. In addition to identifying tissue-specific consequences of checkpoint dysfunction, these data highlight a robust, cooperative configuration for the mammalian DNA damage response network and further suggest HUS1 and related genes in the ATR pathway as candidate modifiers of disease severity in A-T patients. PMID:22575700

Checkpoints: it takes more than time to heal some wounds.

PubMed

Rhind, N; Russell, P

The S-phase DNA damage checkpoint seems to provide a twist on the checkpoint theme. Instead of delaying replication and allowing repair as a consequence, it may activate repair and delay replication as a consequence.

Phosphorylation of microtubule-binding protein Hec1 by mitotic kinase Aurora B specifies spindle checkpoint kinase Mps1 signaling at the kinetochore.

PubMed

Zhu, Tongge; Dou, Zhen; Qin, Bo; Jin, Changjiang; Wang, Xinghui; Xu, Leilei; Wang, Zhaoyang; Zhu, Lijuan; Liu, Fusheng; Gao, Xinjiao; Ke, Yuwen; Wang, Zhiyong; Aikhionbare, Felix; Fu, Chuanhai; Ding, Xia; Yao, Xuebiao

2013-12-13

The spindle assembly checkpoint (SAC) is a quality control device to ensure accurate chromosome attachment to spindle microtubule for equal segregation of sister chromatid. Aurora B is essential for SAC function by sensing chromosome bi-orientation via spatial regulation of kinetochore substrates. However, it has remained elusive as to how Aurora B couples kinetochore-microtubule attachment to SAC signaling. Here, we show that Hec1 interacts with Mps1 and specifies its kinetochore localization via its calponin homology (CH) domain and N-terminal 80 amino acids. Interestingly, phosphorylation of the Hec1 by Aurora B weakens its interaction with microtubules but promotes Hec1 binding to Mps1. Significantly, the temporal regulation of Hec1 phosphorylation orchestrates kinetochore-microtubule attachment and Mps1 loading to the kinetochore. Persistent expression of phosphomimetic Hec1 mutant induces a hyperactivation of SAC, suggesting that phosphorylation-elicited Hec1 conformational change is used as a switch to orchestrate SAC activation to concurrent destabilization of aberrant kinetochore attachment. Taken together, these results define a novel role for Aurora B-Hec1-Mps1 signaling axis in governing accurate chromosome segregation in mitosis.

Phosphorylation of Microtubule-binding Protein Hec1 by Mitotic Kinase Aurora B Specifies Spindle Checkpoint Kinase Mps1 Signaling at the Kinetochore*

PubMed Central

Zhu, Tongge; Dou, Zhen; Qin, Bo; Jin, Changjiang; Wang, Xinghui; Xu, Leilei; Wang, Zhaoyang; Zhu, Lijuan; Liu, Fusheng; Gao, Xinjiao; Ke, Yuwen; Wang, Zhiyong; Aikhionbare, Felix; Fu, Chuanhai; Ding, Xia; Yao, Xuebiao

2013-01-01

The spindle assembly checkpoint (SAC) is a quality control device to ensure accurate chromosome attachment to spindle microtubule for equal segregation of sister chromatid. Aurora B is essential for SAC function by sensing chromosome bi-orientation via spatial regulation of kinetochore substrates. However, it has remained elusive as to how Aurora B couples kinetochore-microtubule attachment to SAC signaling. Here, we show that Hec1 interacts with Mps1 and specifies its kinetochore localization via its calponin homology (CH) domain and N-terminal 80 amino acids. Interestingly, phosphorylation of the Hec1 by Aurora B weakens its interaction with microtubules but promotes Hec1 binding to Mps1. Significantly, the temporal regulation of Hec1 phosphorylation orchestrates kinetochore-microtubule attachment and Mps1 loading to the kinetochore. Persistent expression of phosphomimetic Hec1 mutant induces a hyperactivation of SAC, suggesting that phosphorylation-elicited Hec1 conformational change is used as a switch to orchestrate SAC activation to concurrent destabilization of aberrant kinetochore attachment. Taken together, these results define a novel role for Aurora B-Hec1-Mps1 signaling axis in governing accurate chromosome segregation in mitosis. PMID:24187132

Checkpoint Inhibition in Hodgkin Lymphoma - a Review.

PubMed

Bröckelmann, Paul J; Engert, Andreas

2017-01-01

Physiological immune checkpoint pathways are important to regulate self-tolerance, limit immune reactions, and moderate autoimmunity. Various cancers are commonly exploiting these mechanisms to evade the host immune system by restraining a durable, efficient anti-tumor immune response. Immune checkpoints include, but are not limited to, the programmed death 1 (PD1) and the cytotoxic T-lymphocyte-associated protein-4 (CTLA4) axis, which are both druggable by monoclonal antibodies referred to as checkpoint inhibitors (CIs). To date, the anti-PD1 antibodies nivolumab and pembrolizumab are approved for relapsed or refractory classical Hodgkin lymphoma (cHL) due to high response rates with a favorable yet distinct safety profile, and other agents are under investigation. This review summarizes the available preclinical and clinical data including the toxicity and efficacy of different CIs in cHL. It also provides future perspectives based on ongoing clinical trials, potentially synergistic combinatory approaches, and their fit in the therapeutic landscape in cHL. © 2017 S. Karger GmbH, Freiburg.

Checkpoints: It takes more than time to heal some wounds

PubMed Central

Rhind, Nicholas; Russell, Paul

2010-01-01

The S-phase DNA damage checkpoint seems to provide a twist on the checkpoint theme. Instead of delaying replication and allowing repair as a consequence, it may activate repair and delay replication as a consequence. PMID:11137027

[Genetic Mutation Accumulation and Clinical Outcome of Immune Checkpoint Blockade Therapy].

PubMed

Takahashi, Masanobu

2016-06-01

Immune checkpoint blockade therapy has recently attracted great attention in the area of oncology. In Japan, since 2014, an anti-PD-1 antibody nivolumab and anti-CTLA-4 antibody ipilimumab have been available for the treatment of patients with malignant melanoma, and nivolumab has been available for patients with non-small cell lung cancer. Clinical trials using these drugs and other immune checkpoint inhibitors are currently in progress worldwide. The immune checkpoint blockade therapy is a promising new cancer therapy; however, not all patients with cancer can benefit from this therapy. Recent evidence shows that markers reflecting the extent of genetic mutation accumulation, including mutation burden, non-synonymous mutation that produces neoantigen, and microsatellite instability, possibly serve as promising marker to predict who can benefit from the immune checkpoint blockade therapy. Here, I introduce the recent evidence and discuss the correlation between genetic mutation accumulation and clinical outcome of immune checkpoint blockade therapy.

Adrenergic Signaling: A Targetable Checkpoint Limiting Development of the Antitumor Immune Response

PubMed Central

Qiao, Guanxi; Chen, Minhui; Bucsek, Mark J.; Repasky, Elizabeth A.; Hylander, Bonnie L.

2018-01-01

An immune response must be tightly controlled so that it will be commensurate with the level of response needed to protect the organism without damaging normal tissue. The roles of cytokines and chemokines in orchestrating these processes are well known, but although stress has long been thought to also affect immune responses, the underlying mechanisms were not as well understood. Recently, the role of nerves and, specifically, the sympathetic nervous system, in regulating immune responses is being revealed. Generally, an acute stress response is beneficial but chronic stress is detrimental because it suppresses the activities of effector immune cells while increasing the activities of immunosuppressive cells. In this review, we first discuss the underlying biology of adrenergic signaling in cells of both the innate and adaptive immune system. We then focus on the effects of chronic adrenergic stress in promoting tumor growth, giving examples of effects on tumor cells and immune cells, explaining the methods commonly used to induce stress in preclinical mouse models. We highlight how this relates to our observations that mandated housing conditions impose baseline chronic stress on mouse models, which is sufficient to cause chronic immunosuppression. This problem is not commonly recognized, but it has been shown to impact conclusions of several studies of mouse physiology and mouse models of disease. Moreover, the fact that preclinical mouse models are chronically immunosuppressed has critical ramifications for analysis of any experiments with an immune component. Our group has found that reducing adrenergic stress by housing mice at thermoneutrality or treating mice housed at cooler temperatures with β-blockers reverses immunosuppression and significantly improves responses to checkpoint inhibitor immunotherapy. These observations are clinically relevant because there are numerous retrospective epidemiological studies concluding that cancer patients who were

Adrenergic Signaling: A Targetable Checkpoint Limiting Development of the Antitumor Immune Response.

PubMed

Qiao, Guanxi; Chen, Minhui; Bucsek, Mark J; Repasky, Elizabeth A; Hylander, Bonnie L

2018-01-01

An immune response must be tightly controlled so that it will be commensurate with the level of response needed to protect the organism without damaging normal tissue. The roles of cytokines and chemokines in orchestrating these processes are well known, but although stress has long been thought to also affect immune responses, the underlying mechanisms were not as well understood. Recently, the role of nerves and, specifically, the sympathetic nervous system, in regulating immune responses is being revealed. Generally, an acute stress response is beneficial but chronic stress is detrimental because it suppresses the activities of effector immune cells while increasing the activities of immunosuppressive cells. In this review, we first discuss the underlying biology of adrenergic signaling in cells of both the innate and adaptive immune system. We then focus on the effects of chronic adrenergic stress in promoting tumor growth, giving examples of effects on tumor cells and immune cells, explaining the methods commonly used to induce stress in preclinical mouse models. We highlight how this relates to our observations that mandated housing conditions impose baseline chronic stress on mouse models, which is sufficient to cause chronic immunosuppression. This problem is not commonly recognized, but it has been shown to impact conclusions of several studies of mouse physiology and mouse models of disease. Moreover, the fact that preclinical mouse models are chronically immunosuppressed has critical ramifications for analysis of any experiments with an immune component. Our group has found that reducing adrenergic stress by housing mice at thermoneutrality or treating mice housed at cooler temperatures with β-blockers reverses immunosuppression and significantly improves responses to checkpoint inhibitor immunotherapy. These observations are clinically relevant because there are numerous retrospective epidemiological studies concluding that cancer patients who were

Phenotypic Checkpoints Regulate Neuronal Development

PubMed Central

Ben-Ari, Yehezkel; Spitzer, Nicholas C.

2010-01-01

Nervous system development proceeds by sequential gene expression mediated by cascades of transcription factors in parallel with sequences of patterned network activity driven by receptors and ion channels. These sequences are cell type- and developmental stage-dependent and modulated by paracrine actions of substances released by neurons and glia. How and to what extent these sequences interact to enable neuronal network development is not understood. Recent evidence demonstrates that CNS development requires intermediate stages of differentiation providing functional feedback that influences gene expression. We suggest that embryonic neuronal functions constitute a series of phenotypic checkpoint signatures; neurons failing to express these functions are delayed or developmentally arrested. Such checkpoints are likely to be a general feature of neuronal development and may constitute presymptomatic signatures of neurological disorders when they go awry. PMID:20864191

Genomic correlates of response to immune checkpoint therapies in clear cell renal cell carcinoma.

PubMed

Miao, Diana; Margolis, Claire A; Gao, Wenhua; Voss, Martin H; Li, Wei; Martini, Dylan J; Norton, Craig; Bossé, Dominick; Wankowicz, Stephanie M; Cullen, Dana; Horak, Christine; Wind-Rotolo, Megan; Tracy, Adam; Giannakis, Marios; Hodi, Frank Stephen; Drake, Charles G; Ball, Mark W; Allaf, Mohamad E; Snyder, Alexandra; Hellmann, Matthew D; Ho, Thai; Motzer, Robert J; Signoretti, Sabina; Kaelin, William G; Choueiri, Toni K; Van Allen, Eliezer M

2018-02-16

Immune checkpoint inhibitors targeting the programmed cell death 1 receptor (PD-1) improve survival in a subset of patients with clear cell renal cell carcinoma (ccRCC). To identify genomic alterations in ccRCC that correlate with response to anti-PD-1 monotherapy, we performed whole-exome sequencing of metastatic ccRCC from 35 patients. We found that clinical benefit was associated with loss-of-function mutations in the PBRM1 gene ( P = 0.012), which encodes a subunit of the PBAF switch-sucrose nonfermentable (SWI/SNF) chromatin remodeling complex. We confirmed this finding in an independent validation cohort of 63 ccRCC patients treated with PD-1 or PD-L1 (PD-1 ligand) blockade therapy alone or in combination with anti-CTLA-4 (cytotoxic T lymphocyte-associated protein 4) therapies ( P = 0.0071). Gene-expression analysis of PBAF-deficient ccRCC cell lines and PBRM1 -deficient tumors revealed altered transcriptional output in JAK-STAT (Janus kinase-signal transducers and activators of transcription), hypoxia, and immune signaling pathways. PBRM1 loss in ccRCC may alter global tumor-cell expression profiles to influence responsiveness to immune checkpoint therapy. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Cycle Checkpoint Abnormalities during Dementia: A Plausible Association with the Loss of Protection against Oxidative Stress in Alzheimer’s Disease

PubMed Central

Katsel, Pavel; Tan, Weilun; Fam, Peter; Purohit, Dushyant P.; Haroutunian, Vahram

2013-01-01

Background Increasing evidence suggests an association between neuronal cell cycle (CCL) events and the processes that underlie neurodegeneration in Alzheimer’s disease (AD). Elevated levels of oxidative stress markers and mitochondrial dysfunction are also among early events in AD. Recent studies have reported the role of CCL checkpoint proteins and tumor suppressors, such as ATM and p53 in the control of glycolysis and oxidative metabolism in cancer, but their involvement in AD remains uncertain. Methods and Findings In this postmortem study, we measured gene expression levels of eight CCL checkpoint proteins in the superior temporal cortex (STC) of persons with varying severities of AD dementia and compare them to those of cognitively normal controls. To assess whether the CCL changes associated with cognitive impairment in AD are specific to dementia, gene expression of the same proteins was also measured in STC of persons with schizophrenia (SZ), which is also characterized by mitochondrial dysfunction. The expression of CCL-checkpoint and DNA damage response genes: MDM4, ATM and ATR was strongly upregulated and associated with progression of dementia (cognitive dementia rating, CDR), appearing as early as questionable or mild dementia (CDRs 0.5–1). In addition to gene expression changes, the downstream target of ATM-p53 signaling - TIGAR, a p53-inducible protein, the activation of which can regulate energy metabolism and protect against oxidative stress was progressively decreased as severity of dementia evolved, but it was unaffected in subjects with SZ. In contrast to AD, different CCL checkpoint proteins, which include p53, CHEK1 and BRCA1 were significantly downregulated in SZ. Conclusions These results support the activation of an ATM signaling and DNA damage response network during the progression of AD dementia, while the progressive decrease in the levels of TIGAR suggests loss of protection initiated by ATM-p53 signaling against intensifying

Development of cell-cycle checkpoint therapy for solid tumors.

PubMed

Tamura, Kenji

2015-12-01

Cellular proliferation is tightly controlled by several cell-cycle checkpoint proteins. In cancer, the genes encoding these proteins are often disrupted and cause unrestrained cancer growth. The proteins are over-expressed in many malignancies; thus, they are potential targets for anti-cancer therapies. These proteins include cyclin-dependent kinase, checkpoint kinase, WEE1 kinase, aurora kinase and polo-like kinase. Cyclin-dependent kinase inhibitors are the most advanced cell-cycle checkpoint therapeutics available. For instance, palbociclib (PD0332991) is a first-in-class, oral, highly selective inhibitor of CDK4/6 and, in combination with letrozole (Phase II; PALOMA-1) or with fulvestrant (Phase III; PALOMA-3), it has significantly prolonged progression-free survival, in patients with metastatic estrogen receptor-positive, HER2-negative breast cancer, in comparison with that observed in patients using letrozole, or fulvestrant alone, respectively. In this review, we provide an overview of the current compounds available for cell-cycle checkpoint protein-directed therapy for solid tumors. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Distinct chromosome segregation roles for spindle checkpoint proteins.

PubMed

Warren, Cheryl D; Brady, D Michelle; Johnston, Raymond C; Hanna, Joseph S; Hardwick, Kevin G; Spencer, Forrest A

2002-09-01

The spindle checkpoint plays a central role in the fidelity of chromosome transmission by ensuring that anaphase is initiated only after kinetochore-microtubule associations of all sister chromatid pairs are complete. In this study, we find that known spindle checkpoint proteins do not contribute equally to chromosome segregation fidelity in Saccharomyces cerevisiae. Loss of Bub1 or Bub3 protein elicits the largest effect. Analysis of Bub1p reveals the presence of two molecular functions. An N-terminal 608-amino acid (nonkinase) portion of the protein supports robust checkpoint activity, and, as expected, contributes to chromosome segregation. A C-terminal kinase-encoding segment independently contributes to chromosome segregation through an unknown mechanism. Both molecular functions depend on association with Bub3p. A 156-amino acid fragment of Bub1p functions in Bub3p binding and in kinetochore localization by one-hybrid assay. An adjacent segment is required for Mad1p binding, detected by deletion analysis and coimmunoprecipitation. Finally, overexpression of wild-type BUB1 or MAD3 genes leads to chromosome instability. Analysis of this activity indicates that the Bub3p-binding domain of Bub1p contributes to this phenotype through disruption of checkpoint activity as well as through introduction of kinetochore or spindle damage.

Distinct Chromosome Segregation Roles for Spindle Checkpoint Proteins

PubMed Central

Warren, Cheryl D.; Brady, D. Michelle; Johnston, Raymond C.; Hanna, Joseph S.; Hardwick, Kevin G.; Spencer, Forrest A.

2002-01-01

The spindle checkpoint plays a central role in the fidelity of chromosome transmission by ensuring that anaphase is initiated only after kinetochore-microtubule associations of all sister chromatid pairs are complete. In this study, we find that known spindle checkpoint proteins do not contribute equally to chromosome segregation fidelity in Saccharomyces cerevisiae. Loss of Bub1 or Bub3 protein elicits the largest effect. Analysis of Bub1p reveals the presence of two molecular functions. An N-terminal 608-amino acid (nonkinase) portion of the protein supports robust checkpoint activity, and, as expected, contributes to chromosome segregation. A C-terminal kinase-encoding segment independently contributes to chromosome segregation through an unknown mechanism. Both molecular functions depend on association with Bub3p. A 156-amino acid fragment of Bub1p functions in Bub3p binding and in kinetochore localization by one-hybrid assay. An adjacent segment is required for Mad1p binding, detected by deletion analysis and coimmunoprecipitation. Finally, overexpression of wild-type BUB1 or MAD3 genes leads to chromosome instability. Analysis of this activity indicates that the Bub3p-binding domain of Bub1p contributes to this phenotype through disruption of checkpoint activity as well as through introduction of kinetochore or spindle damage. PMID:12221113

An ATM-independent S-phase checkpoint response involves CHK1 pathway

NASA Technical Reports Server (NTRS)

Zhou, Xiang-Yang; Wang, Xiang; Hu, Baocheng; Guan, Jun; Iliakis, George; Wang, Ya

2002-01-01

After exposure to genotoxic stress, proliferating cells actively slow down the DNA replication through a S-phase checkpoint to provide time for repair. We report that in addition to the ataxia-telangiectasia mutated (ATM)-dependent pathway that controls the fast response, there is an ATM-independent pathway that controls the slow response to regulate the S-phase checkpoint after ionizing radiation in mammalian cells. The slow response of S-phase checkpoint, which is resistant to wortmannin, sensitive to caffeine and UCN-01, and related to cyclin-dependent kinase phosphorylation, is much stronger in CHK1 overexpressed cells, and it could be abolished by Chk1 antisense oligonucleotides. These results provide evidence that the ATM-independent slow response of S-phase checkpoint involves CHK1 pathway.

Phosphorylated (pT371)TRF1 is recruited to sites of DNA damage to facilitate homologous recombination and checkpoint activation

PubMed Central

McKerlie, Megan; Walker, John R.; Mitchell, Taylor R. H.; Wilson, Florence R.; Zhu, Xu-Dong

2013-01-01

TRF1, a duplex telomeric DNA-binding protein, plays an important role in telomere metabolism. We have previously reported that a fraction of endogenous TRF1 can stably exist free of telomere chromatin when it is phosphorylated at T371 by Cdk1; however, the role of this telomere-free (pT371)TRF1 has yet to be fully characterized. Here we show that phosphorylated (pT371)TRF1 is recruited to sites of DNA damage, forming damage-induced foci in response to ionizing radiation (IR), etoposide and camptothecin. We find that IR-induced (pT371)TRF1 foci formation is dependent on the ATM- and Mre11/Rad50/Nbs1-mediated DNA damage response. While loss of functional BRCA1 impairs the formation of IR-induced (pT371)TRF1 foci, depletion of either 53BP1 or Rif1 stimulates IR-induced (pT371)TRF1 foci formation. In addition, we show that TRF1 depletion or the lack of its phosphorylation at T371 impairs DNA end resection and repair of nontelomeric DNA double-strand breaks by homologous recombination. The lack of TRF1 phosphorylation at T371 also hampers the activation of the G2/M checkpoint and sensitizes cells to PARP inhibition, IR and camptothecin. Collectively, these results reveal a novel but important function of phosphorylated (pT371)TRF1 in facilitating DNA double-strand break repair and the maintenance of genome integrity. PMID:23997120

Tumor Microenvironment Metabolism: A New Checkpoint for Anti-Tumor Immunity

PubMed Central

Scharping, Nicole E.; Delgoffe, Greg M.

2016-01-01

When a T cell infiltrates a tumor, it is subjected to a variety of immunosuppressive and regulatory signals in the microenvironment. However, it is becoming increasingly clear that due to the proliferative and energetically-deregulated nature of tumor cells, T cells also operate at a metabolic disadvantage. The nutrient dearth of the tumor microenvironment (TME) creates “metabolic checkpoints” upon infiltrating T cells, impacting their ability to survive, proliferate and function effectively. In this review, we summarize the basics of tumor cell and T cell metabolism and discuss recent advances elucidating the individual metabolic checkpoints exerted on T cells that drive their dysfunction in the TME. PMID:27929420

Parallelization and checkpointing of GPU applications through program transformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solano-Quinde, Lizandro Damian

2012-01-01

GPUs have emerged as a powerful tool for accelerating general-purpose applications. The availability of programming languages that makes writing general-purpose applications for running on GPUs tractable have consolidated GPUs as an alternative for accelerating general purpose applications. Among the areas that have benefited from GPU acceleration are: signal and image processing, computational fluid dynamics, quantum chemistry, and, in general, the High Performance Computing (HPC) Industry. In order to continue to exploit higher levels of parallelism with GPUs, multi-GPU systems are gaining popularity. In this context, single-GPU applications are parallelized for running in multi-GPU systems. Furthermore, multi-GPU systems help to solvemore » the GPU memory limitation for applications with large application memory footprint. Parallelizing single-GPU applications has been approached by libraries that distribute the workload at runtime, however, they impose execution overhead and are not portable. On the other hand, on traditional CPU systems, parallelization has been approached through application transformation at pre-compile time, which enhances the application to distribute the workload at application level and does not have the issues of library-based approaches. Hence, a parallelization scheme for GPU systems based on application transformation is needed. Like any computing engine of today, reliability is also a concern in GPUs. GPUs are vulnerable to transient and permanent failures. Current checkpoint/restart techniques are not suitable for systems with GPUs. Checkpointing for GPU systems present new and interesting challenges, primarily due to the natural differences imposed by the hardware design, the memory subsystem architecture, the massive number of threads, and the limited amount of synchronization among threads. Therefore, a checkpoint/restart technique suitable for GPU systems is needed. The goal of this work is to exploit higher levels of

Replication licensing and the DNA damage checkpoint

PubMed Central

Cook, Jeanette Gowen

2011-01-01

Accurate and timely duplication of chromosomal DNA requires that replication be coordinated with processes that ensure genome integrity. Significant advances in determining how the earliest steps in DNA replication are affected by DNA damage have highlighted some of the mechanisms to establish that coordination. Recent insights have expanded the relationship between the ATM and ATR-dependent checkpoint pathways and the proteins that bind and function at replication origins. These findings suggest that checkpoints and replication are more intimately associated than previously appreciated, even in the absence of exogenous DNA damage. This review summarizes some of these developments. PMID:19482602

Identifying security checkpoints locations to protect the major U.S. urban areas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cuellar-Hengartner, Leticia; Watkins, Daniel; Kubicek, Deborah A.

Transit networks are integral to the economy and to society, but at the same time they could allow terrorists to transport weapons of mass destruction into any city. Road networks are especially vulnerable, because they lack natural checkpoints unlike air networks that have security measures in place at all major airports. One approach to mitigate this risk is ensuring that every road route passes through at least one security checkpoint. Using the Ford-Fulkerson maximum-flow algorithm, we generate a minimum set of checkpoint locations within a ring-shaped buffer area surrounding the 50 largest US urban areas. We study how the numbermore » of checkpoints changes as we increase the buffer width to perform a cost-benefit analysis and to identify groups of cities that behave similarly. The set of required checkpoints is surprisingly small (10-124) despite the hundreds of thousands of road arcs in those areas, making it feasible to protect all major cities.« less

A smart checkpointing scheme for improving the reliability of clustering routing protocols.

PubMed

Min, Hong; Jung, Jinman; Kim, Bongjae; Cho, Yookun; Heo, Junyoung; Yi, Sangho; Hong, Jiman

2010-01-01

In wireless sensor networks, system architectures and applications are designed to consider both resource constraints and scalability, because such networks are composed of numerous sensor nodes with various sensors and actuators, small memories, low-power microprocessors, radio modules, and batteries. Clustering routing protocols based on data aggregation schemes aimed at minimizing packet numbers have been proposed to meet these requirements. In clustering routing protocols, the cluster head plays an important role. The cluster head collects data from its member nodes and aggregates the collected data. To improve reliability and reduce recovery latency, we propose a checkpointing scheme for the cluster head. In the proposed scheme, backup nodes monitor and checkpoint the current state of the cluster head periodically. We also derive the checkpointing interval that maximizes reliability while using the same amount of energy consumed by clustering routing protocols that operate without checkpointing. Experimental comparisons with existing non-checkpointing schemes show that our scheme reduces both energy consumption and recovery latency.

Identifying security checkpoints locations to protect the major U.S. urban areas

DOE PAGES

Cuellar-Hengartner, Leticia; Watkins, Daniel; Kubicek, Deborah A.; ...

2015-09-01

Transit networks are integral to the economy and to society, but at the same time they could allow terrorists to transport weapons of mass destruction into any city. Road networks are especially vulnerable, because they lack natural checkpoints unlike air networks that have security measures in place at all major airports. One approach to mitigate this risk is ensuring that every road route passes through at least one security checkpoint. Using the Ford-Fulkerson maximum-flow algorithm, we generate a minimum set of checkpoint locations within a ring-shaped buffer area surrounding the 50 largest US urban areas. We study how the numbermore » of checkpoints changes as we increase the buffer width to perform a cost-benefit analysis and to identify groups of cities that behave similarly. The set of required checkpoints is surprisingly small (10-124) despite the hundreds of thousands of road arcs in those areas, making it feasible to protect all major cities.« less

Analyzing checkpointing trends for applications on the IBM Blue Gene/P system.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naik, H.; Gupta, R.; Beckman, P.

Current petascale systems have tens of thousands of hardware components and complex system software stacks, which increase the probability of faults occurring during the lifetime of a process. Checkpointing has been a popular method of providing fault tolerance in high-end systems. While considerable research has been done to optimize checkpointing, in practice the method still involves a high-cost overhead for users. In this paper, we study the checkpointing overhead seen by applications running on leadership-class machines such as the IBM Blue Gene/P at Argonne National Laboratory. We study various applications and design a methodology to assist users in understanding andmore » choosing checkpointing frequency and reducing the overhead incurred. In particular, we study three popular applications -- the Grid-Based Projector-Augmented Wave application, the Carr-Parrinello Molecular Dynamics application, and a Nek5000 computational fluid dynamics application -- and analyze their memory usage and possible checkpointing trends on 32,768 processors of the Blue Gene/P system.« less

A Smart Checkpointing Scheme for Improving the Reliability of Clustering Routing Protocols

PubMed Central

Min, Hong; Jung, Jinman; Kim, Bongjae; Cho, Yookun; Heo, Junyoung; Yi, Sangho; Hong, Jiman

2010-01-01

In wireless sensor networks, system architectures and applications are designed to consider both resource constraints and scalability, because such networks are composed of numerous sensor nodes with various sensors and actuators, small memories, low-power microprocessors, radio modules, and batteries. Clustering routing protocols based on data aggregation schemes aimed at minimizing packet numbers have been proposed to meet these requirements. In clustering routing protocols, the cluster head plays an important role. The cluster head collects data from its member nodes and aggregates the collected data. To improve reliability and reduce recovery latency, we propose a checkpointing scheme for the cluster head. In the proposed scheme, backup nodes monitor and checkpoint the current state of the cluster head periodically. We also derive the checkpointing interval that maximizes reliability while using the same amount of energy consumed by clustering routing protocols that operate without checkpointing. Experimental comparisons with existing non-checkpointing schemes show that our scheme reduces both energy consumption and recovery latency. PMID:22163389

RING finger and WD repeat domain 3 (RFWD3) associates with replication protein A (RPA) and facilitates RPA-mediated DNA damage response.

PubMed

Liu, Shangfeng; Chu, Jessica; Yucer, Nur; Leng, Mei; Wang, Shih-Ya; Chen, Benjamin P C; Hittelman, Walter N; Wang, Yi

2011-06-24

DNA damage response is crucial for maintaining genomic integrity and preventing cancer by coordinating the activation of checkpoints and the repair of damaged DNA. Central to DNA damage response are the two checkpoint kinases ATM and ATR that phosphorylate a wide range of substrates. RING finger and WD repeat domain 3 (RFWD3) was initially identified as a substrate of ATM/ATR from a proteomic screen. Subsequent studies showed that RFWD3 is an E3 ubiquitin ligase that ubiquitinates p53 in vitro and positively regulates p53 levels in response to DNA damage. We report here that RFWD3 associates with replication protein A (RPA), a single-stranded DNA-binding protein that plays essential roles in DNA replication, recombination, and repair. Binding of RPA to single-stranded DNA (ssDNA), which is generated by DNA damage and repair, is essential for the recruitment of DNA repair factors to damaged sites and the activation of checkpoint signaling. We show that RFWD3 is physically associated with RPA and rapidly localizes to sites of DNA damage in a RPA-dependent manner. In vitro experiments suggest that the C terminus of RFWD3, which encompass the coiled-coil domain and the WD40 domain, is necessary for binding to RPA. Furthermore, DNA damage-induced phosphorylation of RPA and RFWD3 is dependent upon each other. Consequently, loss of RFWD3 results in the persistent foci of DNA damage marker γH2AX and the repair protein Rad51 in damaged cells. These findings suggest that RFWD3 is recruited to sites of DNA damage and facilitates RPA-mediated DNA damage signaling and repair.

Presaccadic perceptual facilitation effects depend on saccade execution: evidence from the stop-signal paradigm.

PubMed

Born, Sabine; Mottet, Isaline; Kerzel, Dirk

2014-03-05

Prior to the onset of a saccadic eye movement, perception is facilitated at the saccade target location. This has been attributed to a shift of attention. To test whether presaccadic attention shifts are strictly dependent on saccade execution, we examined whether they are found when observers are required to cancel the eye movement. We combined a dual task with the stop-signal paradigm: Subjects made saccades as quickly as possible to a cued location while discriminating a stimulus either at the saccade target or at the opposite location. A stop signal was presented on a subset of trials, asking subjects to cancel the eye movement. The delay of the stop signal was adjusted to yield successful inhibition of the saccade in 50% of trials. Results show similar perceptual facilitation at the saccade target for saccades with or without a stop signal, suggesting that presaccadic attention shifts are obligatory for all saccades. However, there was facilitation only when saccades were actually performed, not when observers successfully inhibited them. Thus, preparing an eye movement without subsequently executing it does not result in an attention shift. The results speak to a difference between saccade preparation and saccade programming. In light of the strong dependence on saccade execution, we discuss the functional role and causes of presaccadic attention shifts.

Tumor cell-associated immune checkpoint molecules - Drivers of malignancy and stemness.

PubMed

Marcucci, Fabrizio; Rumio, Cristiano; Corti, Angelo

2017-12-01

Inhibitory or stimulatory immune checkpoint molecules are expressed on a sizeable fraction of tumor cells in different tumor types. It was thought that the main function of tumor cell-associated immune checkpoint molecules would be the modulation (down- or upregulation) of antitumor immune responses. In recent years, however, it has become clear that the expression of immune checkpoint molecules on tumor cells has important consequences on the biology of the tumor cells themselves. In particular, a causal relationship between the expression of these molecules and the acquisition of malignant traits has been demonstrated. Thus, immune checkpoint molecules have been shown to promote the epithelial-mesenchymal transition of tumor cells, the acquisition of tumor-initiating potential and resistance to apoptosis and antitumor drugs, as well as the propensity to disseminate and metastasize. Herein, we review this evidence, with a main focus on PD-L1, the most intensively investigated tumor cell-associated immune checkpoint molecule and for which most information is available. Then, we discuss more concisely other tumor cell-associated immune checkpoint molecules that have also been shown to induce the acquisition of malignant traits, such as PD-1, B7-H3, B7-H4, Tim-3, CD70, CD28, CD137, CD40 and CD47. Open questions in this field as well as some therapeutic approaches that can be derived from this knowledge, are also addressed. Copyright © 2017 Elsevier B.V. All rights reserved.

Defective Cell Cycle Checkpoint Functions in Melanoma Are Associated with Altered Patterns of Gene Expression

PubMed Central

Kaufmann, William K.; Nevis, Kathleen R.; Qu, Pingping; Ibrahim, Joseph G.; Zhou, Tong; Zhou, Yingchun; Simpson, Dennis A.; Helms-Deaton, Jennifer; Cordeiro-Stone, Marila; Moore, Dominic T.; Thomas, Nancy E.; Hao, Honglin; Liu, Zhi; Shields, Janiel M.; Scott, Glynis A.; Sharpless, Norman E.

2009-01-01

Defects in DNA damage responses may underlie genetic instability and malignant progression in melanoma. Cultures of normal human melanocytes (NHMs) and melanoma lines were analyzed to determine whether global patterns of gene expression could predict the efficacy of DNA damage cell cycle checkpoints that arrest growth and suppress genetic instability. NHMs displayed effective G1 and G2 checkpoint responses to ionizing radiation-induced DNA damage. A majority of melanoma cell lines (11/16) displayed significant quantitative defects in one or both checkpoints. Melanomas with B-RAF mutations as a class displayed a significant defect in DNA damage G2 checkpoint function. In contrast the epithelial-like subtype of melanomas with wild-type N-RAS and B-RAF alleles displayed an effective G2 checkpoint but a significant defect in G1 checkpoint function. RNA expression profiling revealed that melanoma lines with defects in the DNA damage G1 checkpoint displayed reduced expression of p53 transcriptional targets, such as CDKN1A and DDB2, and enhanced expression of proliferation-associated genes, such as CDC7 and GEMININ. A Bayesian analysis tool was more accurate than significance analysis of microarrays for predicting checkpoint function using a leave-one-out method. The results suggest that defects in DNA damage checkpoints may be recognized in melanomas through analysis of gene expression. PMID:17597816

Asynchronous Two-Level Checkpointing Scheme for Large-Scale Adjoints in the Spectral-Element Solver Nek5000

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schanen, Michel; Marin, Oana; Zhang, Hong

Adjoints are an important computational tool for large-scale sensitivity evaluation, uncertainty quantification, and derivative-based optimization. An essential component of their performance is the storage/recomputation balance in which efficient checkpointing methods play a key role. We introduce a novel asynchronous two-level adjoint checkpointing scheme for multistep numerical time discretizations targeted at large-scale numerical simulations. The checkpointing scheme combines bandwidth-limited disk checkpointing and binomial memory checkpointing. Based on assumptions about the target petascale systems, which we later demonstrate to be realistic on the IBM Blue Gene/Q system Mira, we create a model of the expected performance of our checkpointing approach and validatemore » it using the highly scalable Navier-Stokes spectralelement solver Nek5000 on small to moderate subsystems of the Mira supercomputer. In turn, this allows us to predict optimal algorithmic choices when using all of Mira. We also demonstrate that two-level checkpointing is significantly superior to single-level checkpointing when adjoining a large number of time integration steps. To our knowledge, this is the first time two-level checkpointing had been designed, implemented, tuned, and demonstrated on fluid dynamics codes at large scale of 50k+ cores.« less

Optimal message log reclamation for independent checkpointing

NASA Technical Reports Server (NTRS)

Wang, Yi-Min; Fuchs, W. Kent

1993-01-01

Independent (uncoordinated) check pointing for parallel and distributed systems allows maximum process autonomy but suffers from possible domino effects and the associated storage space overhead for maintaining multiple checkpoints and message logs. In most research on check pointing and recovery, it was assumed that only the checkpoints and message logs older than the global recovery line can be discarded. It is shown how recovery line transformation and decomposition can be applied to the problem of efficiently identifying all discardable message logs, thereby achieving optimal garbage collection. Communication trace-driven simulation for several parallel programs is used to show the benefits of the proposed algorithm for message log reclamation.

Revised genetic requirements for the decatenation G2 checkpoint: the role of ATM

PubMed Central

Bower, Jacquelyn J.; Zhou, Yingchun; Zhou, Tong; Simpson, Dennis A.; Arlander, Sonnet J.; Paules, Richard S.; Cordeiro-Stone, Marila; Kaufmann, William K.

2010-01-01

The decatenation G2 checkpoint is proposed to delay cellular progression from G2 into mitosis when intertwined daughter chromatids are insufficiently decatenated. Previous studies indicated that the ATM- and Rad3-related (ATR) checkpoint kinase, but not the ataxia telangiectasia-mutated (ATM) kinase, was required for decatenation G2 checkpoint function. Here, we show that the method used to quantify decatenation G2 checkpoint function can influence the identification of genetic requirements for the checkpoint. Normal human diploid fibroblast (NHDF) lines responded to the topoisomerase II (topo II) catalytic inhibitor ICRF-193 with a stringent G2 arrest and a reduction in the mitotic index. While siRNA-mediated depletion of ATR and CHEK1 increased the mitotic index in ICRF-193 treated NHDF lines, depletion of these proteins did not affect the mitotic entry rate, indicating that the decatenation G2 checkpoint was functional. These results suggest that ATR and CHEK1 are not required for the decatenation G2 checkpoint, but may influence mitotic exit after inhibition of topo II. A re-evaluation of ataxia telangiectasia (AT) cell lines using the mitotic entry assay indicated that ATM was required for the decatenation G2 checkpoint. Three NHDF cell lines responded to ICRF-193 with a mean 98% inhibition of the mitotic entry rate. Examination of the mitotic entry rates in AT fibroblasts upon treatment with ICRF-193 revealed a significantly attenuated decatenation G2 checkpoint response, with a mean 59% inhibition of the mitotic entry rate. In addition, a normal lymphoblastoid line exhibited a 95% inhibition of the mitotic entry rate after incubation with ICRF-193, whereas two AT lymphoblastoid lines displayed only 36% and 20% inhibition of the mitotic entry rate. Stable depletion of ATM in normal human fibroblasts with short hairpin RNA also attenuated decatenation G2 checkpoint function by an average of 40%. Western immunoblot analysis demonstrated that treatment with ICRF

The pachytene checkpoint and its relationship to evolutionary patterns of polyploidization and hybrid sterility.

PubMed

Li, X C; Barringer, B C; Barbash, D A

2009-01-01

Sterility is a commonly observed phenotype in interspecific hybrids. Sterility may result from chromosomal or genic incompatibilities, and much progress has been made toward understanding the genetic basis of hybrid sterility in various taxa. The underlying mechanisms causing hybrid sterility, however, are less well known. The pachytene checkpoint is a meiotic surveillance system that many organisms use to detect aberrant meiotic products, in order to prevent the production of defective gametes. We suggest that activation of the pachytene checkpoint may be an important mechanism contributing to two types of hybrid sterility. First, the pachytene checkpoint may form the mechanistic basis of some gene-based hybrid sterility phenotypes. Second, the pachytene checkpoint may be an important mechanism that mediates chromosomal-based hybrid sterility phenotypes involving gametes with non-haploid (either non-reduced or aneuploid) chromosome sets. Studies in several species suggest that the strength of the pachytene checkpoint is sexually dimorphic, observations that warrant future investigation into whether such variation may contribute to differences in patterns of sterility between male and female interspecific hybrids. In addition, plants seem to lack the pachytene checkpoint, which correlates with increased production of unreduced gametes and a higher incidence of polyploid species in plants versus animals. Although the pachytene checkpoint occurs in many animals and in fungi, at least some of the genes that execute the pachytene checkpoint are different among organisms. This finding suggests that the penetrance of the pachytene checkpoint, and even its presence or absence can evolve rapidly. The surprising degree of evolutionary flexibility in this meiotic surveillance system may contribute to the observed variation in patterns of hybrid sterility and in rates of polyploidization.

mus304 encodes a novel DNA damage checkpoint protein required during Drosophila development

PubMed Central

Brodsky, Michael H.; Sekelsky, Jeff J.; Tsang, Garson; Hawley, R. Scott; Rubin, Gerald M.

2000-01-01

Checkpoints block cell cycle progression in eukaryotic cells exposed to DNA damaging agents. We show that several Drosophila homologs of checkpoint genes, mei-41, grapes, and 14-3-3ε, regulate a DNA damage checkpoint in the developing eye. We have used this assay to show that the mutagen-sensitive gene mus304 is also required for this checkpoint. mus304 encodes a novel coiled-coil domain protein, which is targeted to the cytoplasm. Similar to mei-41, mus304 is required for chromosome break repair and for genomic stability. mus304 animals also exhibit three developmental defects, abnormal bristle morphology, decreased meiotic recombination, and arrested embryonic development. We suggest that these phenotypes reflect distinct developmental consequences of a single underlying checkpoint defect. Similar mechanisms may account for the puzzling array of symptoms observed in humans with mutations in the ATM tumor suppressor gene. PMID:10733527

Next generation of immune checkpoint therapy in cancer: new developments and challenges.

PubMed

Marin-Acevedo, Julian A; Dholaria, Bhagirathbhai; Soyano, Aixa E; Knutson, Keith L; Chumsri, Saranya; Lou, Yanyan

2018-03-15

Immune checkpoints consist of inhibitory and stimulatory pathways that maintain self-tolerance and assist with immune response. In cancer, immune checkpoint pathways are often activated to inhibit the nascent anti-tumor immune response. Immune checkpoint therapies act by blocking or stimulating these pathways and enhance the body's immunological activity against tumors. Cytotoxic T lymphocyte-associated molecule-4 (CTLA-4), programmed cell death receptor-1 (PD-1), and programmed cell death ligand-1(PD-L1) are the most widely studied and recognized inhibitory checkpoint pathways. Drugs blocking these pathways are currently utilized for a wide variety of malignancies and have demonstrated durable clinical activities in a subset of cancer patients. This approach is rapidly extending beyond CTLA-4 and PD-1/PD-L1. New inhibitory pathways are under investigation, and drugs blocking LAG-3, TIM-3, TIGIT, VISTA, or B7/H3 are being investigated. Furthermore, agonists of stimulatory checkpoint pathways such as OX40, ICOS, GITR, 4-1BB, CD40, or molecules targeting tumor microenvironment components like IDO or TLR are under investigation. In this article, we have provided a comprehensive review of immune checkpoint pathways involved in cancer immunotherapy, and discuss their mechanisms and the therapeutic interventions currently under investigation in phase I/II clinical trials. We also reviewed the limitations, toxicities, and challenges and outline the possible future research directions.

Impaired tRNA nuclear export links DNA damage and cell-cycle checkpoint.

PubMed

Ghavidel, Ata; Kislinger, Thomas; Pogoutse, Oxana; Sopko, Richelle; Jurisica, Igor; Emili, Andrew

2007-11-30

In response to genotoxic stress, cells evoke a plethora of physiological responses collectively aimed at enhancing viability and maintaining the integrity of the genome. Here, we report that unspliced tRNA rapidly accumulates in the nuclei of yeast Saccharomyces cerevisiae after DNA damage. This response requires an intact MEC1- and RAD53-dependent signaling pathway that impedes the nuclear export of intron-containing tRNA via differential relocalization of the karyopherin Los1 to the cytoplasm. The accumulation of unspliced tRNA in the nucleus signals the activation of Gcn4 transcription factor, which, in turn, contributes to cell-cycle arrest in G1 in part by delaying accumulation of the cyclin Cln2. The regulated nucleocytoplasmic tRNA trafficking thus constitutes an integral physiological adaptation to DNA damage. These data further illustrate how signal-mediated crosstalk between distinct functional modules, namely, tRNA nucleocytoplasmic trafficking, protein synthesis, and checkpoint execution, allows for functional coupling of tRNA biogenesis and cell-cycle progression.

Chromatin Remodeling Factors Isw2 and Ino80 Regulate Checkpoint Activity and Chromatin Structure in S Phase

PubMed Central

Lee, Laura; Rodriguez, Jairo; Tsukiyama, Toshio

2015-01-01

When cells undergo replication stress, proper checkpoint activation and deactivation are critical for genomic stability and cell survival and therefore must be highly regulated. Although mechanisms of checkpoint activation are well studied, mechanisms of checkpoint deactivation are far less understood. Previously, we reported that chromatin remodeling factors Isw2 and Ino80 attenuate the S-phase checkpoint activity in Saccharomyces cerevisiae, especially during recovery from hydroxyurea. In this study, we found that Isw2 and Ino80 have a more pronounced role in attenuating checkpoint activity during late S phase in the presence of methyl methanesulfonate (MMS). We therefore screened for checkpoint factors required for Isw2 and Ino80 checkpoint attenuation in the presence of MMS. Here we demonstrate that Isw2 and Ino80 antagonize checkpoint activators and attenuate checkpoint activity in S phase in MMS either through a currently unknown pathway or through RPA. Unexpectedly, we found that Isw2 and Ino80 increase chromatin accessibility around replicating regions in the presence of MMS through a novel mechanism. Furthermore, through growth assays, we provide additional evidence that Isw2 and Ino80 partially counteract checkpoint activators specifically in the presence of MMS. Based on these results, we propose that Isw2 and Ino80 attenuate S-phase checkpoint activity through a novel mechanism. PMID:25701287

Understanding checkpointing overheads on massive-scale systems : analysis of the IBM Blue Gene/P system.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, R.; Naik, H.; Beckman, P.

Providing fault tolerance in high-end petascale systems, consisting of millions of hardware components and complex software stacks, is becoming an increasingly challenging task. Checkpointing continues to be the most prevalent technique for providing fault tolerance in such high-end systems. Considerable research has focussed on optimizing checkpointing; however, in practice, checkpointing still involves a high-cost overhead for users. In this paper, we study the checkpointing overhead seen by various applications running on leadership-class machines like the IBM Blue Gene/P at Argonne National Laboratory. In addition to studying popular applications, we design a methodology to help users understand and intelligently choose anmore » optimal checkpointing frequency to reduce the overall checkpointing overhead incurred. In particular, we study the Grid-Based Projector-Augmented Wave application, the Carr-Parrinello Molecular Dynamics application, the Nek5000 computational fluid dynamics application and the Parallel Ocean Program application-and analyze their memory usage and possible checkpointing trends on 65,536 processors of the Blue Gene/P system.« less

Myasthenia triggered by immune checkpoint inhibitors: New case and literature review.

PubMed

Gonzalez, Natalia L; Puwanant, Araya; Lu, Angela; Marks, Stanley M; Živković, Saša A

2017-03-01

Immune checkpoint molecules are potent regulators of immunologic homeostasis that prevent the development of autoimmunity while maintaining self-tolerance. Inhibitors of immune checkpoint molecules are used as immunotherapy in the treatment of melanoma and different types of refractory cancer, and can trigger various autoimmune complications including myositis and myasthenia gravis. We describe a case of generalized myasthenia gravis induced by pembrolizumab and review 11 other cases. Five patients also had elevated serum CK levels ranging from 1200 to 8729 IU/L, and biopsy showed myositis in one. Severity was highly variable as symptoms normalized spontaneously in one patient, but three others developed myasthenic crisis (including two with fatal outcomes). Steroids have been recommended as a preferred treatment of autoimmune complications of immune-checkpoint inhibitors. Myasthenia gravis should be considered when weakness, diplopia or bulbar symptoms are seen after treatment with immune checkpoint inhibitors, and additional studies are needed to characterize association with hyperCKemia. Copyright © 2017 Elsevier B.V. All rights reserved.

Expression of immune checkpoints in T cells of esophageal cancer patients.

PubMed

Xie, Jinhua; Wang, Ji; Cheng, Shouliang; Zheng, Liangfeng; Ji, Feiyue; Yang, Lin; Zhang, Yan; Ji, Haoming

2016-09-27

Inhibition of immune checkpoint proteins (checkpoints) has become a promising anti-esophageal cancer strategy. We here tested expressions of immune checkpoints in human esophageal cancers. Our results showed the expressions of many immune checkpoints, including CD28, CD27, CD137L, programmed death 1 (PD-1), T cell immunoglobulin mucin-3 (TIM-3), T cell Ig and ITIM domain (TIGIT), CD160, cytotoxic T lymphocyte antigen 4 (CTLA-4), CD200, CD137 and CD158, were dysregulated in peripheral T cells of esophageal cancer patients. Further, the expressions of PD-1, TIM-3 and TIGIT were upregulated in tumor infiltrating lymphocytes (TILs), which might be associated with TILs exhaustion. Meanwhile, the expressions of PD-1 and TIM-3 on CD4+ T cells were closely associated with clinic pathological features of esophageal cancer patients. These results indicate that co-inhibitory receptors PD-1, TIM-3 and TIGIT may be potential therapeutic oncotargets for esophageal cancer.

Topoisomerase II Inhibitors and Poisons, and the Influence of Cell Cycle Checkpoints.

PubMed

D Arcy, Nicholas; Gabrielli, Brian

2017-01-01

Interactions between the decatenation checkpoint and Topoisomerase II (TopoII) are vital for maintaining integrity of the genome. Agents that target this enzyme have been in clinical use in cancer therapy for over 30 years with great success. The types of compounds that have been developed to target TopoII are broadly divided into poisons and catalytic inhibitors. The TopoII poisons are in clinical use as anti-cancer therapies, although in common to most chemotherapeutic agents, they display considerable normal tissue toxicity. Inhibition of the TopoIIb isoform has been implicated in this cytotoxicity. Response to TopoII active agents is determined by several factors, but cell cycle checkpoints play a large role in sensitivity and resistance. The G2/M phase checkpoints are of particular importance in considering the effectiveness of these drugs and are reviewed in this article. Functionality of the ATM dependent decatenation checkpoint may represent a new avenue for selective cancer therapy. Here we review the function of TopoII, the anti-cancer mechanisms and limitations of current catalytic inhibitors and poisons, and their influence on cell cycle checkpoints. We will also assess potential new mechanisms for targeting this enzyme to limit normal tissue toxicity, and how the cell cycle checkpoint triggered by these drugs may provide an alternative and possibly better target for novel therapies. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Immune-Checkpoint Blockade and Active Immunotherapy for Glioma

PubMed Central

Ahn, Brian J.; Pollack, Ian F.; Okada, Hideho

2013-01-01

Cancer immunotherapy has made tremendous progress, including promising results in patients with malignant gliomas. Nonetheless, the immunological microenvironment of the brain and tumors arising therein is still believed to be suboptimal for sufficient antitumor immune responses for a variety of reasons, including the operation of “immune-checkpoint” mechanisms. While these mechanisms prevent autoimmunity in physiological conditions, malignant tumors, including brain tumors, actively employ these mechanisms to evade from immunological attacks. Development of agents designed to unblock these checkpoint steps is currently one of the most active areas of cancer research. In this review, we summarize recent progresses in the field of brain tumor immunology with particular foci in the area of immune-checkpoint mechanisms and development of active immunotherapy strategies. In the last decade, a number of specific monoclonal antibodies designed to block immune-checkpoint mechanisms have been developed and show efficacy in other cancers, such as melanoma. On the other hand, active immunotherapy approaches, such as vaccines, have shown encouraging outcomes. We believe that development of effective immunotherapy approaches should ultimately integrate those checkpoint-blockade agents to enhance the efficacy of therapeutic approaches. With these agents available, it is going to be quite an exciting time in the field. The eventual success of immunotherapies for brain tumors will be dependent upon not only an in-depth understanding of immunology behind the brain and brain tumors, but also collaboration and teamwork for the development of novel trials that address multiple layers of immunological challenges in gliomas. PMID:24202450

Immune checkpoint inhibitors for metastatic bladder cancer.

PubMed

Massari, Francesco; Di Nunno, Vincenzo; Cubelli, Marta; Santoni, Matteo; Fiorentino, Michelangelo; Montironi, Rodolfo; Cheng, Liang; Lopez-Beltran, Anto; Battelli, Nicola; Ardizzoni, Andrea

2018-03-01

Chemotherapy has represented the standard therapy for unresectable or metastatic urothelial carcinoma for more than 20 years. The growing knowledge of the interaction between tumour and immune system has led to the advent of new classes of drugs, the immune-checkpoints inhibitors, which are intended to change the current scenario. To date, immunotherapy is able to improve the overall responses and survival. Moreover, thanks to its safety profile immune-checkpoint inhibitors could be proposed also to patients unfit for standard chemotherapy. No doubts that these agents have started a revolution expected for years, but despite this encouraging results it appears clear that not all subjects respond to these agents and requiring the development of reliable predictive response factors able to isolate patients who can more benefit from these treatments as well as new strategies aimed to improve immunotherapy clinical outcome. In this review we describe the active or ongoing clinical trials involving Programmed Death Ligand 1 (PD-L1), Programmed Death receptor 1 (PD-1) and Cytotoxic-T Lymphocyte Antigen 4 (CTLA 4) inhibitors in urothelial carcinoma focusing our attention on the developing new immune-agents and combination strategies with immune-checkpoint inhibitors. Copyright © 2017 Elsevier Ltd. All rights reserved.

Immune checkpoint inhibitors for nonsmall cell lung cancer treatment.

PubMed

Chen, Yuh-Min

2017-01-01

Immune checkpoint inhibition with blocking antibodies that target cytotoxic T-lymphocyte antigen-4 (CTLA-4) and the programmed cell death protein 1 (PD-1) pathway [PD-1/programmed death-ligand 1 (PD-L1)] have demonstrated promise in a variety of malignancies. While ipilimumab has been approved as a CTLA-4 blocking antibody by the US Food and Drug Administration for the treatment of advanced melanoma, it is still not approved for lung cancer treatment. In contrast, nivolumab and pembrolizumab, both PD-1 blocking antibodies, have been approved for second-line treatment of nonsmall cell lung cancer in 2015 because of their high potency and long-lasting effects in some patient subgroups. Other PD-1 and PD-L1 monoclonal antibodies are also in active development phase. Treatment with such immune checkpoint inhibitors is associated with a unique pattern of immune-related adverse events or side effects. Combination approaches involving CTLA-4 and PD-1/PD-L1 blockade or checkpoint inhibitors with chemotherapy or radiotherapy are being investigated to determine whether they may enhance the efficacy of treatment. Despite many challenges ahead, immunotherapy with checkpoint inhibitors has already become a new and important treatment modality for lung cancer in the last decade following the discovery of targeted therapy. Copyright © 2016. Published by Elsevier Taiwan LLC.

Checkpoint inhibitors in endometrial cancer: preclinical rationale and clinical activity.

PubMed

Mittica, Gloria; Ghisoni, Eleonora; Giannone, Gaia; Aglietta, Massimo; Genta, Sofia; Valabrega, Giorgio

2017-10-27

Treatment of advanced and recurrent endometrial cancer (EC) is still an unmet need for oncologists and gynecologic oncologists. The Cancer Genome Atlas Research Network (TCGA) recently provided a new genomic classification, dividing EC in four subgroups. Two types of EC, the polymerase epsilon (POLE)-ultra-mutated and the microsatellite instability-hyper-mutated (MSI-H), are characterized by a high mutation rate providing the rationale for a potential activity of checkpoint inhibitors. We analyzed all available evidence supporting the role of tumor microenvironment (TME) in EC development and the therapeutic implications offered by immune checkpoint inhibitors in this setting. We performed a review on Pubmed with Mesh keywords 'endometrial cancer' and the name of each checkpoint inhibitor discussed in the article. The same search was operated on clinicaltrial.gov to identify ongoing clinical trials exploring PD-1/PD-L1 and CTLA-4 axis in EC, particularly focusing on POLE-ultra-muted and MSI-H cancer types. POLE-ultra-mutated and MSI-H ECs showed an active TME expressing high number of neo-antigens and an elevated amount of tumor infiltrating lymphocytes (TILs). Preliminary results from a phase-1 clinical trial (KEYNOTE-028) demonstrated antitumor activity of Pembrolizumab in EC. Moreover, both Pembrolizumab and Nivolumab reported durable clinical responses in POLE-ultra-mutated patients. Immune checkpoint inhibitors are an attractive option in POLE-ultra-mutated and MSI-H ECs. Future investigations in these subgroups include combinations of checkpoints inhibitors with chemotherapy and small tyrosine kinase inhibitors (TKIs) to enhance a more robust intra-tumoral immune response.

Development of small-molecule immune checkpoint inhibitors of PD-1/PD-L1 as a new therapeutic strategy for tumour immunotherapy.

PubMed

Li, Kui; Tian, Hongqi

2018-02-20

Cancer immunotherapy has been increasingly utilised to treat advanced malignancies. The signalling network of immune checkpoints has attracted considerable attention. Immune checkpoint inhibitors are revolutionising the treatment options and expectations for patients with cancer. The reported clinical success of targeting the T-cell immune checkpoint receptors PD-1/PD-L1 has demonstrated the importance of immune modulation. Indeed, antibodies binding to PD-1 or PD-L1 have shown remarkable efficacy. However, antibody drugs have many disadvantages, such as their production cost, stability, and immunogenicity and, therefore, small-molecule inhibitors of PD-1 and its ligand PD-L1 are being introduced. Small-molecule inhibitors could offer inherent advantages in terms of pharmacokinetics and druggability, thereby providing additional methods for cancer treatment and achieving better therapeutic effects. In this review, we first discuss how PD-1/PD-L1-targeting inhibitors modulate the relationship between immune cells and tumour cells in tumour immunotherapy. Second, we discuss how the immunomodulatory potential of these inhibitors can be exploited via rational combinations with immunotherapy and targeted therapy. Third, this review is the first to summarise the current clinical and preclinical evidence regarding small-molecule inhibitors of the PD-1/PD-L1 immune checkpoint, considering features and responses related to the tumours and to the host immune system.

Epigenetic regulation of immune checkpoints: another target for cancer immunotherapy?

PubMed

Ali, Mahmoud A; Matboli, Marwa; Tarek, Marwa; Reda, Maged; Kamal, Kamal M; Nouh, Mahmoud; Ashry, Ahmed M; El-Bab, Ahmed Fath; Mesalam, Hend A; Shafei, Ayman El-Sayed; Abdel-Rahman, Omar

2017-01-01

Epigenetic changes in oncogenes and tumor-suppressor genes contribute to carcinogenesis. Understanding the epigenetic and genetic components of tumor immune evasion is crucial. Few cancer genetic mutations have been linked to direct correlations with immune evasion. Studies on the epigenetic modulation of the immune checkpoints have revealed a critical interaction between epigenetic and immune modulation. Epigenetic modifiers can activate many silenced genes. Some of them are immune checkpoints regulators that turn on immune responses and others turn them off resulting in immune evasion. Many forms of epigenetic inheritance mechanisms may play a role in regulation of immune checkpoints including: covalent modifications, noncoding RNA and histone modifications. In this review, we will show how the potential interaction between epigenetic and immune modulation may lead to new approaches for specific epigenome/immunome-targeted therapies for cancer.

Reconstitution of RPA-covered single-stranded DNA-activated ATR-Chk1 signaling.

PubMed

Choi, Jun-Hyuk; Lindsey-Boltz, Laura A; Kemp, Michael; Mason, Aaron C; Wold, Marc S; Sancar, Aziz

2010-08-03

ATR kinase is a critical upstream regulator of the checkpoint response to various forms of DNA damage. Previous studies have shown that ATR is recruited via its binding partner ATR-interacting protein (ATRIP) to replication protein A (RPA)-covered single-stranded DNA (RPA-ssDNA) generated at sites of DNA damage where ATR is then activated by TopBP1 to phosphorylate downstream targets including the Chk1 signal transducing kinase. However, this critical feature of the human ATR-initiated DNA damage checkpoint signaling has not been demonstrated in a defined system. Here we describe an in vitro checkpoint system in which RPA-ssDNA and TopBP1 are essential for phosphorylation of Chk1 by the purified ATR-ATRIP complex. Checkpoint defective RPA mutants fail to activate ATR kinase in this system, supporting the conclusion that this system is a faithful representation of the in vivo reaction. Interestingly, we find that an alternative form of RPA (aRPA), which does not support DNA replication, can substitute for the checkpoint function of RPA in vitro, thus revealing a potential role for aRPA in the activation of ATR kinase. We also find that TopBP1 is recruited to RPA-ssDNA in a manner dependent on ATRIP and that the N terminus of TopBP1 is required for efficient recruitment and activation of ATR kinase.

The point of no return: The poly(A)-associated elongation checkpoint.

PubMed

Tellier, Michael; Ferrer-Vicens, Ivan; Murphy, Shona

2016-01-01

Cyclin-dependent kinases play critical roles in transcription by RNA polymerase II (pol II) and processing of the transcripts. For example, CDK9 regulates transcription of protein-coding genes, splicing, and 3' end formation of the transcripts. Accordingly, CDK9 inhibitors have a drastic effect on the production of mRNA in human cells. Recent analyses indicate that CDK9 regulates transcription at the early-elongation checkpoint of the vast majority of pol II-transcribed genes. Our recent discovery of an additional CDK9-regulated elongation checkpoint close to poly(A) sites adds a new layer to the control of transcription by this critical cellular kinase. This novel poly(A)-associated checkpoint has the potential to powerfully regulate gene expression just before a functional polyadenylated mRNA is produced: the point of no return. However, many questions remain to be answered before the role of this checkpoint becomes clear. Here we speculate on the possible biological significance of this novel mechanism of gene regulation and the players that may be involved.

The point of no return: The poly(A)-associated elongation checkpoint

PubMed Central

Tellier, Michael; Ferrer-Vicens, Ivan; Murphy, Shona

2016-01-01

abstract Cyclin-dependent kinases play critical roles in transcription by RNA polymerase II (pol II) and processing of the transcripts. For example, CDK9 regulates transcription of protein-coding genes, splicing, and 3′ end formation of the transcripts. Accordingly, CDK9 inhibitors have a drastic effect on the production of mRNA in human cells. Recent analyses indicate that CDK9 regulates transcription at the early-elongation checkpoint of the vast majority of pol II-transcribed genes. Our recent discovery of an additional CDK9-regulated elongation checkpoint close to poly(A) sites adds a new layer to the control of transcription by this critical cellular kinase. This novel poly(A)-associated checkpoint has the potential to powerfully regulate gene expression just before a functional polyadenylated mRNA is produced: the point of no return. However, many questions remain to be answered before the role of this checkpoint becomes clear. Here we speculate on the possible biological significance of this novel mechanism of gene regulation and the players that may be involved. PMID:26853452

Role for the Silencing Protein Dot1 in Meiotic Checkpoint Control

PubMed Central

San-Segundo, Pedro A.; Roeder, G. Shirleen

2000-01-01

During the meiotic cell cycle, a surveillance mechanism called the “pachytene checkpoint” ensures proper chromosome segregation by preventing meiotic progression when recombination and chromosome synapsis are defective. The silencing protein Dot1 (also known as Pch1) is required for checkpoint-mediated pachytene arrest of the zip1 and dmc1 mutants of Saccharomyces cerevisiae. In the absence of DOT1, the zip1 and dmc1 mutants inappropriately progress through meiosis, generating inviable meiotic products. Other components of the pachytene checkpoint include the nucleolar protein Pch2 and the heterochromatin component Sir2. In dot1, disruption of the checkpoint correlates with the loss of concentration of Pch2 and Sir2 in the nucleolus. In addition to its checkpoint function, Dot1 blocks the repair of meiotic double-strand breaks by a Rad54-dependent pathway of recombination between sister chromatids. In vegetative cells, mutation of DOT1 results in delocalization of Sir3 from telomeres, accounting for the impaired telomeric silencing in dot1. PMID:11029058

[Immune checkpoints inhibitors: Recent data from ASCO's meeting 2017 and perspectives].

PubMed

Kfoury, Maria; Disdero, Valentine; Vicier, Cécilé; Le Saux, Olivia; Gougis, Paul; Sajous, Christophe; Vignot, Stéphane

2018-06-19

Immune checkpoint inhibitors anti-PD-1, anti-PD-L1 and anti-CTLA-4 have been in development in several indications and have changed the face of cancer patients' management. Cancer immunotherapy was central in ASCO's meeting 2017. The identification of patients who could benefit most from immune checkpoint inhibitors is essential. The predictive value of PD-L1 status remains insufficient to select patients who could respond to immunotherapy. An extended search for new biomarkers predictive of response (INF-γ, mutational load) is ongoing, in order to better select responders. Immune checkpoint inhibitors have mainly been developed as monotherapy. However, the low response rate, between 10 and 30%, and the occurrence of resistance, contributes to the increment of new therapeutic strategies. This review summarizes the results of combination trials of two immune checkpoint inhibitors, combination of immunotherapy with conventional chemotherapy, radiotherapy or targeted therapies active on the oncogenic addiction pathway. Copyright © 2018 Société Française du Cancer. Published by Elsevier Masson SAS. All rights reserved.

PD-1-PD-L1 immune-checkpoint blockade in malignant lymphomas.

PubMed

Wang, Yi; Wu, Ling; Tian, Chen; Zhang, Yizhuo

2018-02-01

Tumor cells can evade immune surveillance through overexpressing the ligands of checkpoint receptors on tumor cells or adjacent cells, leading T cells to anergy or exhaustion. Growing evidence of the interaction between tumor cells and microenvironment promoted the emergence of immune-checkpoint blockade. By targeting programmed cell death-1 (PD-1) pathway, cytotoxic activity of T cell is enhanced significantly and tumor cell lysis is induced subsequently. Currently, various antibodies against PD-1 and programmed death-ligand 1 (PD-L1) are under clinical studies in lymphomas. In this review, we outline the rationale for investigation of PD-1-PD-L1 immune-checkpoint blockade in lymphomas and discuss their prospect of applications in clinical treatment.

Trial watch: Immune checkpoint blockers for cancer therapy.

PubMed

Vanpouille-Box, Claire; Lhuillier, Claire; Bezu, Lucillia; Aranda, Fernando; Yamazaki, Takahiro; Kepp, Oliver; Fucikova, Jitka; Spisek, Radek; Demaria, Sandra; Formenti, Silvia C; Zitvogel, Laurence; Kroemer, Guido; Galluzzi, Lorenzo

2017-01-01

Immune checkpoint blockers (ICBs) are literally revolutionizing the clinical management of an ever more diversified panel of oncological indications. Although considerable attention persists around the inhibition of cytotoxic T lymphocyte-associated protein 4 (CTLA4) and programmed cell death 1 (PDCD1, best known as PD-1) signaling, several other co-inhibitory T-cell receptors are being evaluated as potential targets for the development of novel ICBs. Moreover, substantial efforts are being devoted to the identification of biomarkers that reliably predict the likelihood of each patient to obtain clinical benefits from ICBs in the absence of severe toxicity. Tailoring the delivery of specific ICBs or combinations thereof to selected patient populations in the context of precision medicine programs constitutes indeed a major objective of the future of ICB-based immunotherapy. Here, we discuss recent preclinical and clinical advances on the development of ICBs for oncological indications.

Checkpointing Shared Memory Programs at the Application-level

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bronevetsky, G; Schulz, M; Szwed, P

2004-09-08

Trends in high-performance computing are making it necessary for long-running applications to tolerate hardware faults. The most commonly used approach is checkpoint and restart(CPR)-the state of the computation is saved periodically on disk, and when a failure occurs, the computation is restarted from the last saved state. At present, it is the responsibility of the programmer to instrument applications for CPR. Our group is investigating the use of compiler technology to instrument codes to make them self-checkpointing and self-restarting, thereby providing an automatic solution to the problem of making long-running scientific applications resilient to hardware faults. Our previous work focusedmore » on message-passing programs. In this paper, we describe such a system for shared-memory programs running on symmetric multiprocessors. The system has two components: (i)a pre-compiler for source-to-source modification of applications, and (ii) a runtime system that implements a protocol for coordinating CPR among the threads of the parallel application. For the sake of concreteness, we focus on a non-trivial subset of OpenMP that includes barriers and locks. One of the advantages of this approach is that the ability to tolerate faults becomes embedded within the application itself, so applications become self-checkpointing and self-restarting on any platform. We demonstrate this by showing that our transformed benchmarks can checkpoint and restart on three different platforms (Windows/x86, Linux/x86, and Tru64/Alpha). Our experiments show that the overhead introduced by this approach is usually quite small; they also suggest ways in which the current implementation can be tuned to reduced overheads further.« less

Combination Controversies: Checkpoint Inhibition Alone or in Combination for the Treatment of Melanoma?

PubMed

Warner, Allison Betof; Postow, Michael A

2018-05-15

The immune checkpoint inhibitors ipilimumab, nivolumab, and pembrolizumab have dramatically improved outcomes for patients with metastatic melanoma; however, not all patients benefit from monotherapy with these agents. To address this issue, complementary combinations of immunotherapy are increasingly being explored as a strategy to improve outcomes. However, combinatorial approaches come with heightened risk of toxicity. In this review, we highlight combinations for which there are prospective data from clinical trials. The combinations discussed include ipilimumab plus anti-programmed death 1 agents, ipilimumab plus granulocyte-macrophage colony-stimulating factor, checkpoint inhibitor plus talimogene laherparepvec, ipilimumab plus chemotherapy, checkpoint inhibitor plus BRAF/MEK targeted therapy, and checkpoint inhibition plus radiation therapy. We discuss data regarding the efficacy and toxicity of combination therapy, and we identify clinical scenarios that may favor treatment with combination therapy.

Immune checkpoint inhibitor colitis: the flip side of the wonder drugs.

PubMed

Assarzadegan, Naziheh; Montgomery, Elizabeth; Anders, Robert A

2018-01-01

Immune checkpoint inhibitors block the co-inhibitory receptors on T cells to activate their cytotoxic immune function and are rapidly being explored for the treatment of various advanced-stage malignancies. These novel drugs have already significantly increased survival rates. The first available immune checkpoint inhibitors were cytotoxic T lymphocyte antigen 4 (CTLA-4) inhibitors (such as ipilimumab), followed by programmed cell death protein 1 (PD-1) and programmed cell death protein ligand 1 (PD-L1) inhibitors (such as pembrolizumab and nivolumab). Anti-PD-1 and anti-PD-L1 therapies have demonstrated better efficacy and tolerability and less severe adverse effects compared to anti-CTLA-4 agents. Idelalisib, a PI3Kδ isoform inhibitor, is another immunotherapeutic agent that is often classified separately and is currently used in treatment of chronic lymphocytic leukemia and non-Hodgkin lymphomas. Despite successful therapeutic responses, immune-related adverse events have been reported with the use of these agents. The gastrointestinal side effects, particularly diarrhea, are among the most commonly reported symptoms. The histologic features of immune checkpoint inhibitor-associated colitis show a spectrum of patterns of injury among various drug classes. There is significant overlap between immune checkpoint inhibitor-associated colitis and other colitides, making the differential diagnosis difficult-especially in the absence of clinical history. The histopathology data on immune checkpoint inhibitor-associated colitis are limited. Here we review clinical features as well as various histologic patterns of colitis associated with these groups of medications.

Checkpoint repair for high-performance out-of-order execution machines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hwu, W.M.W.; Patt, Y.N.

Out-or-order execution and branch prediction are two mechanisms that can be used profitably in the design of supercomputers to increase performance. Proper exception handling and branch prediction miss handling in an out-of-order execution machine to require some kind of repair mechanism which can restore the machine to a known previous state. In this paper the authors present a class of repair mechanisms using the concept of checkpointing. The authors derive several properties of checkpoint repair mechanisms. In addition, they provide algorithms for performing checkpoint repair that incur little overhead in time and modest cost in hardware, which also require nomore » additional complexity or time for use with write-back cache memory systems than they do with write-through cache memory systems, contrary to statements made by previous researchers.« less

Mutant p53 perturbs DNA replication checkpoint control through TopBP1 and Treslin.

PubMed

Liu, Kang; Lin, Fang-Tsyr; Graves, Joshua D; Lee, Yu-Ju; Lin, Weei-Chin

2017-05-09

Accumulating evidence supports the gain-of-function of mutant forms of p53 (mutp53s). However, whether mutp53 directly perturbs the DNA replication checkpoint remains unclear. Previously, we have demonstrated that TopBP1 forms a complex with mutp53s and mediates their gain-of-function through NF-Y and p63/p73. Akt phosphorylates TopBP1 and induces its oligomerization, which inhibits its ATR-activating function. Here we show that various contact and conformational mutp53s bypass Akt to induce TopBP1 oligomerization and attenuate ATR checkpoint response during replication stress. The effect on ATR response caused by mutp53 can be exploited in a synthetic lethality strategy, as depletion of another ATR activator, DNA2, in mutp53-R273H-expressing cancer cells renders cells hypersensitive to cisplatin. Expression of mutp53-R273H also makes cancer cells more sensitive to DNA2 depletion or DNA2 inhibitors. In addition to ATR-activating function during replication stress, TopBP1 interacts with Treslin in a Cdk-dependent manner to initiate DNA replication during normal growth. We find that mutp53 also interferes with TopBP1 replication function. Several contact, but not conformational, mutp53s enhance the interaction between TopBP1 and Treslin and promote DNA replication despite the presence of a Cdk2 inhibitor. Together, these data uncover two distinct mechanisms by which mutp53 enhances DNA replication: ( i ) Both contact and conformational mutp53s can bind TopBP1 and attenuate the checkpoint response to replication stress, and ( ii ) during normal growth, contact (but not conformational) mutp53s can override the Cdk2 requirement to promote replication by facilitating the TopBP1/Treslin interaction.

Structure and substrate recruitment of the human spindle checkpoint kinase Bub1.

PubMed

Kang, Jungseog; Yang, Maojun; Li, Bing; Qi, Wei; Zhang, Chao; Shokat, Kevan M; Tomchick, Diana R; Machius, Mischa; Yu, Hongtao

2008-11-07

In mitosis, the spindle checkpoint detects a single unattached kinetochore, inhibits the anaphase-promoting complex or cyclosome (APC/C), and prevents premature sister chromatid separation. The checkpoint kinase Bub1 contributes to checkpoint sensitivity through phosphorylating the APC/C activator, Cdc20, and inhibiting APC/C catalytically. We report here the crystal structure of the kinase domain of Bub1, revealing the requirement of an N-terminal extension for its kinase activity. Though the activation segment of Bub1 is ordered and has structural features indicative of active kinases, the C-terminal portion of this segment sterically restricts substrate access to the active site. Bub1 uses docking motifs, so-called KEN boxes, outside its kinase domain to recruit Cdc20, one of two known KEN box receptors. The KEN boxes of Bub1 are required for the spindle checkpoint in human cells. Therefore, its unusual active-site conformation and mode of substrate recruitment suggest that Bub1 has an exquisitely tuned specificity for Cdc20.

Checkpoint kinase 1-induced phosphorylation of O-linked β-N-acetylglucosamine transferase regulates the intermediate filament network during cytokinesis.

PubMed

Li, Zhe; Li, Xueyan; Nai, Shanshan; Geng, Qizhi; Liao, Ji; Xu, Xingzhi; Li, Jing

2017-12-01

Checkpoint kinase 1 (Chk1) is a kinase instrumental for orchestrating DNA replication, DNA damage checkpoints, the spindle assembly checkpoint, and cytokinesis. Despite Chk1's pivotal role in multiple cellular processes, many of its substrates remain elusive. Here, we identified O- linked β- N -acetylglucosamine ( O -GlcNAc)-transferase (OGT) as one of Chk1's substrates. We found that Chk1 interacts with and phosphorylates OGT at Ser-20, which not only stabilizes OGT, but also is required for cytokinesis. Phospho-specific antibodies of OGT-pSer-20 exhibited specific signals at the midbody of the cell, consistent with midbody localization of OGT as reported previously. Moreover, phospho-deficient OGT (S20A) cells attenuated cellular O -GlcNAcylation levels and also reduced phosphorylation of Ser-71 in the cytoskeletal protein vimentin, a modification critical for severing vimentin filament during cytokinesis. Consequently, elongated vimentin bridges were observed in cells depleted of OGT via an si OGT- based approach. Lastly, expression of plasmids resistant to si OGT efficiently rescued the vimentin bridge phenotype, but the OGT-S20A rescue plasmids did not. Our results suggest a Chk1-OGT-vimentin pathway that regulates the intermediate filament network during cytokinesis. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Immune checkpoint inhibitors in lung cancer: current status and future directions.

PubMed

Fan, Yun; Mao, Weimin

2017-04-01

Recently, the immune checkpoint inhibitors that target programmed death 1 (PD-1)/programmed death ligand 1 (PD-L1) have made a breakthrough in treating advanced non-small cell lung cancer (NSCLC) with the efficacy of approximately 20%; among which, nivolumab has acquired treatment indications in lung squamous cell carcinoma. The inhibitors targeting cytotoxic T lymphocyte associated antigen 4 (CTLA-4) are also undergoing clinical trials. Researches on immune checkpoint inhibitors have been rapidly implemented in a variety of different types of lung cancer, such as small cell lung cancer (SCLC) and locally advanced NSCLC, and these inhibitors began to be applied in combination with some established treatments, including chemotherapy, targeting therapy and radiotherapy. Undoubtedly, the immune checkpoint inhibitors have become a hot spot in the research and treatment of lung cancer. However, many problems wait to be solved, such as searching for ideal biomarkers, constituting the best criteria for curative effect evaluation, exploring different combination treatment models, and clearly understanding the mechanisms of primary or secondary drug resistance. Along with these problems to be successfully solved, the immune checkpoint inhibitors will have more broad applications in lung cancer therapy.

CHECKPOINT INHIBITOR IMMUNE THERAPY: Systemic Indications and Ophthalmic Side Effects.

PubMed

Dalvin, Lauren A; Shields, Carol L; Orloff, Marlana; Sato, Takami; Shields, Jerry A

2018-06-01

To review immune checkpoint inhibitor indications and ophthalmic side effects. A literature review was performed using a PubMed search for publications between 1990 and 2017. Immune checkpoint inhibitors are designed to treat system malignancies by targeting one of three ligands, leading to T-cell activation for attack against malignant cells. These ligands (and targeted drug) include cytotoxic T-lymphocyte antigen-4 (CTLA-4, ipilimumab), programmed death protein 1 (PD-1, pembrolizumab, nivolumab), and programmed death ligand-1 (PD-L1, atezolizumab, avelumab, durvalumab). These medications upregulate the immune system and cause autoimmune-like side effects. Ophthalmic side effects most frequently manifest as uveitis (1%) and dry eye (1-24%). Other side effects include myasthenia gravis (n = 19 reports), inflammatory orbitopathy (n = 11), keratitis (n = 3), cranial nerve palsy (n = 3), optic neuropathy (n = 2), serous retinal detachment (n = 2), extraocular muscle myopathy (n = 1), atypical chorioretinal lesions (n = 1), immune retinopathy (n = 1), and neuroretinitis (n = 1). Most inflammatory side effects are managed with topical or periocular corticosteroids, but advanced cases require systemic corticosteroids and cessation of checkpoint inhibitor therapy. Checkpoint inhibitors enhance the immune system by releasing inhibition on T cells, with risk of autoimmune-like side effects. Ophthalmologists should include immune-related adverse events in their differential when examining cancer patients with new ocular symptoms.

Checkpoint Defects Leading to Premature Mitosis Also Cause Endoreplication of DNA in Aspergillus nidulans

PubMed Central

De Souza, Colin P. C.; Ye, Xiang S.; Osmani, Stephen A.

1999-01-01

The G2 DNA damage and slowing of S-phase checkpoints over mitosis function through tyrosine phosphorylation of NIMXcdc2 in Aspergillus nidulans. We demonstrate that breaking these checkpoints leads to a defective premature mitosis followed by dramatic rereplication of genomic DNA. Two additional checkpoint functions, uvsB and uvsD, also cause the rereplication phenotype after their mutation allows premature mitosis in the presence of low concentrations of hydroxyurea. uvsB is shown to encode a rad3/ATR homologue, whereas uvsD displays homology to rad26, which has only previously been identified in Schizosaccharomyces pombe. uvsBrad3 and uvsDrad26 have G2 checkpoint functions over mitosis and another function essential for surviving DNA damage. The rereplication phenotype is accompanied by lack of NIMEcyclinB, but ectopic expression of active nondegradable NIMEcyclinB does not arrest DNA rereplication. DNA rereplication can also be induced in cells that enter mitosis prematurely because of lack of tyrosine phosphorylation of NIMXcdc2 and impaired anaphase-promoting complex function. The data demonstrate that lack of checkpoint control over mitosis can secondarily cause defects in the checkpoint system that prevents DNA rereplication in the absence of mitosis. This defines a new mechanism by which endoreplication of DNA can be triggered and maintained in eukaryotic cells. PMID:10564263

Impaired tissue growth is mediated by checkpoint kinase 1 (CHK1) in the integrated stress response

PubMed Central

Malzer, Elke; Daly, Marie-Louise; Moloney, Aileen; Sendall, Timothy J.; Thomas, Sally E.; Ryder, Edward; Ryoo, Hyung Don; Crowther, Damian C.; Lomas, David A.; Marciniak, Stefan J.

2010-01-01

The integrated stress response (ISR) protects cells from numerous forms of stress and is involved in the growth of solid tumours; however, it is unclear how the ISR acts on cellular proliferation. We have developed a model of ISR signalling with which to study its effects on tissue growth. Overexpression of the ISR kinase PERK resulted in a striking atrophic eye phenotype in Drosophila melanogaster that could be rescued by co-expressing the eIF2α phosphatase GADD34. A genetic screen of 3000 transposon insertions identified grapes, the gene that encodes the Drosophila orthologue of checkpoint kinase 1 (CHK1). Knockdown of grapes by RNAi rescued eye development despite ongoing PERK activation. In mammalian cells, CHK1 was activated by agents that induce ER stress, which resulted in a G2 cell cycle delay. PERK was both necessary and sufficient for CHK1 activation. These findings indicate that non-genotoxic misfolded protein stress accesses DNA-damage-induced cell cycle checkpoints to couple the ISR to cell cycle arrest. PMID:20682638

Mps1 directs the assembly of Cdc20 inhibitory complexes during interphase and mitosis to control M phase timing and spindle checkpoint signaling.

PubMed

Maciejowski, John; George, Kelly A; Terret, Marie-Emilie; Zhang, Chao; Shokat, Kevan M; Jallepalli, Prasad V

2010-07-12

The spindle assembly checkpoint (SAC) in mammals uses cytosolic and kinetochore-based signaling pathways to inhibit anaphase. In this study, we use chemical genetics to show that the protein kinase Mps1 regulates both aspects of the SAC. Human MPS1-null cells were generated via gene targeting and reconstituted with either the wild-type kinase (Mps1(wt)) or a mutant version (Mps1(as)) sensitized to bulky purine analogues. Mps1 inhibition sharply accelerated anaphase onset, such that cells completed mitosis in 12 min, and prevented Cdc20's association with either Mad2 or BubR1 during interphase, i.e., before the appearance of functional kinetochores. Furthermore, intramitotic Mps1 inhibition evicted Bub1 and all other known SAC transducers from the outer kinetochore, but contrary to a recent study, did not perturb aurora B-dependent phosphorylation. We conclude that Mps1 has two complementary roles in SAC regulation: (1) initial cytoplasmic activation of Cdc20 inhibitors and (2) recruitment of factors that promote sustained anaphase inhibition and chromosome biorientation to unattached kinetochores.

A cytokinesis checkpoint requiring the yeast homologue of an APC-binding protein

PubMed Central

Muhua, Li; Adames, Neil R.; Murphy, Michael D.; Shields, Colleen R.; Cooper, John A.

2008-01-01

Checkpoint controls ensure that events of the cell-division cycle are completed with fidelity and in the correct order. In budding yeast with a mutation in the motor protein dynein, the mitotic spindle is often misaligned and therefore slow to enter the neck between mother cell and budding daughter cell. When this occurs, cytokinesis (division of the cytoplasm into two) is delayed until the spindle is properly positioned1. Here we describe mutations that abolish this delay, indicating the existence of a new checkpoint mechanism. One mutation lies in the gene encoding the yeast homologue of EB1, a human protein that binds the adenomatous polyposis coli (APC) protein, a tumour suppressor. EB1 is located on microtubules of the mitotic spindle and is important in spindle assembly. EB1 may therefore, by associating with microtubules, contribute to the sensor mechanism that activates the checkpoint. Another mutation affects Stt4, a phosphatidylinositol-4-OH kinase. Cold temperature is an environmental stimulus that causes misalignment of the mitotic spindle in yeast and appears to activate this checkpoint mechanism. PMID:9624007

[Adoptive Cell Therapy with Immune Checkpoint Blockade].

PubMed

Aruga, Atsushi

2017-09-01

Cancer immunotherapy are taking a leading role of cancer therapy due to the development of the immune checkpoint blockade. To date, however, only about 20% of patients have clinical responses and the cancer-specific T cells in cancer site are required to obtain beneficial effects. There has been an innovative development in the field of adoptive cell therapy, especially receptor gene-modified T cells in recent years. The effector cells mostly express PD-1, therefore the cytotoxic reactivity of the effector cells are inhibited by PD-L1. The combination of the adoptive cell therapy and the immune checkpoint blockade is expected to enhance efficacy. On the other hand, the immune-related adverse events may also be enhanced, therefore, it is needed to develop the combination therapy carefully, improving the cancer antigen-specificity or dealing with the cytokine release syndrome.

S-phase-specific activation of Cds1 kinase defines a subpathway of the checkpoint response in Schizosaccharomyces pombe

PubMed Central

Lindsay, Howard D.; Griffiths, Dominic J.F.; Edwards, Rhian J.; Christensen, Per U.; Murray, Johanne M.; Osman, Fekret; Walworth, Nancy; Carr, Antony M.

1998-01-01

Checkpoints that respond to DNA structure changes were originally defined by the inability of yeast mutants to prevent mitosis following DNA damage or S-phase arrest. Genetic analysis has subsequently identified subpathways of the DNA structure checkpoints, including the reversible arrest of DNA synthesis. Here, we show that the Cds1 kinase is required to slow S phase in the presence of DNA-damaging agents. Cds1 is phosphorylated and activated by S-phase arrest and activated by DNA damage during S phase, but not during G1 or G2. Activation of Cds1 during S phase is dependent on all six checkpoint Rad proteins, and Cds1 interacts both genetically and physically with Rad26. Unlike its Saccharomyces cerevisiae counterpart Rad53, Cds1 is not required for the mitotic arrest checkpoints and, thus, defines an S-phase specific subpathway of the checkpoint response. We propose a model for the DNA structure checkpoints that offers a new perspective on the function of the DNA structure checkpoint proteins. This model suggests that an intrinsic mechanism linking S phase and mitosis may function independently of the known checkpoint proteins. PMID:9450932

SNM1B/Apollo interacts with astrin and is required for the prophase cell cycle checkpoint.

PubMed

Liu, Lingling; Akhter, Shamima; Bae, Jae-Bum; Mukhopadhyay, Sudit S; Richie, Christopher T; Liu, Xiaojun; Legerski, Randy

2009-02-15

Previously, we have shown that SNM1A is a multifunctional gene involved in both the DNA damage response and in an early mitotic checkpoint in response to spindle stress. Another member of the SNM1 gene family, SNM1B/Apollo, has been shown to have roles in both the response to DNA interstrand cross-linking agents and in telomere protection during S phase. Here, we demonstrate a novel role for SNM1B/Apollo in mitosis in response to spindle stress. SNM1B-deficient cells exhibit a defect in the prophase checkpoint. Loss of the prophase checkpoint induces an extended mitotic delay, which is due to prolonged activation of the spindle checkpoint. In addition, we show that SNM1B/Apollo interacts with the essential microtubule binding protein Astrin. SNM1B/Apollo interacts with Astrin through its conserved metallo-beta-lactamase domain, and disruption of this interaction by point mutations results in a deficient prophase checkpoint. These findings suggest that SNM1B/Apollo and Astrin function together to enforce the prophase checkpoint in response to spindle stress.

Musculoskeletal and rheumatic diseases induced by immune checkpoint inhibitors: a review of the literature.

PubMed

Benfaremo, Devis; Manfredi, Lucia; Luchetti, Michele Maria; Gabrielli, Armando

2018-05-08

Immune checkpoint inhibitors are a new promising class of antitumor drugs that have been associated to a number of immune-related adverse events (AEs), including musculoskeletal and rheumatic disease. We searched Medline reviewing reports of musculoskeletal and rheumatic AEs induced by immune checkpoint inhibitors. Several musculoskeletal and rheumatic AEs associated with immune checkpoint inhibitors treatment are reported in literature. In particular, arthralgia and myalgia were the most common reported AEs, whereas the prevalence of arthritis, myositis and vasculitis is less characterized and mainly reported in case series and case reports. Other occasionally described AEs are sicca syndrome, polymyalgia rheumatica, systemic lupus erythematosus and sarcoidosis. Newly induced musculoskeletal and rheumatic diseases are a frequent adverse event associated with immune checkpoint inhibitors treatment. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Initial characterization of a low-molecular-weight factor enhancing the checkpoint response.

PubMed

Fan, Xiaoxiang; Cheong, Nge; Iliakis, George

2010-10-01

In higher eukaryotes, DNA double-strand breaks (DSBs) induced by ionizing radiation activate checkpoints that delay progression through the cell cycle. Compared to delays in other phases of the cell cycle, delays induced in G(2) are longer and frequently correlate with resistance to killing by radiation. Therefore, modulation of the G(2) checkpoint offers a means to modulate cellular radiosensitivity. Although compounds are known that reduce the G(2) checkpoint and act as radiosensitizers, compounds enhancing this checkpoint have not been reported. Here we summarize evidence for a factor with such properties. We show that a highly radioresistant rat embryo fibroblast (REF) cell line displays a strong G(2) checkpoint partly as a result of a factor excreted into the growth medium by nonirradiated cells. Various tests indicate that this G(2)-arrest modulating activity (GAMA) is a small molecule showing detectable retention only after passing through filters with a molecular weight cutoff limit of less than 1,000 Da. GAMA is heat stable and resistant to treatment with proteases or nucleases. Electroelution tests show that GAMA is uncharged at neutral pH, a result that is in agreement with the observed failure to bind S- or Q-Sepharose. Investigations on the mechanism of GAMA function indicate ligand-receptor interactions and allow the classification of cells as producers, responders or both. Compounds with properties such as those of GAMA bridge intercellular communication with the DNA damage response and may function as radioprotectors.

Expected Paradigm Shift in Brain Metastases Therapy-Immune Checkpoint Inhibitors.

PubMed

Jindal, Vishal; Gupta, Sorab

2018-01-30

Brain metastasis (BM) is one of the dreadful complications of malignancies. The prognosis after BM is extremely poor and life expectancy is meager. Currently, our treatment modalities are limited to radiotherapy and surgical resection, which also has poor outcomes and leads to various neurological deficits and affects the quality of life of patients. New treatment modality, i.e., immune checkpoint inhibitors, has brought revolution in management of melanoma, renal cancer, and non-small cell lung cancer (NSCLC). Immune checkpoint inhibitors basically enhance the immune response of the body to fight against cancers. Immune response in the brain is highly regulated; therefore, it is challenging to use immune-modulator drugs in BM. The microenvironment of BM is rich in cytotoxic T lymphocytes and which is the target of immune checkpoint inhibitors. Few studies have shown some hope regarding use of immune checkpoint inhibitors in management of BM. It works through inhibiting immune check point gates, i.e., CTLA-4 (cytotoxic T-lymphocyte-associated protein) and PD-1/PD-L1 (programmed cell death protein-1/program death ligand-1). This article explains the basic mechanism of immune check point inhibitors, rationale behind their usage in BM, and some of the clinical studies which have shown the efficacy of immune check point inhibitors in BM.

Emodnet Med Sea Check-Point - Indicators for decision- maker

NASA Astrophysics Data System (ADS)

Besnard, Sophie; Claverie, Vincent; Blanc, Frédérique

2015-04-01

The Emodnet Checkpoint projects aim is to assess the cost-effectiveness, reliability and utility of the existing monitoring at the sea basin level. This involves the development of monitoring system indicators and a GIS Platform to perform the assessment and make it available. Assessment or production of Check-Point information is made by developing targeted products based on the monitoring data and determining whether the products are meeting the needs of industry and public authorities. Check-point users are the research community, the 'institutional' policy makers for IMP and MSFD implementation, the 'intermediate users', i.e., users capable to understand basic raw data but that benefit from seeing the Checkpoint targeted products and the assessment of the fitness for purpose. We define assessment criteria aimed to characterize/depict the input datasets in terms of 3 territories capable to show performance and gaps of the present monitoring system, appropriateness, availability and fitness for purpose. • Appropriateness: What is made available to users? What motivate/decide them to select this observation rather than this one. • Availability: How this is made available to the user? Place to understand the readiness and service performance of the EU infrastructure • Fitness for use / fitness for purpose: Ability for non-expert user to appreciate the data exploitability (feedback on efficiency & reliability of marine data) For each territory (appropriateness, Availability and Fitness for purpose / for use), we define several indicators. For example, for Availability we define Visibility, Accessibility and Performance. And Visibility is itself defined by "Easily found" and "EU service". So these indicators can be classified according to their territory and sub-territory as seen above, but also according to the complexity to build them. Indicators are built from raw descriptors in 3 stages:  Stage 1: to give a neutral and basic status directly computed from

Analysis of Drug Development Paradigms for Immune Checkpoint Inhibitors.

PubMed

Jardim, Denis L; de Melo Gagliato, Débora; Giles, Francis J; Kurzrock, Razelle

2018-04-15

Immune checkpoint inhibitors have unique toxicities and response kinetics compared with cytotoxic and gene-targeted anticancer agents. We investigated the impact of innovative/accelerated immunotherapy drug development/approval models on the accuracy of safety and efficacy assessments by searching the FDA website. Initial phase I trials for each agent were reviewed and safety and efficacy data compared with that found in later trials leading to regulatory approvals of the same agents. As of June 2017, the FDA approved six checkpoint inhibitors for a variety of cancer types. All checkpoint inhibitors received a priority review status and access to at least two additional FDA special access programs, more often breakthrough therapy designation and accelerated approval. Median clinical development time (investigational new drug application to approval) was 60.77 months [avelumab had the shortest timeline (52.33 months)]. Response rates during early phase I trials (median = 16%) are higher than for phase I trials of other agents (with the exception of gene-targeted agents tested with a biomarker). Doses approved were usually not identical to doses recommended on phase I trials. Approximately 50% of types of immune-related and 43% of types of clinically relevant toxicities from later trials were identified in early-phase trials. Even so, treatment-related mortality remains exceedingly low in later studies (0.33% of patients). In conclusion, efficacy and safety of immune checkpoint inhibitors appear to be reasonably predicted from the dose-finding portion of phase I trials, indicating that the fast-track development of these agents is safe and justified. Clin Cancer Res; 24(8); 1785-94. ©2017 AACR . ©2017 American Association for Cancer Research.

Noncoding RNAs and immune checkpoints-clinical implications as cancer therapeutics.

PubMed

Smolle, Maria A; Calin, Horatiu N; Pichler, Martin; Calin, George A

2017-07-01

A major mechanism of tumor development and progression is silencing of the patient's immune response to cancer-specific antigens. Defects in the so-called cancer immunity cycle may occur at any stage of tumor development. Within the tumor microenvironment, aberrant expression of immune checkpoint molecules with activating or inhibitory effects on T lymphocytes induces immune tolerance and cellular immune escape. Targeting immune checkpoint molecules such as programmed cell death protein 1 (PD-1) and its ligand PD-L1 with specific antibodies has proven to be a major advance in the treatment of several types of cancer. Another way to therapeutically influence the tumor microenvironment is by modulating the levels of microRNAs (miRNAs), small noncoding RNAs that shuttle bidirectionally between malignant and tumor microenvironmental cells. These small RNA transcripts have two features: (a) their expression is quite specific to distinct tumors, and (b) they are involved in early regulation of immune responses. Consequently, miRNAs may be ideal molecules for use in cancer therapy. Many miRNAs are aberrantly expressed in human cancer cells, opening new opportunities for cancer therapy, but the exact functions of these miRNAs and their interactions with immune checkpoint molecules have yet to be investigated. This review summarizes recently reported findings about miRNAs as modulators of immune checkpoint molecules and their potential application as cancer therapeutics in clinical practice. © 2017 Federation of European Biochemical Societies.

The RNA-binding proteins Zfp36l1 and Zfp36l2 enforce the thymic β-selection checkpoint by limiting DNA damage response signaling and cell cycle progression

PubMed Central

Galloway, Alison; Ahlfors, Helena; Turner, Martin

2016-01-01

The RNA binding proteins Zfp36l1 and Zfp36l2 act redundantly to enforce the β-selection checkpoint during thymopoiesis, yet their molecular targets remain largely unknown. Here, we identify these targets on a genome wide scale in primary mouse thymocytes and show that Zfp36l1/l2 regulate DNA damage response and cell cycle transcripts to ensure proper β-selection. DN3 thymocytes lacking Zfp36l1/l2 share a gene expression profile with post-selected DN3b cells despite the absence of intracellular TCRβ and reduced IL-7 signaling. Our findings show that in addition to controlling the timing of proliferation at β-selection post-transcriptional control by Zfp36l1/l2 limits DNA damage responses which are known to promote thymocyte differentiation. Zfp36l1/l2 therefore act as post-transcriptional safeguards against chromosomal instability and replication stress by integrating pre-TCR and IL-7 signaling with DNA damage and cell cycle control. PMID:27566829

Response Inhibition Is Facilitated by a Change to Red Over Green in the Stop Signal Paradigm

PubMed Central

Blizzard, Shawn; Fierro-Rojas, Adriela; Fallah, Mazyar

2017-01-01

Actions are informed by the complex interactions of response execution and inhibition networks. These networks integrate sensory information with internal states and behavioral goals to produce an appropriate action or to update an ongoing action. Recent investigations have shown that, behaviorally, attention is captured through a hierarchy of colors. These studies showed how the color hierarchy affected visual processing. To determine whether the color hierarchy can be extended to higher level executive functions such as response execution and inhibition, we conducted several experiments using the stop-signal task (SST). In the first experiment, we modified the classic paradigm so that the go signals could vary in task-irrelevant color, with an auditory stop signal. We found that the task-irrelevant color of the go signals did not differentially affect response times. In the second experiment we determined that making the color of the go signal relevant for response selection still did not affect reaction times(RTs) and, thus, execution. In the third experiment, we modified the paradigm so that the stop signal was a task relevant change in color of the go signal. The mean RT to the red stop signal was approximately 25 ms faster than to the green stop signal. In other words, red stop signals facilitated response inhibition more than green stop signals, however, there was no comparative facilitation of response execution. These findings suggest that response inhibition, but not execution, networks are sensitive to differences in color salience. They also suggest that the color hierarchy is based on attentional networks and not simply on early sensory processing. PMID:28101011

Synergy of Immune Checkpoint Blockade with a Novel Synthetic Consensus DNA Vaccine Targeting TERT.

PubMed

Duperret, Elizabeth K; Wise, Megan C; Trautz, Aspen; Villarreal, Daniel O; Ferraro, Bernadette; Walters, Jewell; Yan, Jian; Khan, Amir; Masteller, Emma; Humeau, Laurent; Weiner, David B

2018-02-07

Immune checkpoint blockade antibodies are setting a new standard of care for cancer patients. It is therefore important to assess any new immune-based therapies in the context of immune checkpoint blockade. Here, we evaluate the impact of combining a synthetic consensus TERT DNA vaccine that has improved capacity to break tolerance with immune checkpoint inhibitors. We observed that blockade of CTLA-4 or, to a lesser extent, PD-1 synergized with TERT vaccine, generating more robust anti-tumor activity compared to checkpoint alone or vaccine alone. Despite this anti-tumor synergy, none of these immune checkpoint therapies showed improvement in TERT antigen-specific immune responses in tumor-bearing mice. αCTLA-4 therapy enhanced the frequency of T-bet + /CD44 + effector CD8 + T cells within the tumor and decreased the frequency of regulatory T cells within the tumor, but not in peripheral blood. CTLA-4 blockade synergized more than Treg depletion with TERT DNA vaccine, suggesting that the effect of CTLA-4 blockade is more likely due to the expansion of effector T cells in the tumor rather than a reduction in the frequency of Tregs. These results suggest that immune checkpoint inhibitors function to alter the immune regulatory environment to synergize with DNA vaccines, rather than boosting antigen-specific responses at the site of vaccination. Copyright © 2017 The American Society of Gene and Cell Therapy. Published by Elsevier Inc. All rights reserved.

FAP positive fibroblasts induce immune checkpoint blockade resistance in colorectal cancer via promoting immunosuppression.

PubMed

Chen, Lingling; Qiu, Xiangting; Wang, Xinhua; He, Jian

2017-05-20

Immune checkpoint blockades that significantly prolonged survival of melanoma patients have been less effective on colorectal cancer (CRC) patients. Growing evidence suggested that fibroblast activation protein-alpha (FAP) on cancer associate fibroblasts (CAFs) has critical roles in regulating antitumor immune response by inducing tumor-promoting inflammation. In this study, we explored the roles of FAP in regulating the tumor immunity and immune checkpoint blockades resistance in CRC experimental systems. We found that CAFs with high FAP expression could induce immune checkpoint blockade resistance in CRC mouse model. Mechanistically, CAFs with high FAP expression promoted immunosuppression in the CRC tumor immune microenvironment by up-regulating CCL2 secretion, recruiting myeloid cells, and decreasing T-cell activity. In human CRC samples, FAP expression was proportional to myeloid cells number, but inversely related to T-cell number. High FAP expression also predicted poor survival of CRC patients. Taken together, our study suggested that high FAP expression in CAFs is one reason leading to immune checkpoint blockades resistance in CRC patients and FAP is an optional target for reversing immune checkpoint blockades resistance. Copyright © 2017 Elsevier Inc. All rights reserved.

Effectiveness of a Brief Parent-Directed Teen Driver Safety Intervention (Checkpoints) Delivered by Driver Education Instructors

PubMed Central

Zakrajsek, Jennifer S.; Shope, Jean T.; Greenspan, Arlene I.; Wang, Jing; Bingham, C. Raymond; Simons-Morton, Bruce G.

2014-01-01

Background The Checkpoints program (Checkpoints) uses a Parent-Teen Driving Agreement (PTDA) to help parents monitor teens' driving, and has shown efficacy in increasing parental restrictions on teens' driving and decreasing teens' risky driving. In previous trials, research staff administered Checkpoints. This study examined the effectiveness of Checkpoints when delivered by driver educators. It was hypothesized that Checkpoints would result in more PTDA use, greater PTDA limits on higher risk driving situations, and less high-risk driving. Methods Eight trained driving instructors were randomly assigned to intervention or control groups in a group randomized trial. Instructors enrolled 148 parent-teen dyads (intervention = 99, control = 49); 35% of those eligible. Intervention parents joined teens for a 30-minute Checkpoints session during driver education. The session included a video, persuasive messages, discussion, and PTDA initiation. Teens completed four surveys: baseline, licensure, and 3- and 6-months post-licensure. Results Intervention teens were more likely to report that they used a PTDA (OR= 15.92, p = .004) and had restrictions on driving with teen passengers (OR = 8.52, p = .009), on weekend nights (OR = 8.71, p = .021), on high-speed roads (OR = 3.56, p = .02), and in bad weather (b = .51, p = .05) during the first six months of licensure. There were no differences in offenses or crashes at six months, but intervention teens reported less high-risk driving (p = .04). Conclusions Although challenges remain to encourage greater parent participation, Checkpoints conducted by driver education instructors resulted in more use of PTDAs, greater restrictions on high-risk driving, and less high-risk driving. Including Checkpoints in driver education parent meetings/classes has potential to enhance teen driver safety. PMID:23481298

Localization of spindle checkpoint proteins in cells undergoing mitosis with unreplicated genomes.

PubMed

Johnson, Mary Kathrine; Cooksey, Amanda M; Wise, Dwayne A

2008-11-01

CHO cells can be arrested with hydoxyurea at the beginning of the DNA synthesis phase of the cell cycle. Subsequent treatment with the xanthine, caffeine, induces cells to bypass the S-phase checkpoint and enter unscheduled mitosis [Schlegel and Pardee,1986, Science 232:1264-1266]. These treated cells build a normal spindle and distribute kinetochores, unattached to chromosomes, to their daughter cells [Brinkley et al.,1988, Nature 336:251-254; Zinkowski et al.,1991, J Cell Biol 113:1091-1110; Wise and Brinkley,1997, Cell Motil Cytoskeleton 36:291-302; Balczon et al.,2003, Chromosoma 112:96-102]. To investigate how these cells distribute kinetochores to daughter cells, we analyzed the spindle checkpoint components, Mad2, CENP-E, and the 3F3 phosphoepitope, using immunofluorescence and digital microscopy. Even though the kinetochores were unpaired and DNA was fragmented, the tension, alignment, and motor components of the checkpoint were found to be present and localized as predicted in prometaphase and metaphase. This unusual mitosis proves that a cell can successfully localize checkpoint proteins and divide even when kinetochores are unpaired and fragmented. (c) 2008 Wiley-Liss, Inc.

Nuclear translocation of Skp2 facilitates its destruction in response to TGFβ signaling

PubMed Central

Wu, George

2011-01-01

Skp2, a F-box protein that determines the substrate specificity for SCF ubiquitin ligase, has recently been demonstrated to be degraded by Cdh1/APC in response to TGFβ signaling. The TGFβ-induced Skp2 proteolysis results in the stabilization of p27 that is necessary to facilitate TGFβ cytostatic effect. Previous observation from immunocytochemistry indicates that Cdh1 principally localizes in the nucleus while Skp2 mainly localizes in the cytosol, which leaves us a puzzle on how Skp2 is recognized and then ubiquitylated by Cdh1/APC in response to TGFβ stimulation. Here, we report that Skp2 is rapidly translocated from the cytosol to the nucleus upon the cellular stimulation with TGFβ. Using a combinatorial approach of immunocytochemistry, biochemical-fraction-coupled immunoprecipitation, mutagenesis as well as protein degradation assay, we have demonstrated that the TGFβ-induced Skp2 nucleus translocation is critical for TGFβ cytostatic effect that allows physical interaction between Cdh1 and Skp2 and in turn facilitates the Skp2 ubquitylation by Cdh1/APC. Disruption of nuclear localization motifs on Skp2 stabilizes Skp2 in the presence of TGFβ signaling, which attenuates TGFβ-induced p27 accumulation and antagonizes TGFβ-induced growth inhibition. Our finding reveals a cellular mechanism that facilitates Skp2 ubiquitylation by Cdh1/APC in response to TGFβ. PMID:21212736

Stable kinetochore-microtubule attachment is sufficient to silence the spindle assembly checkpoint in human cells.

PubMed

Tauchman, Eric C; Boehm, Frederick J; DeLuca, Jennifer G

2015-12-01

During mitosis, duplicated sister chromatids attach to microtubules emanating from opposing sides of the bipolar spindle through large protein complexes called kinetochores. In the absence of stable kinetochore-microtubule attachments, a cell surveillance mechanism known as the spindle assembly checkpoint (SAC) produces an inhibitory signal that prevents anaphase onset. Precisely how the inhibitory SAC signal is extinguished in response to microtubule attachment remains unresolved. To address this, we induced formation of hyper-stable kinetochore-microtubule attachments in human cells using a non-phosphorylatable version of the protein Hec1, a core component of the attachment machinery. We find that stable attachments are sufficient to silence the SAC in the absence of sister kinetochore bi-orientation and strikingly in the absence of detectable microtubule pulling forces or tension. Furthermore, we find that SAC satisfaction occurs despite the absence of large changes in intra-kinetochore distance, suggesting that substantial kinetochore stretching is not required for quenching the SAC signal.

Stable kinetochore–microtubule attachment is sufficient to silence the spindle assembly checkpoint in human cells

PubMed Central

Tauchman, Eric C.; Boehm, Frederick J.; DeLuca, Jennifer G.

2015-01-01

During mitosis, duplicated sister chromatids attach to microtubules emanating from opposing sides of the bipolar spindle through large protein complexes called kinetochores. In the absence of stable kinetochore–microtubule attachments, a cell surveillance mechanism known as the spindle assembly checkpoint (SAC) produces an inhibitory signal that prevents anaphase onset. Precisely how the inhibitory SAC signal is extinguished in response to microtubule attachment remains unresolved. To address this, we induced formation of hyper-stable kinetochore–microtubule attachments in human cells using a non-phosphorylatable version of the protein Hec1, a core component of the attachment machinery. We find that stable attachments are sufficient to silence the SAC in the absence of sister kinetochore bi-orientation and strikingly in the absence of detectable microtubule pulling forces or tension. Furthermore, we find that SAC satisfaction occurs despite the absence of large changes in intra-kinetochore distance, suggesting that substantial kinetochore stretching is not required for quenching the SAC signal. PMID:26620470

Concordance of immune checkpoints within tumor immune contexture and their prognostic significance in gastric cancer.

PubMed

Dai, Congqi; Geng, Ruixuan; Wang, Chenchen; Wong, Angela; Qing, Min; Hu, Jianjun; Sun, Yu; Lo, A W I; Li, Jin

2016-12-01

Checkpoint blockade therapy has emerged as a novel approach for cancer immunotherapy in several malignancies. However, patient prognosis and disease progression relevant to immune checkpoints in gastric tumor microenvironment are not defined. This study aims to investigate the expression and prognostic significance of immune checkpoints within gastric cancer. In the study, a cohort of 398 cancer tissues from stage I to IV gastric cancer patients were assessed for programmed cell death 1 ligand 1 (PD-L1) expression and tumor-infiltrating lymphocyte (TIL) infiltration using immunohistochemistry to ascertain their survival correlation. The data revealed that higher TIL density correlated with less risk of disease progression, and exhibited survival benefits in gastric cancer patients, and PD-L1 positivity showed a significant association with the presence of high TIL infiltration. Furthermore, real-time quantitative polymerase chain reaction was performed to detect expression of multiple immune checkpoints with the relation to clinical outcome in 139 samples randomly selected from the same cohort, and higher messenger RNA levels of most immune checkpoints were associated with favorable outcome, while consistently showing a positive correlation with interferon gamma levels. In situ hybridization was used to determine the localization of Epstein-Barr virus (EBV) in 97 specimens, and showed EBV-positive gastric cancer samples correlated with PD-L1 expression and increased TIL density. These results suggest that induction of immune checkpoint within gastric cancer patients reflects a high immune infiltration density, especially in those with EBV-associated gastric cancer, which may direct patient selection for checkpoint blockade therapy. Copyright © 2016 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

Replication, checkpoint suppression and structure of centromeric DNA

PubMed Central

Romeo, Francesco; Costanzo, Vincenzo

2016-01-01

ABSTRACT Human centromeres contain large amounts of repetitive DNA sequences known as α satellite DNA, which can be difficult to replicate and whose functional role is unclear. Recently, we have characterized protein composition, structural organization and checkpoint response to stalled replication forks of centromeric chromatin reconstituted in Xenopus laevis egg extract. We showed that centromeric DNA has high affinity for SMC2-4 subunits of condensins and for CENP-A, it is enriched for DNA repair factors and suppresses the ATR checkpoint to ensure its efficient replication. We also showed that centromeric chromatin forms condensins enriched and topologically constrained DNA loops, which likely contribute to the overall structure of the centromere. These findings have important implications on how chromosomes are organized and genome stability is maintained in mammalian cells. PMID:27893298

Immune Checkpoint Inhibitors in the Treatment of Patients with Neuroendocrine Neoplasia.

PubMed

Weber, Matthias M; Fottner, Christian

2018-01-01

Well-differentiated neuroendocrine neoplasms (NENs) are usually controlled by antiproliferative, local ablative and/or radionuclide therapies, whereas poorly differentiated NENs generally require cytotoxic chemotherapy. However, treatment options for patients with advanced/metastatic high-grade NENs remain limited. Review of the literature and international congress abstracts on the efficacy and safety of immunotherapy by checkpoint inhibition in advanced/metastatic NENs. Evidence points to an important role of immune phenomena in the pathogenesis and treatment of neuroendocrine tumors (NETs). Programmed cell death 1 (PD-1) protein and its ligand are mainly expressed in poorly differentiated NENs. Microsatellite instability and high mutational load are more pronounced in high-grade NENs and may predict response to immunotherapy. Clinical experience of immune checkpoint blockade mainly exists for Merkel cell carcinoma, a high-grade cutaneous neuroendocrine carcinoma (NEC), which has led to approval of the anti-PD-1 antibody avelumab. In addition, there is anecdotal evidence for the efficacy of checkpoint inhibitors in large-cell lung NECs, ovarian NECs and others, including gastroenteropancreatic NENs. Currently, phase II studies investigate PDR001, pembrolizumab, combined durvalumab and tremelimumab, and avelumab treatment in patients with advanced/metastatic NENs. Immune checkpoint inhibitors are a promising therapeutic option, especially in progressive NECs or high-grade NETs with high tumor burden, microsatellite instability, and/or mutational load. © 2018 S. Karger GmbH, Freiburg.

Beyond CTLA-4 and PD-1, the Generation Z of Negative Checkpoint Regulators.

PubMed

Le Mercier, Isabelle; Lines, J Louise; Noelle, Randolph J

2015-01-01

In the last two years, clinical trials with blocking antibodies to the negative checkpoint regulators CTLA-4 and PD-1 have rekindled the hope for cancer immunotherapy. Multiple negative checkpoint regulators protect the host against autoimmune reactions but also restrict the ability of T cells to effectively attack tumors. Releasing these brakes has emerged as an exciting strategy for cancer treatment. Conversely, these pathways can be manipulated to achieve durable tolerance for treatment of autoimmune diseases and transplantation. In the future, treatment may involve combination therapy to target multiple cell types and stages of the adaptive immune responses. In this review, we describe the current knowledge on the recently discovered negative checkpoint regulators, future targets for immunotherapy.

Beyond CTLA-4 and PD-1, the Generation Z of Negative Checkpoint Regulators

PubMed Central

Le Mercier, Isabelle; Lines, J. Louise; Noelle, Randolph J.

2015-01-01

In the last two years, clinical trials with blocking antibodies to the negative checkpoint regulators CTLA-4 and PD-1 have rekindled the hope for cancer immunotherapy. Multiple negative checkpoint regulators protect the host against autoimmune reactions but also restrict the ability of T cells to effectively attack tumors. Releasing these brakes has emerged as an exciting strategy for cancer treatment. Conversely, these pathways can be manipulated to achieve durable tolerance for treatment of autoimmune diseases and transplantation. In the future, treatment may involve combination therapy to target multiple cell types and stages of the adaptive immune responses. In this review, we describe the current knowledge on the recently discovered negative checkpoint regulators, future targets for immunotherapy. PMID:26347741

Extending the Binomial Checkpointing Technique for Resilience

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walther, Andrea; Narayanan, Sri Hari Krishna

In terms of computing time, adjoint methods offer a very attractive alternative to compute gradient information, re- quired, e.g., for optimization purposes. However, together with this very favorable temporal complexity result comes a memory requirement that is in essence proportional with the operation count of the underlying function, e.g., if algo- rithmic differentiation is used to provide the adjoints. For this reason, checkpointing approaches in many variants have become popular. This paper analyzes an extension of the so-called binomial approach to cover also possible failures of the computing systems. Such a measure of precaution is of special interest for massivemore » parallel simulations and adjoint calculations where the mean time between failure of the large scale computing system is smaller than the time needed to complete the calculation of the adjoint information. We de- scribe the extensions of standard checkpointing approaches required for such resilience, provide a corresponding imple- mentation and discuss numerical results.« less

Overexpression of Mps1 in colon cancer cells attenuates the spindle assembly checkpoint and increases aneuploidy.

PubMed

Ling, Youguo; Zhang, Xiaojuan; Bai, Yuanyuan; Li, Ping; Wei, Congwen; Song, Ting; Zheng, Zirui; Guan, Kai; Zhang, Yanhong; Zhang, Buchang; Liu, Xuedong; Ma, Runlin Z; Cao, Cheng; Zhong, Hui; Xu, Quanbin

2014-08-08

The spindle assembly checkpoint kinase Mps1 is highly expressed in several types of cancers, but its cellular involvement in tumorigenesis is less defined. Herein, we confirm that Mps1 is overexpressed in colon cancer tissues. Further, we find that forced expression of Mps1 in the colon cancer cell line SW480 enables cells to become resistant to both Mps1 inhibition-induced checkpoint depletion and cell death. Overexpression of Mps1 also increases genome instability in tumor cells owing to a weakened spindle assembly checkpoint. Collectively, our findings suggest that high levels of Mps1 contribute to tumorigenesis by attenuating the spindle assembly checkpoint. Copyright © 2014 Elsevier Inc. All rights reserved.

RAD9-dependent G1 arrest defines a second checkpoint for damaged DNA in the cell cycle of Saccharomyces cerevisiae.

PubMed

Siede, W; Friedberg, A S; Friedberg, E C

1993-09-01

Exposure of the yeast Saccharomyces cerevisiae to ultraviolet (UV) light, the UV-mimetic chemical 4-nitroquinoline-1-oxide (4NQO), or gamma radiation after release from G1 arrest induced by alpha factor results in delayed resumption of the cell cycle. As is the case with G2 arrest following ionizing radiation damage [Weinert, T. A. & Hartwell, L. H. (1988) Science 241, 317-322], the normal execution of DNA damage-induced G1 arrest depends on a functional yeast RAD9 gene. We suggest that the RAD9 gene product may interact with cellular components common to the G1/S and G2/M transition points in the cell cycle of this yeast. These observations define a checkpoint in the eukaryotic cell cycle that may facilitate the repair of lesions that are otherwise processed to lethal and/or mutagenic damage during DNA replication. This checkpoint apparently operates after the mating pheromone-induced G1 arrest point but prior to replicative DNA synthesis, S phase-associated maximal induction of histone H2A mRNA, and bud emergence.

PD-1 /PD-L1 checkpoint in hematological malignancies.

PubMed

Annibali, O; Crescenzi, A; Tomarchio, V; Pagano, A; Bianchi, A; Grifoni, A; Avvisati, G

2018-04-01

Programmed cell death protein 1 (PD-1), is a cell surface receptor with an important role in down-regulating the immune system and promoting self-tolerance by suppressing T cell inflammatory activity. PD-1/PDL1 axis represents a checkpoint to control immune responses and it is often used as a mechanism of immune escaping by cancers and infectious diseases. Many data demonstrate its important role in solid tumors and report emerging evidences in lymphoproliferative disorders. In this review, we summarized the available data on the role of PD-1/PD-L1 checkpoint in lymphoproliferative diseases and the therapeutics use of monoclonal blocking antibodies. Copyright © 2018 Elsevier Ltd. All rights reserved.

A Combination of Immune Checkpoint Inhibition with Metronomic Chemotherapy as a Way of Targeting Therapy-Resistant Cancer Cells.

PubMed

Kareva, Irina

2017-10-13

Therapeutic resistance remains a major obstacle in treating many cancers, particularly in advanced stages. It is likely that cytotoxic lymphocytes (CTLs) have the potential to eliminate therapy-resistant cancer cells. However, their effectiveness may be limited either by the immunosuppressive tumor microenvironment, or by immune cell death induced by cytotoxic treatments. High-frequency low-dose (also known as metronomic) chemotherapy can help improve the activity of CTLs by providing sufficient stimulation for cytotoxic immune cells without excessive depletion. Additionally, therapy-induced removal of tumor cells that compete for shared nutrients may also facilitate tumor infiltration by CTLs, further improving prognosis. Metronomic chemotherapy can also decrease the number of immunosuppressive cells in the tumor microenvironment, including regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs). Immune checkpoint inhibition can further augment anti-tumor immune responses by maintaining T cells in an activated state. Combining immune checkpoint inhibition with metronomic administration of chemotherapeutic drugs may create a synergistic effect that augments anti-tumor immune responses and clears metabolic competition. This would allow immune-mediated elimination of therapy-resistant cancer cells, an effect that may be unattainable by using either therapeutic modality alone.

Checkpoint Inhibitors Hold Promise for Rare Melanoma

Cancer.gov

Patients with a rare form of melanoma, called desmoplastic melanoma, may be particularly likely to benefit from immune checkpoint inhibitors, a new study shows. As this Cancer Currents post explains, an NCI-sponsored clinical trial is already testing one such drug, pembrolizumab (Keytruda) in patients with this cancer.

[Dermatologic toxicities of immune checkpoint inhibitors].

PubMed

Sibaud, V; Boulinguez, S; Pagès, C; Riffaud, L; Lamant, L; Chira, C; Boyrie, S; Vigarios, E; Tournier, E; Meyer, N

2018-05-01

The development of immune checkpoint inhibitors (monoclonal antibodies targeting PD-1/PD-L1 or CTLA-4) represents a significant advance in the treatment of multiple cancers. Given their particular mechanism of action, which involves triggering CD4+/CD8+ T-cell activation and proliferation, they are associated with a specific safety profile. Their adverse events are primarily immune-related, and can affect practically all organs. In this context, dermatological toxicity is the most common, though it mostly remains mild to moderate and does not require discontinuation of treatment. More than a third of patients are faced with cutaneous adverse events, usually in the form of a maculopapular rash, pruritus or vitiligo (only in patients treated for melanoma). Much more specific dermatologic disorders, however, may occur such as lichenoid reactions, induced psoriasis, sarcoidosis, auto-immune diseases (bullous pemphigoid, dermatomyositis, alopecia areata), acne-like rash, xerostomia, etc. Rigorous dermatological evaluation is thus mandatory in the case of atypical, persistent/recurrent or severe lesions. In this article, we review the incidence and spectrum of dermatologic adverse events reported with immune checkpoint inhibitors. Finally, a management algorithm is proposed. Copyright © 2018. Published by Elsevier Masson SAS.

Immune Checkpoint Blockade for Breast Cancer.

PubMed

Swoboda, April; Nanda, Rita

An effective antitumor immune response requires interaction between cells of the adaptive and innate immune system. Three key elements are required: generation of activated tumor-directed T cells, infiltration of activated T cells into the tumor microenvironment, and killing of tumor cells by activated T cells. Tumor immune evasion can occur as a result of the disruption of each of these three key T cell activities, resulting in three distinct cancer-immune phenotypes. The immune inflamed phenotype, characterized by the presence of a robust tumor immune infiltrate, suggests impaired activated T cell killing of tumor cells related to the presence of inhibitory factors. Programmed death receptor-1 (PD-1) is an inhibitory transmembrane protein expressed on T cells, B cells, and NK cells. The interaction between PD-1 and its ligands (PD-L1/L2) functions as an immune checkpoint against unrestrained cytotoxic T effector cell activity-it promotes peripheral T effector cell exhaustion and conversion of T effector cells to immunosuppressive T regulatory (Treg) cells. Immune checkpoint inhibitors, which block the PD-1/PD-L1 axis and reactivate cytotoxic T effector cell function, are actively being investigated for the treatment of breast cancer.

T cells in chronic lymphocytic leukemia display dysregulated expression of immune checkpoints and activation markers.

PubMed

Palma, Marzia; Gentilcore, Giusy; Heimersson, Kia; Mozaffari, Fariba; Näsman-Glaser, Barbro; Young, Emma; Rosenquist, Richard; Hansson, Lotta; Österborg, Anders; Mellstedt, Håkan

2017-03-01

Chronic lymphocytic leukemia is characterized by impaired immune functions largely due to profound T-cell defects. T-cell functions also depend on co-signaling receptors, inhibitory or stimulatory, known as immune checkpoints, including cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) and programmed death-1 (PD-1). Here we analyzed the T-cell phenotype focusing on immune checkpoints and activation markers in chronic lymphocytic leukemia patients (n=80) with different clinical characteristics and compared them to healthy controls. In general, patients had higher absolute numbers of CD3 + cells and the CD8 + subset was particularly expanded in previously treated patients. Progressive patients had higher numbers of CD4 + and CD8 + cells expressing PD-1 compared to healthy controls, which was more pronounced in previously treated patients ( P =0.0003 and P =0.001, respectively). A significant increase in antigen-experienced T cells was observed in patients within both the CD4 + and CD8 + subsets, with a significantly higher PD-1 expression. Higher numbers of CD4 + and CD8 + cells with intracellular CTLA-4 were observed in patients, as well as high numbers of proliferating (Ki67 + ) and activated (CD69 + ) CD4 + and CD8 + cells, more pronounced in patients with active disease. The numbers of Th1, Th2, Th17 and regulatory T cells were substantially increased in patients compared to controls ( P <0.05), albeit decreasing to low levels in pre-treated patients. In conclusion, chronic lymphocytic leukemia T cells display increased expression of immune checkpoints, abnormal subset distribution, and a higher proportion of proliferating cells compared to healthy T cells. Disease activity and previous treatment shape the T-cell profile of chronic lymphocytic leukemia patients in different ways. Copyright© Ferrata Storti Foundation.

Twitter as a Tool to Warn Others about Sobriety Checkpoints: A Pilot Observational Study

ERIC Educational Resources Information Center

Seitz, Christopher M.; Orsini, Muhsin Michael; Fearnow-Kenney, Melodie; Hatzudis, Kiki; Wyrick, David L.

2012-01-01

Anecdotal evidence suggests that young people use the website Twitter as a tool to warn drivers about the locations of sobriety checkpoints. Researchers investigated this claim by independently analyzing the website's content regarding a sample of 10 sobriety checkpoints that were conducted in cities throughout the United States during the weekend…

Monopolar spindle 1 (MPS1) kinase promotes production of closed MAD2 (C-MAD2) conformer and assembly of the mitotic checkpoint complex.

PubMed

Tipton, Aaron R; Ji, Wenbin; Sturt-Gillespie, Brianne; Bekier, Michael E; Wang, Kexi; Taylor, William R; Liu, Song-Tao

2013-12-06

MPS1 kinase is an essential component of the spindle assembly checkpoint (SAC), but its functioning mechanisms are not fully understood. We have shown recently that direct interaction between BUBR1 and MAD2 is critical for assembly and function of the human mitotic checkpoint complex (MCC), the SAC effector. Here we report that inhibition of MPS1 kinase activity by reversine disrupts BUBR1-MAD2 as well as CDC20-MAD2 interactions, causing premature activation of the anaphase-promoting complex/cyclosome. The effect of MPS1 inhibition is likely due to reduction of closed MAD2 (C-MAD2), as expressing a MAD2 mutant (MAD2(L13A)) that is locked in the C conformation rescued the checkpoint defects. In the presence of reversine, exogenous C-MAD2 does not localize to unattached kinetochores but is still incorporated into the MCC. Contrary to a previous report, we found that sustained MPS1 activity is required for maintaining both the MAD1·C-MAD2 complex and open MAD2 (O-MAD2) at unattached kinetochores to facilitate C-MAD2 production. Additionally, mitotic phosphorylation of BUBR1 is also affected by MPS1 inhibition but seems dispensable for MCC assembly. Our results support the notion that MPS1 kinase promotes C-MAD2 production and subsequent MCC assembly to activate the SAC.

CDK-dependent potentiation of MPS1 kinase activity is essential to the mitotic checkpoint.

PubMed

Morin, Violeta; Prieto, Susana; Melines, Sabrina; Hem, Sonia; Rossignol, Michel; Lorca, Thierry; Espeut, Julien; Morin, Nathalie; Abrieu, Ariane

2012-02-21

Accurate chromosome segregation relies upon a mitotic checkpoint that monitors kinetochore attachment toward opposite spindle poles before enabling chromosome disjunction [1]. The MPS1/TTK protein kinase is a core component of the mitotic checkpoint that lies upstream of MAD2 and BubR1 both at the kinetochore and in the cytoplasm [2, 3]. To gain insight into the mechanisms underlying the regulation of MPS1 kinase, we undertook the identification of Xenopus MPS1 phosphorylation sites by mass spectrometry. We mapped several phosphorylation sites onto MPS1 and we show that phosphorylation of S283 in the noncatalytic region of MPS1 is required for full kinase activity. This phosphorylation potentiates MPS1 catalytic efficiency without impairing its affinity for the substrates. By using Xenopus egg extracts depleted of endogenous MPS1 and reconstituted with single point mutants, we show that phosphorylation of S283 is essential to activate the mitotic checkpoint. This phosphorylation does not regulate the localization of MPS1 to the kinetochore but is required for the recruitment of MAD1/MAD2, demonstrating its role at the kinetochore. Constitutive phosphorylation of S283 lowers the number of kinetochores required to hold the checkpoint, which suggests that CDK-dependent phosphorylation of MPS1 is essential to sustain the mitotic checkpoint when few kinetochores remain unattached. Copyright © 2012 Elsevier Ltd. All rights reserved.

Preserved DNA Damage Checkpoint Pathway Protects against Complications in Long-Standing Type 1 Diabetes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhatt, Shweta; Gupta, Manoj K.; Khamaisi, Mogher

The mechanisms underlying the development of complications in type 1 diabetes (T1D) are poorly understood. Disease modeling of induced pluripotent stem cells (iPSCs) from patients with longstanding T1D (disease duration ≥ 50 years) with severe (Medalist +C) or absent to mild complications (Medalist -C) revealed impaired growth, reprogramming, and differentiation in Medalist +C. Genomics and proteomics analyses suggested differential regulation of DNA damage checkpoint proteins favoring protection from cellular apoptosis in Medalist -C. In silico analyses showed altered expression patterns of DNA damage checkpoint factors among the Medalist groups to be targets of miR200, whose expression was significantly elevated inmore » Medalist +C serum. Notably, neurons differentiated from Medalist +C iPSCs exhibited enhanced susceptibility to genotoxic stress that worsened upon miR200 overexpression. Furthermore, knockdown of miR200 in Medalist +C fibroblasts and iPSCs rescued checkpoint protein expression and reduced DNA damage. Lastly, we propose miR200-regulated DNA damage checkpoint pathway as a potential therapeutic target for treating complications of diabetes.« less

Preserved DNA Damage Checkpoint Pathway Protects against Complications in Long-Standing Type 1 Diabetes

DOE PAGES

Bhatt, Shweta; Gupta, Manoj K.; Khamaisi, Mogher; ...

2015-08-04

The mechanisms underlying the development of complications in type 1 diabetes (T1D) are poorly understood. Disease modeling of induced pluripotent stem cells (iPSCs) from patients with longstanding T1D (disease duration ≥ 50 years) with severe (Medalist +C) or absent to mild complications (Medalist -C) revealed impaired growth, reprogramming, and differentiation in Medalist +C. Genomics and proteomics analyses suggested differential regulation of DNA damage checkpoint proteins favoring protection from cellular apoptosis in Medalist -C. In silico analyses showed altered expression patterns of DNA damage checkpoint factors among the Medalist groups to be targets of miR200, whose expression was significantly elevated inmore » Medalist +C serum. Notably, neurons differentiated from Medalist +C iPSCs exhibited enhanced susceptibility to genotoxic stress that worsened upon miR200 overexpression. Furthermore, knockdown of miR200 in Medalist +C fibroblasts and iPSCs rescued checkpoint protein expression and reduced DNA damage. Lastly, we propose miR200-regulated DNA damage checkpoint pathway as a potential therapeutic target for treating complications of diabetes.« less

PD-1 checkpoint inhibition: Toxicities and management.

PubMed

Hahn, Andrew W; Gill, David M; Agarwal, Neeraj; Maughan, Benjamin L

2017-12-01

With the recent approval of 5 PD-1/PD-L1 inhibitors for a number of malignancies, PD-1 axis inhibition is drastically changing the treatment landscape of immunotherapy in cancer. As PD-1/PD-L1 are involved in peripheral immune tolerance, inhibition of this immune checkpoint has led to novel immune-related adverse events including colitis, hepatitis, pneumonitis, rash, and endocrinopathies among many others. In this seminar, we will analyze the incidence of immune-related adverse events for nivolumab, pembrolizumab, atezolizumab, durvalumab, and avelumab. Then, we will discuss the specific management of the most common immune-mediated adverse events including colitis, hepatitis, pneumonitis, rash, endocrinopathies, nephritis, and neurologic toxicities. Immune-related adverse events are frequently treated with immunosuppressive medication such as steroids and mycofenolate mofetil. There are specific immune-related adverse events which are frequently seen by the treating oncologist from checkpoint inhibitors. It is essential to understand the recommended treatment options to minimize toxicity and mortality from this important class of anti-neoplastic therapies. Copyright © 2017 Elsevier Inc. All rights reserved.

Immune checkpoint inhibitor toxicity review for the palliative care clinician.

PubMed

Hansen, Eric D; Wang, Xiao; Case, Amy A; Puzanov, Igor; Smith, Tom

2018-05-21

Immune checkpoint inhibitors (ICI) have opened an exciting chapter in the treatment of patients with advanced cancer. For the palliative care clinician, however, ICI present several new challenges, including new ways to define treatment success, as well as treatment-related toxicities which differ in nature and timing from traditional chemotherapy. In this article, we review the mechanism of action of immune checkpoint inhibitors, as well as selected published data supporting the efficacy of ICI in patients with advanced cancer. In addition, we summarize existing data of ICI toxicity prevalence, patterns of severity and timing of onset. Finally, we briefly review key principles from published guidelines on the management of ICI toxicities. Copyright © 2018. Published by Elsevier Inc.

Covering Resilience: A Recent Development for Binomial Checkpointing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walther, Andrea; Narayanan, Sri Hari Krishna

In terms of computing time, adjoint methods offer a very attractive alternative to compute gradient information, required, e.g., for optimization purposes. However, together with this very favorable temporal complexity result comes a memory requirement that is in essence proportional with the operation count of the underlying function, e.g., if algorithmic differentiation is used to provide the adjoints. For this reason, checkpointing approaches in many variants have become popular. This paper analyzes an extension of the so-called binomial approach to cover also possible failures of the computing systems. Such a measure of precaution is of special interest for massive parallel simulationsmore » and adjoint calculations where the mean time between failure of the large scale computing system is smaller than the time needed to complete the calculation of the adjoint information. We describe the extensions of standard checkpointing approaches required for such resilience, provide a corresponding implementation and discuss first numerical results.« less

Mammalian Homologs of Yeast Checkpoint Genes

DTIC Science & Technology

2001-07-01

previous cycle we developed systems and reagents for expression and analysis of all of the pertinent proteins, and are made headway on association of Chk2...function, with emphasis on p53 regulation, cell cycle regulation, and complementation of ATM defects. Saccharomyces Schizosaceharomy Homo sapiens...RAD53, two essential genes, play a central role in DNA damage checkpoints at all cell cycle stages. Our lab showed that Rad9 is a regulator coupling DNA

Casein kinase II is required for the spindle assembly checkpoint by regulating Mad2p in fission yeast

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shimada, Midori; Yamamoto, Ayumu; Murakami-Tonami, Yuko

2009-10-23

The spindle checkpoint is a surveillance mechanism that ensures the fidelity of chromosome segregation in mitosis. Here we show that fission yeast casein kinase II (CK2) is required for this checkpoint function. In the CK2 mutants mitosis occurs in the presence of a spindle defect, and the spindle checkpoint protein Mad2p fails to localize to unattached kinetochores. The CK2 mutants are sensitive to the microtubule depolymerising drug thiabendazole, which is counteracted by ectopic expression of mad2{sup +}. The level of Mad2p is low in the CK2 mutants. These results suggest that CK2 has a role in the spindle checkpoint bymore » regulating Mad2p.« less

Nek2A destruction marks APC/C activation at the prophase-to-prometaphase transition by spindle-checkpoint-restricted Cdc20.

PubMed

Boekhout, Michiel; Wolthuis, Rob

2015-04-15

Nek2 isoform A (Nek2A) is a presumed substrate of the anaphase-promoting complex/cyclosome containing Cdc20 (APC/C(Cdc20)). Nek2A, like cyclin A, is degraded in mitosis while the spindle checkpoint is active. Cyclin A prevents spindle checkpoint proteins from binding to Cdc20 and is recruited to the APC/C in prometaphase. We found that Nek2A and cyclin A avoid being stabilized by the spindle checkpoint in different ways. First, enhancing mitotic checkpoint complex (MCC) formation by nocodazole treatment inhibited the degradation of geminin and cyclin A, whereas Nek2A disappeared at a normal rate. Second, depleting Cdc20 effectively stabilized cyclin A but not Nek2A. Nevertheless, Nek2A destruction crucially depended on Cdc20 binding to the APC/C. Third, in contrast to cyclin A, Nek2A was recruited to the APC/C before the start of mitosis. Interestingly, the spindle checkpoint very effectively stabilized an APC/C-binding mutant of Nek2A, which required the Nek2A KEN box. Apparently, in cells, the spindle checkpoint primarily prevents Cdc20 from binding destruction motifs. Nek2A disappearance marks the prophase-to-prometaphase transition, when Cdc20, regardless of the spindle checkpoint, activates the APC/C. However, Mad2 depletion accelerated Nek2A destruction, showing that spindle checkpoint release further increases APC/C(Cdc20) catalytic activity. © 2015. Published by The Company of Biologists Ltd.

Primary Cilium-Regulated EG-VEGF Signaling Facilitates Trophoblast Invasion.

PubMed

Wang, Chia-Yih; Tsai, Hui-Ling; Syu, Jhih-Siang; Chen, Ting-Yu; Su, Mei-Tsz

2017-06-01

Trophoblast invasion is an important event in embryo implantation and placental development. During these processes, endocrine gland-derived vascular endothelial growth factor (EG-VEGF) is the key regulator mediating the crosstalk at the feto-maternal interface. The primary cilium is a cellular antenna receiving environmental signals and is crucial for proper development. However, little is known regarding the role of the primary cilium in early human pregnancy. Here, we demonstrate that EG-VEGF regulates trophoblast cell invasion via primary cilia. We found that EG-VEGF activated ERK1/2 signaling and subsequent upregulation of MMP2 and MMP9, thereby facilitating cell invasion in human trophoblast HTR-8/SVneo cells. Inhibition of ERK1/2 alleviated the expression of MMPs and trophoblast cell invasion after EG-VEGF treatment. In addition, primary cilia were observed in all the trophoblast cell lines tested and, more importantly, in human first-trimester placental tissue. The receptor of EG-VEGF, PROKR1, was detected in primary cilia. Depletion of IFT88, the intraflagellar transporter required for ciliogenesis, inhibited primary cilium growth, thereby ameliorating ERK1/2 activation, MMP upregulation, and trophoblast cell invasion promoted by EG-VEGF. These findings demonstrate a novel function of primary cilia in controlling EG-VEGF-regulated trophoblast invasion and reveal the underlying molecular mechanism. J. Cell. Physiol. 232: 1467-1477, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Chronic exposure to particulate chromate induces spindle assembly checkpoint bypass in human lung cells.

PubMed

Wise, Sandra S; Holmes, Amie L; Xie, Hong; Thompson, W Douglas; Wise, John Pierce

2006-11-01

One of the hallmarks of lung cancer is chromosome instability (CIN), particularly a tetraploid phenotype, which is normally prevented by the spindle assembly checkpoint. Hexavalent chromium Cr(VI) is an established human lung carcinogen, and Cr(VI) induces tumors at lung bifurcation sites where Cr(VI) particles impact and persist. However, the effects of Cr(VI) on the spindle assembly checkpoint are unknown and little is known about prolonged exposure to particulate Cr(VI). Accordingly, we investigated particulate Cr(VI)-induced bypass of the spindle assembly checkpoint after several days of exposure in WHTBF-6 cells. We found that lead chromate indeed induces spindle assembly checkpoint bypass in human lung cells, as 72, 96, and 120 h treatments with 0.5 or 1 microg/cm2 lead chromate induced significant increases in the percentage of cells with aberrant mitotic figures. For example, treatment with 1 microg/cm2 lead chromate for 96 h induced 11, 12.3, and 14% of cells with premature anaphase, centromere spreading and premature centromere division, respectively. In addition, we found a disruption of mitosis with more cells accumulating in anaphase; cells treated for 96 h increased from 18% in controls to 31% in cells treated with lead chromate. To confirm involvement of the spindle assembly checkpoint, Mad2 expression was used as a marker. Mad2 expression was decreased in cells exposed to chronic treatments of lead chromate, consistent with disruption of the checkpoint. We also found concentration- and time-dependent increases in tetraploid cells, which continued to grow and form colonies. When cells were treated with chronic lead alone there was no increase in aberrant mitotic cells or polyploidy; however, chronic exposure to a soluble Cr(VI) showed an increase in aberrant mitotic cells and polyploidy. These data suggest that lead chromate does induce CIN and may be one mechanism in the development of Cr(VI)-induced lung cancer.

Etoposide radiosensitizes p53-defective cholangiocarcinoma cell lines independent of their G2 checkpoint efficacies

PubMed Central

Hematulin, Arunee; Meethang, Sutiwan; Utapom, Kitsana; Wongkham, Sopit; Sagan, Daniel

2018-01-01

Radiotherapy has been accounted as the most comprehensive cancer treatment modality over the past few decades. However, failure of this treatment modality occurs in several malignancies due to the resistance of cancer cells to radiation. It was previously reported by the present authors that defective cell cycle checkpoints could be used as biomarkers for predicting the responsiveness to radiation in individual patients with cholangiocarcinoma (CCA). However, identification of functional defective cell cycle checkpoints from cells from a patient's tissues is cumbersome and not applicable in the clinic. The present study evaluated the radiosensitization potential of etoposide in p53-defective CCA KKU-M055 and KKU-M214 cell lines. Treatment with etoposide enhanced the responsiveness of two p53-defective CCA cell lines to radiation independent of G2 checkpoint function. In addition, etoposide treatment increased radiation-induced cell death without altering the dominant mode of cell death of the two cell lines. These findings indicate that etoposide could be used as a radiation sensitizer for p53-defective tumors, independent of the function of G2 checkpoint. PMID:29541168

PD-1 immune checkpoint blockade promotes brain leukocyte infiltration and diminishes cyst burden in a mouse model of Toxoplasma infection.

PubMed

Xiao, Jianchun; Li, Ye; Yolken, Robert H; Viscidi, Raphael P

2018-06-15

Tissue cysts, the hallmark of chronic Toxoplasma gondii infection, are predominantly located in the brain making clearance of the parasite difficult. Currently available anti-T. gondii drugs are ineffective on cysts and fail to prevent reactivation of latent toxoplasmosis. We examined whether abrogation of inhibitory signaling pathways that maintain T cells in an exhausted state can be exploited for treating T. gondii tissue cysts. By using a mouse model of chronic toxoplasmosis, we showed immune checkpoint blockade directed against the programmed death-1 (PD-1) pathway results in a significant reduction in brain cyst number (77% lower). We showed leukocyte infiltration (CD3+ T cells, CD8+ T cells, and CD11b + cells) in the leptomeninges, choroid plexus, and subependymal tissue, which are known routes of entry of immune cells into the brain, and in proximal brain parenchyma. Our study provides proof of concept for blockade of immune checkpoint inhibitors as a therapy for chronic toxoplasmosis and potentially for other brain pathogens. Copyright © 2018 Elsevier B.V. All rights reserved.

Immune-related neurological toxicities among solid tumor patients treated with immune checkpoint inhibitors: a systematic review.

PubMed

Eltobgy, Mostafa; Oweira, Hani; Petrausch, Ulf; Helbling, Daniel; Schmidt, Jan; Mehrabi, Arianeb; Schöb, Othmar; Giryes, Anwar; Decker, Michael; Abdel-Rahman, Omar

2017-07-01

Immune-related neurologic toxicities are uncommon but serious adverse events that may be associated with the use of immune checkpoint inhibitors. The objective of this review is to assess the incidence and risk of neurologic toxicities which are potentially immune-related and occur with immune checkpoint treatment of solid tumors. Areas covered: PubMed database has been searched till January 2017. Clinical trials, case series and case reports reporting the occurrence of immune-related neurologic toxicities in solid tumor patients treated with immune checkpoint inhibitors were included. Eighteen trials with 4469 participants were included. The most common neurologic toxicities reported with these agents included sensory and motor peripheral neuropathies. Moreover, 17 case reports describing immune-related neurological events occurring with 22 patients were included. Expert commentary: Immune-related neurological toxicities occur uncommonly in cancer patients treated immune checkpoint inhibitors. Further studies are needed to better describe the course of these events (i.e. time to onset, time to resolution and responsiveness to different immunosuppressives).

Arabidopsis ARGONAUTE7 selects miR390 through multiple checkpoints during RISC assembly

PubMed Central

Endo, Yayoi; Iwakawa, Hiro-oki; Tomari, Yukihide

2013-01-01

Plant ARGONAUTE7 (AGO7) assembles RNA-induced silencing complex (RISC) specifically with miR390 and regulates the auxin-signalling pathway via production of TAS3 trans-acting siRNAs (tasiRNAs). However, how AGO7 discerns miR390 among other miRNAs remains unclear. Here, we show that the 5′ adenosine of miR390 and the central region of miR390/miR390* duplex are critical for the specific interaction with AGO7. Furthermore, despite the existence of mismatches in the seed and central regions of the duplex, cleavage of the miR390* strand is required for maturation of AGO7–RISC. These findings suggest that AGO7 uses multiple checkpoints to select miR390, thereby circumventing promiscuous tasiRNA production. PMID:23732541

Arabidopsis ARGONAUTE7 selects miR390 through multiple checkpoints during RISC assembly.

PubMed

Endo, Yayoi; Iwakawa, Hiro-oki; Tomari, Yukihide

2013-07-01

Plant ARGONAUTE7 (AGO7) assembles RNA-induced silencing complex (RISC) specifically with miR390 and regulates the auxin-signalling pathway via production of TAS3 trans-acting siRNAs (tasiRNAs). However, how AGO7 discerns miR390 among other miRNAs remains unclear. Here, we show that the 5' adenosine of miR390 and the central region of miR390/miR390* duplex are critical for the specific interaction with AGO7. Furthermore, despite the existence of mismatches in the seed and central regions of the duplex, cleavage of the miR390* strand is required for maturation of AGO7-RISC. These findings suggest that AGO7 uses multiple checkpoints to select miR390, thereby circumventing promiscuous tasiRNA production.

Checkpoints couple transcription network oscillator dynamics to cell-cycle progression.

PubMed

Bristow, Sara L; Leman, Adam R; Simmons Kovacs, Laura A; Deckard, Anastasia; Harer, John; Haase, Steven B

2014-09-05

The coupling of cyclin dependent kinases (CDKs) to an intrinsically oscillating network of transcription factors has been proposed to control progression through the cell cycle in budding yeast, Saccharomyces cerevisiae. The transcription network regulates the temporal expression of many genes, including cyclins, and drives cell-cycle progression, in part, by generating successive waves of distinct CDK activities that trigger the ordered program of cell-cycle events. Network oscillations continue autonomously in mutant cells arrested by depletion of CDK activities, suggesting the oscillator can be uncoupled from cell-cycle progression. It is not clear what mechanisms, if any, ensure that the network oscillator is restrained when progression in normal cells is delayed or arrested. A recent proposal suggests CDK acts as a master regulator of cell-cycle processes that have the potential for autonomous oscillatory behavior. Here we find that mitotic CDK is not sufficient for fully inhibiting transcript oscillations in arrested cells. We do find that activation of the DNA replication and spindle assembly checkpoints can fully arrest the network oscillator via overlapping but distinct mechanisms. Further, we demonstrate that the DNA replication checkpoint effector protein, Rad53, acts to arrest a portion of transcript oscillations in addition to its role in halting cell-cycle progression. Our findings indicate that checkpoint mechanisms, likely via phosphorylation of network transcription factors, maintain coupling of the network oscillator to progression during cell-cycle arrest.

Combining Immune Checkpoint Inhibitors and Kinase-Inhibiting Supramolecular Therapeutics for Enhanced Anticancer Efficacy.

PubMed

Kulkarni, Ashish; Natarajan, Siva Kumar; Chandrasekar, Vineethkrishna; Pandey, Prithvi Raj; Sengupta, Shiladitya

2016-09-29

A major limitation of immune checkpoint inhibitors is that only a small subset of patients achieve durable clinical responses. This necessitates the development of combinatorial regimens with immunotherapy. However, some combinations, such as MEK- or PI3K-inhibitors with a PD1-PDL1 checkpoint inhibitor, are pharmacologically challenging to implement. We rationalized that such combinations can be enabled using nanoscale supramolecular targeted therapeutics, which spatially home into tumors and exert temporally sustained inhibition of the target. Here we describe two case studies where nanoscale MEK- and PI3K-targeting supramolecular therapeutics were engineered using a quantum mechanical all-atomistic simulation-based approach. The combinations of nanoscale MEK- and PI3K-targeting supramolecular therapeutics with checkpoint PDL1 and PD1 inhibitors exert enhanced antitumor outcome in melanoma and breast cancers in vivo, respectively. Additionally, the temporal sequence of administration impacts the outcome. The combination of supramolecular therapeutics and immunotherapy could emerge as a paradigm shift in the treatment of cancer.

SPARC: Demonstrate burst-buffer-based checkpoint/restart on ATS-1.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oldfield, Ron A.; Ulmer, Craig D.; Widener, Patrick

Recent high-performance computing (HPC) platforms such as the Trinity Advanced Technology System (ATS-1) feature burst buffer resources that can have a dramatic impact on an application’s I/O performance. While these non-volatile memory (NVM) resources provide a new tier in the storage hierarchy, developers must find the right way to incorporate the technology into their applications in order to reap the benefits. Similar to other laboratories, Sandia is actively investigating ways in which these resources can be incorporated into our existing libraries and workflows without burdening our application developers with excessive, platform-specific details. This FY18Q1 milestone summaries our progress in adaptingmore » the Sandia Parallel Aerodynamics and Reentry Code (SPARC) in Sandia’s ATDM program to leverage Trinity’s burst buffers for checkpoint/restart operations. We investigated four different approaches with varying tradeoffs in this work: (1) simply updating job script to use stage-in/stage out burst buffer directives, (2) modifying SPARC to use LANL’s hierarchical I/O (HIO) library to store/retrieve checkpoints, (3) updating Sandia’s IOSS library to incorporate the burst buffer in all meshing I/O operations, and (4) modifying SPARC to use our Kelpie distributed memory library to store/retrieve checkpoints. Team members were successful in generating initial implementation for all four approaches, but were unable to obtain performance numbers in time for this report (reasons: initial problem sizes were not large enough to stress I/O, and SPARC refactor will require changes to our code). When we presented our work to the SPARC team, they expressed the most interest in the second and third approaches. The HIO work was favored because it is lightweight, unobtrusive, and should be portable to ATS-2. The IOSS work is seen as a long-term solution, and is favored because all I/O work (including checkpoints) can be deferred to a single library.« less

The Pch2 AAA+ ATPase promotes phosphorylation of the Hop1 meiotic checkpoint adaptor in response to synaptonemal complex defects

PubMed Central

Herruzo, Esther; Ontoso, David; González-Arranz, Sara; Cavero, Santiago; Lechuga, Ana; San-Segundo, Pedro A.

2016-01-01

Meiotic cells possess surveillance mechanisms that monitor critical events such as recombination and chromosome synapsis. Meiotic defects resulting from the absence of the synaptonemal complex component Zip1 activate a meiosis-specific checkpoint network resulting in delayed or arrested meiotic progression. Pch2 is an evolutionarily conserved AAA+ ATPase required for the checkpoint-induced meiotic block in the zip1 mutant, where Pch2 is only detectable at the ribosomal DNA array (nucleolus). We describe here that high levels of the Hop1 protein, a checkpoint adaptor that localizes to chromosome axes, suppress the checkpoint defect of a zip1 pch2 mutant restoring Mek1 activity and meiotic cell cycle delay. We demonstrate that the critical role of Pch2 in this synapsis checkpoint is to sustain Mec1-dependent phosphorylation of Hop1 at threonine 318. We also show that the ATPase activity of Pch2 is essential for its checkpoint function and that ATP binding to Pch2 is required for its localization. Previous work has shown that Pch2 negatively regulates Hop1 chromosome abundance during unchallenged meiosis. Based on our results, we propose that, under checkpoint-inducing conditions, Pch2 also possesses a positive action on Hop1 promoting its phosphorylation and its proper distribution on unsynapsed chromosome axes. PMID:27257060

The Pch2 AAA+ ATPase promotes phosphorylation of the Hop1 meiotic checkpoint adaptor in response to synaptonemal complex defects.

PubMed

Herruzo, Esther; Ontoso, David; González-Arranz, Sara; Cavero, Santiago; Lechuga, Ana; San-Segundo, Pedro A

2016-09-19

Meiotic cells possess surveillance mechanisms that monitor critical events such as recombination and chromosome synapsis. Meiotic defects resulting from the absence of the synaptonemal complex component Zip1 activate a meiosis-specific checkpoint network resulting in delayed or arrested meiotic progression. Pch2 is an evolutionarily conserved AAA+ ATPase required for the checkpoint-induced meiotic block in the zip1 mutant, where Pch2 is only detectable at the ribosomal DNA array (nucleolus). We describe here that high levels of the Hop1 protein, a checkpoint adaptor that localizes to chromosome axes, suppress the checkpoint defect of a zip1 pch2 mutant restoring Mek1 activity and meiotic cell cycle delay. We demonstrate that the critical role of Pch2 in this synapsis checkpoint is to sustain Mec1-dependent phosphorylation of Hop1 at threonine 318. We also show that the ATPase activity of Pch2 is essential for its checkpoint function and that ATP binding to Pch2 is required for its localization. Previous work has shown that Pch2 negatively regulates Hop1 chromosome abundance during unchallenged meiosis. Based on our results, we propose that, under checkpoint-inducing conditions, Pch2 also possesses a positive action on Hop1 promoting its phosphorylation and its proper distribution on unsynapsed chromosome axes. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

Crystal structure of checkpoint kinase 2 in complex with NSC 109555, a potent and selective inhibitor

PubMed Central

Lountos, George T; Tropea, Joseph E; Zhang, Di; Jobson, Andrew G; Pommier, Yves; Shoemaker, Robert H; Waugh, David S

2009-01-01

Checkpoint kinase 2 (Chk2), a ser/thr kinase involved in the ATM-Chk2 checkpoint pathway, is activated by genomic instability and DNA damage and results in either arrest of the cell cycle to allow DNA repair to occur or apoptosis if the DNA damage is severe. Drugs that specifically target Chk2 could be beneficial when administered in combination with current DNA-damaging agents used in cancer therapy. Recently, a novel inhibitor of Chk2, NSC 109555, was identified that exhibited high potency (IC50 = 240 nM) and selectivity. This compound represents a new chemotype and lead for the development of novel Chk2 inhibitors that could be used as therapeutic agents for the treatment of cancer. To facilitate the discovery of new analogs of NSC 109555 with even greater potency and selectivity, we have solved the crystal structure of this inhibitor in complex with the catalytic domain of Chk2. The structure confirms that the compound is an ATP-competitive inhibitor, as the electron density clearly reveals that it occupies the ATP-binding pocket. However, the mode of inhibition differs from that of the previously studied structure of Chk2 in complex with debromohymenialdisine, a compound that inhibits both Chk1 and Chk2. A unique hydrophobic pocket in Chk2, located very close to the bound inhibitor, presents an opportunity for the rational design of compounds with higher binding affinity and greater selectivity. PMID:19177354

Caffeine stabilizes Cdc25 independently of Rad3 in S chizosaccharomyces pombe contributing to checkpoint override

PubMed Central

Alao, John P; Sjölander, Johanna J; Baar, Juliane; Özbaki-Yagan, Nejla; Kakoschky, Bianca; Sunnerhagen, Per

2014-01-01

Cdc25 is required for Cdc2 dephosphorylation and is thus essential for cell cycle progression. Checkpoint activation requires dual inhibition of Cdc25 and Cdc2 in a Rad3-dependent manner. Caffeine is believed to override activation of the replication and DNA damage checkpoints by inhibiting Rad3-related proteins in both S chizosaccharomyces pombe and mammalian cells. In this study, we have investigated the impact of caffeine on Cdc25 stability, cell cycle progression and checkpoint override. Caffeine induced Cdc25 accumulation in S . pombe independently of Rad3. Caffeine delayed cell cycle progression under normal conditions but advanced mitosis in cells treated with replication inhibitors and DNA-damaging agents. In the absence of Cdc25, caffeine inhibited cell cycle progression even in the presence of hydroxyurea or phleomycin. Caffeine induces Cdc25 accumulation in S . pombe by suppressing its degradation independently of Rad3. The induction of Cdc25 accumulation was not associated with accelerated progression through mitosis, but rather with delayed progression through cytokinesis. Caffeine-induced Cdc25 accumulation appears to underlie its ability to override cell cycle checkpoints. The impact of Cdc25 accumulation on cell cycle progression is attenuated by Srk1 and Mad2. Together our findings suggest that caffeine overrides checkpoint enforcement by inducing the inappropriate nuclear localization of Cdc25. PMID:24666325

Effects of Selective Checkpoint Kinase 1 Inhibition on Cytarabine Cytotoxicity in Acute Myelogenous Leukemia Cells in Vitro

PubMed Central

Schenk, Erin L.; Koh, Brian D.; Flatten, Karen S.; Peterson, Kevin L.; Parry, David; Hess, Allan D.; Smith, B. Douglas; Karp, Judith E.; Karnitz, Larry M.; Kaufmann, Scott H.

2012-01-01

Purpose Previous studies have demonstrated that the replication checkpoint, which involves the kinases ATR and Chk1, contributes to cytarabine resistance in cell lines. In the present study, we examined whether this checkpoint is activated in clinical AML during cytarabine infusion in vivo and then assessed the impact of combining cytarabine with the recently described Chk1 inhibitor SCH 900776 in vitro. Experimental design AML marrow aspirates harvested before and during cytarabine infusion were examined by immunoblotting. Human AML lines treated with cytarabine in the absence or presence of SCH 900776 were assayed for checkpoint activation by immunoblotting, nucleotide incorporation into DNA and flow cytometry. Long-term effects in AML lines, clinical AML isolates, and normal myeloid progenitors were assayed using clonogenic assays. Results Immunoblotting demonstrated increased Chk1 phosphorylation, a marker of checkpoint activation, in over half of Chk1-containing AMLs after 48 h of cytarabine infusion. In human AML lines, SCH 900776 not only disrupted cytarabine-induced Chk1 activation and S phase arrest, but also markedly increased cytarabine-induced apoptosis. Clonogenic assays demonstrated that SCH 900776 enhanced the anti-proliferative effects of cytarabine in AML cell lines and clinical AML samples at concentrations that had negligible impact on normal myeloid progenitors. Conclusions These results not only provide evidence for cytarabine-induced S phase checkpoint activation in AML in the clinical setting, but also show that a selective Chk1 inhibitor can overcome the S phase checkpoint and enhance the cytotoxicity of cytarabine. Accordingly, further investigation of the cytarabine/SCH 900776 combination in AML appears warranted. PMID:22869869

TopBP1 functions with 53BP1 in the G1 DNA damage checkpoint

PubMed Central

Cescutti, Rachele; Negrini, Simona; Kohzaki, Masaoki; Halazonetis, Thanos D

2010-01-01

TopBP1 is a checkpoint protein that colocalizes with ATR at sites of DNA replication stress. In this study, we show that TopBP1 also colocalizes with 53BP1 at sites of DNA double-strand breaks (DSBs), but only in the G1-phase of the cell cycle. Recruitment of TopBP1 to sites of DNA replication stress was dependent on BRCT domains 1–2 and 7–8, whereas recruitment to sites of DNA DSBs was dependent on BRCT domains 1–2 and 4–5. The BRCT domains 4–5 interacted with 53BP1 and recruitment of TopBP1 to sites of DNA DSBs in G1 was dependent on 53BP1. As TopBP1 contains a domain important for ATR activation, we examined whether it contributes to the G1 cell cycle checkpoint. By monitoring the entry of irradiated G1 cells into S-phase, we observed a checkpoint defect after siRNA-mediated depletion of TopBP1, 53BP1 or ATM. Thus, TopBP1 may mediate the checkpoint function of 53BP1 in G1. PMID:20871591

TopBP1 functions with 53BP1 in the G1 DNA damage checkpoint.

PubMed

Cescutti, Rachele; Negrini, Simona; Kohzaki, Masaoki; Halazonetis, Thanos D

2010-11-03

TopBP1 is a checkpoint protein that colocalizes with ATR at sites of DNA replication stress. In this study, we show that TopBP1 also colocalizes with 53BP1 at sites of DNA double-strand breaks (DSBs), but only in the G1-phase of the cell cycle. Recruitment of TopBP1 to sites of DNA replication stress was dependent on BRCT domains 1-2 and 7-8, whereas recruitment to sites of DNA DSBs was dependent on BRCT domains 1-2 and 4-5. The BRCT domains 4-5 interacted with 53BP1 and recruitment of TopBP1 to sites of DNA DSBs in G1 was dependent on 53BP1. As TopBP1 contains a domain important for ATR activation, we examined whether it contributes to the G1 cell cycle checkpoint. By monitoring the entry of irradiated G1 cells into S-phase, we observed a checkpoint defect after siRNA-mediated depletion of TopBP1, 53BP1 or ATM. Thus, TopBP1 may mediate the checkpoint function of 53BP1 in G1.

Identification and purification of a soluble region of BubR1: a critical component of the mitotic checkpoint complex.

PubMed

Yoon, Jongchul; Kang, Yup; Kim, Kyunggon; Park, Jungeun; Kim, Youngsoo

2005-11-01

The mitotic checkpoint complex (MCC) ensures the fidelity of chromosomal segregation, by delaying the onset of anaphase until all sister chromatids have been properly attached to the mitotic spindle. In essence, this MCC-induced delay is achieved via the inhibition of the anaphase-promoting complex (APC). Among the components of the MCC, BubR1 plays two major roles in the functions of the mitotic checkpoint. First, BubR1 is able to inhibit APC activity, either by itself or as a component of the MCC, by sequestering a APC coactivator, known as Cdc20. Second, BubR1 activates mitotic checkpoint signaling cascades by binding to the centromere-associated protein E, a microtubule motor protein. Obtaining highly soluble BubR1 is a prerequisite for the study of its structure. BubR1 is a multi-domain protein, which includes a KEN box motif, a mad3-like region, a Bub3 binding domain, and a kinase domain. We obtained a soluble BubR1 construct using a three-step expression strategy. First, we obtained two constructs from BLAST sequence homology searches, both of which were expressed abundantly in the inclusion bodies. We then adjusted the lengths of the two constructs by secondary structure prediction, thereby generating partially soluble constructs. Third, we optimized the solubility of the two constructs by either chopping or adding a few residues at the C-terminus. Finally, we obtained a highly soluble BubR1 construct via the Escherichia coli expression system, which allowed for a yield of 10.8 mg/L culture. This report may provide insight into the design of highly soluble constructs of insoluble multi-domain proteins.

crm-1 facilitates BMP signaling to control body size in Caenorhabditis elegans.

PubMed

Fung, Wong Yan; Fat, Ko Frankie Chi; Eng, Cheah Kathryn Song; Lau, Chow King

2007-11-01

We have identified in Caenorhabditis elegans a homologue of the vertebrate Crim1, crm-1, which encodes a putative transmembrane protein with multiple cysteine-rich (CR) domains known to have bone morphogenetic proteins (BMPs) binding activity. Using the body morphology of C. elegans as an indicator, we showed that attenuation of crm-1 activity leads to a small body phenotype reminiscent of that of BMP pathway mutants. We showed that the crm-1 loss-of-function phenotype can be rescued by constitutive supply of sma-4 activity. crm-1 can enhance BMP signaling and this activity is dependent on the presence of the DBL-1 ligand and its receptors. crm-1 is expressed in neurons at the ventral nerve cord, where the DBL-1 ligand is produced. However, ectopic expression experiments reveal that crm-1 gene products act outside the DBL-1 producing cells and function non-autonomously to facilitate dbl/sma pathway signaling to control body size.

c-Myb Coordinates Survival and the Expression of Genes That Are Critical for the Pre-BCR Checkpoint.

PubMed

Fahl, Shawn P; Daamen, Andrea R; Crittenden, Rowena B; Bender, Timothy P

2018-05-15

The c-Myb transcription factor is required for adult hematopoiesis, yet little is known about c-Myb function during lineage-specific differentiation due to the embryonic lethality of Myb -null mutations. We previously used tissue-specific inactivation of the murine Myb locus to demonstrate that c-Myb is required for differentiation to the pro-B cell stage, survival during the pro-B cell stage, and the pro-B to pre-B cell transition during B lymphopoiesis. However, few downstream mediators of c-Myb-regulated function have been identified. We demonstrate that c-Myb regulates the intrinsic survival of CD19 + pro-B cells in the absence of IL-7 by repressing expression of the proapoptotic proteins Bmf and Bim and that levels of Bmf and Bim mRNA are further repressed by IL-7 signaling in pro-B cells. c-Myb regulates two crucial components of the IL-7 signaling pathway: the IL-7Rα-chain and the negative regulator SOCS3 in CD19 + pro-B cells. Bypassing IL-7R signaling through constitutive activation of Stat5b largely rescues survival of c-Myb-deficient pro-B cells, whereas constitutively active Akt is much less effective. However, rescue of pro-B cell survival is not sufficient to rescue proliferation of pro-B cells or the pro-B to small pre-B cell transition, and we further demonstrate that c-Myb-deficient large pre-B cells are hypoproliferative. Analysis of genes crucial for the pre-BCR checkpoint demonstrates that, in addition to IL-7Rα, the genes encoding λ5, cyclin D3, and CXCR4 are downregulated in the absence of c-Myb, and λ5 is a direct c-Myb target. Thus, c-Myb coordinates survival with the expression of genes that are required during the pre-BCR checkpoint. Copyright © 2018 by The American Association of Immunologists, Inc.

Genetic Control of the Trigger for the G2/M Checkpoint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, Eric J.; Smilenov, Lubomir B.; Young, Erik F.

culture system, the engagement of the G2/M checkpoint only occurs at doses where most of the cells are bound for mitotic catastrophe. Further, compound haploinsufficiency of various radiosensitizing genes does not impact the threshold of activation. The experiments confirm a threshold of activation for the G2/M checkpoint, hinting at two separate radiation response programs acting below and above this threshold. Small RNA transfer in bystander effect biology: Small regulatory RNA molecules have now risen in prominence and utility. Specific examples are small interfering RNAs (siRNA) which are employed in cell level expression ablation projects and micro-RNAs (miRNA) which are a pool of short transcription products which serve to modulate the expression of other transcripts emerging from the genome in a meta-regulatory fine tuning of gene expression. The existing tenets of bystander effect radiation biology involve the communication of inflammatory mediators or direct intercellular communication of reactive oxygen/nitrogen species in cell-to-cell communicative organelles called gap junctions. By ablating gap junctions, reducing the ROS/inflammatory cytokine expression one can attenuate bystander effect signaling in cell culture systems. We hypothesized that miRNAs are a competent intercellular communication molecule and therefore a possible component of the bystander response. This view is supported by the observation that miRNA are secreted from cells in exosomes found in the circulation. This circulating pool reports disease type and severity in humans. We proposed use of microbeam irradiation technology at our facilities and enhancement of this capability with a new sorting technology which would allow us to sort irradiated and non-irradiated cells with absolute fidelity. Pursuing direct quantitative transfer assessment, we succeeded in designing and constructing a new add-on sorting appliance which harmonized with our existing instruments. The sorter allowed us to

A drift-diffusion checkpoint model predicts a highly variable and growth-factor-sensitive portion of the cell cycle G1 phase.

PubMed

Jones, Zack W; Leander, Rachel; Quaranta, Vito; Harris, Leonard A; Tyson, Darren R

2018-01-01

Even among isogenic cells, the time to progress through the cell cycle, or the intermitotic time (IMT), is highly variable. This variability has been a topic of research for several decades and numerous mathematical models have been proposed to explain it. Previously, we developed a top-down, stochastic drift-diffusion+threshold (DDT) model of a cell cycle checkpoint and showed that it can accurately describe experimentally-derived IMT distributions [Leander R, Allen EJ, Garbett SP, Tyson DR, Quaranta V. Derivation and experimental comparison of cell-division probability densities. J. Theor. Biol. 2014;358:129-135]. Here, we use the DDT modeling approach for both descriptive and predictive data analysis. We develop a custom numerical method for the reliable maximum likelihood estimation of model parameters in the absence of a priori knowledge about the number of detectable checkpoints. We employ this method to fit different variants of the DDT model (with one, two, and three checkpoints) to IMT data from multiple cell lines under different growth conditions and drug treatments. We find that a two-checkpoint model best describes the data, consistent with the notion that the cell cycle can be broadly separated into two steps: the commitment to divide and the process of cell division. The model predicts one part of the cell cycle to be highly variable and growth factor sensitive while the other is less variable and relatively refractory to growth factor signaling. Using experimental data that separates IMT into G1 vs. S, G2, and M phases, we show that the model-predicted growth-factor-sensitive part of the cell cycle corresponds to a portion of G1, consistent with previous studies suggesting that the commitment step is the primary source of IMT variability. These results demonstrate that a simple stochastic model, with just a handful of parameters, can provide fundamental insights into the biological underpinnings of cell cycle progression.

Endocrine-related adverse events associated with immune checkpoint blockade and expert insights on their management.

PubMed

Sznol, Mario; Postow, Michael A; Davies, Marianne J; Pavlick, Anna C; Plimack, Elizabeth R; Shaheen, Montaser; Veloski, Colleen; Robert, Caroline

2017-07-01

Agents that modulate immune checkpoint proteins, such as cytotoxic T-lymphocyte antigen-4 (CTLA-4) and programmed death receptor-1 (PD-1), have become a mainstay in cancer treatment. The clinical benefit afforded by immune checkpoint inhibitors can be accompanied by immune-related adverse events (irAE) that affect the skin, gastrointestinal tract, liver, and endocrine system. The types of irAEs associated with immune checkpoint inhibitors are generally consistent across tumor types. Immune-related endocrine events can affect the pituitary, thyroid, and adrenal glands, as well as other downstream target organs. These events are unique when compared with other irAEs because the manifestations are often irreversible. Immune-related endocrine events are typically grade 1/2 in severity and often present with non-specific symptoms, making them difficult to diagnose. The mechanisms underlying immune-related target organ damage in select individuals remain mostly undefined. Management includes close patient monitoring, appropriate laboratory testing for endocrine function, replacement of hormones, and consultation with an endocrinologist when appropriate. An awareness of the symptoms and management of immune-related endocrine events may aid in the safe and appropriate use of immune checkpoint inhibitors in clinical practice. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

A tumor suppressor role of the Bub3 spindle checkpoint protein after apoptosis inhibition

PubMed Central

Moutinho-Santos, Tatiana

2013-01-01

Most solid tumors contain aneuploid cells, indicating that the mitotic checkpoint is permissive to the proliferation of chromosomally aberrant cells. However, mutated or altered expression of mitotic checkpoint genes accounts for a minor proportion of human tumors. We describe a Drosophila melanogaster tumorigenesis model derived from knocking down spindle assembly checkpoint (SAC) genes and preventing apoptosis in wing imaginal discs. Bub3-deficient tumors that were also deficient in apoptosis displayed neoplastic growth, chromosomal aneuploidy, and high proliferative potential after transplantation into adult flies. Inducing aneuploidy by knocking down CENP-E and preventing apoptosis does not induce tumorigenesis, indicating that aneuploidy is not sufficient for hyperplasia. In this system, the aneuploidy caused by a deficient SAC is not driving tumorigenesis because preventing Bub3 from binding to the kinetochore does not cause hyperproliferation. Our data suggest that Bub3 has a nonkinetochore-dependent function that is consistent with its role as a tumor suppressor. PMID:23609535

Optimal management of immune-related adverse events resulting from treatment with immune checkpoint inhibitors: a review and update.

PubMed

Nagai, Hiroki; Muto, Manabu

2018-06-01

Over the last two decades, molecular-targeted agents have become mainstream treatment for many types of malignancies and have improved the overall survival of patients. However, most patients eventually develop resistance to these targeted therapies. Recently, immunotherapies such as immune checkpoint inhibitors have revolutionized the treatment paradigm for many types of malignancies. Immune checkpoint inhibitors have been approved for treatment of melanoma, non-small cell lung cancer, renal cell carcinoma, head and neck squamous cell carcinoma, Hodgkin's lymphoma, bladder cancer and gastric cancer. However, oncologists have been faced with immune-related adverse events caused by immune checkpoint inhibitors; these are generally mild but can be fatal in some cases. Because immune checkpoint inhibitors have distinct toxicity profiles from those of chemotherapy or targeted therapy, many oncologists are not familiar with the principles for optimal management of immune-related adverse events, which require early recognition and appropriate treatment without delay. To achieve this, oncologists must educate patients and health-care workers, develop checklists of appropriate tests for immune-related adverse events and collaborate closely with organ specialists. Clinical questions that remain include whether immune checkpoint inhibitors should be administered to patients with autoimmune disease and whether patients for whom immune-related adverse events lead to delays in immunotherapy should be retreated. In addition, the predicted use of combination immunotherapies in the near future means that oncologists will face a higher incidence and severity of immune-related adverse events. This review provides an overview of the optimal management of immune-related adverse events attributed to immune checkpoint inhibitors.

Efficient checkpointing schemes for depletion perturbation solutions on memory-limited architectures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stripling, H. F.; Adams, M. L.; Hawkins, W. D.

2013-07-01

We describe a methodology for decreasing the memory footprint and machine I/O load associated with the need to access a forward solution during an adjoint solve. Specifically, we are interested in the depletion perturbation equations, where terms in the adjoint Bateman and transport equations depend on the forward flux solution. Checkpointing is the procedure of storing snapshots of the forward solution to disk and using these snapshots to recompute the parts of the forward solution that are necessary for the adjoint solve. For large problems, however, the storage cost of just a few copies of an angular flux vector canmore » exceed the available RAM on the host machine. We propose a methodology that does not checkpoint the angular flux vector; instead, we write and store converged source moments, which are typically of a much lower dimension than the angular flux solution. This reduces the memory footprint and I/O load of the problem, but requires that we perform single sweeps to reconstruct flux vectors on demand. We argue that this trade-off is exactly the kind of algorithm that will scale on advanced, memory-limited architectures. We analyze the cost, in terms of FLOPS and memory footprint, of five checkpointing schemes. We also provide computational results that support the analysis and show that the memory-for-work trade off does improve time to solution. (authors)« less

Expanded CAG/CTG Repeat DNA Induces a Checkpoint Response That Impacts Cell Proliferation in Saccharomyces cerevisiae

PubMed Central

Sundararajan, Rangapriya; Freudenreich, Catherine H.

2011-01-01

Repetitive DNA elements are mutational hotspots in the genome, and their instability is linked to various neurological disorders and cancers. Although it is known that expanded trinucleotide repeats can interfere with DNA replication and repair, the cellular response to these events has not been characterized. Here, we demonstrate that an expanded CAG/CTG repeat elicits a DNA damage checkpoint response in budding yeast. Using microcolony and single cell pedigree analysis, we found that cells carrying an expanded CAG repeat frequently experience protracted cell division cycles, persistent arrests, and morphological abnormalities. These phenotypes were further exacerbated by mutations in DSB repair pathways, including homologous recombination and end joining, implicating a DNA damage response. Cell cycle analysis confirmed repeat-dependent S phase delays and G2/M arrests. Furthermore, we demonstrate that the above phenotypes are due to the activation of the DNA damage checkpoint, since expanded CAG repeats induced the phosphorylation of the Rad53 checkpoint kinase in a rad52Δ recombination deficient mutant. Interestingly, cells mutated for the MRX complex (Mre11-Rad50-Xrs2), a central component of DSB repair which is required to repair breaks at CAG repeats, failed to elicit repeat-specific arrests, morphological defects, or Rad53 phosphorylation. We therefore conclude that damage at expanded CAG/CTG repeats is likely sensed by the MRX complex, leading to a checkpoint response. Finally, we show that repeat expansions preferentially occur in cells experiencing growth delays. Activation of DNA damage checkpoints in repeat-containing cells could contribute to the tissue degeneration observed in trinucleotide repeat expansion diseases. PMID:21437275

Implementing forward recovery using checkpointing in distributed systems

NASA Technical Reports Server (NTRS)

Long, Junsheng; Fuchs, W. K.; Abraham, Jacob A.

1991-01-01

The paper describes the implementation of a forward recovery scheme using checkpoints and replicated tasks. The implementation is based on the concept of lookahead execution and rollback validation. In the experiment, two tasks are selected for the normal execution and one for rollback validation. It is shown that the recovery strategy has nearly error-free execution time and an average redundancy lower than TMR.

5-ASA affects cell cycle progression in colorectal cells by reversibly activating a replication checkpoint.

PubMed

Luciani, M Gloria; Campregher, Christoph; Fortune, John M; Kunkel, Thomas A; Gasche, Christoph

2007-01-01

Individuals with inflammatory bowel disease are at risk of developing colorectal cancer (CRC). Epidemiologic, animal, and laboratory studies suggest that 5-amino-salicylic acid (5-ASA) protects from the development of CRC by altering cell cycle progression and by inducing apoptosis. Our previous results indicate that 5-ASA improves replication fidelity in colorectal cells, an effect that is active in reducing mutations. In this study, we hypothesized that 5-ASA restrains cell cycle progression by activating checkpoint pathways in colorectal cell lines, which would prevent tumor development and improve genomic stability. CRC cells with different genetic backgrounds such as HT29, HCT116, HCT116(p53-/-), HCT116+chr3, and LoVo were treated with 5-ASA for 2-96 hours. Cell cycle progression, phosphorylation, and DNA binding of cell cycle checkpoint proteins were analyzed. We found that 5-ASA at concentrations between 10 and 40 mmol/L affects cell cycle progression by inducing cells to accumulate in the S phase. This effect was independent of the hMLH1, hMSH2, and p53 status because it was observed to a similar extent in all cell lines under investigation. Moreover, wash-out experiments demonstrated reversibility within 48 hours. Although p53 did not have a causative role, p53 Ser15 was strongly phosphorylated. Proteins involved in the ATM-and-Rad3-related kinase (ATR)-dependent S-phase checkpoint response (Chk1 and Rad17) were also phosphorylated but not ataxia telengectasia mutated kinase. Our data demonstrate that 5-ASA causes cells to reversibly accumulate in S phase and activate an ATR-dependent checkpoint. The activation of replication checkpoint may slow down DNA replication and improve DNA replication fidelity, which increases the maintenance of genomic stability and counteracts carcinogenesis.

5-ASA Affects Cell Cycle Progression in Colorectal Cells by Reversibly Activating a Replication Checkpoint

PubMed Central

LUCIANI, M. GLORIA; CAMPREGHER, CHRISTOPH; FORTUNE, JOHN M.; KUNKEL, THOMAS A.; GASCHE, CHRISTOPH

2007-01-01

Background & Aims Individuals with inflammatory bowel disease are at risk of developing colorectal cancer (CRC). Epidemiologic, animal, and laboratory studies suggest that 5-amino-salicylic acid (5-ASA) protects from the development of CRC by altering cell cycle progression and by inducing apoptosis. Our previous results indicate that 5-ASA improves replication fidelity in colorectal cells, an effect that is active in reducing mutations. In this study, we hypothesized that 5-ASA restrains cell cycle progression by activating checkpoint pathways in colorectal cell lines, which would prevent tumor development and improve genomic stability. Methods CRC cells with different genetic backgrounds such as HT29, HCT116, HCT116p53−/−, HCT116+chr3, and LoVo were treated with 5-ASA for 2–96 hours. Cell cycle progression, phosphorylation, and DNA binding of cell cycle checkpoint proteins were analyzed. Results We found that 5-ASA at concentrations between 10 and 40 mmol/L affects cell cycle progression by inducing cells to accumulate in the S phase. This effect was independent of the hMLH1, hMSH2, and p53 status because it was observed to a similar extent in all cell lines under investigation. Moreover, wash-out experiments demonstrated reversibility within 48 hours. Although p53 did not have a causative role, p53 Ser15 was strongly phosphorylated. Proteins involved in the ATM-and-Rad3-related kinase (ATR)-dependent S-phase checkpoint response (Chk1 and Rad17) were also phosphorylated but not ataxia telengectasia mutated kinase. Conclusions Our data demonstrate that 5-ASA causes cells to reversibly accumulate in S phase and activate an ATR-dependent checkpoint. The activation of replication checkpoint may slow down DNA replication and improve DNA replication fidelity, which increases the maintenance of genomic stability and counteracts carcinogenesis. PMID:17241873

Latent memory facilitates relearning through molecular signaling mechanisms that are distinct from original learning.

PubMed

Menges, Steven A; Riepe, Joshua R; Philips, Gary T

2015-09-01

A highly conserved feature of memory is that it can exist in a latent, non-expressed state which is revealed during subsequent learning by its ability to significantly facilitate (savings) or inhibit (latent inhibition) subsequent memory formation. Despite the ubiquitous nature of latent memory, the mechanistic nature of the latent memory trace and its ability to influence subsequent learning remains unclear. The model organism Aplysia californica provides the unique opportunity to make strong links between behavior and underlying cellular and molecular mechanisms. Using Aplysia, we have studied the mechanisms of savings due to latent memory for a prior, forgotten experience. We previously reported savings in the induction of three distinct temporal domains of memory: short-term (10min), intermediate-term (2h) and long-term (24h). Here we report that savings memory formation utilizes molecular signaling pathways that are distinct from original learning: whereas the induction of both original intermediate- and long-term memory in naïve animals requires mitogen activated protein kinase (MAPK) activation and ongoing protein synthesis, 2h savings memory is not disrupted by inhibitors of MAPK or protein synthesis, and 24h savings memory is not dependent on MAPK activation. Collectively, these findings reveal that during forgetting, latent memory for the original experience can facilitate relearning through molecular signaling mechanisms that are distinct from original learning. Copyright © 2015 Elsevier Inc. All rights reserved.

[Sea urchin embryo, DNA-damaged cell cycle checkpoint and the mechanisms initiating cancer development].

PubMed

Bellé, Robert; Le Bouffant, Ronan; Morales, Julia; Cosson, Bertrand; Cormier, Patrick; Mulner-Lorillon, Odile

2007-01-01

Cell division is an essential process for heredity, maintenance and evolution of the whole living kingdom. Sea urchin early development represents an excellent experimental model for the analysis of cell cycle checkpoint mechanisms since embryonic cells contain a functional DNA-damage checkpoint and since the whole sea urchin genome is sequenced. The DNA-damaged checkpoint is responsible for an arrest in the cell cycle when DNA is damaged or incorrectly replicated, for activation of the DNA repair mechanism, and for commitment to cell death by apoptosis in the case of failure to repair. New insights in cancer biology lead to two fundamental concepts about the very first origin of cancerogenesis. Cancers result from dysfunction of DNA-damaged checkpoints and cancers appear as a result of normal stem cell (NCS) transformation into a cancer stem cell (CSC). The second aspect suggests a new definition of "cancer", since CSC can be detected well before any clinical evidence. Since early development starts from the zygote, which is a primary stem cell, sea urchin early development allows analysis of the early steps of the cancerization process. Although sea urchins do not develop cancers, the model is alternative and complementary to stem cells which are not easy to isolate, do not divide in a short time and do not divide synchronously. In the field of toxicology and incidence on human health, the sea urchin experimental model allows assessment of cancer risk from single or combined molecules long before any epidemiologic evidence is available. Sea urchin embryos were used to test the worldwide used pesticide Roundup that contains glyphosate as the active herbicide agent; it was shown to activate the DNA-damage checkpoint of the first cell cycle of development. The model therefore allows considerable increase in risk evaluation of new products in the field of cancer and offers a tool for the discovery of molecular markers for early diagnostic in cancer biology

Gaining ground on a cure through synergy: combining checkpoint inhibitors with cancer vaccines.

PubMed

Vreeland, T J; Clifton, G T; Herbert, G S; Hale, D F; Jackson, D O; Berry, J S; Peoples, G E

2016-12-01

The approval of multiple checkpoint inhibitors (CPIs) for the treatment of advanced malignancies has sparked an explosion of research in the field of cancer immunotherapy. Despite the success of these medications, a large number of patients with advanced malignancy do not benefit from therapy. Early research indicates that a therapeutic combination of cancer vaccines with checkpoint inhibitors may lead to synergistic effects and higher response rates than monotherapy. Areas covered: This paper summarizes the previously completed and ongoing research on this exciting combination, including the use of the tumor lysate, particle-loaded dendritic cell (TLPLDC) vaccine combined with checkpoint inhibitors in advanced melanoma. Expert commentary: Increasing experience with CPIs has led to improved understanding of which patients may benefit and it is increasingly clear that the presence of a pre-existing immune response to the tumor, along with tumor-infiltrating lymphocytes, is key to the success of CPIs. One exciting possibility for the future is the addition of a cancer vaccine to CPI therapy, eliciting these crucial T cells, which can then be augmented and protected by the CPI. A number of current and future studies are addressing this very exciting combination therapy.

Extraocular Muscle Enlargement and Thyroid Eye Disease-like Orbital Inflammation Associated with Immune Checkpoint Inhibitor Therapy in Cancer Patients.

PubMed

Sagiv, Oded; Kandl, Thomas J; Thakar, Sudip D; Thuro, Bradley A; Busaidy, Naifa L; Cabanillas, Maria; Jimenez, Camilo; Dadu, Ramona; Graham, Paul H; Debnam, J Matthew; Esmaeli, Bita

2018-06-19

To describe thyroid eye disease (TED)-like orbital inflammatory syndrome in 3 cancer patients treated with immune checkpoint inhibitors. All consecutive patients treated by the senior author who were receiving immune checkpoint inhibitors and developed TED-like orbital inflammation were included. Three cancer patients treated with immune checkpoint inhibitors developed orbital inflammation. The first patient was treated with a combination of a cytotoxic T-lymphocyte antigen-4 inhibitor and a programmed cell death protein 1 inhibitor and developed TED-like orbital inflammation with normal thyroid function and antibody levels. The second patient had a previous diagnosis of Graves disease without TED, and developed TED soon after initiating treatment with a programmed cell death protein 1 inhibitor. The third patient developed acute hyperthyroidism with symptomatic TED following treatment with an investigational cytotoxic T-lymphocyte antigen-4 inhibitor agent. All 3 patients were managed with either systemic steroids or observation, with resolution of their symptoms and without the need to halt immune checkpoint inhibitor treatment for their cancer. TED-like orbital inflammation may occur as a side effect of immune checkpoint inhibitor therapy with anti-cytotoxic T-lymphocyte antigen-4 or anti-PD-1 inhibitors. To the best of their knowledge, this is the first reported case of TED as a result of programmed cell death protein 1 inhibitor monotherapy. All 3 patients were treated with systemic steroids and responded quickly while continuing treatment with immune checkpoint inhibitors for their cancer. With increasing use of this class of drugs, clinicians should be familiar with the clinical manifestations and treatments for this adverse reaction.

Checkpoint-dependent RNR induction promotes fork restart after replicative stress.

PubMed

Morafraile, Esther C; Diffley, John F X; Tercero, José Antonio; Segurado, Mónica

2015-01-20

The checkpoint kinase Rad53 is crucial to regulate DNA replication in the presence of replicative stress. Under conditions that interfere with the progression of replication forks, Rad53 prevents Exo1-dependent fork degradation. However, although EXO1 deletion avoids fork degradation in rad53 mutants, it does not suppress their sensitivity to the ribonucleotide reductase (RNR) inhibitor hydroxyurea (HU). In this case, the inability to restart stalled forks is likely to account for the lethality of rad53 mutant cells after replication blocks. Here we show that Rad53 regulates replication restart through the checkpoint-dependent transcriptional response, and more specifically, through RNR induction. Thus, in addition to preventing fork degradation, Rad53 prevents cell death in the presence of HU by regulating RNR-expression and localization. When RNR is induced in the absence of Exo1 and RNR negative regulators, cell viability of rad53 mutants treated with HU is increased and the ability of replication forks to restart after replicative stress is restored.

Transferrin receptor facilitates TGF-β and BMP signaling activation to control craniofacial morphogenesis

PubMed Central

Lei, R; Zhang, K; Liu, K; Shao, X; Ding, Z; Wang, F; Hong, Y; Zhu, M; Li, H; Li, H

2016-01-01

The Pierre Robin Sequence (PRS), consisting of cleft palate, glossoptosis and micrognathia, is a common human birth defect. However, how this abnormality occurs remains largely unknown. Here we report that neural crest cell (NCC)-specific knockout of transferrin receptor (Tfrc), a well known transferrin transporter protein, caused micrognathia, cleft palate, severe respiratory distress and inability to suckle in mice, which highly resemble human PRS. Histological and anatomical analysis revealed that the cleft palate is due to the failure of palatal shelves elevation that resulted from a retarded extension of Meckel's cartilage. Interestingly, Tfrc deletion dramatically suppressed both transforming growth factor-β (TGF-β) and bone morphogenetic protein (BMP) signaling in cranial NCCs-derived mandibular tissues, suggesting that Tfrc may act as a facilitator of these two signaling pathways during craniofacial morphogenesis. Together, our study uncovers an unknown function of Tfrc in craniofacial development and provides novel insight into the etiology of PRS. PMID:27362800

The leukemia-associated Rho guanine nucleotide exchange factor LARG is required for efficient replication stress signaling

PubMed Central

Beveridge, Ryan D; Staples, Christopher J; Patil, Abhijit A; Myers, Katie N; Maslen, Sarah; Skehel, J Mark; Boulton, Simon J; Collis, Spencer J

2014-01-01

We previously identified and characterized TELO2 as a human protein that facilitates efficient DNA damage response (DDR) signaling. A subsequent yeast 2-hybrid screen identified LARG; Leukemia-Associated Rho Guanine Nucleotide Exchange Factor (also known as Arhgef12), as a potential novel TELO2 interactor. LARG was previously shown to interact with Pericentrin (PCNT), which, like TELO2, is required for efficient replication stress signaling. Here we confirm interactions between LARG, TELO2 and PCNT and show that a sub-set of LARG co-localizes with PCNT at the centrosome. LARG-deficient cells exhibit replication stress signaling defects as evidenced by; supernumerary centrosomes, reduced replication stress-induced γH2AX and RPA nuclear foci formation, and reduced activation of the replication stress signaling effector kinase Chk1 in response to hydroxyurea. As such, LARG-deficient cells are sensitive to replication stress-inducing agents such as hydroxyurea and mitomycin C. Conversely we also show that depletion of TELO2 and the replication stress signaling kinase ATR leads to RhoA signaling defects. These data therefore reveal a level of crosstalk between the RhoA and DDR signaling pathways. Given that mutations in both ATR and PCNT can give rise to the related primordial dwarfism disorders of Seckel Syndrome and Microcephalic osteodysplastic primordial dwarfism type II (MOPDII) respectively, which both exhibit defects in ATR-dependent checkpoint signaling, these data also raise the possibility that mutations in LARG or disruption to RhoA signaling may be contributory factors to the etiology of a sub-set of primordial dwarfism disorders. PMID:25485589

p21 stability: linking chaperones to a cell cycle checkpoint.

PubMed

Liu, Geng; Lozano, Guillermina

2005-02-01

Progression through the cell cycle is regulated by numerous proteins, one of which is the cyclin-dependent kinase inhibitor, p21. A new study identifies a novel protein complex that stabilizes p21. The stability of this complex is critical in effecting the p53-mediated cell cycle checkpoint.

Mitochondria damage checkpoint in apoptosis and genome stability.

PubMed

Singh, Keshav K

2004-11-01

Mitochondria perform multiple cellular functions including energy production, cell proliferation and apoptosis. Studies described in this paper suggest a role for mitochondria in maintaining genomic stability. Genomic stability appears to be dependent on mitochondrial functions involved in maintenance of proper intracellular redox status, ATP-dependent transcription, DNA replication, DNA repair and DNA recombination. To further elucidate the role of mitochondria in genomic stability, I propose a mitochondria damage checkpoint (mitocheckpoint) that monitors and responds to damaged mitochondria. Mitocheckpoint can coordinate and maintain proper balance between apoptotic and anti-apoptotic signals. When mitochondria are damaged, mitocheckpoint can be activated to help cells repair damaged mitochondria, to restore normal mitochondrial function and avoid production of mitochondria-defective cells. If mitochondria are severely damaged, mitocheckpoint may not be able to repair the damage and protect cells. Such an event triggers apoptosis. If damage to mitochondria is continuous or persistent such as damage to mitochondrial DNA resulting in mutations, mitocheckpoint may fail which can lead to genomic instability and increased cell survival in yeast. In human it can cause cancer. In support of this proposal we provide evidence that mitochondrial genetic defects in both yeast and mammalian systems lead to impaired DNA repair, increased genomic instability and increased cell survival. This study reveals molecular genetic mechanisms underlying a role for mitochondria in carcinogenesis in humans.

The subunits of the S-phase checkpoint complex Mrc1/Tof1/Csm3: dynamics and interdependence

PubMed Central

2014-01-01

Background The S-phase checkpoint aims to prevent cells from generation of extensive single-stranded DNA that predisposes to genome instability. The S. cerevisiae complex Tof1/Csm3/Mrc1 acts to restrain the replicative MCM helicase when DNA synthesis is prohibited. Keeping the replication machinery intact allows restart of the replication fork when the block is relieved. Although the subunits of the Tof1/Csm3/Mrc1 complex are well studied, the impact of every single subunit on the triple complex formation and function needs to be established. Findings This work studies the cellular localization and the chromatin binding of GFP-tagged subunits when the complex is intact and when a subunit is missing. We demonstrate that the complex is formed in cell nucleus, not the cytoplasm, as Tof1, Csm3 and Mrc1 enter the nucleus independently from one another. Via in situ chromatin binding assay we show that a Tof1-Csm3 dimer formation and chromatin binding is required to ensure the attachment of Mrc1 to chromatin. Our study indicates that the translocation into the nucleus is not the process to regulate the timing of chromatin association of Mrc1. We also studied the nuclear behavior of Mrc1 subunit in the process of adaptation to the presence hydroxyurea. Our results indicate that after prolonged HU incubation, cells bypass the S-phase checkpoint and proceed throughout the cell cycle. This process is accompanied by Mrc1 chromatin detachment and Rad53 dephosphorylation. Conclusions In S. cerevisiae the subunits of the S-phase checkpoint complex Mrc1/Tof1/Csm3 independently enter the cell nucleus, where a Tof1-Csm3 dimer is formed to ensure the chromatin binding of Mrc1 and favor DNA replication and S-phase checkpoint fork arrest. In the process of adaptation to the presence of hydroxyurea Mrc1 is detached from chromatin and Rad53 checkpoint activity is diminished in order to allow S-phase checkpoint escape and completion of the cell cycle. PMID:25379053

The subunits of the S-phase checkpoint complex Mrc1/Tof1/Csm3: dynamics and interdependence.

PubMed

Uzunova, Sonya Dimitrova; Zarkov, Alexander Stefanov; Ivanova, Anna Marianova; Stoynov, Stoyno Stefanov; Nedelcheva-Veleva, Marina Nedelcheva

2014-01-01

The S-phase checkpoint aims to prevent cells from generation of extensive single-stranded DNA that predisposes to genome instability. The S. cerevisiae complex Tof1/Csm3/Mrc1 acts to restrain the replicative MCM helicase when DNA synthesis is prohibited. Keeping the replication machinery intact allows restart of the replication fork when the block is relieved. Although the subunits of the Tof1/Csm3/Mrc1 complex are well studied, the impact of every single subunit on the triple complex formation and function needs to be established. This work studies the cellular localization and the chromatin binding of GFP-tagged subunits when the complex is intact and when a subunit is missing. We demonstrate that the complex is formed in cell nucleus, not the cytoplasm, as Tof1, Csm3 and Mrc1 enter the nucleus independently from one another. Via in situ chromatin binding assay we show that a Tof1-Csm3 dimer formation and chromatin binding is required to ensure the attachment of Mrc1 to chromatin. Our study indicates that the translocation into the nucleus is not the process to regulate the timing of chromatin association of Mrc1. We also studied the nuclear behavior of Mrc1 subunit in the process of adaptation to the presence hydroxyurea. Our results indicate that after prolonged HU incubation, cells bypass the S-phase checkpoint and proceed throughout the cell cycle. This process is accompanied by Mrc1 chromatin detachment and Rad53 dephosphorylation. In S. cerevisiae the subunits of the S-phase checkpoint complex Mrc1/Tof1/Csm3 independently enter the cell nucleus, where a Tof1-Csm3 dimer is formed to ensure the chromatin binding of Mrc1 and favor DNA replication and S-phase checkpoint fork arrest. In the process of adaptation to the presence of hydroxyurea Mrc1 is detached from chromatin and Rad53 checkpoint activity is diminished in order to allow S-phase checkpoint escape and completion of the cell cycle.

ATM-dependent DNA damage checkpoint functions regulate gene expression in human fibroblasts

PubMed Central

Zhou, Tong; Chou, Jeff; Zhou, Yingchun; Simpson, Dennis A.; Cao, Feng; Bushel, Pierre R.; Paules, Richard S.; Kaufmann, William K.

2013-01-01

The relationships between profiles of global gene expression and DNA damage checkpoint functions were studied in cells from patients with ataxia telangiectasia (AT). Three telomerase-expressing AT fibroblast lines displayed the expected hypersensitivity to ionizing radiation (IR) and defects in DNA damage checkpoints. Profiles of global gene expression in AT cells were determined at 2, 6 and 24 h after treatment with 1.5 Gy IR or sham-treatment, and were compared to those previously recognized in normal human fibroblasts. Under basal conditions 160 genes or ESTs were differentially expressed in AT and normal fibroblasts, and these were associated by gene ontology with insulin-like growth factor binding and regulation of cell growth. Upon DNA damage, 1091 gene mRNAs were changed in at least two of the three AT cell lines. When compared with the 1811 genes changed in normal human fibroblasts after the same treatment, 715 were found in both AT and normal fibroblasts, including most genes categorized by gene ontology into cell cycle, cell growth and DNA damage response pathways. However, the IR-induced changes in these 715 genes in AT cells usually were delayed or attenuated in comparison to normal cells. The reduced change in DNA-damage-response genes and the attenuated repression of cell-cycle-regulated genes may account for the defects in cell cycle checkpoint function in AT cells. PMID:17699107

Protein Phosphatase 1 inactivates Mps1 to ensure efficient Spindle Assembly Checkpoint silencing.

PubMed

Moura, Margarida; Osswald, Mariana; Leça, Nelson; Barbosa, João; Pereira, António J; Maiato, Helder; Sunkel, Claudio E; Conde, Carlos

2017-05-02

Faithfull genome partitioning during cell division relies on the Spindle Assembly Checkpoint (SAC), a conserved signaling pathway that delays anaphase onset until all chromosomes are attached to spindle microtubules. Mps1 kinase is an upstream SAC regulator that promotes the assembly of an anaphase inhibitor through a sequential multi-target phosphorylation cascade. Thus, the SAC is highly responsive to Mps1, whose activity peaks in early mitosis as a result of its T-loop autophosphorylation. However, the mechanism controlling Mps1 inactivation once kinetochores attach to microtubules and the SAC is satisfied remains unknown. Here we show in vitro and in Drosophila that Protein Phosphatase 1 (PP1) inactivates Mps1 by dephosphorylating its T-loop. PP1-mediated dephosphorylation of Mps1 occurs at kinetochores and in the cytosol, and inactivation of both pools of Mps1 during metaphase is essential to ensure prompt and efficient SAC silencing. Overall, our findings uncover a mechanism of SAC inactivation required for timely mitotic exit.

Linking TGF-beta-mediated Cdc25A inhibition and cytoskeletal regulation through RhoA/p160(ROCK) signaling.

PubMed

Brown, Kimberly; Bhowmick, Neil A

2004-04-01

Transforming growth factor-beta (TGF-beta) can mediate G(1)/S cell-cycle inhibition and changes in the cytoskeletal organization through multiple parallel downstream signaling pathways. Recent findings regarding TGF-beta-mediated cell-cycle checkpoint control and epithelial to mesenchymal transition have converged to the RhoA/p160(ROCK) signaling pathway. The activation of TGF-beta-mediated p160(ROCK)rapidly inhibits the Cdc25A phosphatase as a component of the G(1)/S checkpoint control at the time cytoskeletal re-organization occurs. This can be likened to the ability to preserve genomic integrity in circumstances of genotoxic stress. The inactivation of the RhoA/p160(ROCK) pathway may be a mechanism by which cancer cells bypass growth inhibition even in the presence of TGF-beta.

Targeting Tumor-Associated Macrophages as a Potential Strategy to Enhance the Response to Immune Checkpoint Inhibitors.

PubMed

Cassetta, Luca; Kitamura, Takanori

2018-01-01

Inhibition of immune checkpoint pathways in CD8 + T cell is a promising therapeutic strategy for the treatment of solid tumors that has shown significant anti-tumor effects and is now approved by the FDA to treat patients with melanoma and lung cancer. However the response to this therapy is limited to a certain fraction of patients and tumor types, for reasons still unknown. To ensure success of this treatment, CD8 + T cells, the main target of the checkpoint inhibitors, should exert full cytotoxicity against tumor cells. However recent studies show that tumor-associated macrophages (TAM) can impede this process by different mechanisms. In this mini-review we will summarize recent studies showing the effect of TAM targeting on immune checkpoint inhibitors efficacy. We will also discuss on the limitations of the current strategies as well on the future scientific challenges for the progress of the tumor immunology field.

Gyneco-oncological genomics and emerging biomarkers for cancer treatment with immune-checkpoint inhibitors.

PubMed

Curigliano, Giuseppe

2018-05-15

In gynecological cancers tumor infiltrating lymphocytes and upregulation of immune-related gene signatures have been associated with a better prognosis. Knowledge of tumor immunogenicity and associated gene signatures suggests that the tumor immune landscape is a key determinant to define patient prognosis and potentially to predict response to immune-checkpoint inhibitors. The aim of this review is to give an overview of immune gene signatures across gynecology histological cancer types, defining their prognostic and potential predictive role. In the current review we will present data on these gene signatures, on immunohistochemical features and their potential importance to select patients potentially eligible to trials with immune-checkpoint inhibitors. Copyright © 2018 Elsevier Ltd. All rights reserved.

Cellular miR-2909 RNomics governs the genes that ensure immune checkpoint regulation.

PubMed

Kaul, Deepak; Malik, Deepti; Wani, Sameena

2018-06-20

Cross-talk between coding RNAs and regulatory non-coding microRNAs, within human genome, has provided compelling evidence for the existence of flexible checkpoint control of T-Cell activation. The present study attempts to demonstrate that the interplay between miR-2909 and its effector KLF4 gene has the inherent capacity to regulate genes coding for CTLA4, CD28, CD40, CD134, PDL1, CD80, CD86, IL-6 and IL-10 within normal human peripheral blood mononuclear cells (PBMCs). Based upon these findings, we propose a pathway that links miR-2909 RNomics with the genes coding for immune checkpoint regulators required for the maintenance of immune homeostasis.

EMODnet MedSea Checkpoint for sustainable Blue Growth

NASA Astrophysics Data System (ADS)

Moussat, Eric; Pinardi, Nadia; Manzella, Giuseppe; Blanc, Frederique

2016-04-01

The EMODNET checkpoint is a wide monitoring system assessment activity aiming to support the sustainable Blue Growth at the scale of the European Sea Basins by: 1) Clarifying the observation landscape of all compartments of the marine environment including Air, Water, Seabed, Biota and Human activities, pointing out to the existing programs, national, European and international 2) Evaluating fitness for use indicators that will show the accessibility and usability of observation and modeling data sets and their roles and synergies based upon selected applications by the European Marine Environment Strategy 3) Prioritizing the needs to optimize the overall monitoring Infrastructure (in situ and satellite data collection and assembling, data management and networking, modeling and forecasting, geo-infrastructure) and release recommendations for evolutions to better meet the application requirements in view of sustainable Blue Growth The assessment is designed for : - Institutional stakeholders for decision making on observation and monitoring systems - Data providers and producers to know how their data collected once for a given purpose could fit other user needs - End-users interested in a regional status and possible uses of existing monitoring data Selected end-user applications are of paramount importance for: (i) the blue economy sector (offshore industries, fisheries); (ii) marine environment variability and change (eutrophication, river inputs and ocean climate change impacts); (iii) emergency management (oil spills); and (iv) preservation of natural resources and biodiversity (Marine Protected Areas). End-user applications generate innovative products based on the existing observation landscape. The fitness for use assessment is made thanks to the comparison of the expected product specifications with the quality of the product derived from the selected data. This involves the development of checkpoint information and indicators based on Data quality and

EMODnet Black Sea Checkpoint First Data Adequacy Report

NASA Astrophysics Data System (ADS)

Pinardi, Nadia; Lyubartsev, Vladyslav; Manzella, Giuseppe; Palazov, Atanas; Slabakova, Violeta; Buga, Luminita; Kallos, George; Zodiatis, George; Stylianou, Stavros; Blanc, Frederique; Cesarini, Claudia

2017-04-01

The aim of the first Data Adequacy Report (DAR) of the EMODnet Black Sea Checkpoint project is to assess the basin scale monitoring systems on the basis of input data sets for 11 prescribed Challenges. The first step in this process involved the definition of a "Data Adequacy Framework", which was derived from the ISO 9004:2009 standards. Data Adequacy is essentially defined as the fitness for use of the monitoring data required by the Challenges. The CheckPoint adequacy relates to both the requirements as well as the needs of the Challenges and was developed considering the ISO 9001 Quality Management System. The quality assessment is subdivided into two major "territories": "appropriateness" and "availability". In the first DAR only the "availability" indicators are explored and analyzed. The second step in the analysis is to set up a metadatabase containing standardized information about the input datasets potentially usable by the Challenges to generate their products. The metadatabase is at the back-end of an INSPIRE Web and GIS platform, known as Sextant, and uses the SeaDataNet common vocabulary to identify the categories of characteristics needed by the Challenges and to analyze the statistics of indicators. The DAR contains the first assessment of the Black Sea monitoring system on the basis of the analysis of the availability indicators across all Challenges for the 452 input data sets and the 40 characteristic categories. The 8 availability indicators are classified based upon a three value range color system: "red" meaning "not adequate", "yellow" "partly adequate" and "green" "fully adequate". The analysis shows that for most of the indicators half are "not adequate" and the other half are "adequate". The single most negative score is for the "INSPIRE catalogue service" indicator, which is generally not adequate. Furthermore, the "Pricing" indicator is split in half between "not well documented pricing policy" and "open and free data policy". In

Immunotherapy targeting immune check-point(s) in brain metastases.

PubMed

Di Giacomo, Anna Maria; Valente, Monica; Covre, Alessia; Danielli, Riccardo; Maio, Michele

2017-08-01

Immunotherapy with monoclonal antibodies (mAb) directed to different immune check-point(s) is showing a significant clinical impact in a growing number of human tumors of different histotype, both in terms of disease response and long-term survival patients. In this rapidly changing scenario, treatment of brain metastases remains an high unmeet medical need, and the efficacy of immunotherapy in these highly dismal clinical setting remains to be largely demonstrated. Nevertheless, up-coming observations are beginning to suggest a clinical potential of cancer immunotherapy also in brain metastases, regardless the underlying tumor histotype. These observations remain to be validated in larger clinical trials eventually designed also to address the efficacy of therapeutic mAb to immune check-point(s) within multimodality therapies for brain metastases. Noteworthy, the initial proofs of efficacy on immunotherapy in central nervous system metastases are already fostering clinical trials investigating its therapeutic potential also in primary brain tumors. We here review ongoing immunotherapeutic approaches to brain metastases and primary brain tumors, and the foreseeable strategies to overcome their main biologic hurdles and clinical challenges. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Geography of Deterrence: Exploring the Small Area Effects of Sobriety Checkpoints on Alcohol-Impaired Collision Rates within a City

ERIC Educational Resources Information Center

Nunn, Samuel; Newby, William

2011-01-01

This article examines alcohol-impaired collision metrics around nine sobriety checkpoint locations in Indianapolis, Indiana, before and after implementation of 22 checkpoints, using a pre/post examination, a pre/post nonequivalent comparison group analysis, and an interrupted time series approach. Traffic safety officials used geographical…

Cytomegalovirus reactivation in patients with refractory checkpoint inhibitor-induced colitis.

PubMed

Franklin, Cindy; Rooms, Isabelle; Fiedler, Melanie; Reis, Henning; Milsch, Laura; Herz, Saskia; Livingstone, Elisabeth; Zimmer, Lisa; Schmid, Kurt Werner; Dittmer, Ulf; Schadendorf, Dirk; Schilling, Bastian

2017-11-01

Immune checkpoint inhibitors can cause severe immune-related adverse events, with immune-related diarrhea and colitis (irColitis) being among the most frequent ones. While the majority of patients with irColitis respond well to corticosteroid treatment ± other immunomodulatory drugs such as infliximab, some patients do not show resolution of their symptoms. In the present study, we analysed the frequency of therapy-refractory irColitis, the underlying cause, and useful diagnostic approaches. Between 2006 and 2016, 370 patients with metastatic malignant melanoma were treated with checkpoint inhibitors at the Department of Dermatology at the University Hospital Essen. All patients were identified for whom diarrhea and/or colitis was documented in the digital patient records. Patients who did not respond to standard immunosuppressive therapy within 2 weeks were classified as refractory. Demographic and clinical data of all patients were collected. We identified 41 patients with irColitis, the majority occurring during treatment with ipilimumab. Amongst these, 5 (12.2%) were refractory to standard immunomodulatory treatment with corticosteroids and infliximab. Therapy-refractory cases tended to show more severe inflammation in colonic biopsies (p = 0.04). In all therapy-refractory cases cytomegalovirus (CMV) was detectable. CMV-DNA in colonic biopsies and in plasma was significantly more often detectable in therapy-refractory cases (in colonic biopsies p = 0.005, in plasma: p = 0.002). Presence of serum CMV IgM and positive immunohistochemical stainings of colon biopsies for CMV were also associated with refractory colitis (p=0.021; p = 0.053). This report on CMV reactivation during management of checkpoint inhibitor-induced colitis emphasises the need for repetitive diagnostic measures in treatment-refractory irColitis. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dermatologic Reactions to Immune Checkpoint Inhibitors : Skin Toxicities and Immunotherapy.

PubMed

Sibaud, Vincent

2018-06-01

The development of immune checkpoint inhibitors [monoclonal antibodies targeting cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), programmed cell death protein 1 (PD-1) or programmed death ligand 1 (PD-L1)] represents a major breakthrough in cancer therapy. Although they present a favorable risk/benefit ratio, immune checkpoint blockade therapies have a very specific safety profile. Due to their unique mechanism of action, they entail a new spectrum of adverse events that are mostly immune related [immune-related adverse events (irAEs)], notably mediated by the triggering of cytotoxic CD4+/CD8+ T cell activation. Cutaneous toxicities appear to be one of the most prevalent irAEs, both with anti-PD-1 and anti-CTLA-4 agents or with the newly developed anti-PD-L1 agents, which corresponds to a class effect. They are observed in more than one-third of the treated patients, mainly in the form of a maculopapular rash (eczema-like spongiotic dermatitis) and pruritus. A wide range of other dermatologic manifestations can also occur, including lichenoid reactions, psoriasis, acneiform rashes, vitiligo-like lesions, autoimmune skin diseases (e.g., bullous pemphigoid, dermatomyositis, alopecia areata), sarcoidosis or nail and oral mucosal changes. In addition, the use of anti-CTLA-4 and anti-PD-1 therapies in combination is associated with the development of more frequent, more severe and earlier cutaneous irAEs compared to single agents. In most cases, these dysimmune dermatologic adverse events remain self-limiting and readily manageable. Early recognition and adequate management, however, are critical to prevent exacerbation of the lesions, to limit treatment interruption and to minimize quality of life impairment. This review describes the variable clinical and histopathologic aspects of dermatologic irAEs induced by immune checkpoint inhibitors. Appropriate treatment and counseling are also proposed, with a step-by-step approach for optimized management by both

Cloud object store for checkpoints of high performance computing applications using decoupling middleware

DOEpatents

Bent, John M.; Faibish, Sorin; Grider, Gary

2016-04-19

Cloud object storage is enabled for checkpoints of high performance computing applications using a middleware process. A plurality of files, such as checkpoint files, generated by a plurality of processes in a parallel computing system are stored by obtaining said plurality of files from said parallel computing system; converting said plurality of files to objects using a log structured file system middleware process; and providing said objects for storage in a cloud object storage system. The plurality of processes may run, for example, on a plurality of compute nodes. The log structured file system middleware process may be embodied, for example, as a Parallel Log-Structured File System (PLFS). The log structured file system middleware process optionally executes on a burst buffer node.

Endocrine toxicity of immune checkpoint inhibitors: essential crosstalk between endocrinologists and oncologists.

PubMed

Illouz, Frédéric; Briet, Claire; Cloix, Lucie; Le Corre, Yannick; Baize, Nathalie; Urban, Thierry; Martin, Ludovic; Rodien, Patrice

2017-08-01

Two types of immune checkpoint inhibitors, both antibodies that target cytotoxic T-lymphocyte antigen-4 and those that target programmed cell death-protein 1, have been approved for use in melanoma, non-small-cell lung cancer, and renal cell carcinoma as first-line or second-line therapy. Their adverse events are primarily regarded as immune-related adverse events. We felt it was important to pinpoint and discuss certain preconceptions or misconceptions regarding thyroid dysfunction, hypophysitis, and diabetes induced by immune checkpoint inhibitors. We have identified areas of uncertainty and unmet requirements, including essential interaction between endocrinologists and oncologists. Five issues have been identified for discussion: (1) diagnosis of endocrine toxicity, (2) assessment of toxicity severity, (3) treatment of toxicity, (4) withdrawal or continuation of immunotherapy, (5) preventive action. © 2017 The Authors. Cancer Medicine published by John Wiley & Sons Ltd.

Seeing is believing: anti-PD-1/PD-L1 monoclonal antibodies in action for checkpoint blockade tumor immunotherapy

PubMed Central

Tan, Shuguang; Zhang, Catherine W-H; Gao, George F

2016-01-01

Structural immunology, focusing on structures of host immune related molecules, enables the immunologists to see what the molecules look like, and more importantly, how they work together. Antibody-based PD-1/PD-L1 blockade therapy has achieved brilliant successes in clinical applications. The recent breakthrough of the complex structures of checkpoint blockade antibodies with their counterparts, pembrolizumab with PD-1 and avelumab with PD-L1, have made it clear how these monoclonal antibodies compete the binding of PD-1/PD-L1 and function to blockade the receptor-ligand interaction. Herein, we summarize the structural findings of these two reports and look into the future for how this information would facilitate the development of more efficient PD-1/PD-L1 targeting antibodies, small molecule drugs, and other protein or non-protein inhibitors. PMID:29263905

Pilot test of selected DWI detection procedures for use at sobriety checkpoints

DOT National Transportation Integrated Search

1985-04-01

This report presents the results of a study designed to evaluate a variety of potential screening procedures police officers could use at the brief initial stop at a sobriety checkpoint to discriminate between impaired and sober drivers. The potentia...

Central Tolerance Blockade to Augment Checkpoint Immunotherapy in Melanoma

DTIC Science & Technology

2017-09-01

unique mode of action . By itself, anti- RANKL antibody improves the survival of mice injected with melanoma cells. Because anti-RANKL antibody and...anti-RANKL antibody or anti-CTLA-4 antibody alone. These findings are of potential clinical importance because it may pave the way to testing the...combination. If anti-RANKL 7 antibody increases the effectiveness of checkpoint inhibitors, this could potentially have a major impact on how

Understanding and Managing Immune-Related Adverse Events Associated With Immune Checkpoint Inhibitors in Patients With Advanced Melanoma

PubMed Central

Weinstein, Alyona; Gordon, Ruth-Ann; Kasler, Mary Kate; Burke, Matthew; Ranjan, Smita; Hodgetts, Jackie; Reed, Vanessa; Shames, Yelena; Prempeh-Keteku, Nana; Lingard, Karla

2017-01-01

The immune checkpoint inhibitors ipilimumab, nivolumab, and pembrolizumab represent a substantial improvement in treating advanced melanoma but are associated with adverse events (AEs) likely related to general immunologic enhancement. To ensure that patients receive optimal benefit from these agents, prompt assessment and treatment of AEs are essential. We review the efficacy and safety profiles of these immune checkpoint inhibitors and describe guidelines for managing immune-related AEs. We also present case studies describing the management of toxicities in patients receiving immune checkpoint inhibitor therapy. These cases illustrate the importance of collecting a detailed medical history when administering immunotherapy, as this information is necessary to establish baseline, inform monitoring, and determine the etiology of symptoms. Advanced practice nurses and physician assistants are uniquely positioned to educate patients on the early recognition of AEs and have an important role in establishing appropriate monitoring and open dialogue among services. PMID:29900017

PD-1 and its ligands are important immune checkpoints in cancer

PubMed Central

Dong, Yinan; Sun, Qian; Zhang, Xinwei

2017-01-01

Checkpoint programmed death-1 (PD-1)/programmed cell death ligands (PD-Ls) have been identified as negative immunoregulatory molecules that promote immune evasion of tumor cells. The interaction of PD-1 and PD-Ls inhibits the function of T cells and tumor-infiltrating lymphocytes (TIL) while increasing the function of immunosuppressive regulatory T cells (Tregs). This condition causes the tumor cells to evade immune response. Thus, the blockade of PD-1/PD-L1 enhances anti-tumor immunity by reducing the number and/or the suppressive activity of Tregs and by restoring the activity of effector T cells. Furthermore, some monoclonal antibodies blockading PD-1/PD-Ls axis have achieved good effect and received Food and Drug Administration approval. The role of PD-1/PD-Ls in tumors has been well studied, but little is known on the mechanism by which PD-1 blocks T-cell activation. In this study, we provide a brief overview on the discovery and regulatory mechanism of PD-1 and PD-L1 dysregulation in tumors, as well as the function and signaling pathway of PD-1 and its ligands; their roles in tumor evasion and clinical treatment were also studied. PMID:27974689

Aquaporin-facilitated transmembrane diffusion of hydrogen peroxide.

PubMed

Bienert, Gerd P; Chaumont, François

2014-05-01

Hydrogen peroxide (H2O2) is an important signaling compound that has recently been identified as a new substrate for several members of the aquaporin superfamily in various organisms. Evidence is emerging about the physiological significance of aquaporin-facilitated H2O2 diffusion. This review summarizes current knowledge about aquaporin-facilitated H2O2 diffusion across cellular membranes. It focuses on physicochemical and experimental evidence demonstrating the involvement of aquaporins in the transport of this redox signaling compound and discusses the regulation and structural prerequisites of these channels to transmit this signal. It also provides perspectives about the potential importance of aquaporin-facilitated H2O2 diffusion processes and places this knowledge in the context of the current understanding of transmembrane redox signaling processes. Specific aquaporin isoforms facilitate the passive diffusion of H2O2 across biological membranes and control H2O2 membrane permeability and signaling in living organisms. Redox signaling is a very important process regulating the physiology of cells and organisms in a similar way to the well-characterized hormonal and calcium signaling pathways. Efficient transmembrane diffusion of H2O2, a key molecule in the redox signaling network, requires aquaporins and makes these channels important players in this signaling process. Channel-mediated membrane transport allows the fine adjustment of H2O2 levels in the cytoplasm, intracellular organelles, the apoplast, and the extracellular space, which are essential for it to function as a signal molecule. This article is part of a Special Issue entitled Aquaporins. © 2013.

Immune Checkpoints in Leprosy: Immunotherapy As a Feasible Approach to Control Disease Progression.

PubMed

Lima, Hayana Ramos; Gasparoto, Thaís Helena; de Souza Malaspina, Tatiana Salles; Marques, Vinícius Rizzo; Vicente, Marina Jurado; Marcos, Elaine Camarinha; Souza, Fabiana Corvolo; Nogueira, Maria Renata Sales; Barreto, Jaison Antônio; Garlet, Gustavo Pompermaier; da Silva, João Santana; Brito-de-Souza, Vânia Nieto; Campanelli, Ana Paula

2017-01-01

Leprosy remains a health problem in several countries. Current management of patients with leprosy is complex and requires multidrug therapy. Nonetheless, antibiotic treatment is insufficient to prevent nerve disabilities and control Mycobacterium leprae . Successful infectious disease treatment demands an understanding of the host immune response against a pathogen. Immune-based therapy is an effective treatment option for malignancies and infectious diseases. A promising therapeutic approach to improve the clinical outcome of malignancies is the blockade of immune checkpoints. Immune checkpoints refer to a wide range of inhibitory or regulatory pathways that are critical for maintaining self-tolerance and modulating the immune response. Programmed cell-death protein-1 (PD-1), programmed cell death ligand-1 (PD-L1), cytotoxic T-lymphocyte-associated protein 4, and lymphocyte-activation gene-3 are the most important immune checkpoint molecules. Several pathogens, including M. leprae , are supposed to utilize these mechanisms to evade the host immune response. Regulatory T cells and expression of co-inhibitory molecules on lymphocytes induce specific T-cell anergy/exhaustion, leading to disseminated and progressive disease. From this perspective, we outline how the co-inhibitory molecules PD-1, PD-L1, and Th1/Th17 versus Th2/Treg cells are balanced, how antigen-presenting cell maturation acts at different levels to inhibit T cells and modulate the development of leprosy, and how new interventions interfere with leprosy development.

Centromere replication timing determines different forms of genomic instability in Saccharomyces cerevisiae checkpoint mutants during replication stress.

PubMed

Feng, Wenyi; Bachant, Jeff; Collingwood, David; Raghuraman, M K; Brewer, Bonita J

2009-12-01

Yeast replication checkpoint mutants lose viability following transient exposure to hydroxyurea, a replication-impeding drug. In an effort to understand the basis for this lethality, we discovered that different events are responsible for inviability in checkpoint-deficient cells harboring mutations in the mec1 and rad53 genes. By monitoring genomewide replication dynamics of cells exposed to hydroxyurea, we show that cells with a checkpoint deficient allele of RAD53, rad53K227A, fail to duplicate centromeres. Following removal of the drug, however, rad53K227A cells recover substantial DNA replication, including replication through centromeres. Despite this recovery, the rad53K227A mutant fails to achieve biorientation of sister centromeres during recovery from hydroxyurea, leading to secondary activation of the spindle assembly checkpoint (SAC), aneuploidy, and lethal chromosome segregation errors. We demonstrate that cell lethality from this segregation defect could be partially remedied by reinforcing bipolar attachment. In contrast, cells with the mec1-1 sml1-1 mutations suffer from severely impaired replication resumption upon removal of hydroxyurea. mec1-1 sml1-1 cells can, however, duplicate at least some of their centromeres and achieve bipolar attachment, leading to abortive segregation and fragmentation of incompletely replicated chromosomes. Our results highlight the importance of replicating yeast centromeres early and reveal different mechanisms of cell death due to differences in replication fork progression.

Wi-Fi location fingerprinting using an intelligent checkpoint sequence

NASA Astrophysics Data System (ADS)

Retscher, Günther; Hofer, Hannes

2017-09-01

For Wi-Fi positioning location fingerprinting is very common but has the disadvantage that it is very labour consuming for the establishment of a database (DB) with received signal strength (RSS) scans measured on a large number of known reference points (RPs). To overcome this drawback a novel approach is developed which uses a logical sequence of intelligent checkpoints (iCPs) instead of RPs distributed in a regular grid. The iCPs are the selected RPs which have to be passed along the way for navigation from a start point A to the destination B. They are twofold intelligent because of the fact that they depend on their meaningful selection and because of their logical sequence in their correct order. Thus, always the following iCP is known due to a vector graph allocation in the DB and only a small limited number of iCPs needs to be tested when matching the current RSS scans. This reduces the required processing time significantly. It is proven that the iCP approach achieves a higher success rate than conventional approaches. In average correct matching results of 90.0% were achieved using a joint DB including RSS scans of all employed smartphones. An even higher success rate is achieved if the same mobile device is used in both the training and positioning phase.

Stop and go: hematopoietic cell transplantation in the era of chimeric antigen receptor T cells and checkpoint inhibitors.

PubMed

Ghosh, Arnab; Politikos, Ioannis; Perales, Miguel-Angel

2017-11-01

For several decades, hematopoietic cell transplantation (HCT) has been considered the standard curative therapy for many patients with hematological malignancies. In addition to the cytotoxic effects of the chemotherapy and radiation used in the conditioning regimen, the benefits of HCT are derived from a reset of the immune system and harnessing the ability of donor T cells to eliminate malignant cells. With the dawn of the era of immunotherapies in the form of checkpoint inhibitors and chimeric antigen receptor (CAR) T cells, the role of HCT has evolved. Immunotherapy with checkpoint inhibitors is increasingly being used for relapsed Hodgkin and non-Hodgkin lymphoma after autologous HCT. Checkpoint inhibitors are also being tested after allogeneic HCT with observable benefits in treating hematological malignancies, but with a potential risk of increased graft versus host disease and transplant-related mortality. Immunotherapy with Cluster of differentiation 19 CAR T cells are powerful options with aggressive B-cell malignancies both for therapy and as induction leading to allogeneic HCT. Although immunotherapies with checkpoint inhibition and CAR T cells are increasingly being used to treat hematological malignancies, HCT remains a standard of care for most of the diseases with the best chance of cure. Combination of these therapies with HCT has the potential to more effectively treat hematological malignancies.

[Clinical Development of Immune Checkpoint Inhibitors in Patients with Small Cell Lung Cancer].

PubMed

Zhang, Shuang; Liu, Jingjing; Cheng, Ying

2017-09-20

Small cell lung cancer (SCLC) is a poorly differentiated high-grade neuroendocrine tumor, accounts for approximately 14% of all lung cancers. SCLC is characterized by rapid growth, early metastasis without effective treatments after recurrence. It is urgently need to improve the therapy of patients with SCLC. In recent years Tumor immunotherapy has shown promising efficacy, especially in immune checkpoints including inhibitors programmed cell-death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4). These immune checkpoint inhibitors of the researches are changing the clinical practice of many kinds of solid tumor. SCLC is a potential ideal type of tumor immunotherapy for tobacco exposure and the highest mutational load. In this report, the authors review the current state of the immunotherapy in SCLC, to discussing the problems, challenge and application development prospect.

CSF1/CSF1R Blockade Reprograms Tumor-Infiltrating Macrophages and Improves Response to T Cell Checkpoint Immunotherapy in Pancreatic Cancer Models

PubMed Central

Zhu, Yu; Knolhoff, Brett L.; Meyer, Melissa A.; Nywening, Timothy M.; West, Brian L.; Luo, Jingqin; Wang-Gillam, Andrea; Goedegebuure, S Peter; Linehan, David C.; DeNardo, David G.

2014-01-01

Cancer immunotherapy generally offers limited clinical benefit without coordinated strategies to mitigate the immunosuppressive nature of the tumor microenvironment. Critical drivers of immune escape in the tumor microenvironment include tumor-associated macrophages (TAM) and myeloid-derived suppressor cells (MDSC), which not only mediate immune suppression but also promote metastatic dissemination and impart resistance to cytotoxic therapies. Thus, strategies to ablate the effects of these myeloid cell populations may offer great therapeutic potential. In this report, we demonstrate in a mouse model of pancreatic ductal adenocarcinoma (PDAC) that inhibiting signaling by the myeloid growth factor receptor CSF1R can functionally reprogram macrophage responses that enhance antigen presentation and productive anti-tumor T cell responses. Investigations of this response revealed that CSF1R blockade also upregulated T cell checkpoint molecules, including PDL1 and CTLA4, thereby restraining beneficial therapeutic effects. We found that PD1 and CTLA4 antagonists showed limited efficacy as single agents to restrain PDAC growth, but that that combining these agents with CSF1R blockade potently elicited tumor regressions, even in larger established tumors. Taken together, our findings provide a rationale to reprogram immunosuppressive myeloid cell populations in the tumor microenvironment under conditions that can significantly empower the therapeutic effects of checkpoint-based immunotherapeutics. PMID:25082815

CSF1/CSF1R blockade reprograms tumor-infiltrating macrophages and improves response to T-cell checkpoint immunotherapy in pancreatic cancer models.

PubMed

Zhu, Yu; Knolhoff, Brett L; Meyer, Melissa A; Nywening, Timothy M; West, Brian L; Luo, Jingqin; Wang-Gillam, Andrea; Goedegebuure, S Peter; Linehan, David C; DeNardo, David G

2014-09-15

Cancer immunotherapy generally offers limited clinical benefit without coordinated strategies to mitigate the immunosuppressive nature of the tumor microenvironment. Critical drivers of immune escape in the tumor microenvironment include tumor-associated macrophages and myeloid-derived suppressor cells, which not only mediate immune suppression, but also promote metastatic dissemination and impart resistance to cytotoxic therapies. Thus, strategies to ablate the effects of these myeloid cell populations may offer great therapeutic potential. In this report, we demonstrate in a mouse model of pancreatic ductal adenocarcinoma (PDAC) that inhibiting signaling by the myeloid growth factor receptor CSF1R can functionally reprogram macrophage responses that enhance antigen presentation and productive antitumor T-cell responses. Investigations of this response revealed that CSF1R blockade also upregulated T-cell checkpoint molecules, including PDL1 and CTLA4, thereby restraining beneficial therapeutic effects. We found that PD1 and CTLA4 antagonists showed limited efficacy as single agents to restrain PDAC growth, but that combining these agents with CSF1R blockade potently elicited tumor regressions, even in larger established tumors. Taken together, our findings provide a rationale to reprogram immunosuppressive myeloid cell populations in the tumor microenvironment under conditions that can significantly empower the therapeutic effects of checkpoint-based immunotherapeutics. ©2014 American Association for Cancer Research.

Protein Phosphatase 1 inactivates Mps1 to ensure efficient Spindle Assembly Checkpoint silencing

PubMed Central

Moura, Margarida; Osswald, Mariana; Leça, Nelson; Barbosa, João; Pereira, António J; Maiato, Helder; Sunkel, Claudio E; Conde, Carlos

2017-01-01

Faithfull genome partitioning during cell division relies on the Spindle Assembly Checkpoint (SAC), a conserved signaling pathway that delays anaphase onset until all chromosomes are attached to spindle microtubules. Mps1 kinase is an upstream SAC regulator that promotes the assembly of an anaphase inhibitor through a sequential multi-target phosphorylation cascade. Thus, the SAC is highly responsive to Mps1, whose activity peaks in early mitosis as a result of its T-loop autophosphorylation. However, the mechanism controlling Mps1 inactivation once kinetochores attach to microtubules and the SAC is satisfied remains unknown. Here we show in vitro and in Drosophila that Protein Phosphatase 1 (PP1) inactivates Mps1 by dephosphorylating its T-loop. PP1-mediated dephosphorylation of Mps1 occurs at kinetochores and in the cytosol, and inactivation of both pools of Mps1 during metaphase is essential to ensure prompt and efficient SAC silencing. Overall, our findings uncover a mechanism of SAC inactivation required for timely mitotic exit. DOI: http://dx.doi.org/10.7554/eLife.25366.001 PMID:28463114

Leptin Regulation of Gonadotrope Gonadotropin-Releasing Hormone Receptors As a Metabolic Checkpoint and Gateway to Reproductive Competence

PubMed Central

Odle, Angela K.; Akhter, Noor; Syed, Mohsin M.; Allensworth-James, Melody L.; Beneš, Helen; Melgar Castillo, Andrea I.; MacNicol, Melanie C.; MacNicol, Angus M.; Childs, Gwen V.

2018-01-01

The adipokine leptin signals the body’s nutritional status to the brain, and particularly, the hypothalamus. However, leptin receptors (LEPRs) can be found all throughout the body and brain, including the pituitary. It is known that leptin is permissive for reproduction, and mice that cannot produce leptin (Lep/Lep) are infertile. Many studies have pinpointed leptin’s regulation of reproduction to the hypothalamus. However, LEPRs exist at all levels of the hypothalamic–pituitary–gonadal axis. We have previously shown that deleting the signaling portion of the LEPR specifically in gonadotropes impairs fertility in female mice. Our recent studies have targeted this regulation to the control of gonadotropin releasing hormone receptor (GnRHR) expression. The hypotheses presented here are twofold: (1) cyclic regulation of pituitary GnRHR levels sets up a target metabolic checkpoint for control of the reproductive axis and (2) multiple checkpoints are required for the metabolic signaling that regulates the reproductive axis. Here, we emphasize and explore the relationship between the hypothalamus and the pituitary with regard to the regulation of GnRHR. The original data we present strengthen these hypotheses and build on our previous studies. We show that we can cause infertility in 70% of female mice by deleting all isoforms of LEPR specifically in gonadotropes. Our findings implicate activin subunit (InhBa) mRNA as a potential leptin target in gonadotropes. We further show gonadotrope-specific upregulation of GnRHR protein (but not mRNA levels) following leptin stimulation. In order to try and understand this post-transcriptional regulation, we tested candidate miRNAs (identified with in silico analysis) that may be binding the Gnrhr mRNA. We show significant upregulation of one of these miRNAs in our gonadotrope-Lepr-null females. The evidence provided here, combined with our previous work, lay the foundation for metabolically regulated post

Immune Checkpoint Inhibition in Hepatocellular Carcinoma: Basics and Ongoing Clinical Trials.

PubMed

Kudo, Masatoshi

2017-01-01

Clinical trials of antibodies targeting the immune checkpoint inhibitors programmed cell death 1 (PD-1), programmed cell death ligand 1 (PD-L1), or cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) for the treatment of advanced hepatocellular carcinoma (HCC) are ongoing. Expansion cohorts of a phase I/II trial of the anti-PD-1 antibody nivolumab in advanced HCC showed favorable results. Two phase III studies are currently ongoing: a comparison of nivolumab and sorafenib in the first-line setting for advanced HCC, and a comparison of the anti-PD-1 antibody pembrolizumab and a placebo in the second-line setting for patients with advanced HCC who progressed on sorafenib therapy. The combination of anti-PD-1/PD-L1 and anti-CTLA-4 antibodies is being evaluated in other phase I/II trials, and the results suggest that an anti-PD-1 antibody combined with locoregional therapy or other molecular targeted agents is an effective treatment strategy for HCC. Immune checkpoint inhibitors may therefore open new doors to the treatment of HCC. © 2017 S. Karger AG, Basel.

Characterization of tumor-associated T-lymphocyte subsets and immune checkpoint molecules in head and neck squamous cell carcinoma

PubMed Central

Thelen, Martin; Reuter, Sabrina; Zentis, Peter; Shimabukuro-Vornhagen, Alexander; Theurich, Sebastian; Wennhold, Kerstin; Garcia-Marquez, Maria; Tharun, Lars; Quaas, Alexander; Schauss, Astrid; Isensee, Jörg; Hucho, Tim; Huebbers, Christian

2017-01-01

The composition of tumor-infiltrating lymphocytes (TIL) reflects biology and immunogenicity of cancer. Here, we characterize T-cell subsets and expression of immune checkpoint molecules in head and neck squamous cell carcinoma (HNSCC). We analyzed TIL subsets in primary tumors (n = 34), blood (peripheral blood mononuclear cells (PBMC); n = 34) and non-cancerous mucosa (n = 7) of 34 treatment-naïve HNSCC patients and PBMC of 15 healthy controls. Flow cytometry analyses revealed a highly variable T-cell infiltration mainly of an effector memory phenotype (CD45RA−/CCR7−). Naïve T cells (CD45RA+/CCR7+) were decreased in the microenvironment compared to PBMC of patients, while regulatory T cells (CD4+/CD25+/CD127low and CD4+/CD39+) were elevated. Furthermore, we performed digital image analyses of entire cross sections of HNSCC to define the ‘Immunoscore’ (CD3+ and CD8+ cell infiltration in tumor core and invasive margin) and quantified MHC class I expression on tumor cells by immunohistochemistry. Immune checkpoint molecules cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), programmed cell death 1 (PD-1) and programmed cell death 1 ligand 1 (PD-L1) were increased in TILs compared to peripheral T cells in flow-cytometric analysis. Human papillomavirus (HPV) positive tumors showed higher numbers of TILs, but a similar composition of T-cell subsets and checkpoint molecule expression compared to HPV negative tumors. Taken together, the tumor microenvironment of HNSCC is characterized by a strong infiltration of regulatory T cells and high checkpoint molecule expression on T-cell subsets. In view of increasingly used immunotherapies, a detailed knowledge of TILs and checkpoint molecule expression on TILs is of high translational relevance. PMID:28574843

Molecular checkpoint decisions made by subverted vascular niche transform indolent tumor cells into chemoresistant cancer stem cells

PubMed Central

Cao, Zhongwei; Scandura, Joseph M; Inghirami, Giorgio G.; Shido, Koji; Ding, Bi-Sen; Rafii, Shahin

2017-01-01

Summary Tumor-associated endothelial cells (TECs) regulate tumor cell aggressiveness. However, the “core” mechanism by which TECs confer stem cell-like activity to indolent tumors is unknown. Here, we used in vivo murine and human tumor models to identify tumor-suppressive checkpoint role of TEC-expressed insulin growth factor (IGF) binding protein-7 (IGFBP7/angiomodulin). During tumorigenesis, IGFBP7 blocks IGF1 and inhibits expansion and engraftment of tumor stem-like cells (TSCs) expressing IGF1-receptor (IGF1R). However, chemotherapy triggers TECs to suppress IGFBP7, and this stimulates IGF1R+ TSCs to express FGF4, inducing a feed-forward FGFR1-ETS2 angiocrine cascade that obviates TEC IGFBP7. Thus, loss of IGFBP7 and upregulation of IGF1 activates the FGF4-FGFR1-ETS2 pathway in TECs and converts naive tumor cells to chemoresistant TSCs, thereby facilitating their engraftment and progression. PMID:27989801

Molecular Checkpoint Decisions Made by Subverted Vascular Niche Transform Indolent Tumor Cells into Chemoresistant Cancer Stem Cells.

PubMed

Cao, Zhongwei; Scandura, Joseph M; Inghirami, Giorgio G; Shido, Koji; Ding, Bi-Sen; Rafii, Shahin

2017-01-09

Tumor-associated endothelial cells (TECs) regulate tumor cell aggressiveness. However, the core mechanism by which TECs confer stem cell-like activity to indolent tumors is unknown. Here, we used in vivo murine and human tumor models to identify the tumor-suppressive checkpoint role of TEC-expressed insulin growth factor (IGF) binding protein-7 (IGFBP7/angiomodulin). During tumorigenesis, IGFBP7 blocks IGF1 and inhibits expansion and aggresiveness of tumor stem-like cells (TSCs) expressing IGF1 receptor (IGF1R). However, chemotherapy triggers TECs to suppress IGFBP7, and this stimulates IGF1R + TSCs to express FGF4, inducing a feedforward FGFR1-ETS2 angiocrine cascade that obviates TEC IGFBP7. Thus, loss of IGFBP7 and upregulation of IGF1 activates the FGF4-FGFR1-ETS2 pathway in TECs and converts naive tumor cells to chemoresistant TSCs, thereby facilitating their invasiveness and progression. Copyright © 2017 Elsevier Inc. All rights reserved.

Elevated lung cancer risk is associated with deficiencies in cell cycle checkpoints: Genotype and phenotype analyses from a case-control study

PubMed Central

Zheng, Yun-Ling; Kosti, Ourania; Loffredo, Christopher; Bowman, Elise; Mechanic, Leah; Perlmutter, Donna; Jones, Raymond; Shields, Peter G.; Harris, Curtis

2010-01-01

Cell cycle checkpoints play critical roles in the maintenance of genomic integrity and inactivation of checkpoint genes, and are frequently perturbed in most cancers. In a case-control study of 299 non-small cell lung cancer cases and 550 controls in Maryland, we investigated the association between γ-radiation-induced G2/M arrest in cultured blood lymphocytes and lung cancer risk, and examined genotype-phenotype correlations between genetic polymorphisms of 20 genes involving in DNA repair and cell cycle control and γ-radiation-induced G2/M arrest. The study was specifically designed to examine race and gender differences in risk factors. Our data indicated that a less efficient DNA damage-induced G2/M checkpoint was associated with an increased risk of lung cancer in African American women with an adjusted odds ratio (OR) of 2.63 (95% CI = 1.01 – 7.26); there were no statistically significant associations for Caucasians, or African American men. When the African American women were categorized into quartiles, a significant reverse trend of decreased G2/M checkpoint function and increased lung cancer risk was present, with lowest-vs-highest quartile OR of 13.72 (95% CI = 2.30 – 81.92, Ptrend < 0.01). Genotype-phenotype correlation analysis indicated that polymorphisms in ATM, CDC25C, CDKN1A, BRCA2, ERCC6, TP53, and TP53BP1 genes were significantly associated with the γ-radiation-induced G2/M arrest phenotype. This study provides evidence that a less efficient G2/M checkpoint is significantly associated with lung cancer risk in African American women. The data also suggested that the function of G2/M checkpoint is modulated by genetic polymorphisms in genes involved in DNA repair and cell cycle control. PMID:19626602

Evidence for a Transketolase-Mediated Metabolic Checkpoint Governing Biotrophic Growth in Rice Cells by the Blast Fungus Magnaporthe oryzae

PubMed Central

Fernandez, Jessie; Marroquin-Guzman, Margarita; Wilson, Richard A.

2014-01-01

The blast fungus Magnaporthe oryzae threatens global food security through the widespread destruction of cultivated rice. Foliar infection requires a specialized cell called an appressorium that generates turgor to force a thin penetration hypha through the rice cuticle and into the underlying epidermal cells, where the fungus grows for the first days of infection as a symptomless biotroph. Understanding what controls biotrophic growth could open new avenues for developing sustainable blast intervention programs. Here, using molecular genetics and live-cell imaging, we dismantled M. oryzae glucose-metabolizing pathways to reveal that the transketolase enzyme, encoded by TKL1, plays an essential role in facilitating host colonization during rice blast disease. In the absence of transketolase, Δtkl1 mutant strains formed functional appressoria that penetrated rice cuticles successfully and developed invasive hyphae (IH) in rice cells from primary hyphae. However, Δtkl1 could not undertake sustained biotrophic growth or cell-to-cell movement. Transcript data and observations using fluorescently labeled histone H1:RFP fusion proteins indicated Δtkl1 mutant strains were alive in host cells but were delayed in mitosis. Mitotic delay could be reversed and IH growth restored by the addition of exogenous ATP, a metabolite depleted in Δtkl1 mutant strains. We show that ATP might act via the TOR signaling pathway, and TOR is likely a downstream target of activation for TKL1. TKL1 is also involved in controlling the migration of appressorial nuclei into primary hyphae in host cells. When taken together, our results indicate transketolase has a novel role in mediating - via ATP and TOR signaling - an in planta-specific metabolic checkpoint that controls nuclear migration from appressoria into primary hyphae, prevents mitotic delay in early IH and promotes biotrophic growth. This work thus provides new information about the metabolic strategies employed by M. oryzae to

Fission Yeast Apc15 Stabilizes MCC-Cdc20-APC/C Complexes, Ensuring Efficient Cdc20 Ubiquitination and Checkpoint Arrest.

PubMed

May, Karen M; Paldi, Flora; Hardwick, Kevin G

2017-04-24

During mitosis, cells must segregate the replicated copies of their genome to their daughter cells with extremely high fidelity. Segregation errors lead to an abnormal chromosome number (aneuploidy), which typically results in disease or cell death [1]. Chromosome segregation and anaphase onset are initiated through the action of the multi-subunit E3 ubiquitin ligase known as the anaphase-promoting complex or cyclosome (APC/C [2]). The APC/C is inhibited by the spindle checkpoint in the presence of kinetochore attachment defects [3, 4]. Here we demonstrate that two non-essential APC/C subunits (Apc14 and Apc15) regulate association of spindle checkpoint proteins, in the form of the mitotic checkpoint complex (MCC), with the APC/C. apc14Δ mutants display increased MCC association with the APC/C and are unable to silence the checkpoint efficiently. Conversely, apc15Δ mutants display reduced association between the MCC and APC/C, are defective in poly-ubiquitination of Cdc20, and are checkpoint defective. In vitro reconstitution studies have shown that human MCC-APC/C can contain two molecules of Cdc20 [5-7]. Using a yeast strain expressing two Cdc20 genes with different epitope tags, we show by co-immunoprecipitation that this is true in vivo. MCC binding to the second molecule of Cdc20 is mediated via the C-terminal KEN box in Mad3. Somewhat surprisingly, complexes containing both molecules of Cdc20 accumulate in apc15Δ cells, and the implications of this observation are discussed. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Deficiency of the Arabidopsis Helicase RTEL1 Triggers a SOG1-Dependent Replication Checkpoint in Response to DNA Cross-Links

PubMed Central

Hu, Zhubing; Cools, Toon; Kalhorzadeh, Pooneh; Heyman, Jefri; De Veylder, Lieven

2015-01-01

To maintain genome integrity, DNA replication is executed and regulated by a complex molecular network of numerous proteins, including helicases and cell cycle checkpoint regulators. Through a systematic screening for putative replication mutants, we identified an Arabidopsis thaliana homolog of human Regulator of Telomere Length 1 (RTEL1), which functions in DNA replication, DNA repair, and recombination. RTEL1 deficiency retards plant growth, a phenotype including a prolonged S-phase duration and decreased cell proliferation. Genetic analysis revealed that rtel1 mutant plants show activated cell cycle checkpoints, specific sensitivity to DNA cross-linking agents, and increased homologous recombination, but a lack of progressive shortening of telomeres, indicating that RTEL1 functions have only been partially conserved between mammals and plants. Surprisingly, RTEL1 deficiency induces tolerance to the deoxynucleotide-depleting drug hydroxyurea, which could be mimicked by DNA cross-linking agents. This resistance does not rely on the essential replication checkpoint regulator WEE1 but could be blocked by a mutation in the SOG1 transcription factor. Taken together, our data indicate that RTEL1 is required for DNA replication and that its deficiency activates a SOG1-dependent replication checkpoint. PMID:25595823

Avelumab: combining immune checkpoint inhibition and antibody-dependent cytotoxicity.

PubMed

Hamilton, Gerhard; Rath, Barbara

2017-04-01

Immune checkpoint inhibition holds great promise for selected tumors. The human monoclonal antibody (mAB) avelumab is directed to programmed death ligand-1 (PD-L1) and is supposed to inhibit the immunosuppressive PD-L1/PD-1 interaction and, furthermore, effect antibody-dependent cytotoxicity (ADCC) lysis of tumor cells. Areas covered: This article presents an overview of the current means to activate the antitumor immune defense by targeting PD-1 or PD-L1 with mABs and their possible role in ADCC-mediated tumor cell elimination. Expert opinion: Avelumab contains a Fc region which can bind cognate receptors on immune effector cells and induce ADCC-mediated tumor cell lysis, in contrast to other mABs directed to PD-1/PD-L1 which lack the ability to trigger ADCC due to belonging to the IgG4 subclass or possessing a mutated Fc region. Preclinical and clinical data indicate that avelumab can be safely administered to cancer patients with a toxicity profile comparable to other mABs and without lysis of PD-L1-positive activated immune cells. This antibody yielded durable responses in a phase II trial in advanced Merkel cell carcinoma patients. Tumor cell lysis by avelumab prevents cells from resorting to alternative checkpoints as shown by targeting PD-1 and the upregulation of TIM-3.

Dual personality of Mad1: regulation of nuclear import by a spindle assembly checkpoint protein.

PubMed

Cairo, Lucas V; Ptak, Christopher; Wozniak, Richard W

2013-01-01

Nuclear transport is a dynamic process that can be modulated in response to changes in cellular physiology. We recently reported that the transport activity of yeast nuclear pore complexes (NPCs) is altered in response to kinetochore-microtubule (KT-MT) interaction defects. Specifically, KT detachment from MTs activates a signaling pathway that prevents the nuclear import of cargos by the nuclear transport factor Kap121p. This loss of Kap121p-mediated import is thought to influence the nuclear environment, including the phosphorylation state of nuclear proteins. A key regulator of this process is the spindle assembly checkpoint protein Mad1p. In response to unattached KTs, Mad1p dynamically cycles between NPCs and KTs. This cycling appears to induce NPC molecular rearrangements that prevent the nuclear import of Kap121p-cargo complexes. Here, we discuss the underlying mechanisms and the physiological relevance of Mad1p cycling and the inhibition of Kap121p-mediated nuclear import, focusing on outstanding questions within the pathway.

Two LXXLL motifs in the N terminus of Mps1 are required for Mps1 nuclear import during G(2)/M transition and sustained spindle checkpoint responses.

PubMed

Zhang, Xiaojuan; Yin, Qingqing; Ling, Youguo; Zhang, Yanhong; Ma, Runlin; Ma, Qingjun; Cao, Cheng; Zhong, Hui; Liu, Xuedong; Xu, Quanbin

2011-08-15

Spindle assembly checkpoint kinase Mps1 is spatially and temporally regulated during cell cycle progression. Mps1 is predominately localized to the cytosol in interphase cells, whereas it is concentrated on kinetochores in prophase and prometaphase cells. The timing and mechanism of Mps1 redistribution during cell cycle transition is currently poorly understood. Here, we show that Mps1 relocates from the cytosol to the nucleus at the G 2/M boundary prior to nuclear envelope breakdown (NEB). This timely translocation depends on two tandem LXXLL motifs in the N terminus of Mps1, and mutations in either motif abolish Mps1 nuclear accumulation. Furthermore, we found that phosphorylation of Mps1 Ser80 (which is located between the two LXXLL motifs) also plays a role in regulating timely nuclear entry of Mps1. Mps1 that is defective in LXXLL motifs has near wild-type kinase activity. Moreover, the kinase activity of Mps1 appears to be dispensable for nuclear translocation, as inhibition of Mps1 by a highly specific small-molecule inhibitor did not perturb its nuclear entry. Remarkably, translocation-deficient Mps1 can mediate activation of spindle assembly checkpoint response; however, it fails to support a sustained mitotic arrest upon prolonged treatment with nocodazole. The mitotic slippage can be attributed to precocious degradation of Mps1 in the arrested cells. Our studies reveal a novel cell cycle-dependent nuclear translocation signal in the N terminus of Mps1 and suggest that timely nuclear entry could be important for sustaining spindle assembly checkpoint responses.

Two LXXLL motifs in the N terminus of Mps1 are required for Mps1 nuclear import during G2/M transition and sustained spindle checkpoint responses

PubMed Central

Zhang, Xiaojuan; Yin, Qingqing; Ling, Youguo; Zhang, Yanhong; Ma, Runlin; Ma, Qingjun; Cao, Cheng; Zhong, Hui

2011-01-01

Spindle assembly checkpoint kinase Mps1 is spatially and temporally regulated during cell cycle progression. Mps1 is predominately localized to the cytosol in interphase cells, whereas it is concentrated on kinetochores in prophase and prometaphase cells. The timing and mechanism of Mps1 redistribution during cell cycle transition is currently poorly understood. Here, we show that Mps1 relocates from the cytosol to the nucleus at the G2/M boundary prior to nuclear envelope breakdown (NEB). This timely translocation depends on two tandem LXXLL motifs in the N terminus of Mps1, and mutations in either motif abolish Mps1 nuclear accumulation. Furthermore, we found that phosphorylation of Mps1 Ser80 (which is located between the two LXXLL motifs) also plays a role in regulating timely nuclear entry of Mps1. Mps1 that is defective in LXXLL motifs has near wild-type kinase activity. Moreover, the kinase activity of Mps1 appears to be dispensable for nuclear translocation, as inhibition of Mps1 by a highly specific small-molecule inhibitor did not perturb its nuclear entry. Remarkably, translocation-deficient Mps1 can mediate activation of spindle assembly checkpoint response; however, it fails to support a sustained mitotic arrest upon prolonged treatment with nocodazole. The mitotic slippage can be attributed to precocious degradation of Mps1 in the arrested cells. Our studies reveal a novel cell cycle-dependent nuclear translocation signal in the N terminus of Mps1 and suggest that timely nuclear entry could be important for sustaining spindle assembly checkpoint responses. PMID:21778823

A p53-independent damage-sensing mechanism that functions as a checkpoint at the G1/S transition in Chinese hamster ovary cells

PubMed Central

Lee, Hoyun; Larner, James M.; Hamlin, Joyce L.

1997-01-01

In response to a moderate dose of radiation, asynchronous mammalian cell populations rapidly and transiently down-regulate the rate of DNA synthesis to ≈50% of preirradiation values. We show here that only half of the reduction in overall replication rate can be accounted for by direct inhibition of initiation at origins in S-phase cells. The other half results from the operation of a newly defined cell cycle checkpoint that functions at the G1/S transition. This checkpoint senses damage incurred at any time during the last 2 hr of G1 and effectively prevents entry into the S period. The G1/S and S-phase checkpoints are both p53-independent and, unlike the p53-mediated G1 checkpoint, respond rapidly to radiation, suggesting that they may represent major damage-sensing mechanisms connecting the replication machinery with DNA repair pathways. PMID:9012817

T-cell-based Immunotherapy: Adoptive Cell Transfer and Checkpoint Inhibition.

PubMed

Houot, Roch; Schultz, Liora Michal; Marabelle, Aurélien; Kohrt, Holbrook

2015-10-01

Tumor immunotherapy has had demonstrable efficacy in patients with cancer. The most promising results have been with T-cell-based therapies. These include adoptive cell transfer of tumor-infiltrating lymphocytes, genetically engineered T cells, and immune checkpoint inhibitor antibodies. In this review, we describe the different T-cell-based strategies currently in clinical trials and put their applications, present and future, into perspective. ©2015 American Association for Cancer Research.

Immune checkpoint inhibitors in advanced renal cell carcinoma: experience to date and future directions.

PubMed

Atkins, M B; Clark, J I; Quinn, D I

2017-07-01

In recent years, there has been dramatic expansion of the treatment armamentarium for patients with advanced renal cell carcinoma (aRCC), including drugs targeting vascular endothelial growth factor and mammalian target of rapamycin (mTOR) pathways. Despite these advances, patient outcomes remain suboptimal, underscoring the need for therapeutic interventions with novel mechanisms of action. The advent of immunotherapy with checkpoint inhibitors has led to significant changes in the treatment landscape for several solid malignancies. Specifically, drugs targeting the programmed death 1 (PD-1) and cytotoxic T-lymphocyte associated antigen (CTLA-4) pathways have demonstrated considerable clinical efficacy and gained regulatory approval as single-agent or combination therapy for the treatment of patients with metastatic melanoma, non-small cell lung cancer, aRCC, advanced squamous cell carcinoma of the head and neck, urothelial cancer and Hodgkin lymphoma. In aRCC, the PD-1 inhibitor nivolumab was approved in both the United States and Europe for the treatment of patients who have received prior therapy, based on improved overall survival compared with the mTOR inhibitor everolimus. Other checkpoint inhibitors, including the CTLA-4 inhibitor ipilimumab in combination with several agents, and the PD-L1 inhibitor atezolizumab, are in various stages of clinical development in patients with aRCC. In this review, current evidence related to the clinical use of checkpoint inhibitors for the treatment of patients with aRCC is discussed, including information on the frequency and management of unconventional responses and the management of immune-related adverse events. In addition, perspectives on the future use of checkpoint inhibitors are discussed, including the potential value of treatment beyond progression, the potential use in earlier lines of care or in combination with other agents, and the identification of biomarkers to guide patient selection and enable

Learning and signal copying facilitate communication among bird species

PubMed Central

Wheatcroft, David; Price, Trevor D.

2013-01-01

Signals relevant to different sets of receivers in different contexts create a conflict for signal design. A classic example is vocal alarm signals, often used both during intraspecific and interspecific interactions. How can signals alert individuals from a variety of other species in some contexts, while also maintaining efficient communication among conspecifics? We studied heterospecific responses to avian alarm signals that drive the formation of anti-predator groups but are also used during intraspecific interactions. In three species-rich communities in the western Himalayas, alarm signals vary drastically across species. We show that, independently of differences in their calls, birds respond strongly to the alarm signals of other species with which they co-occur and much more weakly to those of species with which they do not co-occur. These results suggest that previous exposure and learning maintain heterospecific responses in the face of widespread signal divergence. At an area where only two species regularly interact, one species' calls incorporate the call of the other. We demonstrate experimentally that signal copying allows strong responses even without previous exposure and suggest that such hybrid calls may be especially favoured when pairwise interactions between species are strong. PMID:23446529

Predictors of responses to immune checkpoint blockade in advanced melanoma.

PubMed

Jacquelot, N; Roberti, M P; Enot, D P; Rusakiewicz, S; Ternès, N; Jegou, S; Woods, D M; Sodré, A L; Hansen, M; Meirow, Y; Sade-Feldman, M; Burra, A; Kwek, S S; Flament, C; Messaoudene, M; Duong, C P M; Chen, L; Kwon, B S; Anderson, A C; Kuchroo, V K; Weide, B; Aubin, F; Borg, C; Dalle, S; Beatrix, O; Ayyoub, M; Balme, B; Tomasic, G; Di Giacomo, A M; Maio, M; Schadendorf, D; Melero, I; Dréno, B; Khammari, A; Dummer, R; Levesque, M; Koguchi, Y; Fong, L; Lotem, M; Baniyash, M; Schmidt, H; Svane, I M; Kroemer, G; Marabelle, A; Michiels, S; Cavalcanti, A; Smyth, M J; Weber, J S; Eggermont, A M; Zitvogel, L

2017-09-19

Immune checkpoint blockers (ICB) have become pivotal therapies in the clinical armamentarium against metastatic melanoma (MMel). Given the frequency of immune related adverse events and increasing use of ICB, predictors of response to CTLA-4 and/or PD-1 blockade represent unmet clinical needs. Using a systems biology-based approach to an assessment of 779 paired blood and tumor markers in 37 stage III MMel patients, we analyzed association between blood immune parameters and the functional immune reactivity of tumor-infiltrating cells after ex vivo exposure to ICB. Based on this assay, we retrospectively observed, in eight cohorts enrolling 190 MMel patients treated with ipilimumab, that PD-L1 expression on peripheral T cells was prognostic on overall and progression-free survival. Moreover, detectable CD137 on circulating CD8 + T cells was associated with the disease-free status of resected stage III MMel patients after adjuvant ipilimumab + nivolumab (but not nivolumab alone). These biomarkers should be validated in prospective trials in MMel.The clinical management of metastatic melanoma requires predictors of the response to checkpoint blockade. Here, the authors use immunological assays to identify potential prognostic/predictive biomarkers in circulating blood cells and in tumor-infiltrating lymphocytes from patients with resected stage III melanoma.

Positive regulation of meiotic DNA double-strand break formation by activation of the DNA damage checkpoint kinase Mec1(ATR).

PubMed

Gray, Stephen; Allison, Rachal M; Garcia, Valerie; Goldman, Alastair S H; Neale, Matthew J

2013-07-31

During meiosis, formation and repair of programmed DNA double-strand breaks (DSBs) create genetic exchange between homologous chromosomes-a process that is critical for reductional meiotic chromosome segregation and the production of genetically diverse sexually reproducing populations. Meiotic DSB formation is a complex process, requiring numerous proteins, of which Spo11 is the evolutionarily conserved catalytic subunit. Precisely how Spo11 and its accessory proteins function or are regulated is unclear. Here, we use Saccharomyces cerevisiae to reveal that meiotic DSB formation is modulated by the Mec1(ATR) branch of the DNA damage signalling cascade, promoting DSB formation when Spo11-mediated catalysis is compromised. Activation of the positive feedback pathway correlates with the formation of single-stranded DNA (ssDNA) recombination intermediates and activation of the downstream kinase, Mek1. We show that the requirement for checkpoint activation can be rescued by prolonging meiotic prophase by deleting the NDT80 transcription factor, and that even transient prophase arrest caused by Ndt80 depletion is sufficient to restore meiotic spore viability in checkpoint mutants. Our observations are unexpected given recent reports that the complementary kinase pathway Tel1(ATM) acts to inhibit DSB formation. We propose that such antagonistic regulation of DSB formation by Mec1 and Tel1 creates a regulatory mechanism, where the absolute frequency of DSBs is maintained at a level optimal for genetic exchange and efficient chromosome segregation.

Deficiency of the Arabidopsis helicase RTEL1 triggers a SOG1-dependent replication checkpoint in response to DNA cross-links.

PubMed

Hu, Zhubing; Cools, Toon; Kalhorzadeh, Pooneh; Heyman, Jefri; De Veylder, Lieven

2015-01-01

To maintain genome integrity, DNA replication is executed and regulated by a complex molecular network of numerous proteins, including helicases and cell cycle checkpoint regulators. Through a systematic screening for putative replication mutants, we identified an Arabidopsis thaliana homolog of human Regulator of Telomere Length 1 (RTEL1), which functions in DNA replication, DNA repair, and recombination. RTEL1 deficiency retards plant growth, a phenotype including a prolonged S-phase duration and decreased cell proliferation. Genetic analysis revealed that rtel1 mutant plants show activated cell cycle checkpoints, specific sensitivity to DNA cross-linking agents, and increased homologous recombination, but a lack of progressive shortening of telomeres, indicating that RTEL1 functions have only been partially conserved between mammals and plants. Surprisingly, RTEL1 deficiency induces tolerance to the deoxynucleotide-depleting drug hydroxyurea, which could be mimicked by DNA cross-linking agents. This resistance does not rely on the essential replication checkpoint regulator WEE1 but could be blocked by a mutation in the SOG1 transcription factor. Taken together, our data indicate that RTEL1 is required for DNA replication and that its deficiency activates a SOG1-dependent replication checkpoint. © 2015 American Society of Plant Biologists. All rights reserved.

Methotrexate increases expression of cell cycle checkpoint genes via Jun-N-terminal kinase activation

PubMed Central

Spurlock, Charles F.; Tossberg, John T.; Fuchs, Howard A.; Olsen, Nancy J.; Aune, Thomas M.

2011-01-01

Objective To assess defects in expression of critical cell cycle checkpoint genes and proteins in subjects with rheumatoid arthritis relative to presence or absence of methotrexate medication and assess the role of Jun N-terminal kinase in methotrexate induction of these genes. Methods Flow cytometry analysis was used to quantify changes in intracellular proteins, measure reactive oxygen species (ROS), and determine apoptosis in different lymphoid populations. Quantitative reverse transcriptase polymerase chain reaction (Q-RT-PCR) was employed to determine changes in cell cycle checkpoint target genes. Results RA subjects express lower baseline levels of MAPK9, TP53, CDKN1A, CDKN1B, CHEK2, and RANGAP1 messenger RNA (mRNA) and total JNK protein. MAPK9, TP53, CDKN1A, and CDKN1B mRNA expression, but not CHEK2, and RANGAP1, is higher in patients on low-dose MTX therapy. Further, JNK levels inversely correlate with CRP levels in RA patients. In tissue culture, MTX induces expression of both p53 and p21 by JNK2 and JNK1-dependent mechanisms, respectively, while CHEK2 and RANGAP1 are not induced by MTX. MTX also induces ROS production, JNK activation, and sensitivity to apoptosis in activated T cells. Supplementation with tetrahydrobiopterin blocks these MTX-mediated effects. Conclusions Our findings support the notion that MTX restores some, but not all of the proteins contributing to cell cycle checkpoint deficiencies in RA T cells by a JNK dependent pathway. PMID:22183962

A humanized antibody for imaging immune checkpoint ligand PD-L1 expression in tumors

PubMed Central

Gabrielson, Matthew; Lisok, Ala; Wharram, Bryan; Sysa-Shah, Polina; Azad, Babak Behnam; Pomper, Martin G.; Nimmagadda, Sridhar

2016-01-01

Antibodies targeting the PD-1/PD-L1 immune checkpoint lead to tumor regression and improved survival in several cancers. PD-L1 expression in tumors may be predictive of response to checkpoint blockade therapy. Because tissue samples might not always be available to guide therapy, we developed and evaluated a humanized antibody for non-invasive imaging of PD-L1 expression in tumors. Radiolabeled [111In]PD-L1-mAb and near-infrared dye conjugated NIR-PD-L1-mAb imaging agents were developed using the mouse and human cross-reactive PD-L1 antibody MPDL3280A. We tested specificity of [111In]PD-L1-mAb and NIR-PD-L1-mAb in cell lines and in tumors with varying levels of PD-L1 expression. We performed SPECT/CT imaging, biodistribution and blocking studies in NSG mice bearing tumors with constitutive PD-L1 expression (CHO-PDL1) and in controls (CHO). Results were confirmed in triple negative breast cancer (TNBC) (MDAMB231 and SUM149) and non-small cell lung cancer (NSCLC) (H2444 and H1155) xenografts with varying levels of PD-L1 expression. There was specific binding of [111In]PD-L1-mAb and NIR-PD-L1-mAb to tumor cells in vitro, correlating with PD-L1 expression levels. In mice bearing subcutaneous and orthotopic tumors, there was specific and persistent high accumulation of signal intensity in PD-L1 positive tumors (CHO-PDL1, MDAMB231, H2444) but not in controls. These results demonstrate that [111In]PD-L1-mAb and NIR-PD-L1-mAb can detect graded levels of PD-L1 expression in human tumor xenografts in vivo. As a humanized antibody, these findings suggest clinical translation of radiolabeled versions of MPDL3280A for imaging. Specificity of NIR-PD-L1-mAb indicates the potential for optical imaging of PD-L1 expression in tumors in relevant pre-clinical as well as clinical settings. PMID:26848870

Immunohistochemical and Image Analysis-Based Study Shows That Several Immune Checkpoints are Co-expressed in Non-Small Cell Lung Carcinoma Tumors.

PubMed

Parra, Edwin Roger; Villalobos, Pamela; Zhang, Jiexin; Behrens, Carmen; Mino, Barbara; Swisher, Stephen; Sepesi, Boris; Weissferdt, Annika; Kalhor, Neda; Heymach, John Victor; Moran, Cesar; Zhang, Jianjun; Lee, Jack; Rodriguez-Canales, Jaime; Gibbons, Don; Wistuba, Ignacio I

2018-06-01

The understanding of immune checkpoint molecules' co-expression in non-small cell lung carcinoma (NCLC) is important to potentially design combinatorial immunotherapy approaches. We studied 225 formalin-fixed, paraffin-embedded tumor tissues from stage I-III NCLCs - 142 adenocarcinomas (ADCs) and 83 squamous cell carcinomas (SCCs) - placed in tissue microarrays. Nine immune checkpoint markers were evaluated; four (programmed death ligand 1 [PD-L1], B7-H3, B7-H4, and indoleamine 2,3-dioxygenase 1 [IDO-1]) expressed predominantly in malignant cells (MCs) and five (inducible T cell costimulator, V-set immunoregulatory receptor, T-cell immunoglobulin mucin family member 3, lymphocyte activating 3, and OX40) expressed mostly in stromal tumor-associated inflammatory cells (TAICs). All markers were examined using a quantitative image analysis and correlated with clinicopathologic features, TAICs, and molecular characteristics. Using above the median value as positive expression in MCs and high density of TAICs expressing those markers, we identified higher expression of immune checkpoints in SCC than ADC. Common simultaneous expression by MCs was PD-L1 + B7-H3 + IDO-1 in ADC and PD-L1 + B7-H3, or B7-H3 + B7-H4, in SCC. TAICs expressing checkpoint were significantly higher in current smokers than in never smokers. Almost all the immune checkpoint markers showed positive correlation with TAICs expressing inflammatory cell markers. KRAS-mutant ADC specimens showed higher expression of PD-L1 in MCs and of B7-H3, T-cell immunoglobulin mucin family member 3, and IDO-1 in TAICs than wild type. Kaplan-Meier survival curves showed worse prognosis in ADC patients with higher B7-H4 expression by MCs. We found frequent immunohistochemical co-expression of immune checkpoints in surgically resected NCLC tumors and correlated with tumor histology, smoking history, tumor size, and the density of inflammatory cells and tumor mutational status. Copyright © 2018 International

Loss of p53 induces M-phase retardation following G2 DNA damage checkpoint abrogation.

PubMed

Minemoto, Yuzuru; Uchida, Sanae; Ohtsubo, Motoaki; Shimura, Mari; Sasagawa, Toshiyuki; Hirata, Masato; Nakagama, Hitoshi; Ishizaka, Yukihito; Yamashita, Katsumi

2003-04-01

Most cell lines that lack functional p53 protein are arrested in the G2 phase of the cell cycle due to DNA damage. When the G2 checkpoint is abrogated, these cells are forced into mitotic catastrophe. A549 lung adenocarcinoma cells, in which p53 was eliminated with the HPV16 E6 gene, exhibited efficient arrest in the G2 phase when treated with adriamycin. Administration of caffeine to G2-arrested cells induced a drastic change in cell phenotype, the nature of which depended on the status of p53. Flow cytometric and microscopic observations revealed that cells that either contained or lacked p53 resumed their cell cycles and entered mitosis upon caffeine treatment. However, transit to the M phase was slower in p53-negative cells than in p53-positive cells. Consistent with these observations, CDK1 activity was maintained at high levels, along with stable cyclin B1, in p53-negative cells. The addition of butyrolactone I, which is an inhibitor of CDK1 and CDK2, to the p53-negative cells reduced the floating round cell population and induced the disappearance of cyclin B1. These results suggest a relationship between the p53 pathway and the ubiquitin-mediated degradation of mitotic cyclins and possible cross-talk between the G2-DNA damage checkpoint and the mitotic checkpoint.

A Novel Rrm3 Function in Restricting DNA Replication via an Orc5-Binding Domain Is Genetically Separable from Rrm3 Function as an ATPase/Helicase in Facilitating Fork Progression

PubMed Central

Syed, Salahuddin; Desler, Claus; Rasmussen, Lene J.; Schmidt, Kristina H.

2016-01-01

In response to replication stress cells activate the intra-S checkpoint, induce DNA repair pathways, increase nucleotide levels, and inhibit origin firing. Here, we report that Rrm3 associates with a subset of replication origins and controls DNA synthesis during replication stress. The N-terminal domain required for control of DNA synthesis maps to residues 186–212 that are also critical for binding Orc5 of the origin recognition complex. Deletion of this domain is lethal to cells lacking the replication checkpoint mediator Mrc1 and leads to mutations upon exposure to the replication stressor hydroxyurea. This novel Rrm3 function is independent of its established role as an ATPase/helicase in facilitating replication fork progression through polymerase blocking obstacles. Using quantitative mass spectrometry and genetic analyses, we find that the homologous recombination factor Rdh54 and Rad5-dependent error-free DNA damage bypass act as independent mechanisms on DNA lesions that arise when Rrm3 catalytic activity is disrupted whereas these mechanisms are dispensable for DNA damage tolerance when the replication function is disrupted, indicating that the DNA lesions generated by the loss of each Rrm3 function are distinct. Although both lesion types activate the DNA-damage checkpoint, we find that the resultant increase in nucleotide levels is not sufficient for continued DNA synthesis under replication stress. Together, our findings suggest a role of Rrm3, via its Orc5-binding domain, in restricting DNA synthesis that is genetically and physically separable from its established catalytic role in facilitating fork progression through replication blocks. PMID:27923055

A Novel Rrm3 Function in Restricting DNA Replication via an Orc5-Binding Domain Is Genetically Separable from Rrm3 Function as an ATPase/Helicase in Facilitating Fork Progression.

PubMed

Syed, Salahuddin; Desler, Claus; Rasmussen, Lene J; Schmidt, Kristina H

2016-12-01

In response to replication stress cells activate the intra-S checkpoint, induce DNA repair pathways, increase nucleotide levels, and inhibit origin firing. Here, we report that Rrm3 associates with a subset of replication origins and controls DNA synthesis during replication stress. The N-terminal domain required for control of DNA synthesis maps to residues 186-212 that are also critical for binding Orc5 of the origin recognition complex. Deletion of this domain is lethal to cells lacking the replication checkpoint mediator Mrc1 and leads to mutations upon exposure to the replication stressor hydroxyurea. This novel Rrm3 function is independent of its established role as an ATPase/helicase in facilitating replication fork progression through polymerase blocking obstacles. Using quantitative mass spectrometry and genetic analyses, we find that the homologous recombination factor Rdh54 and Rad5-dependent error-free DNA damage bypass act as independent mechanisms on DNA lesions that arise when Rrm3 catalytic activity is disrupted whereas these mechanisms are dispensable for DNA damage tolerance when the replication function is disrupted, indicating that the DNA lesions generated by the loss of each Rrm3 function are distinct. Although both lesion types activate the DNA-damage checkpoint, we find that the resultant increase in nucleotide levels is not sufficient for continued DNA synthesis under replication stress. Together, our findings suggest a role of Rrm3, via its Orc5-binding domain, in restricting DNA synthesis that is genetically and physically separable from its established catalytic role in facilitating fork progression through replication blocks.

Phospho-Bcl-x(L)(Ser62) plays a key role at DNA damage-induced G(2) checkpoint.

PubMed

Wang, Jianfang; Beauchemin, Myriam; Bertrand, Richard

2012-06-01

Accumulating evidence suggests that Bcl-xL, an anti-apoptotic member of the Bcl-2 family, also functions in cell cycle progression and cell cycle checkpoints. Analysis of a series of phosphorylation site mutants reveals that cells expressing Bcl-xL(Ser62Ala) mutant are less stable at the G 2 checkpoint and enter mitosis more rapidly than cells expressing wild-type Bcl-xL or Bcl-xL phosphorylation site mutants, including Thr41Ala, Ser43Ala, Thr47Ala, Ser56Ala and Thr115Ala. Analysis of the dynamic phosphorylation and location of phospho-Bcl-xL(Ser62) in unperturbed, synchronized cells and during DNA damage-induced G 2 arrest discloses that a pool of phospho-Bcl-xL(Ser62) accumulates into nucleolar structures in etoposide-exposed cells during G 2 arrest. In a series of in vitro kinase assays, pharmacological inhibitors and specific siRNAs experiments, we found that Polo kinase 1 and MAPK9/JNK2 are major protein kinases involved in Bcl-xL(Ser62) phosphorylation and accumulation into nucleolar structures during the G 2 checkpoint. In nucleoli, phospho-Bcl-xL(Ser62) binds to and co-localizes with Cdk1(cdc2), the key cyclin-dependent kinase required for entry into mitosis. These data indicate that during G 2 checkpoint, phospho-Bcl-xL(Ser62) stabilizes G 2 arrest by timely trapping of Cdk1(cdc2) in nucleolar structures to slow mitotic entry. It also highlights that DNA damage affects the dynamic composition of the nucleolus, which now emerges as a piece of the DNA damage response.

Poly(ADP-ribose) binding to Chk1 at stalled replication forks is required for S-phase checkpoint activation

NASA Astrophysics Data System (ADS)

Min, Wookee; Bruhn, Christopher; Grigaravicius, Paulius; Zhou, Zhong-Wei; Li, Fu; Krüger, Anja; Siddeek, Bénazir; Greulich, Karl-Otto; Popp, Oliver; Meisezahl, Chris; Calkhoven, Cornelis F.; Bürkle, Alexander; Xu, Xingzhi; Wang, Zhao-Qi

2013-12-01

Damaged replication forks activate poly(ADP-ribose) polymerase 1 (PARP1), which catalyses poly(ADP-ribose) (PAR) formation; however, how PARP1 or poly(ADP-ribosyl)ation is involved in the S-phase checkpoint is unknown. Here we show that PAR, supplied by PARP1, interacts with Chk1 via a novel PAR-binding regulatory (PbR) motif in Chk1, independent of ATR and its activity. iPOND studies reveal that Chk1 associates readily with the unperturbed replication fork and that PAR is required for efficient retention of Chk1 and phosphorylated Chk1 at the fork. A PbR mutation, which disrupts PAR binding, but not the interaction with its partners Claspin or BRCA1, impairs Chk1 and the S-phase checkpoint activation, and mirrors Chk1 knockdown-induced hypersensitivity to fork poisoning. We find that long chains, but not short chains, of PAR stimulate Chk1 kinase activity. Collectively, we disclose a previously unrecognized mechanism of the S-phase checkpoint by PAR metabolism that modulates Chk1 activity at the replication fork.

Role of replication protein A as sensor in activation of the S-phase checkpoint in Xenopus egg extracts

PubMed Central

Recolin, Bénédicte; Van Der Laan, Siem; Maiorano, Domenico

2012-01-01

Uncoupling between DNA polymerases and helicase activities at replication forks, induced by diverse DNA lesions or replication inhibitors, generate long stretches of primed single-stranded DNA that is implicated in activation of the S-phase checkpoint. It is currently unclear whether nucleation of the essential replication factor RPA onto this substrate stimulates the ATR-dependent checkpoint response independently of its role in DNA synthesis. Using Xenopus egg extracts to investigate the role of RPA recruitment at uncoupled forks in checkpoint activation we have surprisingly found that in conditions in which DNA synthesis occurs, RPA accumulation at forks stalled by either replication stress or UV irradiation is dispensable for Chk1 phosphorylation. In contrast, when both replication fork uncoupling and RPA hyperloading are suppressed, Chk1 phosphorylation is inhibited. Moreover, we show that extracts containing reduced levels of RPA accumulate ssDNA and induce spontaneous, caffeine-sensitive, Chk1 phosphorylation in S-phase. These results strongly suggest that disturbance of enzymatic activities of replication forks, rather than RPA hyperloading at stalled forks, is a critical determinant of ATR activation. PMID:22187152

Checkpoint and restart procedures for single and multi-stage structural model analysis in NASTRAN/COSMIC on a CDC 176

NASA Technical Reports Server (NTRS)

Camp, George H.; Fallon, Dennis J.

1987-01-01

The Underwater Explosions Research Division (UERD) of the David Taylor Naval Ship Research and Development Center makes extensive use of NASTRAN/COSMIC on a CDC 176 to evaluate the structural response of ship structures subjected to underwater explosion shock loadings in the time domain. As relatively new users, UERD engineers have experienced difficulties with the checkpoint/restart feature because of the vague instructions in the user manual. Working procedures for the application of the checkpoint/restart feature to the transient analysis using NASTRAN/COSMIC are illustrated.

Interdependent IL-7 and IFN-γ signalling in T-cell controls tumour eradication by combined α-CTLA-4+α-PD-1 therapy

PubMed Central

Shi, Lewis Zhichang; Fu, Tihui; Guan, Baoxiang; Chen, Jianfeng; Blando, Jorge M.; Allison, James P.; Xiong, Liangwen; Subudhi, Sumit K.; Gao, Jianjun; Sharma, Padmanee

2016-01-01

Combination therapy with α-CTLA-4 and α-PD-1 has shown significant clinical responses in different types of cancer. However, the underlying mechanisms remain elusive. Here, combining detailed analysis of human tumour samples with preclinical tumour models, we report that concomitant blockade of CTLA-4 and PD-1 improves anti-tumour immune responses and synergistically eradicates tumour. Mechanistically, combination therapy relies on the interdependence between IL-7 and IFN-γ signalling in T cells, as lack of either pathway abrogates the immune-boosting and therapeutic effects of combination therapy. Combination treatment increases IL-7Rα expression on tumour-infiltrating T cells in an IFN-γ/IFN-γR signalling-dependent manner, which may serve as a potential biomarker for clinical trials with immune checkpoint blockade. Our data suggest that combining immune checkpoint blockade with IL-7 signalling could be an effective modality to improve immunotherapeutic efficacy. Taken together, we conclude that combination therapy potently reverses immunosuppression and eradicates tumours via an intricate interplay between IFN-γ/IFN-γR and IL-7/IL-7R pathways. PMID:27498556

Rituximab does not reset defective early B cell tolerance checkpoints

PubMed Central

Chamberlain, Nicolas; Massad, Christopher; Oe, Tyler; Cantaert, Tineke; Herold, Kevan C.; Meffre, Eric

2015-01-01

Type 1 diabetes (T1D) patients show abnormalities in early B cell tolerance checkpoints, resulting in the accumulation of large numbers of autoreactive B cells in their blood. Treatment with rituximab, an anti-CD20 mAb that depletes B cells, has been shown to preserve β cell function in T1D patients and improve other autoimmune diseases, including rheumatoid arthritis and multiple sclerosis. However, it remains largely unknown how anti–B cell therapy thwarts autoimmunity in these pathologies. Here, we analyzed the reactivity of Abs expressed by single, mature naive B cells from 4 patients with T1D before and 52 weeks after treatment to determine whether rituximab resets early B cell tolerance checkpoints. We found that anti–B cell therapy did not alter the frequencies of autoreactive and polyreactive B cells, which remained elevated in the blood of all patients after rituximab treatment. Moreover, the limited proliferative history of autoreactive B cells after treatment revealed that these clones were newly generated B cells and not self-reactive B cells that had escaped depletion and repopulated the periphery through homeostatic expansion. We conclude that anti–B cell therapy may provide a temporary dampening of autoimmune processes through B cell depletion. However, repletion with autoreactive B cells may explain the relapse that occurs in many autoimmune patients after anti–B cell therapy. PMID:26642366

Roles of nibrin and AtM/ATR kinases on the G2 checkpoint under endogenous or radio-induced DNA damage.

PubMed

Marcelain, Katherine; De La Torre, Consuelo; González, Patricio; Pincheira, Juana

2005-01-01

Checkpoint response to DNA damage involves the activation of DNA repair and G2 lengthening subpathways. The roles of nibrin (NBS1) and the ATM/ATR kinases in the G2 DNA damage checkpoint, evoked by endogenous and radio-induced DNA damage, were analyzed in control, A-T and NBS lymphoblast cell lines. Short-term responses to G2 treatments were evaluated by recording changes in the yield of chromosomal aberrations in the ensuing mitosis, due to G2 checkpoint adaptation, and also in the duration of G2 itself. The role of ATM/ATR in the G2 checkpoint pathway repairing chromosomal aberrations was unveiled by caffeine inhibition of both kinases in G2. In the control cell lines, nibrin and ATM cooperated to provide optimum G2 repair for endogenous DNA damage. In the A-T cells, ATR kinase substituted successfully for ATM, even though no G2 lengthening occurred. X-ray irradiation (0.4 Gy) in G2 increased chromosomal aberrations and lengthened G2, in both mutant and control cells. However, the repair of radio-induced DNA damage took place only in the controls. It was associated with nibrin-ATM interaction, and ATR did not substitute for ATM. The absence of nibrin prevented the repair of both endogenous and radio-induced DNA damage in the NBS cells and partially affected the induction of G2 lengthening.

Cervical spinal erythropoietin induces phrenic motor facilitation via ERK and Akt signaling

PubMed Central

Dale, Erica A.; Satriotomo, Irawan; Mitchell, Gordon S.

2012-01-01

Erythropoietin (EPO) is typically known for its role in erythropoiesis, but is also a potent neurotrophic/neuroprotective factor for spinal motor neurons. Another trophic factor regulated by Hypoxia-Inducible Factor-1, vascular endothelial growth factor (VEGF), signals via ERK and Akt activation to elicit long-lasting phrenic motor facilitation (pMF). Since EPO also signals via ERK and Akt activation, we tested the hypothesis that EPO elicits similar pMF. Using retrograde labeling and immunohistochemical techniques, we demonstrate in adult, male, Sprague-Dawley rats that EPO and its receptor, EPO-R, are expressed in identified phrenic motor neurons. Intrathecal EPO at C4 elicits long-lasting pMF; integrated phrenic nerve burst amplitude increased >90 min post-injection (63±12% baseline 90 min post-injection; p<0.001). EPO increased phosphorylation (and presumed activation) of ERK (1.6 fold vs controls; p<0.05) in phrenic motor neurons; EPO also increased pAkt (1.6 fold vs controls; p<0.05). EPO-induced pMF was abolished by the MEK/ERK inhibitor U0126 and the PI3 kinase/Akt inhibitor LY294002, demonstrating that ERK MAP kinases and Akt are both required for EPO-induced pMF. Pre-treatment with U0126 and LY294002 decreased both pERK and pAkt in phrenic motor neurons (p<0.05), indicating a complex interaction between these kinases. We conclude that EPO elicits spinal plasticity in respiratory motor control. Since EPO expression is hypoxia-sensitive, it may play a role in respiratory plasticity in conditions of prolonged or recurrent low oxygen. PMID:22539857

Checkpoint Pathways Activated by Re-Replication in Breast Cancer Cells

DTIC Science & Technology

2011-05-01

107- 13. 9. Zhu W DA. An ATR- and BRCA1-Mediated Fanconi Anemia Pathway Is Required for Activating the G2/M Checkpoint and DNA Damage Repair upon...re-replication. J Biol Chem 2007;282:30357-62. 25. Montes de Oca R, Andreassen PR, Margossian SP, et al. Regulated interaction of the Fanconi anemia ...protein, FANCD2, with chromatin. Blood 2005;105:1003-9. 26. Zhu W DA. An ATR- and BRCA1-Mediated Fanconi Anemia Pathway Is Required for Activating

Histone H3 K79 methylation states play distinct roles in UV-induced sister chromatid exchange and cell cycle checkpoint arrest in Saccharomyces cerevisiae

PubMed Central

Rossodivita, Alyssa A.; Boudoures, Anna L.; Mecoli, Jonathan P.; Steenkiste, Elizabeth M.; Karl, Andrea L.; Vines, Eudora M.; Cole, Arron M.; Ansbro, Megan R.; Thompson, Jeffrey S.

2014-01-01

Histone post-translational modifications have been shown to contribute to DNA damage repair. Prior studies have suggested that specific H3K79 methylation states play distinct roles in the response to UV-induced DNA damage. To evaluate these observations, we examined the effect of altered H3K79 methylation patterns on UV-induced G1/S checkpoint response and sister chromatid exchange (SCE). We found that the di- and trimethylated states both contribute to activation of the G1/S checkpoint to varying degrees, depending on the synchronization method, although methylation is not required for checkpoint in response to high levels of UV damage. In contrast, UV-induced SCE is largely a product of the trimethylated state, which influences the usage of gene conversion versus popout mechanisms. Regulation of H3K79 methylation by H2BK123 ubiquitylation is important for both checkpoint function and SCE. H3K79 methylation is not required for the repair of double-stranded breaks caused by transient HO endonuclease expression, but does play a modest role in survival from continuous exposure. The overall results provide evidence for the participation of H3K79 methylation in UV-induced recombination repair and checkpoint activation, and further indicate that the di- and trimethylation states play distinct roles in these DNA damage response pathways. PMID:24748660

DNA damage checkpoint kinase ATM regulates germination and maintains genome stability in seeds

PubMed Central

Waterworth, Wanda M.; Footitt, Steven; Bray, Clifford M.; Finch-Savage, William E.; West, Christopher E.

2016-01-01

Genome integrity is crucial for cellular survival and the faithful transmission of genetic information. The eukaryotic cellular response to DNA damage is orchestrated by the DNA damage checkpoint kinases ATAXIA TELANGIECTASIA MUTATED (ATM) and ATM AND RAD3-RELATED (ATR). Here we identify important physiological roles for these sensor kinases in control of seed germination. We demonstrate that double-strand breaks (DSBs) are rate-limiting for germination. We identify that desiccation tolerant seeds exhibit a striking transcriptional DSB damage response during germination, indicative of high levels of genotoxic stress, which is induced following maturation drying and quiescence. Mutant atr and atm seeds are highly resistant to aging, establishing ATM and ATR as determinants of seed viability. In response to aging, ATM delays germination, whereas atm mutant seeds germinate with extensive chromosomal abnormalities. This identifies ATM as a major factor that controls germination in aged seeds, integrating progression through germination with surveillance of genome integrity. Mechanistically, ATM functions through control of DNA replication in imbibing seeds. ATM signaling is mediated by transcriptional control of the cell cycle inhibitor SIAMESE-RELATED 5, an essential factor required for the aging-induced delay to germination. In the soil seed bank, seeds exhibit increased transcript levels of ATM and ATR, with changes in dormancy and germination potential modulated by environmental signals, including temperature and soil moisture. Collectively, our findings reveal physiological functions for these sensor kinases in linking genome integrity to germination, thereby influencing seed quality, crucial for plant survival in the natural environment and sustainable crop production. PMID:27503884

DNA damage checkpoint kinase ATM regulates germination and maintains genome stability in seeds.

PubMed

Waterworth, Wanda M; Footitt, Steven; Bray, Clifford M; Finch-Savage, William E; West, Christopher E

2016-08-23

Genome integrity is crucial for cellular survival and the faithful transmission of genetic information. The eukaryotic cellular response to DNA damage is orchestrated by the DNA damage checkpoint kinases ATAXIA TELANGIECTASIA MUTATED (ATM) and ATM AND RAD3-RELATED (ATR). Here we identify important physiological roles for these sensor kinases in control of seed germination. We demonstrate that double-strand breaks (DSBs) are rate-limiting for germination. We identify that desiccation tolerant seeds exhibit a striking transcriptional DSB damage response during germination, indicative of high levels of genotoxic stress, which is induced following maturation drying and quiescence. Mutant atr and atm seeds are highly resistant to aging, establishing ATM and ATR as determinants of seed viability. In response to aging, ATM delays germination, whereas atm mutant seeds germinate with extensive chromosomal abnormalities. This identifies ATM as a major factor that controls germination in aged seeds, integrating progression through germination with surveillance of genome integrity. Mechanistically, ATM functions through control of DNA replication in imbibing seeds. ATM signaling is mediated by transcriptional control of the cell cycle inhibitor SIAMESE-RELATED 5, an essential factor required for the aging-induced delay to germination. In the soil seed bank, seeds exhibit increased transcript levels of ATM and ATR, with changes in dormancy and germination potential modulated by environmental signals, including temperature and soil moisture. Collectively, our findings reveal physiological functions for these sensor kinases in linking genome integrity to germination, thereby influencing seed quality, crucial for plant survival in the natural environment and sustainable crop production.

Molecular basis of APC/C regulation by the spindle assembly checkpoint

PubMed Central

Zhang, Ziguo; Yang, Jing; Maslen, Sarah; Skehel, Mark; Barford, David

2016-01-01

In the dividing eukaryotic cell the spindle assembly checkpoint (SAC) ensures each daughter cell inherits an identical set of chromosomes. The SAC coordinates the correct attachment of sister chromatid kinetochores to the mitotic spindle with activation of the anaphase-promoting complex/cyclosome (APC/C), the E3 ubiquitin ligase that initiates chromosome separation. In response to unattached kinetochores, the SAC generates the mitotic checkpoint complex (MCC), a multimeric assembly that inhibits the APC/C, delaying chromosome segregation. Here, using cryo-electron microscopy we determined the near-atomic resolution structure of an APC/C-MCC complex (APC/CMCC). We reveal how degron-like sequences of the MCC subunit BubR1 block degron recognition sites on Cdc20, the APC/C coactivator subunit (Cdc20APC/C) responsible for substrate interactions. BubR1 also obstructs binding of UbcH10 (APC/C’s initiating E2) to repress APC/C ubiquitination activity. Conformational variability of the complex allows for UbcH10 association, and we show from a structure of APC/CMCC in complex with UbcH10 how the Cdc20 subunit intrinsic to the MCC (Cdc20MCC) is ubiquitinated, a process that results in APC/C reactivation when the SAC is silenced. PMID:27509861

Comprehensive analysis of cancers of unknown primary for the biomarkers of response to immune checkpoint blockade therapy.

PubMed

Gatalica, Zoran; Xiu, Joanne; Swensen, Jeff; Vranic, Semir

2018-05-01

Cancer of unknown primary (CUP) accounts for approximately 3% of all malignancies. Avoiding immune destruction is a major cancer characteristic and therapies aimed at immune checkpoint blockade are in use for several specific cancer types. A comprehensive survey of predictive biomarkers to immune checkpoint blockade in CUP were explored in this study. About 389 cases of CUP were analysed for mutations in 592 genes and 52 gene fusions using a massively parallel DNA sequencing platform (next-generation sequencing [NGS]). Total mutational load (TML) and microsatellite instability (MSI) were calculated from NGS data. PD-L1 expression was explored using immunohistochemistry (with 5% cutoff value). High TML was seen in 11.8% (46/389) of tumours. MSI-high (MSI-H) was detected in 7/384 (1.8%) of tumours. Tumour PD-L1 expression was detected in 80/362 CUP (22%). A small proportion of CUP cases harboured genetic alterations of negative predictive biomarkers to immune checkpoint inhibitors (predictors to hyperprogression) including MDM2 gene amplification (2%) and loss of function JAK2 gene mutations (1%). Amplifications of CD274 (PD-L1) and PDCD1LG2 (PD-L2) genes were also rare (1.4% and 0.8%, respectively). The most frequently mutated genes were TP53 (54%), KRAS (22%), ARID1A (13%), PIK3CA (9%), CDKN2A (8%), SMARCA4 (7%) and PBRM1, STK11, APC, RB1 (5%, respectively). Using a multiplex testing approach, 28% of CUP carried one or more predictive biomarkers (MSI-H, PD-L1 and/or TML-H) to the immune checkpoint blockade, providing a novel option for treatment in patients with CUP. Copyright © 2018 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Characterization of Spindle Checkpoint Kinase Mps1 Reveals Domain with Functional and Structural Similarities to Tetratricopeptide Repeat Motifs of Bub1 and BubR1 Checkpoint Kinases*

PubMed Central

Lee, Semin; Thebault, Philippe; Freschi, Luca; Beaufils, Sylvie; Blundell, Tom L.; Landry, Christian R.; Bolanos-Garcia, Victor M.; Elowe, Sabine

2012-01-01

Kinetochore targeting of the mitotic kinases Bub1, BubR1, and Mps1 has been implicated in efficient execution of their functions in the spindle checkpoint, the self-monitoring system of the eukaryotic cell cycle that ensures chromosome segregation occurs with high fidelity. In all three kinases, kinetochore docking is mediated by the N-terminal region of the protein. Deletions within this region result in checkpoint failure and chromosome segregation defects. Here, we use an interdisciplinary approach that includes biophysical, biochemical, cell biological, and bioinformatics methods to study the N-terminal region of human Mps1. We report the identification of a tandem repeat of the tetratricopeptide repeat (TPR) motif in the N-terminal kinetochore binding region of Mps1, with close homology to the tandem TPR motif of Bub1 and BubR1. Phylogenetic analysis indicates that TPR Mps1 was acquired after the split between deutorostomes and protostomes, as it is distinguishable in chordates and echinoderms. Overexpression of TPR Mps1 resulted in decreased efficiency of both chromosome alignment and mitotic arrest, likely through displacement of endogenous Mps1 from the kinetochore and decreased Mps1 catalytic activity. Taken together, our multidisciplinary strategy provides new insights into the evolution, structural organization, and function of Mps1 N-terminal region. PMID:22187426

Characterization of spindle checkpoint kinase Mps1 reveals domain with functional and structural similarities to tetratricopeptide repeat motifs of Bub1 and BubR1 checkpoint kinases.

PubMed

Lee, Semin; Thebault, Philippe; Freschi, Luca; Beaufils, Sylvie; Blundell, Tom L; Landry, Christian R; Bolanos-Garcia, Victor M; Elowe, Sabine

2012-02-17

Kinetochore targeting of the mitotic kinases Bub1, BubR1, and Mps1 has been implicated in efficient execution of their functions in the spindle checkpoint, the self-monitoring system of the eukaryotic cell cycle that ensures chromosome segregation occurs with high fidelity. In all three kinases, kinetochore docking is mediated by the N-terminal region of the protein. Deletions within this region result in checkpoint failure and chromosome segregation defects. Here, we use an interdisciplinary approach that includes biophysical, biochemical, cell biological, and bioinformatics methods to study the N-terminal region of human Mps1. We report the identification of a tandem repeat of the tetratricopeptide repeat (TPR) motif in the N-terminal kinetochore binding region of Mps1, with close homology to the tandem TPR motif of Bub1 and BubR1. Phylogenetic analysis indicates that TPR Mps1 was acquired after the split between deutorostomes and protostomes, as it is distinguishable in chordates and echinoderms. Overexpression of TPR Mps1 resulted in decreased efficiency of both chromosome alignment and mitotic arrest, likely through displacement of endogenous Mps1 from the kinetochore and decreased Mps1 catalytic activity. Taken together, our multidisciplinary strategy provides new insights into the evolution, structural organization, and function of Mps1 N-terminal region.

PP2A-B56 opposes Mps1 phosphorylation of Knl1 and thereby promotes spindle assembly checkpoint silencing.

PubMed

Espert, Antonio; Uluocak, Pelin; Bastos, Ricardo Nunes; Mangat, Davinderpreet; Graab, Philipp; Gruneberg, Ulrike

2014-09-29

The spindle assembly checkpoint (SAC) monitors correct attachment of chromosomes to microtubules, an important safeguard mechanism ensuring faithful chromosome segregation in eukaryotic cells. How the SAC signal is turned off once all the chromosomes have successfully attached to the spindle remains an unresolved question. Mps1 phosphorylation of Knl1 results in recruitment of the SAC proteins Bub1, Bub3, and BubR1 to the kinetochore and production of the wait-anaphase signal. SAC silencing is therefore expected to involve a phosphatase opposing Mps1. Here we demonstrate in vivo and in vitro that BubR1-associated PP2A-B56 is a key phosphatase for the removal of the Mps1-mediated Knl1 phosphorylations necessary for Bub1/BubR1 recruitment in mammalian cells. SAC silencing is thus promoted by a negative feedback loop involving the Mps1-dependent recruitment of a phosphatase opposing Mps1. Our findings extend the previously reported role for BubR1-associated PP2A-B56 in opposing Aurora B and suggest that BubR1-bound PP2A-B56 integrates kinetochore surveillance and silencing of the SAC. © 2014 Espert et al.

The Role of Replication in Activation of the DNA Damage Checkpoint

DTIC Science & Technology

2006-03-01

St AD Award Number : W81XWH-04-1-0311 TITLE: The Role of Replication in Activation of the DNA Damage Checkpoint PRINCIPAL INVESTIGATOR: Christopher...Van CONTRACTING ORGANIZATION: Stanford University Stanford, CA 94305 REPORT DATE: March 2006 TYPE OF REPORT: Annual Summary PREPARED FOR: U.S. Army...to comply with a collection of information if it does not display a currently valid OMB control number . PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE

Improvement of Antitumor Therapies Based on Vaccines and Immune-Checkpoint Inhibitors by Counteracting Tumor-Immunostimulation.

PubMed

Chiarella, Paula; Vermeulen, Mónica; Montagna, Daniela R; Vallecorsa, Pablo; Strazza, Ariel Ramiro; Meiss, Roberto P; Bustuoabad, Oscar D; Ruggiero, Raúl A; Prehn, Richmond T

2018-01-01

Immune-checkpoint inhibitors and antitumor vaccines may produce both tumor-inhibitory and tumor-stimulatory effects on growing tumors depending on the stage of tumor growth at which treatment is initiated. These paradoxical results are not necessarily incompatible with current tumor immunology but they might better be explained assuming the involvement of the phenomenon of tumor immunostimulation. This phenomenon was originally postulated on the basis that the immune response (IR) evoked in Winn tests by strong chemical murine tumors was not linear but biphasic, with strong IR producing inhibition and weak IR inducing stimulation of tumor growth. Herein, we extended those former observations to weak spontaneous murine tumors growing in pre-immunized, immune-competent and immune-depressed mice. Furthermore, we demonstrated that the interaction of specifical T cells and target tumor cells at low stimulatory ratios enhanced the production of chemokines aimed to recruit macrophages at the tumor site, which, upon activation of toll-like receptor 4 and p38 signaling pathways, would recruit and activate more macrophages and other inflammatory cells which would produce growth-stimulating signals leading to an accelerated tumor growth. On this basis, the paradoxical effects achieved by immunological therapies on growing tumors could be explained depending upon where the therapy-induced IR stands on the biphasic IR curve at each stage of tumor growth. At stages where tumor growth was enhanced (medium and large-sized tumors), counteraction of the tumor-immunostimulatory effect with anti-inflammatory strategies or, more efficiently, with selective inhibitors of p38 signaling pathways enabled the otherwise tumor-promoting immunological strategies to produce significant inhibition of tumor growth.

Improvement of Antitumor Therapies Based on Vaccines and Immune-Checkpoint Inhibitors by Counteracting Tumor-Immunostimulation

PubMed Central

Chiarella, Paula; Vermeulen, Mónica; Montagna, Daniela R.; Vallecorsa, Pablo; Strazza, Ariel Ramiro; Meiss, Roberto P.; Bustuoabad, Oscar D.; Ruggiero, Raúl A.; Prehn, Richmond T.

2018-01-01

Immune-checkpoint inhibitors and antitumor vaccines may produce both tumor-inhibitory and tumor-stimulatory effects on growing tumors depending on the stage of tumor growth at which treatment is initiated. These paradoxical results are not necessarily incompatible with current tumor immunology but they might better be explained assuming the involvement of the phenomenon of tumor immunostimulation. This phenomenon was originally postulated on the basis that the immune response (IR) evoked in Winn tests by strong chemical murine tumors was not linear but biphasic, with strong IR producing inhibition and weak IR inducing stimulation of tumor growth. Herein, we extended those former observations to weak spontaneous murine tumors growing in pre-immunized, immune-competent and immune-depressed mice. Furthermore, we demonstrated that the interaction of specifical T cells and target tumor cells at low stimulatory ratios enhanced the production of chemokines aimed to recruit macrophages at the tumor site, which, upon activation of toll-like receptor 4 and p38 signaling pathways, would recruit and activate more macrophages and other inflammatory cells which would produce growth-stimulating signals leading to an accelerated tumor growth. On this basis, the paradoxical effects achieved by immunological therapies on growing tumors could be explained depending upon where the therapy-induced IR stands on the biphasic IR curve at each stage of tumor growth. At stages where tumor growth was enhanced (medium and large-sized tumors), counteraction of the tumor-immunostimulatory effect with anti-inflammatory strategies or, more efficiently, with selective inhibitors of p38 signaling pathways enabled the otherwise tumor-promoting immunological strategies to produce significant inhibition of tumor growth. PMID:29435437

Reactive Oxygen Species Signaling Facilitates FOXO-3a/FBXO-Dependent Vascular BK Channel β1 Subunit Degradation in Diabetic Mice

PubMed Central

Lu, Tong; Chai, Qiang; Yu, Ling; d’Uscio, Livius V.; Katusic, Zvonimir S.; He, Tongrong; Lee, Hon-Chi

2012-01-01

Activity of the vascular large conductance Ca2+-activated K+ (BK) channel is tightly regulated by its accessory β1 subunit (BK-β1). Downregulation of BK-β1 expression in diabetic vessels is associated with upregulation of the forkhead box O subfamily transcription factor-3a (FOXO-3a)–dependent F-box–only protein (FBXO) expression. However, the upstream signaling regulating this process is unclear. Overproduction of reactive oxygen species (ROS) is a common finding in diabetic vasculopathy. We hypothesized that ROS signaling cascade facilitates the FOXO-3a/FBXO-mediated BK-β1 degradation and leads to diabetic BK channel dysfunction. Using cellular biology, patch clamp, and videomicroscopy techniques, we found that reduced BK-β1 expression in streptozotocin (STZ)-induced diabetic mouse arteries and in human coronary smooth muscle cells (SMCs) cultured with high glucose was attributable to an increase in protein kinase C (PKC)-β and NADPH oxidase expressions and accompanied by attenuation of Akt phosphorylation and augmentation of atrogin-1 expression. Treatment with ruboxistaurin (a PKCβ inhibitor) or with GW501516 (a peroxisome proliferator–activated receptor δ activator) reduced atrogin-1 expression and restored BK channel-mediated coronary vasodilation in diabetic mice. Our results suggested that oxidative stress inhibited Akt signaling and facilitated the FOXO-3a/FBXO-dependent BK-β1 degradation in diabetic vessels. Suppression of the FOXO-3a/FBXO pathway prevented vascular BK-β1 degradation and protected coronary function in diabetes. PMID:22586590

Rad52 phosphorylation by Ipl1 and Mps1 contributes to Mps1 kinetochore localization and spindle assembly checkpoint regulation

PubMed Central

Lim, Gyubum

2017-01-01

Rad52 is well known as a key factor in homologous recombination. Here, we report that Rad52 has functions unrelated to homologous recombination in Saccharomyces cerevisiae; it plays a role in the recruitment of Mps1 to the kinetochores and the maintenance of spindle assembly checkpoint (SAC) activity. Deletion of RAD52 causes various phenotypes related to the dysregulation of chromosome biorientation. Rad52 directly affects efficient operation of the SAC and accurate chromosome segregation. Remarkably, by using an in vitro kinase assay, we found that Rad52 is a substrate of Ipl1/Aurora and Mps1 in yeast and humans. Ipl1-dependent phosphorylation of Rad52 facilitates the kinetochore accumulation of Mps1, and Mps1-dependent phosphorylation of Rad52 is important for the accurate regulation of the SAC under spindle damage conditions. Taken together, our data provide detailed insights into the regulatory mechanism of chromosome biorientation by mitotic kinases. PMID:29078282

Rad52 phosphorylation by Ipl1 and Mps1 contributes to Mps1 kinetochore localization and spindle assembly checkpoint regulation.

PubMed

Lim, Gyubum; Huh, Won-Ki

2017-10-31

Rad52 is well known as a key factor in homologous recombination. Here, we report that Rad52 has functions unrelated to homologous recombination in Saccharomyces cerevisiae ; it plays a role in the recruitment of Mps1 to the kinetochores and the maintenance of spindle assembly checkpoint (SAC) activity. Deletion of RAD52 causes various phenotypes related to the dysregulation of chromosome biorientation. Rad52 directly affects efficient operation of the SAC and accurate chromosome segregation. Remarkably, by using an in vitro kinase assay, we found that Rad52 is a substrate of Ipl1/Aurora and Mps1 in yeast and humans. Ipl1-dependent phosphorylation of Rad52 facilitates the kinetochore accumulation of Mps1, and Mps1-dependent phosphorylation of Rad52 is important for the accurate regulation of the SAC under spindle damage conditions. Taken together, our data provide detailed insights into the regulatory mechanism of chromosome biorientation by mitotic kinases. Published under the PNAS license.

Squalene Inhibits ATM-Dependent Signaling in γIR-Induced DNA Damage Response through Induction of Wip1 Phosphatase.

PubMed

Tatewaki, Naoto; Konishi, Tetsuya; Nakajima, Yuki; Nishida, Miyako; Saito, Masafumi; Eitsuka, Takahiro; Sakamaki, Toshiyuki; Ikekawa, Nobuo; Nishida, Hiroshi

2016-01-01

Ataxia telangiectasia mutated (ATM) kinase plays a crucial role as a master controller in the cellular DNA damage response. Inhibition of ATM leads to inhibition of the checkpoint signaling pathway. Hence, addition of checkpoint inhibitors to anticancer therapies may be an effective targeting strategy. A recent study reported that Wip1, a protein phosphatase, de-phosphorylates serine 1981 of ATM during the DNA damage response. Squalene has been proposed to complement anticancer therapies such as chemotherapy and radiotherapy; however, there is little mechanistic information supporting this idea. Here, we report the inhibitory effect of squalene on ATM-dependent DNA damage signals. Squalene itself did not affect cell viability and the cell cycle of A549 cells, but it enhanced the cytotoxicity of gamma-irradiation (γIR). The in vitro kinase activity of ATM was not altered by squalene. However, squalene increased Wip1 expression in cells and suppressed ATM activation in γIR-treated cells. Consistent with the potential inhibition of ATM by squalene, IR-induced phosphorylation of ATM effectors such as p53 (Ser15) and Chk1 (Ser317) was inhibited by cell treatment with squalene. Thus, squalene inhibits the ATM-dependent signaling pathway following DNA damage through intracellular induction of Wip1 expression.

Mitotic Checkpoint Kinase Mps1 Has a Role in Normal Physiology which Impacts Clinical Utility

PubMed Central

Martinez, Ricardo; Blasina, Alessandra; Hallin, Jill F.; Hu, Wenyue; Rymer, Isha; Fan, Jeffery; Hoffman, Robert L.; Murphy, Sean; Marx, Matthew; Yanochko, Gina; Trajkovic, Dusko; Dinh, Dac; Timofeevski, Sergei; Zhu, Zhou; Sun, Peiquing; Lappin, Patrick B.; Murray, Brion W.

2015-01-01

Cell cycle checkpoint intervention is an effective therapeutic strategy for cancer when applied to patients predisposed to respond and the treatment is well-tolerated. A critical cell cycle process that could be targeted is the mitotic checkpoint (spindle assembly checkpoint) which governs the metaphase-to-anaphase transition and insures proper chromosomal segregation. The mitotic checkpoint kinase Mps1 was selected to explore whether enhancement in genomic instability is a viable therapeutic strategy. The basal-a subset of triple-negative breast cancer was chosen as a model system because it has a higher incidence of chromosomal instability and Mps1 expression is up-regulated. Depletion of Mps1 reduces tumor cell viability relative to normal cells. Highly selective, extremely potent Mps1 kinase inhibitors were created to investigate the roles of Mps1 catalytic activity in tumor cells and normal physiology (PF-7006, PF-3837; K i<0.5 nM; cellular IC50 2–6 nM). Treatment of tumor cells in vitro with PF-7006 modulates expected Mps1-dependent biology as demonstrated by molecular and phenotypic measures (reduced pHH3-Ser10 levels, shorter duration of mitosis, micro-nucleation, and apoptosis). Tumor-bearing mice treated with PF-7006 exhibit tumor growth inhibition concomitant with pharmacodynamic modulation of a downstream biomarker (pHH3-Ser10). Unfortunately, efficacy only occurs at drug exposures that cause dose-limiting body weight loss, gastrointestinal toxicities, and neutropenia. Mps1 inhibitor toxicities may be mitigated by inducing G1 cell cycle arrest in Rb1-competent cells with the cyclin-dependent kinase-4/6 inhibitor palbociclib. Using an isogenic cellular model system, PF-7006 is shown to be selectively cytotoxic to Rb1-deficient cells relative to Rb1-competent cells (also a measure of kinase selectivity). Human bone marrow cells pretreated with palbociclib have decreased PF-7006-dependent apoptosis relative to cells without palbociclib pretreatment

Mitotic Checkpoint Kinase Mps1 Has a Role in Normal Physiology which Impacts Clinical Utility.

PubMed

Martinez, Ricardo; Blasina, Alessandra; Hallin, Jill F; Hu, Wenyue; Rymer, Isha; Fan, Jeffery; Hoffman, Robert L; Murphy, Sean; Marx, Matthew; Yanochko, Gina; Trajkovic, Dusko; Dinh, Dac; Timofeevski, Sergei; Zhu, Zhou; Sun, Peiquing; Lappin, Patrick B; Murray, Brion W

2015-01-01

Cell cycle checkpoint intervention is an effective therapeutic strategy for cancer when applied to patients predisposed to respond and the treatment is well-tolerated. A critical cell cycle process that could be targeted is the mitotic checkpoint (spindle assembly checkpoint) which governs the metaphase-to-anaphase transition and insures proper chromosomal segregation. The mitotic checkpoint kinase Mps1 was selected to explore whether enhancement in genomic instability is a viable therapeutic strategy. The basal-a subset of triple-negative breast cancer was chosen as a model system because it has a higher incidence of chromosomal instability and Mps1 expression is up-regulated. Depletion of Mps1 reduces tumor cell viability relative to normal cells. Highly selective, extremely potent Mps1 kinase inhibitors were created to investigate the roles of Mps1 catalytic activity in tumor cells and normal physiology (PF-7006, PF-3837; Ki<0.5 nM; cellular IC50 2-6 nM). Treatment of tumor cells in vitro with PF-7006 modulates expected Mps1-dependent biology as demonstrated by molecular and phenotypic measures (reduced pHH3-Ser10 levels, shorter duration of mitosis, micro-nucleation, and apoptosis). Tumor-bearing mice treated with PF-7006 exhibit tumor growth inhibition concomitant with pharmacodynamic modulation of a downstream biomarker (pHH3-Ser10). Unfortunately, efficacy only occurs at drug exposures that cause dose-limiting body weight loss, gastrointestinal toxicities, and neutropenia. Mps1 inhibitor toxicities may be mitigated by inducing G1 cell cycle arrest in Rb1-competent cells with the cyclin-dependent kinase-4/6 inhibitor palbociclib. Using an isogenic cellular model system, PF-7006 is shown to be selectively cytotoxic to Rb1-deficient cells relative to Rb1-competent cells (also a measure of kinase selectivity). Human bone marrow cells pretreated with palbociclib have decreased PF-7006-dependent apoptosis relative to cells without palbociclib pretreatment

A Mini-Review for Cancer Immunotherapy: Molecular Understanding of PD-1/PD-L1 Pathway & Translational Blockade of Immune Checkpoints

PubMed Central

Li, Yongshu; Li, Fangfei; Jiang, Feng; Lv, Xiaoqing; Zhang, Rongjiang; Lu, Aiping; Zhang, Ge

2016-01-01

Interference of the binding of programmed cell death protein 1 (PD-1) and programmed death-ligand 1 (PD-L1) has become a new inspiring immunotherapy for resisting cancers. To date, the FDA has approved two PD-1 monoclonal antibody drugs against cancer as well as a monoclonal antibody for PD-L1. More PD-1 and PD-L1 monoclonal antibody drugs are on their way in clinical trials. In this review, we focused on the mechanism of the PD-1/PD-L1 signaling pathway and the monoclonal antibodies (mAbs) against PD-1 and PD-L1, which were approved by the FDA or are still in clinical trials. And also presented is the prospect of the PD-1/PD-L1 immune checkpoint blockade in the next generation of immunotherapy. PMID:27438833

Meclozine Facilitates Proliferation and Differentiation of Chondrocytes by Attenuating Abnormally Activated FGFR3 Signaling in Achondroplasia

PubMed Central

Matsushita, Masaki; Kitoh, Hiroshi; Ohkawara, Bisei; Mishima, Kenichi; Kaneko, Hiroshi; Ito, Mikako; Masuda, Akio; Ishiguro, Naoki; Ohno, Kinji

2013-01-01

Achondroplasia (ACH) is one of the most common skeletal dysplasias with short stature caused by gain-of-function mutations in FGFR3 encoding the fibroblast growth factor receptor 3. We used the drug repositioning strategy to identify an FDA-approved drug that suppresses abnormally activated FGFR3 signaling in ACH. We found that meclozine, an anti-histamine drug that has long been used for motion sickness, facilitates chondrocyte proliferation and mitigates loss of extracellular matrix in FGF2-treated rat chondrosarcoma (RCS) cells. Meclozine also ameliorated abnormally suppressed proliferation of human chondrosarcoma (HCS-2/8) cells that were infected with lentivirus expressing constitutively active mutants of FGFR3-K650E causing thanatophoric dysplasia, FGFR3-K650M causing SADDAN, and FGFR3-G380R causing ACH. Similarly, meclozine alleviated abnormally suppressed differentiation of ATDC5 chondrogenic cells expressing FGFR3-K650E and -G380R in micromass culture. We also confirmed that meclozine alleviates FGF2-mediated longitudinal growth inhibition of embryonic tibia in bone explant culture. Interestingly, meclozine enhanced growth of embryonic tibia in explant culture even in the absence of FGF2 treatment. Analyses of intracellular FGFR3 signaling disclosed that meclozine downregulates phosphorylation of ERK but not of MEK in FGF2-treated RCS cells. Similarly, meclozine enhanced proliferation of RCS cells expressing constitutively active mutants of MEK and RAF but not of ERK, which suggests that meclozine downregulates the FGFR3 signaling by possibly attenuating ERK phosphorylation. We used the C-natriuretic peptide (CNP) as a potent inhibitor of the FGFR3 signaling throughout our experiments, and found that meclozine was as efficient as CNP in attenuating the abnormal FGFR3 signaling. We propose that meclozine is a potential therapeutic agent for treating ACH and other FGFR3-related skeletal dysplasias. PMID:24324705

Early programming and late-acting checkpoints governing the development of CD4 T cell memory.

PubMed

Dhume, Kunal; McKinstry, K Kai

2018-04-27

CD4 T cells contribute to protection against pathogens through numerous mechanisms. Incorporating the goal of memory CD4 T cell generation into vaccine strategies thus offers a powerful approach to improve their efficacy, especially in situations where humoral responses alone cannot confer long-term immunity. These threats include viruses such as influenza that mutate coat proteins to avoid neutralizing antibodies, but that are targeted by T cells that recognize more conserved protein epitopes shared by different strains. A major barrier in the design of such vaccines is that the mechanisms controlling the efficiency with which memory cells form remain incompletely understood. Here, we discuss recent insights into fate decisions controlling memory generation. We focus on the importance of three general cues: interleukin-2, antigen, and costimulatory interactions. It is increasingly clear that these signals have a powerful influence on the capacity of CD4 T cells to form memory during two distinct phases of the immune response. First, through 'programming' that occurs during initial priming, and second, through 'checkpoints' that operate later during the effector stage. These findings indicate that novel vaccine strategies must seek to optimize cognate interactions, during which interleukin-2-, antigen, and costimulation-dependent signals are tightly linked, well beyond initial antigen encounter to induce robust memory CD4 T cells. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

R-spondin 2 facilitates differentiation of proliferating chondrocytes into hypertrophic chondrocytes by enhancing Wnt/β-catenin signaling in endochondral ossification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takegami, Yasuhiko; Department of Orthopaedic Surgery, Nagoya University School of Medicine, Nagoya; Ohkawara, Bisei

Endochondral ossification is a crucial process for longitudinal growth of bones. Differentiating chondrocytes in growth cartilage form four sequential zones of proliferation, alignment into column, hypertrophy, and substitution of chondrocytes with osteoblasts. Wnt/β-catenin signaling is essential for differentiation of proliferating chondrocytes into hypertrophic chondrocytes in growth cartilage. R-spondin 2 (Rspo2), a member of R-spondin family, is an agonist for Wnt signaling, but its role in chondrocyte differentiation remains unknown. Here we report that growth cartilage of Rspo2-knockout mice shows a decreased amount of β-catenin and increased amounts collagen type II (CII) and Sox9 in the abnormally extended proliferating zone. Inmore » contrast, expression of collagen type X (CX) in the hypertrophic zone remains unchanged. Differentiating chondrogenic ATDC5 cells, mimicking proliferating chondrocytes, upregulate Rspo2 and its putative receptor, Lgr5, in parallel. Addition of recombinant human Rspo2 to differentiating ATDC5 cells decreases expressions of Col2a1, Sox9, and Acan, as well as production of proteoglycans. In contrast, lentivirus-mediated knockdown of Rspo2 has the opposite effect. The effect of Rspo2 on chondrogenic differentiation is mediated by Wnt/β-catenin signaling, and not by Wnt/PCP or Wnt/Ca{sup 2+} signaling. We propose that Rspo2 activates Wnt/β-catenin signaling to reduce Col2a1 and Sox9 and to facilitate differentiation of proliferating chondrocytes into hypertrophic chondrocytes in growth cartilage. - Highlights: • Rspo2 is a secreted activator of Wnt, and its knockout shows extended proliferating chondrocytes in endochondral ossification. • In proliferating chondrocytes of Rspo2-knockout mice, Sox9 and collagen type 2 are increased and β-catenin is decreased. • Rspo2 and its receptor Lgr5, as well as Sox9 and collagen type 2, are expressed in differentiating ATDC5 chondrogenic cells. • In ATDC5 cells, Rspo2 decreases

Neuromuscular complications of immune checkpoint inhibitor therapy.

PubMed

Kolb, Noah A; Trevino, Christopher R; Waheed, Waqar; Sobhani, Fatemeh; Landry, Kara K; Thomas, Alissa A; Hehir, Mike

2018-01-17

Immune checkpoint inhibitor (ICPI) therapy unleashes the body's natural immune system to fight cancer. ICPIs improve overall cancer survival, however, the unbridling of the immune system may induce a variety of immune-related adverse events. Neuromuscular immune complications are rare but they can be severe. Myasthenia gravis and inflammatory neuropathy are the most common neuromuscular adverse events but a variety of others including inflammatory myopathy are reported. The pathophysiologic mechanism of these autoimmune disorders may differ from that of non-ICPI-related immune diseases. Accordingly, while the optimal treatment for ICPI-related neuromuscular disorders generally follows a traditional paradigm, there are important novel considerations in selecting appropriate immunosuppressive therapy. This review presents 2 new cases, a summary of neuromuscular ICPI complications, and an approach to the diagnosis and treatment of these disorders. Muscle Nerve, 2018. © 2018 Wiley Periodicals, Inc.

Immunotherapy in urothelial cancer, part 1: T-cell checkpoint inhibition in advanced or metastatic disease.

PubMed

Yu, Steven S; Dorff, Tanya B; Ballas, Leslie K; Sadeghi, Sarmad; Skinner, Eila C; Quinn, David I

2017-06-01

Cancer of the urothelium is the sixth most common cancer in the United States and is seen predominantly in men. Most cases of this disease present as non-muscle-invasive bladder cancer (NMIBC), with cancer recurrence or progression to muscle-invasive cancer in more than 50% of patients after initial therapy. NMIBC is an immune-responsive disease, as indicated by the use of intravesical bacillus Calmette-Guérin as treatment for more than 3 decades. More recently, immunotherapy has seen much progress in a variety of cancers, including advanced and metastatic bladder cancer, in which historical 5-year survival rates are approximately 15%. The advent of T-cell checkpoint inhibitors, especially those directed at programmed death 1 (PD-1) and its ligand (PD-L1), has had a significant effect on the therapy of advanced urothelial cancer. This had led to accelerated approval by the US Food and Drug Administration for atezolizumab and nivolumab in advanced urothelial cancer previously treated with platinum-based chemotherapy. In addition, level 1 evidence supports the use of pembrolizumab over single-agent tubulin-directed chemotherapy in the same setting. Several other treatments with immune-mediating mechanisms of action are in development and hold great promise, including monoclonal antibodies directed at other checkpoint molecules, oncolytic virus therapy, adoptive T-cell therapy, combination immunotherapy, and antibody-drug conjugates. This review focuses on the recent development of T-cell checkpoint inhibitors in advanced and metastatic urothelial cancer and addresses their potential use in combination. It also discusses a spectrum of novel immunotherapies with potential use in urothelial cancer.

Preclinical efficacy of immune-checkpoint monotherapy does not recapitulate corresponding biomarkers-based clinical predictions in glioblastoma

PubMed Central

Vandenberk, Lien; Van Woensel, Matthias; Schaaf, Marco; De Vleeschouwer, Steven; Agostinis, Patrizia

2017-01-01

ABSTRACT Glioblastoma (GBM) is resistant to most multimodal therapies. Clinical success of immune-checkpoint inhibitors (ICIs) has spurred interest in applying ICIs targeting CTLA4, PD1 or IDO1 against GBM. This amplifies the need to ascertain GBM's intrinsic susceptibility (or resistance) toward these ICIs, through clinical biomarkers that may also “guide and prioritize” preclinical testing. Here, we interrogated the TCGA and/or REMBRANDT human patient-cohorts to predict GBM's predisposition toward ICIs. We exploited various broad clinical biomarkers, including mutational or predicted-neoantigen burden, pre-existing or basal levels of tumor-infiltrating T lymphocytes (TILs), differential expression of immune-checkpoints within the tumor and their correlation with particular TILs/Treg-associated functional signature and prognostic impact of differential immune-checkpoint expression. Based on these analyses, we found that predictive biomarkers of ICI responsiveness exhibited inconsistent patterns in GBM patients, i.e., they either predicted ICI resistance (as compared with typical ICI-responsive cancer-types like melanoma, lung cancer or bladder cancer) or susceptibility to therapeutic targeting of CTLA4 or IDO1. On the other hand, our comprehensive literature meta-analysis and preclinical testing of ICIs using an orthotopic GL261-glioma mice model, indicated significant antitumor properties of anti-PD1 antibody, whereas blockade of IDO1 or CTLA4 either failed or provided very marginal advantage. These trends raise the need to better assess the applicability of ICIs and associated biomarkers for GBM. PMID:28507806

A Review of Immune Checkpoint Inhibitors for the Management of Locally Advanced or Metastatic Urothelial Carcinoma.

PubMed

Hanna, Kirollos S

2017-11-01

Urothelial carcinoma (UC) is the second most common malignancy of the genitourinary system and the sixth most common cancer in the United States. The overall incidence of UC appears to be on the decline, but death rates have remained stable. Stage IV metastatic disease is associated with only a 5% survival rate at 5 years. Gemcitabine and cisplatin combinations or dose-dense methotrexate, vinblastine, doxorubicin, and cisplatin are the preferred regimens for individuals with advance, metastatic disease and a good performance status and organ function. Second-line therapies in this setting are limited. During the course of 1 year, five immune checkpoint inhibitors were approved for treatment of cancers in the locally advanced or metastatic setting: atezolizumab, nivolumab, durvalumab, avelumab, and pembrolizumab. Immunotherapies have played a significant role in the treatment of various cancers and have continued to expand. It is of utmost importance that practitioners include checkpoint inhibitors as treatment options for UC. Based on the limited data, pembrolizumab and atezolizumab may be the drugs of choice, as they are supported by the most influential data to date; however, further research is warranted. Ongoing clinical trials will further assess the benefits of inducing cellular immunity in the treatment of UC. These therapies mark a new landscape in the treatment of UC. In this article, the available data on immune checkpoint inhibitors for the treatment of locally advanced or metastatic UC and their place in therapy are reviewed. © 2017 Pharmacotherapy Publications, Inc.

Silencing of human DNA polymerase λ causes replication stress and is synthetically lethal with an impaired S phase checkpoint

PubMed Central

Zucca, Elisa; Bertoletti, Federica; Wimmer, Ursula; Ferrari, Elena; Mazzini, Giuliano; Khoronenkova, Svetlana; Grosse, Nicole; van Loon, Barbara; Dianov, Grigory; Hübscher, Ulrich; Maga, Giovanni

2013-01-01

Human DNA polymerase (pol) λ functions in base excision repair and non-homologous end joining. We have previously shown that DNA pol λ is involved in accurate bypass of the two frequent oxidative lesions, 7,8-dihydro-8-oxoguanine and 1,2-dihydro-2-oxoadenine during the S phase. However, nothing is known so far about the relationship of DNA pol λ with the S phase DNA damage response checkpoint. Here, we show that a knockdown of DNA pol λ, but not of its close homologue DNA pol β, results in replication fork stress and activates the S phase checkpoint, slowing S phase progression in different human cancer cell lines. We furthermore show that DNA pol λ protects cells from oxidative DNA damage and also functions in rescuing stalled replication forks. Its absence becomes lethal for a cell when a functional checkpoint is missing, suggesting a DNA synthesis deficiency. Our results provide the first evidence, to our knowledge, that DNA pol λ is required for cell cycle progression and is functionally connected to the S phase DNA damage response machinery in cancer cells. PMID:23118481

The effect of tributyltin chloride on Caenorhabditis elegans germline is mediated by a conserved DNA damage checkpoint pathway.

PubMed

Cheng, Zhe; Tian, Huimin; Chu, Hongran; Wu, Jianjian; Li, Yingying; Wang, Yanhai

2014-03-21

Tributyltin (TBT), one of the environmental pollutants, has been shown to impact the reproduction of animals. However, due to the lack of appropriate animal model, analysis of the affected molecular pathways in germ cells is lagging and has been particularly challenging. In the present study, we investigated the effects of tributyltin chloride (TBTCL) on the nematode Caenorhabditis elegans germline. We show that exposure of C. elegans to TBTCL causes significantly elevated level of sterility and embryonic lethality. TBTCL exposure results in an increased number of meiotic DNA double-strand breaks in germ cells, subsequently leading to activated DNA damage checkpoint. Exposing C. elegans to TBTCL causes dose- and time-dependent germline apoptosis. This apoptotic response was blocked in loss-of-function mutants of hus-1 (op241), mrt-2 (e2663) and p53/cep-1 (gk138), indicating that checkpoints and p53 are essential for mediating TBTCL-induced germ cell apoptosis. Moreover, TBTCL exposure can inhibit germ cell proliferation, which is also mediated by the conserved checkpoint pathway. We thereby propose that TBT exhibits its effects on the germline by inducing DNA damage and impaired maintenance of genomic integrity. Copyright © 2014 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

The flavonoid eupatorin inactivates the mitotic checkpoint leading to polyploidy and apoptosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Salmela, Anna-Leena; Turku Graduate School of Biomedical Sciences, Turku; Turku Centre for Biotechnology, P.O. Box 123, University of Turku

The spindle assembly checkpoint (SAC) is a conserved mechanism that ensures the fidelity of chromosome distribution in mitosis by preventing anaphase onset until the correct bipolar microtubule-kinetochore attachments are formed. Errors in SAC function may contribute to tumorigenesis by inducing numerical chromosome anomalies (aneuploidy). On the other hand, total disruption of SAC can lead to massive genomic imbalance followed by cell death, a phenomena that has therapeutic potency. We performed a cell-based high-throughput screen with a compound library of 2000 bioactives for novel SAC inhibitors and discovered a plant-derived phenolic compound eupatorin (3 Prime ,5-dihydroxy-4 Prime ,6,7-trimethoxyflavone) as an anti-mitoticmore » flavonoid. The premature override of the microtubule drug-imposed mitotic arrest by eupatorin is dependent on microtubule-kinetochore attachments but not interkinetochore tension. Aurora B kinase activity, which is essential for maintenance of normal SAC signaling, is diminished by eupatorin in cells and in vitro providing a mechanistic explanation for the observed forced mitotic exit. Eupatorin likely has additional targets since eupatorin treatment of pre-mitotic cells causes spindle anomalies triggering a transient M phase delay followed by impaired cytokinesis and polyploidy. Finally, eupatorin potently induces apoptosis in multiple cancer cell lines and suppresses cancer cell proliferation in organotypic 3D cell culture model.« less

Arabidopsis pdr2 reveals a phosphate-sensitive checkpoint in root development.

PubMed

Ticconi, Carla A; Delatorre, Carla A; Lahner, Brett; Salt, David E; Abel, Steffen

2004-03-01

Plants have evolved complex strategies to maintain phosphate (Pi) homeostasis and to maximize Pi acquisition when the macronutrient is limiting. Adjustment of root system architecture via changes in meristem initiation and activity is integral to the acclimation process. However, the mechanisms that monitor external Pi status and interpret the nutritional signal remain to be elucidated. Here, we present evidence that the Pi deficiency response, pdr2, mutation disrupts local Pi sensing. The sensitivity and amplitude of metabolic Pi-starvation responses, such as Pi-responsive gene expression or accumulation of anthocyanins and starch, are enhanced in pdr2 seedlings. However, the most conspicuous alteration of pdr2 is a conditional short-root phenotype that is specific for Pi deficiency and caused by selective inhibition of root cell division followed by cell death below a threshold concentration of about 0.1 mm external Pi. Measurements of general Pi uptake and of total phosphorus (P) in root tips exclude a defect in high-affinity Pi acquisition. Rescue of root meristem activity in Pi-starved pdr2 by phosphite (Phi), a non-metabolizable Pi analog, and divided-root experiments suggest that pdr2 disrupts sensing of low external Pi availability. Thus, PDR2 is proposed to function at a Pi-sensitive checkpoint in root development, which monitors environmental Pi status, maintains and fine-tunes meristematic activity, and finally adjusts root system architecture to maximize Pi acquisition.

ARHGEF17 is an essential spindle assembly checkpoint factor that targets Mps1 to kinetochores

PubMed Central

Isokane, Mayumi; Walter, Thomas; Mahen, Robert; Nijmeijer, Bianca; Hériché, Jean-Karim; Miura, Kota; Maffini, Stefano; Ivanov, Miroslav Penchev; Kitajima, Tomoya S.; Peters, Jan-Michael

2016-01-01

To prevent genome instability, mitotic exit is delayed until all chromosomes are properly attached to the mitotic spindle by the spindle assembly checkpoint (SAC). In this study, we characterized the function of ARHGEF17, identified in a genome-wide RNA interference screen for human mitosis genes. Through a series of quantitative imaging, biochemical, and biophysical experiments, we showed that ARHGEF17 is essential for SAC activity, because it is the major targeting factor that controls localization of the checkpoint kinase Mps1 to the kinetochore. This mitotic function is mediated by direct interaction of the central domain of ARHGEF17 with Mps1, which is autoregulated by the activity of Mps1 kinase, for which ARHGEF17 is a substrate. This mitosis-specific role is independent of ARHGEF17’s RhoGEF activity in interphase. Our study thus assigns a new mitotic function to ARHGEF17 and reveals the molecular mechanism for a key step in SAC establishment. PMID:26953350

ARHGEF17 is an essential spindle assembly checkpoint factor that targets Mps1 to kinetochores.

PubMed

Isokane, Mayumi; Walter, Thomas; Mahen, Robert; Nijmeijer, Bianca; Hériché, Jean-Karim; Miura, Kota; Maffini, Stefano; Ivanov, Miroslav Penchev; Kitajima, Tomoya S; Peters, Jan-Michael; Ellenberg, Jan

2016-03-14

To prevent genome instability, mitotic exit is delayed until all chromosomes are properly attached to the mitotic spindle by the spindle assembly checkpoint (SAC). In this study, we characterized the function of ARHGEF17, identified in a genome-wide RNA interference screen for human mitosis genes. Through a series of quantitative imaging, biochemical, and biophysical experiments, we showed that ARHGEF17 is essential for SAC activity, because it is the major targeting factor that controls localization of the checkpoint kinase Mps1 to the kinetochore. This mitotic function is mediated by direct interaction of the central domain of ARHGEF17 with Mps1, which is autoregulated by the activity of Mps1 kinase, for which ARHGEF17 is a substrate. This mitosis-specific role is independent of ARHGEF17's RhoGEF activity in interphase. Our study thus assigns a new mitotic function to ARHGEF17 and reveals the molecular mechanism for a key step in SAC establishment. © 2016 Isokane et al.

Validate Mitotic Checkpoint and Kinetochore Motor Proteins in Breast Cancer Cells as Targets for the Development of Novel Anti-Mitotic Drugs

DTIC Science & Technology

2004-07-01

checkpoint pathway remains to MAD1 MAD1 xMADI be clarified, it is dear that all of them MAD2 MAD2 xMAD2 are essential for cells to arrest in mitosis MPS1 ...TrK in response to unattached kineto- chores. Given that MPS1 , BUB1 and (G) Structural Proteins/Unknown Functions the Mad3-related BUBR1 are all pro...BUB3, MADI, MAD2, MAD3, and MPS1 have been shown to be essential for establishing the checkpoint response in all eukaryotes examined to date (Abrieu et

Photothermal therapy with immune-adjuvant nanoparticles together with checkpoint blockade for effective cancer immunotherapy

NASA Astrophysics Data System (ADS)

Chen, Qian; Xu, Ligeng; Liang, Chao; Wang, Chao; Peng, Rui; Liu, Zhuang

2016-10-01

A therapeutic strategy that can eliminate primary tumours, inhibit metastases, and prevent tumour relapses is developed herein by combining adjuvant nanoparticle-based photothermal therapy with checkpoint-blockade immunotherapy. Indocyanine green (ICG), a photothermal agent, and imiquimod (R837), a Toll-like-receptor-7 agonist, are co-encapsulated by poly(lactic-co-glycolic) acid (PLGA). The formed PLGA-ICG-R837 nanoparticles composed purely by three clinically approved components can be used for near-infrared laser-triggered photothermal ablation of primary tumours, generating tumour-associated antigens, which in the presence of R837-containing nanoparticles as the adjuvant can show vaccine-like functions. In combination with the checkpoint-blockade using anti-cytotoxic T-lymphocyte antigen-4 (CTLA4), the generated immunological responses will be able to attack remaining tumour cells in mice, useful in metastasis inhibition, and may potentially be applicable for various types of tumour models. Furthermore, such strategy offers a strong immunological memory effect, which can provide protection against tumour rechallenging post elimination of their initial tumours.

Drosophila MOF controls Checkpoint protein2 and regulates genomic stability during early embryogenesis

PubMed Central

2013-01-01

Background In Drosophila embryos, checkpoints maintain genome stability by delaying cell cycle progression that allows time for damage repair or to complete DNA synthesis. Drosophila MOF, a member of MYST histone acetyl transferase is an essential component of male X hyperactivation process. Until recently its involvement in G2/M cell cycle arrest and defects in ionizing radiation induced DNA damage pathways was not well established. Results Drosophila MOF is highly expressed during early embryogenesis. In the present study we show that haplo-insufficiency of maternal MOF leads to spontaneous mitotic defects like mitotic asynchrony, mitotic catastrophe and chromatid bridges in the syncytial embryos. Such abnormal nuclei are eliminated and digested in the yolk tissues by nuclear fall out mechanism. MOF negatively regulates Drosophila checkpoint kinase 2 tumor suppressor homologue. In response to DNA damage the checkpoint gene Chk2 (Drosophila mnk) is activated in the mof mutants, there by causing centrosomal inactivation suggesting its role in response to genotoxic stress. A drastic decrease in the fall out nuclei in the syncytial embryos derived from mof1/+; mnkp6/+ females further confirms the role of DNA damage response gene Chk2 to ensure the removal of abnormal nuclei from the embryonic precursor pool and maintain genome stability. The fact that mof mutants undergo DNA damage has been further elucidated by the increased number of single and double stranded DNA breaks. Conclusion mof mutants exhibited genomic instability as evidenced by the occurance of frequent mitotic bridges in anaphase, asynchronous nuclear divisions, disruption of cytoskeleton, inactivation of centrosomes finally leading to DNA damage. Our findings are consistent to what has been reported earlier in mammals that; reduced levels of MOF resulted in increased genomic instability while total loss resulted in lethality. The study can be further extended using Drosophila as model system and carry

Drosophila MOF controls Checkpoint protein2 and regulates genomic stability during early embryogenesis.

PubMed

Pushpavalli, Sreerangam N C V L; Sarkar, Arpita; Ramaiah, M Janaki; Chowdhury, Debabani Roy; Bhadra, Utpal; Pal-Bhadra, Manika

2013-01-24

In Drosophila embryos, checkpoints maintain genome stability by delaying cell cycle progression that allows time for damage repair or to complete DNA synthesis. Drosophila MOF, a member of MYST histone acetyl transferase is an essential component of male X hyperactivation process. Until recently its involvement in G2/M cell cycle arrest and defects in ionizing radiation induced DNA damage pathways was not well established. Drosophila MOF is highly expressed during early embryogenesis. In the present study we show that haplo-insufficiency of maternal MOF leads to spontaneous mitotic defects like mitotic asynchrony, mitotic catastrophe and chromatid bridges in the syncytial embryos. Such abnormal nuclei are eliminated and digested in the yolk tissues by nuclear fall out mechanism. MOF negatively regulates Drosophila checkpoint kinase 2 tumor suppressor homologue. In response to DNA damage the checkpoint gene Chk2 (Drosophila mnk) is activated in the mof mutants, there by causing centrosomal inactivation suggesting its role in response to genotoxic stress. A drastic decrease in the fall out nuclei in the syncytial embryos derived from mof¹/+; mnkp⁶/+ females further confirms the role of DNA damage response gene Chk2 to ensure the removal of abnormal nuclei from the embryonic precursor pool and maintain genome stability. The fact that mof mutants undergo DNA damage has been further elucidated by the increased number of single and double stranded DNA breaks. mof mutants exhibited genomic instability as evidenced by the occurance of frequent mitotic bridges in anaphase, asynchronous nuclear divisions, disruption of cytoskeleton, inactivation of centrosomes finally leading to DNA damage. Our findings are consistent to what has been reported earlier in mammals that; reduced levels of MOF resulted in increased genomic instability while total loss resulted in lethality. The study can be further extended using Drosophila as model system and carry out the interaction of MOF

Biosynthetically directed fractional 13C labeling facilitates identification of Phe and Tyr aromatic signals in proteins.

PubMed

Jacob, Jaison; Louis, John M; Nesheiwat, Issa; Torchia, Dennis A

2002-11-01

Analysis of 2D [(13)C,(1)H]-HSQC spectra of biosynthetic fractionally (13)C labeled proteins is a reliable, straightforward means to obtain stereospecific assignments of Val and Leu methyl sites in proteins. Herein we show that the same fractionally labeled protein sample facilitates observation and identification of Phe and Tyr aromatic signals. This is the case, in part, because the fractional (13)C labeling yields aromatic rings in which some of the (13)C-(13)C J-couplings, present in uniformly labeled samples, are absent. Also, the number of homonuclear J-coupling partners differs for the delta-, epsilon- and zeta-carbons. This enabled us to vary their signal intensities in distinctly different ways by appropriately setting the (13)C constant-time period in 2D [(13)C,(1)H]-HSQC spectra. We illustrate the application of this approach to an 18 kDa protein, c-VIAF, a modulator of apoptosis. In addition, we show that cancellation of the aromatic (13)C CSA and (13)C-(1)H dipolar interactions can be fruitfully utilized in the case of the fractionally labeled sample to obtain high resolution (13)C constant-time spectra with good sensitivity.

Profiling the dynamic expression of checkpoint molecules on cytokine-induced killer cells from non-small-cell lung cancer patients.

PubMed

Zhang, Lin; Wang, Jian; Wei, Feng; Wang, Kaiyuan; Sun, Qian; Yang, Fan; Jin, Hao; Zheng, Yu; Zhao, Hua; Wang, Limei; Yu, Wenwen; Zhang, Xiying; An, Yang; Yang, Lili; Zhang, Xinwei; Ren, Xiubao

2016-07-12

Immune checkpoints associate with dysfunctional T cells, which have a reduced ability to clear pathogens or cancer cells. T-cell checkpoint blockade may improve patient survival. However, checkpoint molecules on cytokine-induced killer (CIK) cell, a non-specific adoptive immunotherapy, remain unknown. In present study, we detected the dynamic expression of eight major checkpoint molecules (CTLA-4, PD-1, PD-L1, TIM- 3, CEACAM-1, LAG-3, TIGIT and BTLA) on CIK cells from NSCLC patients. The majority of these molecules, except BTLA, were sharply elevated during the early stage of CIK cell culture. Thereafter, PD-1 and TIGIT expressions decreased gradually towards the initial level (day 0). Moreover, CTLA-4 faded away during the later stage of CIK culture. LAG-3 expression decreased but was still significantly higher than the initial level. Of note, PD-L1 remained stably upregulated during CIK culture compared with PD-1, indicating that PD-L1 might act as an inhibitory molecule on CIK cells instead of PD-1. Furthermore, TIM-3 and CEACAM1 were strongly expressed simultaneously during long-term CIK culture and showed a significant and mutually positive correlation. BTLA displayed a distinct pattern, and its expression gradually decreased throughout the CIK culture. These observations suggested that CIK cells might be partly exhausted before clinical transfusion, characterized by the high expression of PD-L1, LAG-3, TIM- 3, and CEACAM-1 and the low expression of TIGIT, BTLA, PD-1, and CTLA-4 compared with initial culture. Our results imply that implementing combined treatment on CIK cells before transfusion via antibodies targeting PD-L1, LAG-3, TIM-3, and CEACAM-1 might improve the efficiency of CIK therapy for NSCLC patients.

Lack of a p21waf1/cip -dependent G1/S checkpoint in neural stem and progenitor cells after DNA damage in vivo.

PubMed

Roque, Telma; Haton, Céline; Etienne, Olivier; Chicheportiche, Alexandra; Rousseau, Laure; Martin, Ludovic; Mouthon, Marc-André; Boussin, François D

2012-03-01

The cyclin-dependent kinase inhibitor p21(waf1/cip) mediates the p53-dependent G1/S checkpoint, which is generally considered to be a critical requirement to maintain genomic stability after DNA damage. We used staggered 5-ethynyl-2'deoxyuridine/5-bromo-2'-deoxyuridine double-labeling in vivo to investigate the cell cycle progression and the role of p21(waf1/cip) in the DNA damage response of neural stem and progenitor cells (NSPCs) after exposure of the developing mouse cortex to ionizing radiation. We observed a radiation-induced p21-dependent apoptotic response in migrating postmitotic cortical cells. However, neural stem and progenitor cells (NSPCs) did not initiate a p21(waf1/cip1) -dependent G1/S block and continued to enter S-phase at a similar rate to the non-irradiated controls. The G1/S checkpoint is not involved in the mechanisms underlying the faithful transmission of the NSPC genome and/or the elimination of critically damaged cells. These processes typically involve intra-S and G2/M checkpoints that are rapidly activated after irradiation. p21 is normally repressed in neural cells during brain development except at the G1 to G0 transition. Lack of activation of a G1/S checkpoint and apoptosis of postmitotic migrating cells after DNA damage appear to depend on the expression of p21 in neural cells, since substantial cell-to-cell variations are found in the irradiated cortex. This suggests that repression of p21 during brain development prevents the induction of the G1/S checkpoint after DNA damage. Copyright © 2011 AlphaMed Press.

The budding yeast Rad9 checkpoint protein is subjected to Mec1/Tel1-dependent hyperphosphorylation and interacts with Rad53 after DNA damage.

PubMed

Vialard, J E; Gilbert, C S; Green, C M; Lowndes, N F

1998-10-01

The Saccharomyces cerevisiae RAD9 checkpoint gene is required for transient cell-cycle arrests and transcriptional induction of DNA repair genes in response to DNA damage. Polyclonal antibodies raised against the Rad9 protein recognized several polypeptides in asynchronous cultures, and in cells arrested in S or G2/M phases while a single form was observed in G1-arrested cells. Treatment with various DNA damaging agents, i.e. UV, ionizing radiation or methyl methane sulfonate, resulted in the appearance of hypermodified forms of the protein. All modifications detected during a normal cell cycle and after DNA damage were sensitive to phosphatase treatment, indicating that they resulted from phosphorylation. Damage-induced hyperphosphorylation of Rad9 correlated with checkpoint functions (cell-cycle arrest and transcriptional induction) and was cell-cycle stage- and progression-independent. In asynchronous cultures, Rad9 hyperphosphorylation was dependent on MEC1 and TEL1, homologues of the ATR and ATM genes. In G1-arrested cells, damage-dependent hyperphosphorylation required functional MEC1 in addition to RAD17, RAD24, MEC3 and DDC1, demonstrating cell-cycle stage specificity of the checkpoint genes in this response to DNA damage. Analysis of checkpoint protein interactions after DNA damage revealed that Rad9 physically associates with Rad53.

Immune checkpoint inhibitors in urothelial cancer: recent updates and future outlook.

PubMed

Gopalakrishnan, Dharmesh; Koshkin, Vadim S; Ornstein, Moshe C; Papatsoris, Athanasios; Grivas, Petros

2018-01-01

Bladder cancer is the sixth most common cancer in the US and most tumors have urothelial (transitional cell) histology. Platinum-based chemotherapy has long been the standard of care in advanced disease, but long-term outcomes have largely remained poor. Since the peak incidence of bladder cancer is in the eighth decade of life and beyond, medical comorbidities may often limit the use of chemotherapy. Immune checkpoint inhibitors with their favorable toxicity profiles and notable antitumor activity have ushered in a new era in the treatment of advanced urothelial cancer (UC) with five agents targeting the PD-1/PD-L1 pathway being recently approved by the US Food and Drug administration. A plethora of clinical trials are ongoing in diverse disease settings, employing agents targeting PD-1/PD-L1 and related immune checkpoint pathways. While reactivating anti-tumor immunity, these agents may lead to a unique constellation of immune-related adverse events, which may warrant discontinuation of therapy and potential use of immunosuppression. Novel combinations with various treatment modalities and optimal sequencing of active therapies are being investigated in prospective clinical trials and retrospective registries. At the era of precision molecular medicine, and since patients do not respond uniformly to these agents, there is a growing need for identification and validation of biomarkers that can accurately predict treatment response and assist in patient selection. This review discusses current updates and future directions of immunotherapy in advanced UC.

Incorporation of Immune Checkpoint Blockade into Chimeric Antigen Receptor T Cells (CAR-Ts): Combination or Built-In CAR-T

PubMed Central

Yoon, Dok Hyun; Osborn, Mark J.; Tolar, Jakub; Kim, Chong Jai

2018-01-01

Chimeric antigen receptor (CAR) T cell therapy represents the first U.S. Food and Drug Administration approved gene therapy and these engineered cells function with unprecedented efficacy in the treatment of refractory CD19 positive hematologic malignancies. CAR translation to solid tumors is also being actively investigated; however, efficacy to date has been variable due to tumor-evolved mechanisms that inhibit local immune cell activity. To bolster the potency of CAR-T cells, modulation of the immunosuppressive tumor microenvironment with immune-checkpoint blockade is a promising strategy. The impact of this approach on hematological malignancies is in its infancy, and in this review we discuss CAR-T cells and their synergy with immune-checkpoint blockade. PMID:29364163

Checkpoint-dependent and independent roles of the Werner syndrome protein in preserving genome integrity in response to mild replication stress

PubMed Central

Basile, Giorgia; Leuzzi, Giuseppe; Pichierri, Pietro; Franchitto, Annapaola

2014-01-01

Werner syndrome (WS) is a human chromosomal instability disorder associated with cancer predisposition and caused by mutations in the WRN gene. WRN helicase activity is crucial in limiting breakage at common fragile sites (CFS), which are the preferential targets of genome instability in precancerous lesions. However, the precise function of WRN in response to mild replication stress, like that commonly used to induce breaks at CFS, is still missing. Here, we establish that WRN plays a role in mediating CHK1 activation under moderate replication stress. We provide evidence that phosphorylation of CHK1 relies on the ATR-mediated phosphorylation of WRN, but not on WRN helicase activity. Analysis of replication fork dynamics shows that loss of WRN checkpoint mediator function as well as of WRN helicase activity hamper replication fork progression, and lead to new origin activation to allow recovery from replication slowing upon replication stress. Furthermore, bypass of WRN checkpoint mediator function through overexpression of a phospho-mimic form of CHK1 restores fork progression and chromosome stability to the wild-type levels. Together, these findings are the first demonstration that WRN regulates the ATR-checkpoint activation upon mild replication stress, preventing chromosome fragility. PMID:25352544

Salmonella Typhimurium disrupts Sirt1/AMPK checkpoint control of mTOR to impair autophagy

PubMed Central

Ganesan, Raja; Hos, Nina Judith; Gutierrez, Saray; Fischer, Julia; Stepek, Joanna Magdalena; Daglidu, Evmorphia; Krönke, Martin

2017-01-01

During intracellular infections, autophagy significantly contributes to the elimination of pathogens, regulation of pro-inflammatory signaling, secretion of immune mediators and in coordinating the adaptive immune system. Intracellular pathogens such as S. Typhimurium have evolved mechanisms to circumvent autophagy. However, the regulatory mechanisms targeted by S. Typhimurium to modulate autophagy have not been fully resolved. Here we report that cytosolic energy loss during S. Typhimurium infection triggers transient activation of AMPK, an important checkpoint of mTOR activity and autophagy. The activation of AMPK is regulated by LKB1 in a cytosolic complex containing Sirt1 and LKB1, where Sirt1 is required for deacetylation and subsequent activation of LKB1. S. Typhimurium infection targets Sirt1, LKB1 and AMPK to lysosomes for rapid degradation resulting in the disruption of the AMPK-mediated regulation of mTOR and autophagy. The degradation of cytosolic Sirt1/LKB1/AMPK complex was not observed with two mutant strains of S. Typhimurium, ΔssrB and ΔssaV, both compromising the pathogenicity island 2 (SPI2). The results highlight virulence factor-dependent degradation of host cell proteins as a previously unrecognized strategy of S. Typhimurium to evade autophagy. PMID:28192515

Set2 Methyltransferase Facilitates DNA Replication and Promotes Genotoxic Stress Responses through MBF-Dependent Transcription.

PubMed

Pai, Chen-Chun; Kishkevich, Anastasiya; Deegan, Rachel S; Keszthelyi, Andrea; Folkes, Lisa; Kearsey, Stephen E; De León, Nagore; Soriano, Ignacio; de Bruin, Robertus Antonius Maria; Carr, Antony M; Humphrey, Timothy C

2017-09-12

Chromatin modification through histone H3 lysine 36 methylation by the SETD2 tumor suppressor plays a key role in maintaining genome stability. Here, we describe a role for Set2-dependent H3K36 methylation in facilitating DNA replication and the transcriptional responses to both replication stress and DNA damage through promoting MluI cell-cycle box (MCB) binding factor (MBF)-complex-dependent transcription in fission yeast. Set2 loss leads to reduced MBF-dependent ribonucleotide reductase (RNR) expression, reduced deoxyribonucleoside triphosphate (dNTP) synthesis, altered replication origin firing, and a checkpoint-dependent S-phase delay. Accordingly, prolonged S phase in the absence of Set2 is suppressed by increasing dNTP synthesis. Furthermore, H3K36 is di- and tri-methylated at these MBF gene promoters, and Set2 loss leads to reduced MBF binding and transcription in response to genotoxic stress. Together, these findings provide new insights into how H3K36 methylation facilitates DNA replication and promotes genotoxic stress responses in fission yeast. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Immune Checkpoint Inhibitors: An Innovation in Immunotherapy for the Treatment and Management of Patients with Cancer.

PubMed

Dine, Jennifer; Gordon, RuthAnn; Shames, Yelena; Kasler, Mary Kate; Barton-Burke, Margaret

2017-01-01

Cancer survival rates are generally increasing in the United States. These trends have been partially attributed to improvement in therapeutic strategies. Cancer immunotherapy is an example of one of the newer strategies used to fight cancer, which primes or activates the immune system to produce antitumor effects. The first half of this review paper concisely describes the cell mechanisms that control antitumor immunity and the major immunotherapeutic strategies developed to target these mechanisms. The second half of the review discusses in greater depth immune checkpoint inhibitors that have recently demonstrated tremendous promise for the treatment of diverse solid tumor types, including melanoma, non-small cell lung cancer, and others. More specifically, the mechanisms of action, side effects, and patient and family management and education concerns are discussed to provide oncology nurses up-to-date information relevant to caring for cancer-affected patients treated with immune checkpoint inhibitors. Future directions for cancer immunotherapy are considered.

Immune Checkpoint Inhibitors for Patients With Advanced Non-Small-Cell Lung Cancer: A Systematic Review.

PubMed

Ellis, Peter M; Vella, Emily T; Ung, Yee C

2017-09-01

Second-line treatment options are limited for patients with advanced non-small-cell lung cancer (NSCLC). Standard therapy includes the cytotoxic agents docetaxel and pemetrexed, and the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors erlotinib and gefitinib. Immune checkpoint inhibitors are a new class of treatment that have shown durable overall radiologic response rates and have been well tolerated. The objective of this systematic review was to investigate the efficacy of immune checkpoint inhibitors compared with other chemotherapies in patients with advanced NSCLC. Medline, Embase, and PubMed were searched for randomized controlled trials comparing treatment with immune checkpoint inhibitors against treatment with chemotherapy in patients with stage IIIB or IV NSCLC. Nine randomized controlled trials with 15 publications were included. A significant overall survival benefit of second-line nivolumab (nonsquamous: hazard ratio [HR] = 0.72, 95% confidence interval [CI], 0.60-0.77; P < .001; squamous: HR = 0.59, 95% CI, 0.44-0.79; P < .001) or second-line atezolizumab (HR = 0.73, 95% CI, 0.62-0.87; P = .0003) or second-line pembrolizumab (in patients with programmed cell death ligand 1 [PD-L1]-positive tumors) (pembrolizumab 2 mg/kg HR = 0.71, 95% CI, 0.58-0.88; P = .0008; pembrolizumab 10 mg/kg HR = 0.61, 95% CI, 0.49-0.75; P < .0001) or first-line pembrolizumab (HR = 0.60, 95% CI, 0.41-0.89; P = .005) compared with chemotherapy was found. The adverse effects were mainly higher in the chemotherapy arms. For patients with advanced stage IIIB/IV NSCLC, the improvement in overall survival outweighed the harms and supported the use of first-line pembrolizumab (in patients with ≥ 50% PD-L1-positive tumors) or second-line nivolumab, atezolizumab, or pembrolizumab (in patients with PD-L1-positive tumors). Copyright © 2017 Elsevier Inc. All rights reserved.

Interferon gamma, an important marker of response to immune checkpoint blockade in non-small cell lung cancer and melanoma patients

PubMed Central

Karachaliou, Niki; Gonzalez-Cao, Maria; Crespo, Guillermo; Drozdowskyj, Ana; Aldeguer, Erika; Gimenez-Capitan, Ana; Teixido, Cristina; Molina-Vila, Miguel Angel; Viteri, Santiago; De Los Llanos Gil, Maria; Algarra, Salvador Martin; Perez-Ruiz, Elisabeth; Marquez-Rodas, Ivan; Rodriguez-Abreu, Delvys; Blanco, Remedios; Puertolas, Teresa; Royo, Maria Angeles; Rosell, Rafael

2018-01-01

Background: Programmed death-ligand 1 (PD-L1) may be induced by oncogenic signals or can be upregulated via interferon gamma (IFN-γ). We have explored whether the expression of IFNG, the gene encoding IFN-γ, is associated with clinical response to the immune checkpoint blockade in non-small cell lung cancer (NSCLC) and melanoma patients. The role of inflammation-associated transcription factors STAT3, IKBKE, STAT1 and other associated genes has also been examined. Methods: Total RNA from 17 NSCLC and 21 melanoma patients was analyzed by quantitative reverse transcription PCR. STAT3 and Rantes, YAP1 and CXCL5, DNMT1, RIG1 and TET1, EOMES, IFNG, PD-L1 and CTLA4, IKBKE and NFATC1 mRNA were examined. PD-L1 protein expression in tumor and immune cells and stromal infiltration of CD8+ T-cells were also evaluated. Progression-free survival and overall survival were estimated. Results: A total of 17 NSCLC patients received nivolumab and 21 melanoma patients received pembrolizumab. Progression-free survival with nivolumab was significantly longer in NSCLC patients with high versus low IFNG expression (5.1 months versus 2 months, p = 0.0124). Progression-free survival with pembrolizumab was significantly longer in melanoma patients with high versus low IFNG expression (5.0 months versus 1.9 months, p = 0.0099). Significantly longer overall survival was observed for melanoma patients with high versus low IFNG expression (not reached versus 10.2 months p = 0.0183). There was a trend for longer overall survival for NSCLC patients with high versus low IFNG expression. Conclusions: IFN-γ is an important marker for prediction of response to immune checkpoint blockade. Further research is warranted in order to validate whether IFNG is more accurate than PD-L1. PMID:29383037

Cop9/signalosome subunits and Pcu4 regulate ribonucleotide reductase by both checkpoint-dependent and -independent mechanisms

PubMed Central

Liu, Cong; Powell, Kelly A.; Mundt, Kirsten; Wu, LeJung; Carr, Antony M.; Caspari, Thomas

2003-01-01

The signalosome is implicated in regulating cullin-dependent ubiquitin ligases. We find that two signalosome subunits, Csn1 and Csn2, are required to regulate ribonucleotide reductase (RNR) through the degradation of a small protein, Spd1, that acts to anchor the small RNR subunit in the nucleus. Spd1 destruction correlates with the nuclear export of the small RNR subunit, which, in turn, correlates with a requirement for RNR in replication and repair. Spd1 degradation is promoted by two separate CSN-dependent mechanisms. During unperturbed S phase, Spd1 degradation is independent of checkpoint proteins. In irradiated G2 cells, Spd1 degradation requires the DNA damage checkpoint. The signalosome copurifies with Pcu4 (cullin 4). Pcu4, Csn1, and Csn2 promote the degradation of Spd1, identifying a new function for the signalosome as a regulator of Pcu4-containing E3 ubiquitin ligase. PMID:12695334

Discovery of a novel class of triazolones as checkpoint kinase inhibitors--hit to lead exploration.

PubMed

Oza, Vibha; Ashwell, Susan; Brassil, Patrick; Breed, Jason; Deng, Chun; Ezhuthachan, Jay; Haye, Heather; Horn, Candice; Janetka, James; Lyne, Paul; Newcombe, Nicholas; Otterbien, Ludo; Pass, Martin; Read, Jon; Roswell, Sian; Su, Mei; Toader, Dorin; Yu, Dingwei; Yu, Yan; Valentine, Anna; Webborn, Peter; White, Ann; Zabludoff, Sonya; Zheng, Xiaolan

2010-09-01

Checkpoint Kinase-1 (Chk1, CHK1, CHEK1) is a Ser/Thr protein kinase that mediates cellular responses to DNA-damage. A novel class of Chk1 inhibitors, triazoloquinolones/triazolones (TZ's) was identified by high throughput screening. The optimization of these hits to provide a lead series is described. Copyright 2010 Elsevier Ltd. All rights reserved.

Neurochemical excitation of propriospinal neurons facilitates locomotor command signal transmission in the lesioned spinal cord.

PubMed

Zaporozhets, Eugene; Cowley, Kristine C; Schmidt, Brian J

2011-06-01

Previous studies of the in vitro neonatal rat brain stem-spinal cord showed that propriospinal relays contribute to descending transmission of a supraspinal command signal that is capable of activating locomotion. Using the same preparation, the present series examines whether enhanced excitation of thoracic propriospinal neurons facilitates propagation of the locomotor command signal in the lesioned spinal cord. First, we identified neurotransmitters contributing to normal endogenous propriospinal transmission of the locomotor command signal by testing the effect of receptor antagonists applied to cervicothoracic segments during brain stem-induced locomotor-like activity. Spinal cords were either intact or contained staggered bilateral hemisections located at right T1/T2 and left T10/T11 junctions designed to abolish direct long-projecting bulbospinal axons. Serotonergic, noradrenergic, dopaminergic, and glutamatergic, but not cholinergic, receptor antagonists blocked locomotor-like activity. Approximately 73% of preparations with staggered bilateral hemisections failed to generate locomotor-like activity in response to electrical stimulation of the brain stem alone; such preparations were used to test the effect of neuroactive substances applied to thoracic segments (bath barriers placed at T3 and T9) during brain stem stimulation. The percentage of preparations developing locomotor-like activity was as follows: 5-HT (43%), 5-HT/N-methyl-D-aspartate (NMDA; 33%), quipazine (42%), 8-hydroxy-2-(di-n-propylamino)tetralin (20%), methoxamine (45%), and elevated bath K(+) concentration (29%). Combined norepinephrine and dopamine increased the success rate (67%) compared with the use of either agent alone (4 and 7%, respectively). NMDA, Mg(2+) ion removal, clonidine, and acetylcholine were ineffective. The results provide proof of principle that artificial excitation of thoracic propriospinal neurons can improve supraspinal control over hindlimb locomotor networks in the

G1 arrest induction represents a critical determinant for cisplatin cytotoxicity in G1 checkpoint-retaining human cancers.

PubMed

Un, Frank

2007-04-01

Cisplatin has been used effectively to treat various human cancer types; yet, the precise mechanism underlying its cytotoxicity remains unknown. In eukaryotes, progression through G1 is monitored by a checkpoint, which executes G1 arrest in the event of DNA damage to allow time for repair before initiating DNA replication. The retinoblastoma tumor suppressor gene is an integral component of the mammalian G1 checkpoint. The utility of the retinoblastoma gene as a therapeutic for human cancers has been investigated. Intriguingly, the cytotoxicity profile of the retinoblastoma gene therapy closely parallels the clinical targets of cisplatin. It prompted an investigation into the potential role of the checkpoint-induced G1 arrest in cisplatin cytotoxicity. Here, the evidence that G1 arrest induction represents a critical step in cisplatin-induced lytic path is presented. First, cisplatin-treated human cancer cells undergo a prolonged G1 arrest before dying. Second, triggering G1 arrest via infection with a recombinant adenovirus expressing the human retinoblastoma gene is sufficient to potentiate lethality in the absence of cisplatin. Third, the extent of the lethality induced correlates with the G1-arresting potential of the ectopically expressed human retinoblastoma polypeptide. Fourth, human cancer cells resistant to cisplatin do not undergo G1 arrest despite cisplatin treatment. The above mechanism may be exploited to develop therapeutics that preserve the efficacy of cisplatin yet bypass its mutagenicity associated with the formation of secondary tumors.

Activation of Ras-ERK Signaling and GSK-3 by Amyloid Precursor Protein and Amyloid Beta Facilitates Neurodegeneration in Alzheimer's Disease.

PubMed

Kirouac, Lisa; Rajic, Alexander J; Cribbs, David H; Padmanabhan, Jaya

2017-01-01

It is widely accepted that amyloid β (Aβ) generated from amyloid precursor protein (APP) oligomerizes and fibrillizes to form neuritic plaques in Alzheimer's disease (AD), yet little is known about the contribution of APP to intracellular signaling events preceding AD pathogenesis. The data presented here demonstrate that APP expression and neuronal exposure to oligomeric Aβ42 enhance Ras/ERK signaling cascade and glycogen synthase kinase 3 (GSK-3) activation. We find that RNA interference (RNAi)-directed knockdown of APP in B103 rat neuroblastoma cells expressing APP inhibits Ras-ERK signaling and GSK-3 activation, indicating that APP acts upstream of these signal transduction events. Both ERK and GSK-3 are known to induce hyperphosphorylation of tau and APP at Thr668, and our findings suggest that aberrant signaling by APP facilitates these events. Supporting this notion, analysis of human AD brain samples showed increased expression of Ras, activation of GSK-3, and phosphorylation of APP and tau, which correlated with Aβ levels in the AD brains. Furthermore, treatment of primary rat neurons with Aβ recapitulated these events and showed enhanced Ras-ERK signaling, GSK-3 activation, upregulation of cyclin D1, and phosphorylation of APP and tau. The finding that Aβ induces Thr668 phosphorylation on APP, which enhances APP proteolysis and Aβ generation, denotes a vicious feedforward mechanism by which APP and Aβ promote tau hyperphosphorylation and neurodegeneration in AD. Based on these results, we hypothesize that aberrant proliferative signaling by APP plays a fundamental role in AD neurodegeneration and that inhibition of this would impede cell cycle deregulation and neurodegeneration observed in AD.

Chk1 phosphorylation at Ser286 and Ser301 occurs with both stalled DNA replication and damage checkpoint stimulation.

PubMed

Ikegami, Yosuke; Goto, Hidemasa; Kiyono, Tohru; Enomoto, Masato; Kasahara, Kousuke; Tomono, Yasuko; Tozawa, Keiichi; Morita, Akimichi; Kohri, Kenjiro; Inagaki, Masaki

2008-12-26

We previously reported Chk1 to be phosphorylated at Ser286 and Ser301 by cyclin-dependent kinase (Cdk) 1 during mitosis [T. Shiromizu et al., Genes Cells 11 (2006) 477-485]. Here, we demonstrated that Chk1-Ser286 and -Ser301 phosphorylation also occurs in hydroxyurea (HU)-treated or ultraviolet (UV)-irradiated cells. Unlike the mitosis case, however, Chk1 was phosphorylated not only at Ser286 and Ser301 but also at Ser317 and Ser345 in the checkpoint response. Treatment with Cdk inhibitors diminished Chk1 phosphorylation at Ser286 and Ser301 but not at Ser317 and Ser345 with the latter. In vitro analyses revealed Ser286 and Ser301 on Chk1 to serve as two major phosphorylation sites for Cdk2. Immunoprecipitation analyses further demonstrated that Ser286/Ser301 and Ser317/Ser345 phosphorylation occur in the same Chk1 molecule during the checkpoint response. In addition, Ser286/Ser301 phosphorylation by Cdk2 was observed in Chk1 mutated to Ala at Ser317 and Ser345 (S317A/S345A), as well as Ser317/Ser345 phosphorylation by ATR was in S286A/S301A. Therefore, Chk1 phosphorylation in the checkpoint response is regulated not only by ATR but also by Cdk2.

ProAtlantic - The Atlantic Checkpoint - Data Availability and Adequacy in the Atlantic Basin

NASA Astrophysics Data System (ADS)

McGrath, F.

2017-12-01

DG MAREs Atlantic Checkpoint is a basin scale wide monitoring system assessment activity based upon targeted end-user applications. It is designed to be a benchmark for the assessment of hydrographic, geological, habitat, climate and fisheries data existence and availability in the Atlantic basin. DG MAREs Atlantic Checkpoint service will be delivered by the ProAtlantic project. The objective of this project is to investigate, through appropriate methodologies in the framework of 11 key marine challenges, how current international and national data providers - e.g. EMODNet, Copernicus - meet the requirements of the stakeholders and deliver fit for purpose data. By so doing, the main thematic and geographic gaps will be readily identified in the Atlantic basin for future consideration by DG MARE. For each challenge, specific web products in the form of maps, metadata, spreadsheets and reports will be delivered. These products are not an end by themselves but rather a means of showing whether data were available, let alone accessible. For example, the Fisheries Impact Challenge outputs include data grids (VMS/Seabed) and data adequacy reports. Production of gridded data layers in order to show the extent of fisheries impact on the seafloor involved the identification, acquisition and collation of data sources for the required data types (VMS/Seabed/Habitats Data) in the Atlantic basin. The resulting spatial coverage of these grids indicates the relatively low level of data availability and adequacy across the Atlantic basin. Aside from the data delivered by programmes such as EMODNet and Copernicus, there are a lot of initiatives by regional bodies such as OSPAR and ICES that consist of assembling and disseminating data to address specific issues. Several international projects have delivered research, data collection, and networking around several of the Atlantic Checkpoint challenge topics, namely MPAs, renewable energy assessment, seabed mapping, oil spill

Role of Immune Checkpoint Inhibitors in Small Cell Lung Cancer.

PubMed

Cooper, Maryann R; Alrajhi, Abdullah M; Durand, Cheryl R

Small cell lung cancer (SCLC) accounts for approximately 13% of all lung cancer diagnoses each year. SCLC is characterized by a rapid doubling time, early metastatic spread, and an unfavorable prognosis overall. Most patients with SCLC will respond to initial treatment; however, the majority will experience a disease recurrence and response to second-line therapies is poor. Immune checkpoint inhibitors may be an option given the success in other diseases. A literature search was conducted using Medline (1946-July week 1, 2017) and Embase (1996-2017 week 28) with the search terms small cell lung cancer combined with nivolumab or ipilimumab or pembrolizumab or atezolizumab or tremelimumab or durvalumab. Five clinical trials, including extended follow-up for 2, that evaluated immune checkpoint inhibitors in limited stage or extensive stage SCLC were included. In 2 phase 2 trials, ipilimumab was added to upfront chemotherapy. In both trials, an improvement in progression-free survival was seen. Toxicity, when combined with a platinum and etoposide, was significant. In a confirmatory phase 3 trial, ipilimumab did not prolong overall survival when added to first-line chemotherapy. Overall, response rates were similar between the placebo and ipilimumab groups. A phase 1/2 trial evaluated nivolumab alone or in combination with ipilimumab in recurrent SCLC. Results revealed that nivolumab monotherapy and the combination of nivolumab and ipilimumab were relatively safe and had antitumor activity. Pembrolizumab has been evaluated in a multicohort, phase 1b trial. Preliminary data showed a durable response in the second-line setting. Given the lack of overall survival data and significant toxicity associated with the combination of ipilimumab with first-line chemotherapy, this treatment is not a reasonable option at this time. Nivolumab alone or in combination with ipilimumab is a valid option for recurrent SCLC.

A case of pembrolizumab-induced type-1 diabetes mellitus and discussion of immune checkpoint inhibitor-induced type 1 diabetes.

PubMed

Chae, Young Kwang; Chiec, Lauren; Mohindra, Nisha; Gentzler, Ryan; Patel, Jyoti; Giles, Francis

2017-01-01

Immune checkpoint inhibitors such as pembrolizumab, ipilimumab, and nivolumab, now FDA-approved for use in treating several types of cancer, have been associated with immune-related adverse effects. Specifically, the antibodies targeting the programmed-cell death-1 immune checkpoint, pembrolizumab and nivolumab, have been rarely reported to induce the development of type 1 diabetes mellitus. Here we describe a case of a patient who developed antibody-positive type 1 diabetes mellitus following treatment with pembrolizumab in combination with systemic chemotherapy for metastatic adenocarcinoma of the lung. We will also provide a brief literature review of other rarely reported cases of type 1 diabetes presenting after treatment with pembrolizumab and nivolumab, as well as discussion regarding potential mechanisms of this adverse effect and its importance as these drugs continue to become even more widespread.

Leucine facilitates the insulin-stimulated glucose uptake and insulin signaling in skeletal muscle cells: involving mTORC1 and mTORC2.

PubMed

Liu, Hui; Liu, Rui; Xiong, Yufang; Li, Xiang; Wang, Xiaolei; Ma, Yan; Guo, Huailan; Hao, Liping; Yao, Ping; Liu, Liegang; Wang, Di; Yang, Xuefeng

2014-08-01

Leucine, a branched-chain amino acid, has been shown to promote glucose uptake and increase insulin sensitivity in skeletal muscle, but the exact mechanism remains unestablished. We addressed this issue in cultured skeletal muscle cells in this study. Our results showed that leucine alone did not have an effect on glucose uptake or phosphorylation of protein kinase B (AKT), but facilitated the insulin-induced glucose uptake and AKT phosphorylation. The insulin-stimulated glucose uptake and AKT phosphorylation were inhibited by the phosphatidylinositol 3-kinase inhibitor, wortmannin, but the inhibition was partially reversed by leucine. The inhibitor of mammalian target of rapamycin complex 1 (mTORC1), rapamycin, had no effect on the insulin-stimulated glucose uptake, but eliminated the facilitating effect of leucine in the insulin-stimulated glucose uptake and AKT phosphorylation. In addition, leucine facilitation of the insulin-induced AKT phosphorylation was neutralized by knocking down the core component of the mammalian target of rapamycin complex 2 (mTORC2) with specific siRNA. Together, these findings show that leucine can facilitate the insulin-induced insulin signaling and glucose uptake in skeletal muscle cells through both mTORC1 and mTORC2, implicating the potential importance of this amino acid in glucose homeostasis and providing new mechanistic insights.

The vigorous immune microenvironment of microsatellite instable colon cancer is balanced by multiple counter-inhibitory checkpoints

PubMed Central

Llosa, Nicolas J.; Cruise, Michael; Tam, Ada; Wick, Elizabeth C.; Hechenbleikner, Elizabeth M.; Taube, Janis M.; Blosser, Lee; Fan, Hongni; Wang, Hao; Luber, Brandon; Zhang, Ming; Papadopoulos, Nickolas; Kinzler, Kenneth W.; Vogelstein, Bert; Sears, Cynthia L.; Anders, Robert A.; Pardoll, Drew M.; Housseau, Franck

2014-01-01

We examined the immune microenvironment of primary colorectal cancer (CRC) using immunohistochemistry, laser capture microdissection/qRT-PCR, flow cytometry and functional analysis of tumor infiltrating lymphocytes. A subset of CRC displayed high infiltration with activated CD8+ CTL as well as activated Th1 cells characterized by IFN-γ production and the Th1 transcription factor Tbet. Parallel analysis of tumor genotypes revealed that virtually all of the tumors with this active Th1/CTL microenvironment had defects in mismatch repair, as evidenced by microsatellite instability (MSI). Counterbalancing this active Th1/CTL microenvironment, MSI tumors selectively demonstrated highly up-regulated expression of multiple immune checkpoints, including five – PD-1, PD-L1, CTLA-4, LAG-3 and IDO – currently being targeted clinically with inhibitors. These findings link tumor genotype with the immune microenvironment, and explain why MSI tumors are not naturally eliminated despite a hostile Th1/CTL microenvironment. They further suggest that blockade of specific checkpoints may be selectively efficacious in the MSI subset of CRC. PMID:25358689

Damage tolerance protein Mus81 associates with the FHA1 domain of checkpoint kinase Cds1.

PubMed

Boddy, M N; Lopez-Girona, A; Shanahan, P; Interthal, H; Heyer, W D; Russell, P

2000-12-01

Cds1, a serine/threonine kinase, enforces the S-M checkpoint in the fission yeast Schizosaccharomyces pombe. Cds1 is required for survival of replicational stress caused by agents that stall replication forks, but how Cds1 performs these functions is largely unknown. Here we report that the forkhead-associated-1 (FHA1) protein-docking domain of Cds1 interacts with Mus81, an evolutionarily conserved damage tolerance protein. Mus81 has an endonuclease homology domain found in the XPF nucleotide excision repair protein. Inactivation of mus81 reveals a unique spectrum of phenotypes. Mus81 enables survival of deoxynucleotide triphosphate starvation, UV radiation, and DNA polymerase impairment. Mus81 is essential in the absence of Bloom's syndrome Rqh1 helicase and is required for productive meiosis. Genetic epistasis studies suggest that Mus81 works with recombination enzymes to properly replicate damaged DNA. Inactivation of Mus81 triggers a checkpoint-dependent delay of mitosis. We propose that Mus81 is involved in the recruitment of Cds1 to aberrant DNA structures where Cds1 modulates the activity of damage tolerance enzymes.

Pharmacological activation of a novel p53-dependent S-phase checkpoint involving CHK-1

PubMed Central

Ahmed, A; Yang, J; Maya-Mendoza, A; Jackson, D A; Ashcroft, M

2011-01-01

We have recently shown that induction of the p53 tumour suppressor protein by the small-molecule RITA (reactivation of p53 and induction of tumour cell apoptosis; 2,5-bis(5-hydroxymethyl-2-thienyl)furan) inhibits hypoxia-inducible factor-1α and vascular endothelial growth factor expression in vivo and induces p53-dependent tumour cell apoptosis in normoxia and hypoxia. Here, we demonstrate that RITA activates the canonical ataxia telangiectasia mutated/ataxia telangiectasia and Rad3-related DNA damage response pathway. Interestingly, phosphorylation of checkpoint kinase (CHK)-1 induced in response to RITA was influenced by p53 status. We found that induction of p53, phosphorylated CHK-1 and γH2AX proteins was significantly increased in S-phase. Furthermore, we found that RITA stalled replication fork elongation, prolonged S-phase progression and induced DNA damage in p53 positive cells. Although CHK-1 knockdown did not significantly affect p53-dependent DNA damage or apoptosis induced by RITA, it did block the ability for DNA integrity to be maintained during the immediate response to RITA. These data reveal the existence of a novel p53-dependent S-phase DNA maintenance checkpoint involving CHK-1. PMID:21593792

Biomarkers for immune-related toxicities of checkpoint inhibitors: current progress and the road ahead.

PubMed

Patil, Pradnya D; Burotto, Mauricio; Velcheti, Vamsidhar

2018-03-01

Immune checkpoint pathways are key immune regulatory pathways that play a physiologic role in maintaining immune-homeostasis and are often co-opted by cancer cells to evade the host immune system. Recent developments in cancer immunotherapy, mainly drugs blocking the immune checkpoint pathways, have revolutionized the treatment paradigm for many solid tumors. A wide spectrum of immune-related adverse events (irAEs) have been described with the use of these agents which necessitate treatment with immunosuppression, lead to disruption of therapy and can on occasion be life-threatening. There are currently no clinically validated biomarkers to predict the risk of irAEs. Areas covered: In this review, the authors describe the current progress in identifying biomarkers for irAEs and potential future directions. Literature search was conducted using PubMed-MEDLINE, Embase and Scopus. In addition, abstracts from major conference proceedings were reviewed for relevant content. Expert commentary: The discovery of biomarkers for irAEs is currently in its infancy, however there are a lot of promising candidate biomarkers that are currently being investigated. Biomarkers that can identify patients at a higher risk of developing irAEs or lead to early detection of autoimmune toxicities are crucial to optimize patient selection for immune-oncology agents and to minimize toxicity with their use.

Regulation of cancer immune escape: The roles of miRNAs in immune checkpoint proteins.

PubMed

Yang, Qin; Cao, Wenjie; Wang, Zi; Zhang, Bin; Liu, Jing

2018-09-01

Immune checkpoint proteins (ICPs) are regulators of immune system. The ICP dysregulation silences the host immune response to cancer-specific antigens, contributing to the occurrence and progress of various cancers. MiRNAs are regulatory molecules and function in mRNA silencing and post-transcriptional regulation of gene expression. MiRNAs that modulate the immunity via ICPs have received increasing attention. Many studies have shown that the expressions of ICPs are directly or indirectly repressed by miRNAs in multiple types of cancers. MiRNAs are also subject to regulation by ICPs. In this review, recent studies of the relationship between miRNAs and ICPs (including the PD-1, PD-L1, CTLA-4, ICOS, B7-1, B7-2, B7-H2, B7-H3, CD27, CD70, CD40, and CD40L) in cancer immune escape are comprehensively discussed, which provide critical detailed mechanistic insights into the functions of the miRNA-ICP axes and their effects on immune escape, and will be beneficial for the potential applications of immune checkpoint therapy and miRNA-based guidance for personalized medicine as well as for predicting the prognosis. Copyright © 2018 Elsevier B.V. All rights reserved.

Using ergonomics checkpoints to support a participatory ergonomics intervention in an industrially developing country (IDC)--a case study.

PubMed

Helali, Faramarz

2009-01-01

To achieve ergonomics awareness in 3 subsidiary companies, an intervention team was formed. The aims of this study were to implement basic ergonomics through a participatory ergonomics intervention process that can support a continuous learning process and lead to an improvement in health and safety as well as in the work systems in the organization. The findings of this study (i.e., method, continuous learning and integration) were key to making the participatory ergonomics intervention successful. Furthermore, 4 issues of the ergonomics checkpoints (i.e., work schedules, work tasks, healthy work organization and learning) for assessing the work system were found suitable for both changing work schedules and for improving the work system. This paper describes the result of this project and also the experiences gained and the conclusions reached from using the International Labour Office's ergonomics checkpoints in the industries of industrially developing country.

The p53-p21WAF1 checkpoint pathway plays a protective role in preventing DNA rereplication induced by abrogation of FOXF1 function

PubMed Central

Lo, Pang-Kuo; Lee, Ji Shin; Sukumar, Saraswati

2011-01-01

We previously identified FOXF1 as a potential tumor suppressor gene with an essential role in preventing DNA rereplication to maintain genomic stability, which is frequently inactivated in breast cancer through the epigenetic mechanism. Here we further addressed the role of the p53-p21WAF1 checkpoint pathway in DNA rereplication induced by silencing of FOXF1. Knockdown of FOXF1 by small interference RNA (siRNA) rendered colorectal p53-null and p21WAF1-null HCT116 cancer cells more susceptible to rereplication and apoptosis than the wild-type parental cells. In parental HCT116 cells with a functional p53 checkpoint, the p53-p21WAF1 checkpoint pathway was activated upon FOXF1 knockdown, which was concurrent with suppression of the CDK2-Rb cascade and induction of G1 arrest. In contrast, these events were not observed in FOXF1-depleted HCT116-p53−/− and HCT116-p21−/− cells, indicating the p53-dependent checkpoint function is vital for inhibiting CDK2 to induce G1 arrest and protect cells from rereplication. The pharmacologic inhibitor (caffeine) of Ataxia telangiectasia mutated (ATM) and ataxia telangiectasia and Rad3 related (ATR) protein kinases abolished activation of the p53-p21WAF1 pathway upon FOXF1 knockdown, suggesting that suppression of FOXF1 function triggered the ATM/ATR-mediated DNA damage response. Cosilencing of p53 by siRNA synergistically enhanced the effect of FOXF1 depletion on stimulation of DNA rereplication and apoptosis in wild-type HCT116. Finally, we show that FOXF1 expression is predominantly silenced in breast and colorectal cancer cell lines with inactive p53. Our study demonstrated that the p53-p21WAF1 checkpoint pathway is an intrinsically protective mechanism to prevent DNA rereplication induced by silencing of FOXF1. PMID:21964066

Ki-67 Contributes to Normal Cell Cycle Progression and Inactive X Heterochromatin in p21 Checkpoint-Proficient Human Cells

PubMed Central

Sun, Xiaoming; Bizhanova, Aizhan; Matheson, Timothy D.; Yu, Jun; Zhu, Lihua Julie

2017-01-01

ABSTRACT The Ki-67 protein is widely used as a tumor proliferation marker. However, whether Ki-67 affects cell cycle progression has been controversial. Here we demonstrate that depletion of Ki-67 in human hTERT-RPE1, WI-38, IMR90, and hTERT-BJ cell lines and primary fibroblast cells slowed entry into S phase and coordinately downregulated genes related to DNA replication. Some gene expression changes were partially relieved in Ki-67-depleted hTERT-RPE1 cells by codepletion of the Rb checkpoint protein, but more thorough suppression of the transcriptional and cell cycle defects was observed upon depletion of the cell cycle inhibitor p21. Notably, induction of p21 upon depletion of Ki-67 was a consistent hallmark of cell types in which transcription and cell cycle distribution were sensitive to Ki-67; these responses were absent in cells that did not induce p21. Furthermore, upon Ki-67 depletion, a subset of inactive X (Xi) chromosomes in female hTERT-RPE1 cells displayed several features of compromised heterochromatin maintenance, including decreased H3K27me3 and H4K20me1 labeling. These chromatin alterations were limited to Xi chromosomes localized away from the nuclear lamina and were not observed in checkpoint-deficient 293T cells. Altogether, our results indicate that Ki-67 integrates normal S-phase progression and Xi heterochromatin maintenance in p21 checkpoint-proficient human cells. PMID:28630280

Noncanonical ATM Activation and Signaling in Response to Transcription-Blocking DNA Damage.

PubMed

Marteijn, Jurgen A; Vermeulen, Wim; Tresini, Maria

2017-01-01

Environmental genotoxins and metabolic byproducts generate DNA lesions that can cause genomic instability and disrupt tissue homeostasis. To ensure genomic integrity, cells employ mechanisms that convert signals generated by stochastic DNA damage into organized responses, including activation of repair systems, cell cycle checkpoints, and apoptotic mechanisms. DNA damage response (DDR) signaling pathways coordinate these responses and determine cellular fates in part, by transducing signals that modulate RNA metabolism. One of the master DDR coordinators, the Ataxia Telangiectasia Mutated (ATM) kinase, has a fundamental role in mediating DNA damage-induced changes in mRNA synthesis. ATM acts by modulating a variety of RNA metabolic pathways including nascent RNA splicing, a process catalyzed by the spliceosome. Interestingly, ATM and the spliceosome influence each other's activity in a reciprocal manner by a pathway that initiates when transcribing RNA polymerase II (RNAPII) encounters DNA lesions that prohibit forward translocation. In response to stalling of RNAPII assembly of late-stage spliceosomes is disrupted resulting in increased splicing factor mobility. Displacement of spliceosomes from lesion-arrested RNA polymerases facilitates formation of R-loops between the nascent RNA and DNA adjacent to the transcription bubble. R-loops signal for noncanonical ATM activation which in quiescent cells occurs in absence of detectable dsDNA breaks. In turn, activated ATM signals to regulate spliceosome dynamics and AS genome wide.This chapter describes the use of fluorescence microscopy methods that can be used to evaluate noncanonical ATM activation by transcription-blocking DNA damage. First, we present an immunofluorescence-detection method that can be used to evaluate ATM activation by autophosphorylation, in fixed cells. Second, we present a protocol for Fluorescence Recovery After Photobleaching (FRAP) of GFP-tagged splicing factors, a highly sensitive and

Use of Multiscale Entropy to Facilitate Artifact Detection in Electroencephalographic Signals

PubMed Central

Mariani, Sara; Borges, Ana F. T.; Henriques, Teresa; Goldberger, Ary L.; Costa, Madalena D.

2016-01-01

Electroencephalographic (EEG) signals present a myriad of challenges to analysis, beginning with the detection of artifacts. Prior approaches to noise detection have utilized multiple techniques, including visual methods, independent component analysis and wavelets. However, no single method is broadly accepted, inviting alternative ways to address this problem. Here, we introduce a novel approach based on a statistical physics method, multiscale entropy (MSE) analysis, which quantifies the complexity of a signal. We postulate that noise corrupted EEG signals have lower information content, and, therefore, reduced complexity compared with their noise free counterparts. We test the new method on an open-access database of EEG signals with and without added artifacts due to electrode motion. PMID:26738116

The ATM signaling network in development and disease.

PubMed

Stracker, Travis H; Roig, Ignasi; Knobel, Philip A; Marjanović, Marko

2013-01-01

The DNA damage response (DDR) rapidly recognizes DNA lesions and initiates the appropriate cellular programs to maintain genome integrity. This includes the coordination of cell cycle checkpoints, transcription, translation, DNA repair, metabolism, and cell fate decisions, such as apoptosis or senescence (Jackson and Bartek, 2009). DNA double-strand breaks (DSBs) represent one of the most cytotoxic DNA lesions and defects in their metabolism underlie many human hereditary diseases characterized by genomic instability (Stracker and Petrini, 2011; McKinnon, 2012). Patients with hereditary defects in the DDR display defects in development, particularly affecting the central nervous system, the immune system and the germline, as well as aberrant metabolic regulation and cancer predisposition. Central to the DDR to DSBs is the ataxia-telangiectasia mutated (ATM) kinase, a master controller of signal transduction. Understanding how ATM signaling regulates various aspects of the DDR and its roles in vivo is critical for our understanding of human disease, its diagnosis and its treatment. This review will describe the general roles of ATM signaling and highlight some recent advances that have shed light on the diverse roles of ATM and related proteins in human disease.

The ATM signaling network in development and disease

PubMed Central

Stracker, Travis H.; Roig, Ignasi; Knobel, Philip A.; Marjanović, Marko

2013-01-01

The DNA damage response (DDR) rapidly recognizes DNA lesions and initiates the appropriate cellular programs to maintain genome integrity. This includes the coordination of cell cycle checkpoints, transcription, translation, DNA repair, metabolism, and cell fate decisions, such as apoptosis or senescence (Jackson and Bartek, 2009). DNA double-strand breaks (DSBs) represent one of the most cytotoxic DNA lesions and defects in their metabolism underlie many human hereditary diseases characterized by genomic instability (Stracker and Petrini, 2011; McKinnon, 2012). Patients with hereditary defects in the DDR display defects in development, particularly affecting the central nervous system, the immune system and the germline, as well as aberrant metabolic regulation and cancer predisposition. Central to the DDR to DSBs is the ataxia-telangiectasia mutated (ATM) kinase, a master controller of signal transduction. Understanding how ATM signaling regulates various aspects of the DDR and its roles in vivo is critical for our understanding of human disease, its diagnosis and its treatment. This review will describe the general roles of ATM signaling and highlight some recent advances that have shed light on the diverse roles of ATM and related proteins in human disease. PMID:23532176

Structure of an intermediate conformer of the spindle checkpoint protein Mad2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hara, Mayuko; Özkan, Engin; Sun, Hongbin

2015-08-24

The spindle checkpoint senses unattached kinetochores during prometaphase and inhibits the anaphase-promoting complex or cyclosome (APC/C), thus ensuring accurate chromosome segregation. The checkpoint protein mitotic arrest deficient 2 (Mad2) is an unusual protein with multiple folded states. Mad2 adopts the closed conformation (C-Mad2) in a Mad1–Mad2 core complex. In mitosis, kinetochore-bound Mad1–C-Mad2 recruits latent, open Mad2 (O-Mad2) from the cytosol and converts it to an intermediate conformer (I-Mad2), which can then bind and inhibit the APC/C activator cell division cycle 20 (Cdc20) as C-Mad2. In this paper, we report the crystal structure and NMR analysis of I-Mad2 bound to C-Mad2.more » Although I-Mad2 retains the O-Mad2 fold in crystal and in solution, its core structural elements undergo discernible rigid-body movements and more closely resemble C-Mad2. Residues exhibiting methyl chemical shift changes in I-Mad2 form a contiguous, interior network that connects its C-Mad2–binding site to the conformationally malleable C-terminal region. Mutations of residues at the I-Mad2–C-Mad2 interface hinder I-Mad2 formation and impede the structural transition of Mad2. Finally, our study provides insight into the conformational activation of Mad2 and establishes the basis of allosteric communication between two distal sites in Mad2.« less

Phosphorylation of Nucleotide Excision Repair Factor Xeroderma Pigmentosum Group A by Ataxia Telangiectasia Mutated and Rad3-Related-Dependent Checkpoint Pathway Promotes Cell Survival in Response to UV Irradiation

PubMed Central

Wu, Xiaoming; Shell, Steven M.; Yang, Zhengguan; Zou, Yue

2006-01-01

DNA damage triggers complex cellular responses in eukaryotic cells, including initiation of DNA repair and activation of cell cycle checkpoints. In addition to inducing cell cycle arrest, checkpoint also has been suggested to modulate a variety of other cellular processes in response to DNA damage. In this study, we present evidence showing that the cellular function of xeroderma pigmentosum group A (XPA), a major nucleotide excision repair (NER) factor, could be modulated by checkpoint kinase ataxia-telangiectasia mutated and Rad3-related (ATR) in response to UV irradiation. We observed the apparent interaction and colocalization of XPA with ATR in response to UV irradiation. We showed that XPA was a substrate for in vitro phosphorylation by phosphatidylinositol-3-kinase-related kinase family kinases whereas in cells XPA was phosphorylated in an ATR-dependent manner and stimulated by UV irradiation. The Ser196 of XPA was identified as a biologically significant residue to be phosphorylated in vivo. The XPA-deficient cells complemented with XPA-S196A mutant, in which Ser196 was substituted with an alanine, displayed significantly higher UV sensitivity compared with the XPA cells complemented with wild-type XPA. Moreover, substitution of Ser196 with aspartic acid for mimicking the phosphorylation of XPA increased the cell survival to UV irradiation. Taken together, our results revealed a potential physical and functional link between NER and the ATR-dependent checkpoint pathway in human cells and suggested that the ATR checkpoint pathway could modulate the cellular activity of NER through phosphorylation of XPA at Ser196 on UV irradiation. PMID:16540648

Kinetochore localized Mad2 and Cdc20 is itself insufficient for triggering the mitotic checkpoint when Mps1 is low in Drosophila melanogaster neuroblasts.

PubMed

Herriott, Ashleigh; Sweeney, Michele; Whitaker, Michael; Taggart, Michael; Huang, Jun-Yong

2012-12-15

The relationships between the kinetochore and checkpoint control remain unresolved. Here, we report the characterization of the in vivo behavior of Cdc20 and Mad2 and the relevant spindle assembly checkpoint (SAC) functions in the neuroblasts of a Drosophila Mps1 weak allele (ald (B4-2) ). ald (B4-2) third instar larvae brain samples contain only around 16% endogenous Mps1 protein, and the SAC function is abolished. However, this does not lead to rapid anaphase onset and mitotic exit, in contrast to the loss of Mad2 alone in a mad2 (EY) mutant. The level of GFP-Cdc20 recruitment to the kinetochore is unaffected in ald (B4-2) neuroblasts, while the level of GFP-Mad2 is reduced to just about 20%. Cdc20 and Mad2 display only monophasic exponential kinetics at the kinetochores. The ald (B4-2) heterozygotes expressed approximately 65% of normal Mps1 protein levels, and this is enough to restore the SAC function. The kinetochore recruitment of GFP-Mad2 in response to SAC activation increases by around 80% in heterozygotes, compared with just about 20% in ald (B4-2) mutant. This suggests a correlation between Mps1 levels and Mad2 kinetochore localization and perhaps the existence of a threshold level at which Mps1 is fully functional. The failure to arrest the mitotic progression in ald (B4-2) neuroblasts in response to colchicine treatment suggests that when Mps1 levels are low, approximately 20% of normal GFP-Mad2, alongside normal levels of GFP-Cdc20 kinetochore recruitments, is insufficient for triggering SAC signal propagation.

Checkpoint kinase 1 expression is an adverse prognostic marker and therapeutic target in MYC-driven medulloblastoma

PubMed Central

Shah, Monil; Mulcahy Levy, Jean M.; Griesinger, Andrea M.; Alimova, Irina; Harris, Peter S.; Birks, Diane K.; Donson, Andrew M.; Davidson, Nathan; Remke, Marc; Taylor, Michael D.; Handler, Michael H.; Foreman, Nicholas K.; Venkataraman, Sujatha; Vibhakar, Rajeev

2016-01-01

Checkpoint kinase 1 (CHK1) is an integral component of the cell cycle as well as the DNA Damage Response (DDR) pathway. Previous work has demonstrated the effectiveness of inhibiting CHK1 with small-molecule inhibitors, but the role of CHK1 mediated DDR in medulloblastoma is unknown. CHK1, both at the mRNA and protein level, is highly expressed in medulloblastoma and elevated CHK1 expression in Group3 medulloblastoma is an adverse prognostic marker. CHK1 inhibition with the small-molecule drug AZD7762, results in decreased cell growth, increased DNA damage and cell apoptosis. Furthermore, AZD7762 acts in synergy with cisplatin in reducing cell proliferation in medulloblastoma. Similar phenotypic changes were observed with another CHK1 inhibitor, PF477736, as well as genetic knockdown using siRNA against CHK1. Treatments with small-molecule inhibitors of CHK1 profoundly modulated the expression of both upstream and downstream target proteins within the CHK1 signaling pathways. This suggests the presence of a feedback loop in activating CHK1. Overall, our results demonstrate that small-molecule inhibition of CHK1 in combination with, cisplatin, is more advantageous than either treatment alone, especially for Group 3 medulloblastoma, and therefore this combined therapeutic approach serves as an avenue for further investigation. PMID:27449089

Checkpoint kinase 1 expression is an adverse prognostic marker and therapeutic target in MYC-driven medulloblastoma.

PubMed

Prince, Eric W; Balakrishnan, Ilango; Shah, Monil; Mulcahy Levy, Jean M; Griesinger, Andrea M; Alimova, Irina; Harris, Peter S; Birks, Diane K; Donson, Andrew M; Davidson, Nathan; Remke, Marc; Taylor, Michael D; Handler, Michael H; Foreman, Nicholas K; Venkataraman, Sujatha; Vibhakar, Rajeev

2016-08-16

Checkpoint kinase 1 (CHK1) is an integral component of the cell cycle as well as the DNA Damage Response (DDR) pathway. Previous work has demonstrated the effectiveness of inhibiting CHK1 with small-molecule inhibitors, but the role of CHK1 mediated DDR in medulloblastoma is unknown. CHK1, both at the mRNA and protein level, is highly expressed in medulloblastoma and elevated CHK1 expression in Group3 medulloblastoma is an adverse prognostic marker. CHK1 inhibition with the small-molecule drug AZD7762, results in decreased cell growth, increased DNA damage and cell apoptosis. Furthermore, AZD7762 acts in synergy with cisplatin in reducing cell proliferation in medulloblastoma. Similar phenotypic changes were observed with another CHK1 inhibitor, PF477736, as well as genetic knockdown using siRNA against CHK1. Treatments with small-molecule inhibitors of CHK1 profoundly modulated the expression of both upstream and downstream target proteins within the CHK1 signaling pathways. This suggests the presence of a feedback loop in activating CHK1. Overall, our results demonstrate that small-molecule inhibition of CHK1 in combination with, cisplatin, is more advantageous than either treatment alone, especially for Group 3 medulloblastoma, and therefore this combined therapeutic approach serves as an avenue for further investigation.

Successful treatment of arthritis induced by checkpoint inhibitors with tocilizumab: a case series.

PubMed

Kim, Sang Taek; Tayar, Jean; Trinh, Van Anh; Suarez-Almazor, Maria; Garcia, Salvador; Hwu, Patrick; Johnson, Daniel Hartman; Uemura, Marc; Diab, Adi

2017-12-01

Immune checkpoint inhibitors (ICIs) have significantly improved outcomes for patients with numerous cancers. However, these therapies are associated with immune-related adverse events (irAEs), which are inflammatory side effects potentially affecting any organ. Cases of ICI-induced inflammatory arthritis have also been reported. In general, mild irAEs are treated with corticosteroids, while tumour necrosis factor-α (TNFα) inhibitors are reserved for refractory cases. However, prolonged use of TNFα inhibitor (TNFαi) can induce widespread, significant immunosuppression, which can negatively impact the antitumour efficacy of ICI therapy. Therefore, in clinical scenarios where patients develop severe immunotherapy-induced irAEs, an unmet need exists for alternative therapeutic strategies that are effective and without immune dampening effects. The anti-interleukin (IL)-6 receptor antibody, tocilizumab, is a biological agent Food and Drug Administration approved for the treatment of rheumatoid arthritis and juvenile idiopathic arthritis. Here, we report on three patients who developed severe polyarthritis while receiving ICI therapy and were treated with tocilizumab. All three patients demonstrated significant clinical improvement; one patient maintained a durable antitumour response derived from checkpoint inhibition. These three cases suggest that anti-IL-6 receptor antibody may be an effective alternative to corticosteroids or TNFαi for the treatment of arthritis irAEs. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

A role for the Rab6A′ GTPase in the inactivation of the Mad2-spindle checkpoint

PubMed Central

Miserey-Lenkei, Stéphanie; Couëdel-Courteille, Anne; Del Nery, Elaine; Bardin, Sabine; Piel, Matthieu; Racine, Victor; Sibarita, Jean-Baptiste; Perez, Franck; Bornens, Michel; Goud, Bruno

2006-01-01

The two isoforms of the Rab6 GTPase, Rab6A and Rab6A′, regulate a retrograde transport route connecting early endosomes and the endoplasmic reticulum via the Golgi complex in interphasic cells. Here we report that when Rab6A′ function is altered cells are unable to progress normally through mitosis. Such cells are blocked in metaphase, despite displaying a normal Golgi fragmentation and with the Mad2-spindle checkpoint activated. Furthermore, the Rab6 effector p150Glued, a subunit of the dynein/dynactin complex, remains associated with some kinetochores. A similar phenotype was observed when GAPCenA, a GTPase-activating protein of Rab6, was depleted from cells. Our results suggest that Rab6A′ likely regulates the dynamics of the dynein/dynactin complex at the kinetochores and consequently the inactivation of the Mad2-spindle checkpoint. Rab6A′, through its interaction with p150Glued and GAPCenA, may thus participate in a pathway involved in the metaphase/anaphase transition. PMID:16395330

Checkpoint-based forward recovery using lookahead execution and rollback validation in parallel and distributed systems. Ph.D. Thesis, 1992

NASA Technical Reports Server (NTRS)

Long, Junsheng

1994-01-01

This thesis studies a forward recovery strategy using checkpointing and optimistic execution in parallel and distributed systems. The approach uses replicated tasks executing on different processors for forwared recovery and checkpoint comparison for error detection. To reduce overall redundancy, this approach employs a lower static redundancy in the common error-free situation to detect error than the standard N Module Redundancy scheme (NMR) does to mask off errors. For the rare occurrence of an error, this approach uses some extra redundancy for recovery. To reduce the run-time recovery overhead, look-ahead processes are used to advance computation speculatively and a rollback process is used to produce a diagnosis for correct look-ahead processes without rollback of the whole system. Both analytical and experimental evaluation have shown that this strategy can provide a nearly error-free execution time even under faults with a lower average redundancy than NMR.

Transcriptional and post-transcriptional regulation of Cdc20 during the spindle assembly checkpoint in S. cerevisiae

PubMed Central

Wang, Ruiwen; Burton, Janet L.; Solomon, Mark J.

2017-01-01

The anaphase-promoting complex (APC) is a ubiquitin ligase responsible for promoting the degradation of many cell cycle regulators. One of the activators and substrate-binding proteins for the APC is Cdc20. It has been shown previously that Cdc20 can promote its own degradation by the APC in normal cycling cells mainly through a cis-degradation mode (i.e. via an intramolecular mechanism). However, how Cdc20 is degraded during the spindle assembly checkpoint (SAC) is still not fully clear. In this study, we used a dual-Cdc20 system to investigate this issue and found that the cis-degradation mode is also the major pathway responsible for Cdc20 degradation during the SAC. In addition, we found that there is an inverse relationship between APCCdc20 activity and the transcriptional activity of the CDC20 promoter, which likely occurs through feedback regulation by APCCdc20 substrates, such as the cyclins Clb2 and Clb5. These findings contribute to our understanding of how the inhibition of APCCdc20 activity and enhanced Cdc20 degradation are required for proper spindle checkpoint arrest. PMID:28189585

Host-Pathogen Checkpoints and Population Bottlenecks in Persistent and Intracellular Uropathogenic E. coli Bladder Infection

PubMed Central

Hannan, Thomas J.; Totsika, Makrina; Mansfield, Kylie J.; Moore, Kate H.; Schembri, Mark A.; Hultgren, Scott J.

2013-01-01

Bladder infections affect millions of people yearly, and recurrent symptomatic infections (cystitis) are very common. The rapid increase in infections caused by multi-drug resistant uropathogens threatens to make recurrent cystitis an increasingly troubling public health concern. Uropathogenic E. coli (UPEC) cause the vast majority of bladder infections. Upon entry into the lower urinary tract, UPEC face obstacles to colonization that constitute population bottlenecks, reducing diversity and selecting for fit clones. A critical mucosal barrier to bladder infection is the epithelium (urothelium). UPEC bypass this barrier when they invade urothelial cells and form intracellular bacterial communities (IBCs), a process which requires type 1 pili. IBCs are transient in nature, occurring primarily during acute infection. Chronic bladder infection is common and can be either latent, in the form of the Quiescent Intracellular Reservoir (QIR), or active, in the form of asymptomatic bacteriuria (ASB/ABU) or chronic cystitis. In mice, the fate of bladder infection: QIR, ASB, or chronic cystitis, is determined within the first 24 hours of infection and constitutes a putative host-pathogen mucosal checkpoint that contributes to susceptibility to recurrent cystitis. Knowledge of these checkpoints and bottlenecks is critical for our understanding of bladder infection and efforts to devise novel therapeutic strategies. PMID:22404313

Eukaryotic Initiation Factor 4E Binding Protien Family of Protiens: Sentinels at a Translational Control Checkpoint in Lung Tumor Defense

PubMed Central

Kim, Yong Y; Von Weymarn, Linda; Larsson, Ola; Fan, Danhua; Underwood, Jon M; Hecht, Stephen S; Polunovsky, Vitaly A; Bitterman, Peter B

2009-01-01

The usurping of translational control by sustained activation of translation initiation factors is oncogenic. Here we show that the primary negative regulators of these oncogenic initiation factors - the 4E-BP protein family - operate as guardians of a translational control checkpoint in lung tumor defense. When challenged with the tobacco carcinogen NNK, 4ebp1−/−/4ebp2−/− mice showed increased sensitivity to tumorigenesis compared to their wild type counterparts. The 4E-BP deficient state per se creates pro-oncogenic, genome-wide skewing of the molecular landscape - with translational activation of genes governing angiogenesis, growth and proliferation; and translational activation of the precise cytochrome p450 enzyme isoform (CYP2A5) that bioactivates NNK into mutagenic metabolites. Our study provides in vivo proof for a translational control checkpoint in lung tumor defense. PMID:19843855

Immune Checkpoint Molecules on Tumor-Infiltrating Lymphocytes and Their Association with Tertiary Lymphoid Structures in Human Breast Cancer

PubMed Central

Solinas, Cinzia; Garaud, Soizic; De Silva, Pushpamali; Boisson, Anaïs; Van den Eynden, Gert; de Wind, Alexandre; Risso, Paolo; Rodrigues Vitória, Joel; Richard, François; Migliori, Edoardo; Noël, Grégory; Duvillier, Hugues; Craciun, Ligia; Veys, Isabelle; Awada, Ahmad; Detours, Vincent; Larsimont, Denis; Piccart-Gebhart, Martine; Willard-Gallo, Karen

2017-01-01

There is an exponentially growing interest in targeting immune checkpoint molecules in breast cancer (BC), particularly in the triple-negative subtype where unmet treatment needs remain. This study was designed to analyze the expression, localization, and prognostic role of PD-1, PD-L1, PD-L2, CTLA-4, LAG3, and TIM3 in primary BC. Gene expression analysis using the METABRIC microarray dataset found that all six immune checkpoint molecules are highly expressed in basal-like and HER2-enriched compared to the other BC molecular subtypes. Flow cytometric analysis of fresh tissue homogenates from untreated primary tumors show that PD-1 is principally expressed on CD4+ or CD8+ T cells and CTLA-4 is expressed on CD4+ T cells. The global proportion of PD-L1+, PD-L2+, LAG3+, and TIM3+ tumor-infiltrating lymphocytes (TIL) was low and detectable in only a small number of tumors. Immunohistochemically staining fixed tissues from the same tumors was employed to score TIL and tertiary lymphoid structures (TLS). PD-L1+, PD-L2+, LAG3+, and TIM3+ cells were detected in some TLS in a pattern that resembles secondary lymphoid organs. This observation suggests that TLS are important sites of immune activation and regulation, particularly in tumors with extensive baseline immune infiltration. Significantly improved overall survival was correlated with PD-1 expression in the HER2-enriched and PD-L1 or CTLA-4 expression in basal-like BC. PD-1 and CTLA-4 proteins were most frequently detected on TIL, which supports the correlations observed between their gene expression and improved long-term outcome in basal-like and HER2-enriched BC. PD-L1 expression by tumor or immune cells is uncommon in BC. Overall, the data presented here distinguish PD-1 as a marker of T cell activity in both the T and B cell areas of BC associated TLS. We found that immune checkpoint molecule expression parallels the extent of TIL and TLS, although there is a noteworthy amount of heterogeneity between tumors even

LED traffic signal replacement schedules : facilitating smooth freight flows.

DOT National Transportation Integrated Search

2011-11-01

This research details a field study of LED traffic signals in Missouri and develops a replacement schedule based on key findings. : Rates of degradation were statistically analyzed using Analysis of Variance (ANOVA). Results of this research will pro...

Heat Shock Protein 83 (Hsp83) Facilitates Methoprene-tolerant (Met) Nuclear Import to Modulate Juvenile Hormone Signaling*

PubMed Central

He, Qianyu; Wen, Di; Jia, Qiangqiang; Cui, Chunlai; Wang, Jian; Palli, Subba R.; Li, Sheng

2014-01-01

Juvenile hormone (JH) receptors, methoprene-tolerant (Met) and Germ-cell expressed (Gce), transduce JH signals to induce Kr-h1 expression in Drosophila. Dual luciferase assay identified a 120-bp JH response region (JHRR) in the Kr-h1α promoter. Both in vitro and in vivo experiments revealed that Met and Gce transduce JH signals to induce Kr-h1 expression through the JHRR. DNA affinity purification identified chaperone protein Hsp83 as one of the proteins bound to the JHRR in the presence of JH. Interestingly, Hsp83 physically interacts with PAS-B and basic helix-loop-helix domains of Met, and JH induces Met-Hsp83 interaction. As determined by immunohistochemistry, Met is mainly distributed in the cytoplasm of fat body cells of the larval when the JH titer is low and JH induces Met nuclear import. Hsp83 was accumulated in the cytoplasm area adjunct to the nucleus in the presence of JH and Met/Gce. Loss-of-function of Hsp83 attenuated JH binding and JH-induced nuclear import of Met, resulting in a decrease in the JHRR-driven reporter activity leading to reduction of Kr-h1 expression. These data show that Hsp83 facilitates the JH-induced nuclear import of Met that induces Kr-h1 expression through the JHRR. PMID:25122763

T Cell Calcium Signaling Regulation by the Co-Receptor CD5

PubMed Central

Freitas, Claudia M. Tellez

2018-01-01

Calcium influx is critical for T cell effector function and fate. T cells are activated when T cell receptors (TCRs) engage peptides presented by antigen-presenting cells (APC), causing an increase of intracellular calcium (Ca2+) concentration. Co-receptors stabilize interactions between the TCR and its ligand, the peptide-major histocompatibility complex (pMHC), and enhance Ca2+ signaling and T cell activation. Conversely, some co-receptors can dampen Ca2+ signaling and inhibit T cell activation. Immune checkpoint therapies block inhibitory co-receptors, such as cytotoxic T-lymphocyte associated antigen 4 (CTLA-4) and programmed death 1 (PD-1), to increase T cell Ca2+ signaling and promote T cell survival. Similar to CTLA-4 and PD-1, the co-receptor CD5 has been known to act as a negative regulator of T cell activation and to alter Ca2+ signaling and T cell function. Though much is known about the role of CD5 in B cells, recent research has expanded our understanding of CD5 function in T cells. Here we review these recent findings and discuss how our improved understanding of CD5 Ca2+ signaling regulation could be useful for basic and clinical research. PMID:29701673

Pseudoprogression and hyperprogression during immune checkpoint inhibitor therapy for urothelial and kidney cancer.

PubMed

Soria, Francesco; Beleni, Andrea I; D'Andrea, David; Resch, Irene; Gust, Kilian M; Gontero, Paolo; Shariat, Shahrokh F

2018-03-16

A small subset of patients treated with immune checkpoint inhibitors manifest atypical patterns of response, the so-called pseudoprogression (PP) and hyperprogression (HP). Their prevalence in urothelial (UC) and renal cancer (RCC) remains, to date, mostly uninvestigated. Therefore, we aimed to provide a summary of the current knowledge about PP and HP during immune checkpoint inhibitor therapy in UC and RCC patients. A systematic medline/pubmed © literature search was performed. The atypical patterns of response to systemic immunotherapy were reviewed. Endpoints were PP and HP in UC and RCC. Tumors respond differently to immunotherapy compared to systemic chemotherapy. To evaluate response to immunotherapy, new guidelines (iRECIST) have been developed. To date, no studies focused on PP in UC and RCC, and the only way to evaluate its role is to take patients who respond to treatment beyond progression as surrogate for pseudoprogressors. PP seems to occur in a non-negligible rate of UC and RCC (from 1.5 to 17% and from 5 to 15%, respectively). The concept of HP, defined as a rapid progression after treatment, just took the first steps, and therefore, data from ongoing trials are awaited to elucidate its impact in genitourinary cancers. PP and HP are not uncommon entities in UC and RCC patients, treated with PD-1/PD-L1 inhibitors. Further investigation is warranted to define which patients are likely to experience PP and could benefit from treatment beyond progression and which ones will instead rapidly experience progression despite treatment and should, therefore, avoid systemic immunotherapy.

Antiproliferation potential of withaferin A on human osteosarcoma cells via the inhibition of G2/M checkpoint proteins

PubMed Central

LV, TING-ZHUO; WANG, GUANG-SHUN

2015-01-01

Withaferin A (WA) is a well-known steroidal lactone of the medicinally important plant, Withania somnifera. This secondary metabolite has been noted for its anticancer effects against a number of human cancer cell lines. However, there are a limited number of studies investigating the growth inhibitory potential of WA against human osteosarcoma cells and the underlying molecular mechanisms. Thus, in the present study, the antiproliferative activities of WA, along with the underlying mechanisms of action, were investigated using flow cytometry for cell cycle distribution and western blot analysis for the assessment of various checkpoint proteins. In addition, the antiproliferative activity was evaluated using a sulforhodamine B assay, where MG-63 and U2OS human osteosarcoma cell lines were treated with different concentrations of WA. Furthermore, the mRNA expression levels of the checkpoint proteins in the WA-treated MG-63 and U2OS cells were examined. The results obtained corresponded with the western blot analysis results. Furthermore, WA was shown to significantly inhibit the proliferation of the two types of treated cell lines (MG-63 and U2OS). Flow cytometric analysis revealed that WA induced cell cycle arrest at the G2/M phase, which was associated with the inhibition of cyclin B1, cyclin A, Cdk2 and p-Cdc2 (Tyr15) expression and an increase in the levels of p-Chk1 (Ser345) and p-Chk2 (Thr68). In conclusion, the present study found that the antiproliferative potential of WA was associated with the induction of cell cycle arrest at the G2/M phase, which was a result of the attenuation of the expression levels of G2/M checkpoint proteins. PMID:26170956

Antiproliferation potential of withaferin A on human osteosarcoma cells via the inhibition of G2/M checkpoint proteins.

PubMed

Lv, Ting-Zhuo; Wang, Guang-Shun

2015-07-01

Withaferin A (WA) is a well-known steroidal lactone of the medicinally important plant, Withania somnifera . This secondary metabolite has been noted for its anticancer effects against a number of human cancer cell lines. However, there are a limited number of studies investigating the growth inhibitory potential of WA against human osteosarcoma cells and the underlying molecular mechanisms. Thus, in the present study, the antiproliferative activities of WA, along with the underlying mechanisms of action, were investigated using flow cytometry for cell cycle distribution and western blot analysis for the assessment of various checkpoint proteins. In addition, the antiproliferative activity was evaluated using a sulforhodamine B assay, where MG-63 and U2OS human osteosarcoma cell lines were treated with different concentrations of WA. Furthermore, the mRNA expression levels of the checkpoint proteins in the WA-treated MG-63 and U2OS cells were examined. The results obtained corresponded with the western blot analysis results. Furthermore, WA was shown to significantly inhibit the proliferation of the two types of treated cell lines (MG-63 and U2OS). Flow cytometric analysis revealed that WA induced cell cycle arrest at the G2/M phase, which was associated with the inhibition of cyclin B1, cyclin A, Cdk2 and p-Cdc2 (Tyr15) expression and an increase in the levels of p-Chk1 (Ser345) and p-Chk2 (Thr68). In conclusion, the present study found that the antiproliferative potential of WA was associated with the induction of cell cycle arrest at the G2/M phase, which was a result of the attenuation of the expression levels of G2/M checkpoint proteins.

Calibration and Validation of the Checkpoint Model to the Air Force Electronic Systems Center Software Database

DTIC Science & Technology

1997-09-01

Illinois Institute of Technology Research Institute (IITRI) calibrated seven parametric models including SPQR /20, the forerunner of CHECKPOINT. The...a semicolon); thus, SPQR /20 was calibrated using SLOC sizing data (IITRI, 1989: 3-4). The results showed only slight overall improvements in accuracy...even when validating the calibrated models with the same data sets. The IITRI study demonstrated SPQR /20 to be one of two models that were most

NDR1 modulates the UV-induced DNA-damage checkpoint and nucleotide excision repair

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Jeong-Min; Choi, Ji Ye; Yi, Joo Mi

2015-06-05

Nucleotide excision repair (NER) is the sole mechanism of UV-induced DNA lesion repair in mammals. A single round of NER requires multiple components including seven core NER factors, xeroderma pigmentosum A–G (XPA–XPG), and many auxiliary effector proteins including ATR serine/threonine kinase. The XPA protein helps to verify DNA damage and thus plays a rate-limiting role in NER. Hence, the regulation of XPA is important for the entire NER kinetic. We found that NDR1, a novel XPA-interacting protein, modulates NER by modulating the UV-induced DNA-damage checkpoint. In quiescent cells, NDR1 localized mainly in the cytoplasm. After UV irradiation, NDR1 accumulated inmore » the nucleus. The siRNA knockdown of NDR1 delayed the repair of UV-induced cyclobutane pyrimidine dimers in both normal cells and cancer cells. It did not, however, alter the expression levels or the chromatin association levels of the core NER factors following UV irradiation. Instead, the NDR1-depleted cells displayed reduced activity of ATR for some set of its substrates including CHK1 and p53, suggesting that NDR1 modulates NER indirectly via the ATR pathway. - Highlights: • NDR1 is a novel XPA-interacting protein. • NDR1 accumulates in the nucleus in response to UV irradiation. • NDR1 modulates NER (nucleotide excision repair) by modulating the UV-induced DNA-damage checkpoint response.« less

Upregulated Op18/stathmin activity causes chromosomal instability through a mechanism that evades the spindle assembly checkpoint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holmfeldt, Per; Sellin, Mikael E.; Gullberg, Martin, E-mail: Martin.Gullberg@molbiol.umu.se

2010-07-15

Op18/stathmin (Op18) is a microtubule-destabilizing protein that is phosphorylation-inactivated during mitosis and its normal function is to govern tubulin subunit partitioning during interphase. Human tumors frequently overexpress Op18 and a tumor-associated Q18{yields}E mutation has been identified that confers hyperactivity, destabilizes spindle microtubules, and causes mitotic aberrancies, polyploidization, and chromosome loss in K562 leukemia cells. Here we determined whether wild-type and mutant Op18 have the potential to cause chromosomal instability by some means other than interference with spindle assembly, and thereby bypassing the spindle assembly checkpoint. Our approach was based on Op18 derivatives with distinct temporal order of activity during mitosis,more » conferred either by differential phosphorylation inactivation or by anaphase-specific degradation through fusion with the destruction box of cyclin B1. We present evidence that excessive Op18 activity generates chromosomal instability through interference occurring subsequent to the metaphase-to-anaphase transition, which reduces the fidelity of chromosome segregation to spindle poles during anaphase. Similar to uncorrected merotelic attachment, this mechanism evades detection by the spindle assembly checkpoint and thus provides an additional route to chromosomal instability.« less

Inhibition of the spindle assembly checkpoint kinase Mps-1 as a novel therapeutic strategy in malignant mesothelioma

PubMed Central

Szymiczek, Agata; Carbone, Michele; Pastorino, Sandra; Napolitano, Andrea; Tanji, Mika; Minaai, Michael; Pagano, Ian; Mason, Jacqueline M.; Pass, Harvey I.; Bray, Mark R.; Mak, Tak W.; Yang, Haining

2017-01-01

Malignant mesothelioma (MM) is an aggressive malignancy, highly resistant to current medical and surgical therapies, whose tumor cells characteristically show a high level of aneuploidy and genomic instability. We tested our hypothesis that targeting chromosomal instability in MM would improve response to therapy. TTK/Mps-1 (monopolar spindle 1 kinase) is a kinase of the spindle assembly checkpoint that controls cell division and cell fate. CFI-402257 is a novel, selective inhibitor of Mps-1 with antineoplastic activity. We found that CFI-402257 suppresses MM growth. We found that Mps-1 is overexpressed in MM and that its expression correlates with poor patients’ outcome. In vitro, CFI-402257-mediated inhibition of Mps-1 resulted in abrogation of the mitotic checkpoint, premature progression through mitosis, marked aneuploidy and mitotic catastrophe. In vivo, CFI-402257 reduced MM growth in an orthotopic, syngeneic model, when used as a single agent, and more so when used in combination with cisplatin+pemetrexed, the current standard of care. Our preclinical findings indicate that CFI-402257 is a promising novel therapeutic agent to improve the efficacy of the current chemotherapeutic regimens for MM patients. PMID:28759042

The effect on teen driving outcomes of the Checkpoints Program in a state-wide trial.

PubMed

Simons-Morton, Bruce G; L Hartos, Jessica; Leaf, William A; Preusser, David F

2006-09-01

Crash rates among teenagers are highly elevated during the first months of licensure. Parent-imposed driving restrictions on initial driving privileges can reduce exposure to high-risk driving conditions, thus reducing crash risk while teens' driving proficiency develops. This report describes the effect of the Checkpoints Program on driving limits and outcomes. Connecticut teens who obtained a learners permit over a 9-month period were recruited, providing a final sample of 3743 who obtained driver licenses. Families were randomized to the intervention or comparison condition. Intervention families received by mail a series of persuasive communications related to high-risk teen driving and a parent-teen driving agreement, while comparison families received on the same schedule general information on driving and vehicle maintenance. Relative to the comparison group, teens and parents in the Checkpoints Program reported significantly greater limits on high-risk teen driving conditions at licensure, 3-, and 6-months post-licensure; and intervention teens reported significantly less risky driving at each reporting period. By the 12-month follow up teens in the intervention group were significantly less likely than those in the comparison group to have had a traffic violation. However, no treatment group effect was found for crashes. This is the first study to report significant effects on teen driving behavior and performance of education designed to increase parental-imposed teen driving limits.

Design checkpoint kinase 2 inhibitors by pharmacophore modeling and virtual screening techniques.

PubMed

Wang, Yen-Ling; Lin, Chun-Yuan; Shih, Kuei-Chung; Huang, Jui-Wen; Tang, Chuan-Yi

2013-12-01

Damage to DNA is caused by ionizing radiation, genotoxic chemicals or collapsed replication forks. When DNA is damaged or cells fail to respond, a mutation that is associated with breast or ovarian cancer may occur. Mammalian cells control and stabilize the genome using a cell cycle checkpoint to prevent damage to DNA or to repair damaged DNA. Checkpoint kinase 2 (Chk2) is one of the important kinases, which strongly affects DNA-damage and plays an important role in the response to the breakage of DNA double-strands and related lesions. Therefore, this study concerns Chk2. Its purpose is to find potential inhibitors using the pharmacophore hypotheses (PhModels) and virtual screening techniques. PhModels can identify inhibitors with high biological activities and virtual screening techniques are used to screen the database of the National Cancer Institute (NCI) to retrieve compounds that exhibit all of the pharmacophoric features of potential inhibitors with high interaction energy. Ten PhModels were generated using the HypoGen best algorithm. The established PhModel, Hypo01, was evaluated by performing a cost function analysis of its correlation coefficient (r), root mean square deviation (RMSD), cost difference, and configuration cost, with the values 0.955, 1.28, 192.51, and 16.07, respectively. The result of Fischer's cross-validation test for the Hypo01 model yielded a 95% confidence level, and the correlation coefficient of the testing set (rtest) had a best value of 0.81. The potential inhibitors were then chosen from the NCI database by Hypo01 model screening and molecular docking using the cdocker docking program. Finally, the selected compounds exhibited the identified pharmacophoric features and had a high interaction energy between the ligand and the receptor. Eighty-three potential inhibitors for Chk2 are retrieved for further study. Copyright © 2013 Elsevier Ltd. All rights reserved.

Noninvasive Imaging of Immune Checkpoint Ligand PD-L1 in Tumors and Metastases for Guiding Immunotherapy

PubMed Central

Chatterjee, Samit; Lesniak, Wojciech G.

2017-01-01

Immunotherapy holds great promise in cancer treatment. The challenges in advancing immunotherapies lie in patient stratification and monitoring therapy. Noninvasive detection of immune checkpoint ligand PD-L1 can serve as an important biomarker for guidance and monitoring of immunotherapy. Here in, we provide an overview of our efforts to develop clinically translatable PD-L1-specific imaging agents for quantitative and real-time assessment of PD-L1 expression in tumor microenvironment. PMID:28707500

DNA strand breaks signal the induction of DNA double-strand break repair in Saccharomyces cerevisiae.

PubMed

Singh, Rakesh Kumar; Krishna, Malini

2005-12-01

Genotoxic stress induces a checkpoint signaling cascade to generate a stress response. Saccharomyces cerevisiae shows an altered radiation response under different type of stress. Although the induction of repair has been implicated in enhanced survival after exposure to the challenging stress, the nature of the signal remains poorly understood. This study demonstrates that low doses of gamma radiation and bleomycin induce RAD52-dependent recombination repair pathway in the wild-type strain D-261. Prior exposure of cells to DNA-damaging agents (gamma radiation or bleomycin) equips them better for the subsequent damage caused by challenging doses. However, exposure to UV light, which does not cause strand breaks, was ineffective. This was confirmed by PFGE studies. This indicates that the strand breaks probably serve as the signal for induction of the recombination repair pathway while pyrimidine dimers do not. The nature of the induced repair was investigated by mutation scoring in special strain D-7, which showed that the induced repair is essentially error free.

Prior expectations facilitate metacognition for perceptual decision.

PubMed

Sherman, M T; Seth, A K; Barrett, A B; Kanai, R

2015-09-01

The influential framework of 'predictive processing' suggests that prior probabilistic expectations influence, or even constitute, perceptual contents. This notion is evidenced by the facilitation of low-level perceptual processing by expectations. However, whether expectations can facilitate high-level components of perception remains unclear. We addressed this question by considering the influence of expectations on perceptual metacognition. To isolate the effects of expectation from those of attention we used a novel factorial design: expectation was manipulated by changing the probability that a Gabor target would be presented; attention was manipulated by instructing participants to perform or ignore a concurrent visual search task. We found that, independently of attention, metacognition improved when yes/no responses were congruent with expectations of target presence/absence. Results were modeled under a novel Bayesian signal detection theoretic framework which integrates bottom-up signal propagation with top-down influences, to provide a unified description of the mechanisms underlying perceptual decision and metacognition. Copyright © 2015 Elsevier Inc. All rights reserved.

Dietary flavonoid fisetin induces a forced exit from mitosis by targeting the mitotic spindle checkpoint

PubMed Central

Salmela, Anna-Leena; Pouwels, Jeroen; Varis, Asta; Kukkonen, Anu M.; Toivonen, Pauliina; Halonen, Pasi K.; Perälä, Merja; Kallioniemi, Olli; Gorbsky, Gary J.; Kallio, Marko J.

2009-01-01

Fisetin is a natural flavonol present in edible vegetables, fruits and wine at 2–160 μg/g concentrations and an ingredient in nutritional supplements with much higher concentrations. The compound has been reported to exert anticarcinogenic effects as well as antioxidant and anti-inflammatory activity via its ability to act as an inhibitor of cell proliferation and free radical scavenger, respectively. Our cell-based high-throughput screen for small molecules that override chemically induced mitotic arrest identified fisetin as an antimitotic compound. Fisetin rapidly compromised microtubule drug-induced mitotic block in a proteasome-dependent manner in several human cell lines. Moreover, in unperturbed human cancer cells fisetin caused premature initiation of chromosome segregation and exit from mitosis without normal cytokinesis. To understand the molecular mechanism behind these mitotic errors, we analyzed the consequences of fisetin treatment on the localization and phoshorylation of several mitotic proteins. Aurora B, Bub1, BubR1 and Cenp-F rapidly lost their kinetochore/centromere localization and others became dephosphorylated upon addition of fisetin to the culture medium. Finally, we identified Aurora B kinase as a novel direct target of fisetin. The activity of Aurora B was significantly reduced by fisetin in vitro and in cells, an effect that can explain the observed forced mitotic exit, failure of cytokinesis and decreased cell viability. In conclusion, our data propose that fisetin perturbs spindle checkpoint signaling, which may contribute to the antiproliferative effects of the compound. PMID:19395653

Fibroblast growth factor signaling in oligodendrocyte-lineage cells facilitates recovery of chronically demyelinated lesions but is redundant in acute lesions

PubMed Central

Furusho, M; Roulois, A; Franklin, RJM; Bansal, R

2015-01-01

Remyelination is a potent regenerative process in demyelinating diseases, such as multiple sclerosis, the effective therapeutic promotion of which will fill an unmet clinical need. The development of pro-regenerative therapies requires the identification of key regulatory targets that are likely to be involved in the integration of multiple signaling mechanisms. Fibroblast growth factor (FGF) signaling system, which comprises multiple ligands and receptors, potentially provides one such target. Since the FGF/FGF receptor (FGFR) interactions are complex and regulate multiple diverse functions of oligodendrocyte lineage cells, it is difficult to predict their overall therapeutic potential in the regeneration of oligodendrocytes and myelin. Therefore, to assess the integrated effects of FGFR signaling on this process, we simultaneously inactivated both FGFR1 and FGFR2 in oligodendrocytes and their precursors using two Cre-driver mouse lines. Acute and chronic cuprizone-induced or lysolecithin-induced demyelination was established in Fgfr1/Fgfr2 double knockout mice (dKO). We found that in the acute cuprizone model, there was normal differentiation of oligodendrocytes and recovery of myelin in the corpus callosum of both control and dKO mice. Similarly, in the spinal cord, lysolecithin-induced demyelinated lesions regenerated similarly in the dKO and control mice. In contrast, in the chronic cuprizone model, fewer differentiated oligodendrocytes and less efficient myelin recovery were observed in the dKO compared to control mice. These data suggest that while cell-autonomous FGF signaling is redundant during recovery of acute demyelinated lesions, it facilitates regenerative processes in chronic demyelination. Thus, FGF-based therapies have potential value in stimulating oligodendrocyte and myelin regeneration in late-stage disease. PMID:25913734

Non-genomic oestrogen receptor signal in B lymphocytes: An approach towards therapeutic interventions for infection, autoimmunity and cancer.

PubMed

Seto, Karsen; Hoang, Minh; Santos, Thaddeus; Bandyopadhyay, Mausumi; Kindy, Mark S; Dasgupta, Subhajit

2016-07-01

The non-genomic membrane bound oestrogen receptor (mER) regulates intracellular signals through receptor-ligand interactions. The mER, along with G-protein coupled oestrogen receptor GPR 30 (GPER), induces diverse cell signalling pathways in murine lymphocytes. The mER isoform ER-alpha46 has recently been demonstrated in human B and T lymphocytes as an analogue receptor for chemokine CCL18, the signalling events of which are not clearly understood. Ligand-induced mER and GPER signalling events are shared with BCR, CD19 mediated intracellular signalling through phospholipase C, PIP2/IP3/PI3 mediated activation of Akt, MAP kinase, and mTOR. Oestrogen has the ability to induce CD40-mediated activation of B cells. The complete signalling pathways of mER, GPR30 and their interaction with other signals are targeted areas for novel drug development in B cells during infection, autoimmunity and cancer. Therefore, an in depth investigation is critical for determining shared signal outputs during B cell activation. Here, we focus on the mode of action of membrane bound ER in B cells as therapeutic checkpoints. Copyright © 2016 Elsevier Ltd. All rights reserved.

Protein Phosphatase 2A Antagonizes ATM and ATR in a Cdk2- and Cdc7-Independent DNA Damage Checkpoint

PubMed Central

Petersen, Paris; Chou, Danny M.; You, Zhongsheng; Hunter, Tony; Walter, Johannes C.; Walter, Gernot

2006-01-01

We previously used a soluble cell-free system derived from Xenopus eggs to investigate the role of protein phosphatase 2A (PP2A) in chromosomal DNA replication. We found that immunodepletion of PP2A or inhibition of PP2A by okadaic acid (OA) inhibits initiation of DNA replication by preventing loading of the initiation factor Cdc45 onto prereplication complexes. Evidence was provided that PP2A counteracts an inhibitory protein kinase that phosphorylates and inactivates a crucial Cdc45 loading factor. Here, we report that the inhibitory effect of OA is abolished by caffeine, an inhibitor of the checkpoint kinases ataxia-telangiectasia mutated protein (ATM) and ataxia-telangiectasia related protein (ATR) but not by depletion of ATM or ATR from the extract. Furthermore, we demonstrate that double-strand DNA breaks (DSBs) cause inhibition of Cdc45 loading and initiation of DNA replication and that caffeine, as well as immunodepletion of either ATM or ATR, abolishes this inhibition. Importantly, the DSB-induced inhibition of Cdc45 loading is prevented by addition of the catalytic subunit of PP2A to the extract. These data suggest that DSBs and OA prevent Cdc45 loading through different pathways, both of which involve PP2A, but only the DSB-induced checkpoint implicates ATM and ATR. The inhibitory effect of DSBs on Cdc45 loading does not result from downregulation of cyclin-dependent kinase 2 (Cdk2) or Cdc7 activity and is independent of Chk2. However, it is partially dependent on Chk1, which becomes phosphorylated in response to DSBs. These data suggest that PP2A counteracts ATM and ATR in a DNA damage checkpoint in Xenopus egg extracts. PMID:16479016

Induction of Mitotic Cell Death by Overriding G2/M Checkpoint in Endometrial Cancer Cells with Non-functional p53

PubMed Central

Meng, Xiangbing; Laidler, Laura L.; Kosmacek, Elizabeth A.; Yang, Shujie; Xiong, Zhi; Zhu, Danlin; Wang, Xinjun; Dai, Donghai; Zhang, Yuping; Wang, Xiaofang; Brachova, Pavla; Albitar, Lina; Liu, Dawei; Ianzini, Fiorenza; Mackey, Michael A.; Leslie, Kimberly K.

2012-01-01

Objective Endometrial tumors with non-functional p53, such as serous uterine endometrial carcinomas, are aggressive malignancies with a poor outcome, yet they have an Achilles’ heel: due to loss of p53 function, these tumors may be sensitive to treatments which abrogate the G2/M checkpoint. Our objective was to exploit this weakness to induce mitotic cell death using two strategies: (1) EGFR inhibitor gefitinib combined with paclitaxel to arrest cells at mitosis, or (2) BI2536, an inhibitor of polo-like kinase 1 (PLK1), to block PLK1 activity. Methods We examined the impact of combining gefitinib and paclitaxel or PLK1 inhibitor on expression of G2/M checkpoint controllers, cell viability, and cell cycle progression in endometrial cancer cells with mutant p53. Results In cells lacking normal p53 activity, each treatment activated CDC25C and inactivated Wee1, which in turn activated cdc2 and sent cells rapidly through the G2/M checkpoint and into mitosis. Live cell imaging demonstrated irreversible mitotic arrest and eventual cell death. Combinatorial therapy with paclitaxel and gefitinib was highly synergistic and resulted in a 10-fold reduction in the IC50 for paclitaxel, from 14 nM as a single agent to 1.3 nM in the presence of gefitinib. However, BI2536 alone at low concentrations (5 nM) was the most effective treatment and resulted in massive mitotic cell death. In a xenograft mouse model with p53-deficient cells, low dose BI2536 significantly inhibited tumor growth. Conclusions These findings reveal induction of mitotic cell death as a therapeutic strategy for endometrial tumors lacking functional p53. PMID:23146687

The contribution of the S-phase checkpoint genes MEC1 and SGS1 to genome stability maintenance in Candida albicans

PubMed Central

Legrand, Melanie; Chan, Christine L.; Jauert, Peter A.; Kirkpatrick, David T.

2011-01-01

Genome rearrangements, a common feature of Candida albicans isolates, are often associated with the acquisition of antifungal drug resistance. In Saccharomyces cerevisiae, perturbations in the S-phase checkpoints result in the same sort of Gross Chromosomal Rearrangements (GCRs) observed in C. albicans. Several proteins are involved in the S. cerevisiae cell cycle checkpoints, including Mec1p, a protein kinase of the PIKK (phosphatidyl inositol 3-kinase-like kinase) family and the central player in the DNA damage checkpoint. Sgs1p, the ortholog of BLM, the Bloom’s syndrome gene, is a RecQ-related DNA helicase; cells from BLM patients are characterized by an increase in genome instability. Yeast strains bearing deletions in MEC1 or SGS1 are viable (in contrast to the inviability seen with loss of MEC1 in S. cerevisiae) but the different deletion mutants have significantly different phenotypes. The mec1Δ/Δ colonies have a wild-type colony morphology, while the sgs1Δ/Δ mutants are slow-growing, producing wrinkled colonies with pseudohyphal-like cells. The mec1Δ/Δ mutants are only sensitive to ethylmethane sulfonate (EMS), methylmethane sulfonate (MMS), and hydroxyurea (HU) but the sgs1Δ/Δ mutants exhibit a high sensitivity to all DNA-damaging agents tested. In an assay for chromosome 1 integrity, the mec1Δ/Δ mutants exhibit an increase in genome instability; no change was observed in the sgs1Δ/Δ mutants. Finally, loss of MEC1 does not affect sensitivity to the antifungal drug fluconazole, while loss of SGS1 leads to an increased susceptibility to fluconazole. Neither deletion elevated the level of antifungal drug resistance acquisition. PMID:21511048

Combination therapy of cancer with cancer vaccine and immune checkpoint inhibitors: A mathematical model

PubMed Central

Friedman, Avner

2017-01-01

In this paper we consider a combination therapy of cancer. One drug is a vaccine which activates dendritic cells so that they induce more T cells to infiltrate the tumor. The other drug is a checkpoint inhibitor, which enables the T cells to remain active against the cancer cells. The two drugs are positively correlated in the sense that an increase in the amount of each drug results in a reduction in the tumor volume. We consider the question whether a treatment with combination of the two drugs at certain levels is preferable to a treatment by one of the drugs alone at ‘roughly’ twice the dosage level; if that is the case, then we say that there is a positive ‘synergy’ for this combination of dosages. To address this question, we develop a mathematical model using a system of partial differential equations. The variables include dendritic and cancer cells, CD4+ and CD8+ T cells, IL-12 and IL-2, GM-CSF produced by the vaccine, and a T cell checkpoint inhibitor associated with PD-1. We use the model to explore the efficacy of the two drugs, separately and in combination, and compare the simulations with data from mouse experiments. We next introduce the concept of synergy between the drugs and develop a synergy map which suggests in what proportion to administer the drugs in order to achieve the maximum reduction of tumor volume under the constraint of maximum tolerated dose. PMID:28542574

The human papillomavirus type 58 E7 oncoprotein modulates cell cycle regulatory proteins and abrogates cell cycle checkpoints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Weifang; Department of Microbiology, School of Medicine, Shandong University, Jinan, Shandong; Li Jing

2010-02-05

HPV type 58 (HPV-58) is the third most common HPV type in cervical cancer from Eastern Asia, yet little is known about how it promotes carcinogenesis. In this study, we demonstrate that HPV-58 E7 significantly promoted the proliferation and extended the lifespan of primary human keratinocytes (PHKs). HPV-58 E7 abrogated the G1 and the postmitotic checkpoints, although less efficiently than HPV-16 E7. Consistent with these observations, HPV-58 E7 down-regulated the cellular tumor suppressor pRb to a lesser extent than HPV-16 E7. Similar to HPV-16 E7 expressing PHKs, Cdk2 remained active in HPV-58 E7 expressing PHKs despite the presence of elevatedmore » levels of p53 and p21. Interestingly, HPV-58 E7 down-regulated p130 more efficiently than HPV-16 E7. Our study demonstrates a correlation between the ability of down-regulating pRb/p130 and abrogating cell cycle checkpoints by HPV-58 E7, which also correlates with the biological risks of cervical cancer progression associated with HPV-58 infection.« less

Proteolytic degradation of regulator of G protein signaling 2 facilitates temporal regulation of Gq/11 signaling and vascular contraction.

PubMed

Kanai, Stanley M; Edwards, Alethia J; Rurik, Joel G; Osei-Owusu, Patrick; Blumer, Kendall J

2017-11-24

Regulator of G protein signaling 2 (RGS2) controls signaling by receptors coupled to the G q/11 class heterotrimeric G proteins. RGS2 deficiency causes several phenotypes in mice and occurs in several diseases, including hypertension in which a proteolytically unstable RGS2 mutant has been reported. However, the mechanisms and functions of RGS2 proteolysis remain poorly understood. Here we addressed these questions by identifying degradation signals in RGS2, and studying dynamic regulation of G q/11 -evoked Ca 2+ signaling and vascular contraction. We identified a novel bipartite degradation signal in the N-terminal domain of RGS2. Mutations disrupting this signal blunted proteolytic degradation downstream of E3 ubiquitin ligase binding to RGS2. Analysis of RGS2 mutants proteolyzed at various rates and the effects of proteasome inhibition indicated that proteolytic degradation controls agonist efficacy by setting RGS2 protein expression levels, and affecting the rate at which cells regain agonist responsiveness as synthesis of RGS2 stops. Analyzing contraction of mesenteric resistance arteries supported the biological relevance of this mechanism. Because RGS2 mRNA expression often is strikingly and transiently up-regulated and then down-regulated upon cell stimulation, our findings indicate that proteolytic degradation tightly couples RGS2 transcription, protein levels, and function. Together these mechanisms provide tight temporal control of G q/11 -coupled receptor signaling in the cardiovascular, immune, and nervous systems. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Incidence of Thyroid Function Test Abnormalities in Patients Receiving Immune-Checkpoint Inhibitors for Cancer Treatment.

PubMed

Patel, Nisha Subhash; Oury, Anais; Daniels, Gregory A; Bazhenova, Lyudmila; Patel, Sandip Pravin

2018-05-16

With the advent of immune-checkpoint inhibitor (ICI) therapy (anti-CTLA-4, anti-PD-1), immune-related adverse events such as thyroid function test abnormalities (TFTAs) are common, with a reported incidence range of 2%-15% depending upon the ICI used. The aim of this study is to describe the incidence of TFTAs retrospectively in patients who received ICI therapy. A total of 285 patients were reviewed (178 male, 107 female; 16-94 years of age), of whom 218 had no baseline TFTAs, 61 had baseline TFTAs, and 6 had a history of thyroidectomy (excluded). At least one dose of ipilimumab and/or nivolumab or pembrolizumab was administered. Post-ICI therapy TFTAs were classified according to standard definitions of thyroid conditions when possible. A total of 35% (76/218) patients had new-onset TFTAs on ICI therapy. Of note, 70.5% (43/61) had baseline TFTAs that were exacerbated by ICI therapy. The median times to new-onset or exacerbated baseline TFTA were 46 and 33 days, respectively. Of note, 64.5% (20/31) of patients on both ipilimumab and nivolumab had new-onset TFTAs, compared with 31.3% (15/48) on ipilimumab, 31.5% (28/89) on nivolumab, and 26% (13/50) on pembrolizumab. The incidence of TFTAs with ICI therapy was higher than previously reported. Patients with baseline TFTAs and/or who were receiving ipilimumab and nivolumab combination therapy had a higher incidence of TFTAs than patients receiving single-agent ICI therapy. We recommend more frequent evaluation of thyroid function in the first 8 weeks, especially in patients with baseline TFTAs. Increased use of immune-checkpoint inhibitors in cancer treatment has highlighted the importance of monitoring for and treating immune-related adverse events. This study was conducted to assess the incidence of thyroid function test abnormalities retrospectively in patients with cancer on immune-checkpoint inhibitors, which is not known exactly. This study is unique in that it included patients with a variety of histologic

Immune checkpoint inhibitors for non-small-cell lung cancer: does that represent a 'new frontier'?

PubMed

Pilotto, Sara; Kinspergher, Stefania; Peretti, Umberto; Calio, Anna; Carbognin, Luisa; Ferrara, Roberto; Brunelli, Matteo; Chilosi, Marco; Tortora, Giampaolo; Bria, Emilio

2015-01-01

Advances in the interpretation and understanding of cancer behaviour, particularly of its ability to evade the host immunosurveillance, deregulating the balance between inhibitory and stimulatory factors, led to the development of an innovative category of immunotherapeutic agents, currently under investigation. Although the disappointing data deriving from the employment of vaccines in non-small cell lung cancer (NSCLC), more promising results have been obtained in the early phase trials with immune checkpoint inhibitors, such as cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), programmed cell death protein-1 (PD-1) and programmed death-ligand 1 (PD-L1) inhibitors. This review delineates the main features of the available immunotherapeutic agents, focusing the discussion on immune checkpoint inhibitors, those that have already demonstrated a relevant clinical activity (such as Ipilimumab and Nivolumab) and those molecules still in early development phase. Moreover, we underline the possible emerging issues deriving from the progressive diffusion of Immuno-Oncology into the standard clinical practice. The careful and accurate identification and management of immune-related toxicities, the validation of more reliable immune response criteria and the increasing research of potential predictive biomarkers are key points of discussion. The perspective is that immunotherapy might represent an effective 'magic bullet', able to change the treatment paradigm of NSCLC, particularly of those subgroups featured by a heavily mutant cancer (squamous histology and smokers), where the immunologic agents contribute in cancer development and progression seems to be strong and, concurrently, the efficacy of standard therapies particularly limited.

Modern Languages for Communication. Teaching the Curriculum: Checkpoint A, Grades K-6. Topics, Objectives, Activities in French, German, Italian, and Spanish.

ERIC Educational Resources Information Center

Yonkers City School District, NY.

The modern language curriculum guide for grades K-6 is designed to correlate with Checkpoint A of the New York State Syllabus. It presents major topics, listing instructional objectives, functions, skill areas, suggested instructional materials, suggested activities, cultural content, and games, songs, and puzzles. Introductory sections outline…

Sperm nuclear protamines: A checkpoint to control sperm chromatin quality.

PubMed

Steger, Klaus; Balhorn, Rod

2018-05-23

Protamines are nuclear proteins which are specifically expressed in haploid male germ cells. Their replacement of histones and binding to DNA is followed by chromatin hypercondensation that protects DNA from negative influences by environmental factors. Mammalian sperm contain two types of protamines: PRM1 and PRM2. While the proportion of the two protamines is highly variable between different species, abnormal ratios within a species are known to be associated with male subfertility. Therefore, it is more than likely that correct protamine expression represents a kind of chromatin checkpoint during sperm development rendering protamines as suitable biomarkers for the estimation of sperm quality. This review presents an overview of our current knowledge on protamines comparing gene and protein structures between different mammalian species with particular consideration given to man, mouse and stallion. At last, recent insights into the possible role of inherited sperm histones for early embryo development are provided. © 2018 Blackwell Verlag GmbH.

Mitosis-specific phosphorylation of PML at T409 regulates spindle checkpoint.

PubMed

Jin, J; Liu, J

2016-08-31

During mitosis, Promyelocytic leukemia nuclear bodies (PML NBs) change dramatically in morphology and composition, but little is known about function of PML in mitosis. Here, we show that PML is phosphorylated at T409 (PML p409) in a mitosis-specific manner. More importantly, PML p409 contributes to maintain the duration of pro-metaphase and regulates spindle checkpoint. Deficient PML p409 caused a shortening of pro-metaphase and challenged the nocodazole-triggered mitotic arrest. T409A mutation led to a higher frequency of misaligned chromosomes on metaphase plate, and subsequently death in late mitosis. In addition, inhibition of PML p409 repressed growth of tumor cells, suggesting that PML p409 is a potential target for cancer therapy. Collectively, our study demonstrated an important phosphorylated site of PML, which contributed to explore the role of PML in mitosis.

Proteinase-Activated Receptor 2 May Drive Cancer Progression by Facilitating TGF-β Signaling.

PubMed

Ungefroren, Hendrik; Witte, David; Rauch, Bernhard H; Settmacher, Utz; Lehnert, Hendrik; Gieseler, Frank; Kaufmann, Roland

2017-11-22

The G protein-coupled receptor proteinase-activated receptor 2 (PAR2) has been implicated in various aspects of cellular physiology including inflammation, obesity and cancer. In cancer, it usually acts as a driver of cancer progression in various tumor types by promoting invasion and metastasis in response to activation by serine proteinases. Recently, we discovered another mode through which PAR2 may enhance tumorigenesis: crosstalk with transforming growth factor-β (TGF-β) signaling to promote TGF-β1-induced cell migration/invasion and invasion-associated gene expression in ductal pancreatic adenocarcinoma (PDAC) cells. In this chapter, we review what is known about the cellular TGF-β responses and signaling pathways affected by PAR2 expression, the signaling activities of PAR2 required for promoting TGF-β signaling, and the potential molecular mechanism(s) that underlie(s) the TGF-β signaling-promoting effect. Since PAR2 is activated through various serine proteinases and biased agonists, it may couple TGF-β signaling to a diverse range of other physiological processes that may or may not predispose cells to cancer development such as local inflammation, systemic coagulation and pathogen infection.

Immune checkpoint inhibitors and targeted therapies for metastatic melanoma: A network meta-analysis.

PubMed

Pasquali, Sandro; Chiarion-Sileni, Vanna; Rossi, Carlo Riccardo; Mocellin, Simone

2017-03-01

Immune checkpoint inhibitors and targeted therapies, two new class of drugs for treatment of metastatic melanoma, have not been compared in randomized controlled trials (RCT). We quantitatively summarized the evidence and compared immune and targeted therapies in terms of both efficacy and toxicity. A comprehensive search for RCTs of immune checkpoint inhibitors and targeted therapies was conducted to August 2016. Using a network meta-analysis approach, treatments were compared with each other and ranked based on their effectiveness (as measured by the impact on progression-free survival [PFS]) and acceptability (the inverse of high grade toxicity). Twelve RCTs enrolling 6207 patients were included. Network meta-analysis generated 15 comparisons. Combined BRAF and MEK inhibitors were associated with longer PFS as compared to anti-CTLA4 (HR: 0.22; 95% confidence interval [CI]: 0.12-0.41) and anti-PD1 antibodies alone (HR: 0.38; CI: 0.20-0.72). However, anti-PD1 monoclonal antibodies were less toxic than anti-CTLA4 monoclonal antibodies (RR: 0.65; CI: 0.40-0.78) and their combination significantly increased toxicity compared to either single agent anti-CTLA4 (RR: 2.06; CI: 1.45-2.93) or anti-PD1 monoclonal antibodies (RR: 3.67; CI: 2.27-5.96). Consistently, ranking analysis suggested that the combination of targeted therapies is the most effective strategy, whereas single agent anti-PD1 antibodies have the best acceptability. The GRADE level of evidence quality for these findings was moderate to low. The simultaneous inhibition of BRAF and MEK appears the most effective treatment for melanomas harboring BRAF V600 mutation, although anti-PD1 antibodies appear to be less toxic. Further research is needed to increase the quality of evidence. Copyright © 2017 Elsevier Ltd. All rights reserved.

Histone deacetylase and Cullin3-REN(KCTD11) ubiquitin ligase interplay regulates Hedgehog signalling through Gli acetylation.

PubMed

Canettieri, Gianluca; Di Marcotullio, Lucia; Greco, Azzura; Coni, Sonia; Antonucci, Laura; Infante, Paola; Pietrosanti, Laura; De Smaele, Enrico; Ferretti, Elisabetta; Miele, Evelina; Pelloni, Marianna; De Simone, Giuseppina; Pedone, Emilia Maria; Gallinari, Paola; Giorgi, Alessandra; Steinkühler, Christian; Vitagliano, Luigi; Pedone, Carlo; Schinin, M Eugenià; Screpanti, Isabella; Gulino, Alberto

2010-02-01

Hedgehog signalling is crucial for development and is deregulated in several tumours, including medulloblastoma. Regulation of the transcriptional activity of Gli (glioma-associated oncogene) proteins, effectors of the Hedgehog pathway, is poorly understood. We show here that Gli1 and Gli2 are acetylated proteins and that their HDAC-mediated deacetylation promotes transcriptional activation and sustains a positive autoregulatory loop through Hedgehog-induced upregulation of HDAC1. This mechanism is turned off by HDAC1 degradation through an E3 ubiquitin ligase complex formed by Cullin3 and REN, a Gli antagonist lost in human medulloblastoma. Whereas high HDAC1 and low REN expression in neural progenitors and medulloblastomas correlates with active Hedgehog signalling, loss of HDAC activity suppresses Hedgehog-dependent growth of neural progenitors and tumour cells. Consistent with this, abrogation of Gli1 acetylation enhances cellular proliferation and transformation. These data identify an integrated HDAC- and ubiquitin-mediated circuitry, where acetylation of Gli proteins functions as an unexpected key transcriptional checkpoint of Hedgehog signalling.

Airborne Signals from a Wounded Leaf Facilitate Viral Spreading and Induce Antibacterial Resistance in Neighboring Plants

PubMed Central

Dorokhov, Yuri L.; Komarova, Tatiana V.; Petrunia, Igor V.; Frolova, Olga Y.; Pozdyshev, Denis V.; Gleba, Yuri Y.

2012-01-01

Many plants release airborne volatile compounds in response to wounding due to pathogenic assault. These compounds serve as plant defenses and are involved in plant signaling. Here, we study the effects of pectin methylesterase (PME)-generated methanol release from wounded plants (“emitters”) on the defensive reactions of neighboring “receiver” plants. Plant leaf wounding resulted in the synthesis of PME and a spike in methanol released into the air. Gaseous methanol or vapors from wounded PME-transgenic plants induced resistance to the bacterial pathogen Ralstonia solanacearum in the leaves of non-wounded neighboring “receiver” plants. In experiments with different volatile organic compounds, gaseous methanol was the only airborne factor that could induce antibacterial resistance in neighboring plants. In an effort to understand the mechanisms by which methanol stimulates the antibacterial resistance of “receiver” plants, we constructed forward and reverse suppression subtractive hybridization cDNA libraries from Nicotiana benthamiana plants exposed to methanol. We identified multiple methanol-inducible genes (MIGs), most of which are involved in defense or cell-to-cell trafficking. We then isolated the most affected genes for further analysis: β-1,3-glucanase (BG), a previously unidentified gene (MIG-21), and non-cell-autonomous pathway protein (NCAPP). Experiments with Tobacco mosaic virus (TMV) and a vector encoding two tandem copies of green fluorescent protein as a tracer of cell-to-cell movement showed the increased gating capacity of plasmodesmata in the presence of BG, MIG-21, and NCAPP. The increased gating capacity is accompanied by enhanced TMV reproduction in the “receivers”. Overall, our data indicate that methanol emitted by a wounded plant acts as a signal that enhances antibacterial resistance and facilitates viral spread in neighboring plants. PMID:22496658

The Robustness of a Signaling Complex to Domain Rearrangements Facilitates Network Evolution

PubMed Central

Sato, Paloma M.; Yoganathan, Kogulan; Jung, Jae H.; Peisajovich, Sergio G.

2014-01-01

The rearrangement of protein domains is known to have key roles in the evolution of signaling networks and, consequently, is a major tool used to synthetically rewire networks. However, natural mutational events leading to the creation of proteins with novel domain combinations, such as in frame fusions followed by domain loss, retrotranspositions, or translocations, to name a few, often simultaneously replace pre-existing genes. Thus, while proteins with new domain combinations may establish novel network connections, it is not clear how the concomitant deletions are tolerated. We investigated the mechanisms that enable signaling networks to tolerate domain rearrangement-mediated gene replacements. Using as a model system the yeast mitogen activated protein kinase (MAPK)-mediated mating pathway, we analyzed 92 domain-rearrangement events affecting 11 genes. Our results indicate that, while domain rearrangement events that result in the loss of catalytic activities within the signaling complex are not tolerated, domain rearrangements can drastically alter protein interactions without impairing function. This suggests that signaling complexes can maintain function even when some components are recruited to alternative sites within the complex. Furthermore, we also found that the ability of the complex to tolerate changes in interaction partners does not depend on long disordered linkers that often connect domains. Taken together, our results suggest that some signaling complexes are dynamic ensembles with loose spatial constraints that could be easily re-shaped by evolution and, therefore, are ideal targets for cellular engineering. PMID:25490747

A link between mitotic entry and membrane growth suggests a novel model for cell size control

PubMed Central

Anastasia, Steph D.; Nguyen, Duy Linh; Thai, Vu; Meloy, Melissa; MacDonough, Tracy

2012-01-01

Addition of new membrane to the cell surface by membrane trafficking is necessary for cell growth. In this paper, we report that blocking membrane traffic causes a mitotic checkpoint arrest via Wee1-dependent inhibitory phosphorylation of Cdk1. Checkpoint signals are relayed by the Rho1 GTPase, protein kinase C (Pkc1), and a specific form of protein phosphatase 2A (PP2ACdc55). Signaling via this pathway is dependent on membrane traffic and appears to increase gradually during polar bud growth. We hypothesize that delivery of vesicles to the site of bud growth generates a signal that is proportional to the extent of polarized membrane growth and that the strength of the signal is read by downstream components to determine when sufficient growth has occurred for initiation of mitosis. Growth-dependent signaling could explain how membrane growth is integrated with cell cycle progression. It could also control both cell size and morphogenesis, thereby reconciling divergent models for mitotic checkpoint function. PMID:22451696

A link between mitotic entry and membrane growth suggests a novel model for cell size control.

PubMed

Anastasia, Steph D; Nguyen, Duy Linh; Thai, Vu; Meloy, Melissa; MacDonough, Tracy; Kellogg, Douglas R

2012-04-02

Addition of new membrane to the cell surface by membrane trafficking is necessary for cell growth. In this paper, we report that blocking membrane traffic causes a mitotic checkpoint arrest via Wee1-dependent inhibitory phosphorylation of Cdk1. Checkpoint signals are relayed by the Rho1 GTPase, protein kinase C (Pkc1), and a specific form of protein phosphatase 2A (PP2A(Cdc55)). Signaling via this pathway is dependent on membrane traffic and appears to increase gradually during polar bud growth. We hypothesize that delivery of vesicles to the site of bud growth generates a signal that is proportional to the extent of polarized membrane growth and that the strength of the signal is read by downstream components to determine when sufficient growth has occurred for initiation of mitosis. Growth-dependent signaling could explain how membrane growth is integrated with cell cycle progression. It could also control both cell size and morphogenesis, thereby reconciling divergent models for mitotic checkpoint function.

The Possible Crosstalk of MOB2 With NDR1/2 Kinases in Cell Cycle and DNA Damage Signaling.

PubMed

Gundogdu, Ramazan; Hergovich, Alexander

2016-09-06

This article is the authors' opinion of the roles of the signal transducer Mps one binder 2 (MOB2) in the control of cell cycle progression and the DNA Damage Response (DDR). We recently found that endogenous MOB2 is required to prevent the accumulation of endogenous DNA damage in order to prevent the undesired, and possibly detrimental, activation of cell cycle checkpoints. In this regard, it is noteworthy that MOB2 has been linked biochemically to the regulation of the NDR1/2 (aka STK38/STK38L) protein kinases, which themselves have functions at different steps of the cell cycle. Therefore, we are speculating in this article about the possible connections of MOB2 with NDR1/2 kinases in cell cycle and DDR Signaling.

Transient Suppression of TGFβ Receptor Signaling Facilitates Human Islet Transplantation

PubMed Central

Fischbach, Shane; Song, Zewen; Gaffar, Iljana; Zimmerman, Ray; Wiersch, John; Prasadan, Krishna; Shiota, Chiyo; Guo, Ping; Ramachandran, Sabarinathan; Witkowski, Piotr

2016-01-01

Although islet transplantation is an effective treatment for severe diabetes, its broad application is greatly limited due to a shortage of donor islets. Suppression of TGFβ receptor signaling in β-cells has been shown to increase β-cell proliferation in mice, but has not been rigorously examined in humans. Here, treatment of human islets with a TGFβ receptor I inhibitor, SB-431542 (SB), significantly improved C-peptide secretion by β-cells, and significantly increased β-cell number by increasing β-cell proliferation. In addition, SB increased cell-cycle activators and decreased cell-cycle suppressors in human β-cells. Transplantation of SB-treated human islets into diabetic immune-deficient mice resulted in significant improvement in blood glucose control, significantly higher serum and graft insulin content, and significantly greater increases in β-cell proliferation in the graft, compared with controls. Thus, our data suggest that transient suppression of TGFβ receptor signaling may improve the outcome of human islet transplantation, seemingly through increasing β-cell number and function. PMID:26872091

Alternative assembly of respiratory complex II connects energy stress to metabolic checkpoints.

PubMed

Bezawork-Geleta, Ayenachew; Wen, He; Dong, LanFeng; Yan, Bing; Vider, Jelena; Boukalova, Stepana; Krobova, Linda; Vanova, Katerina; Zobalova, Renata; Sobol, Margarita; Hozak, Pavel; Novais, Silvia Magalhaes; Caisova, Veronika; Abaffy, Pavel; Naraine, Ravindra; Pang, Ying; Zaw, Thiri; Zhang, Ping; Sindelka, Radek; Kubista, Mikael; Zuryn, Steven; Molloy, Mark P; Berridge, Michael V; Pacak, Karel; Rohlena, Jakub; Park, Sunghyouk; Neuzil, Jiri

2018-06-07

Cell growth and survival depend on a delicate balance between energy production and synthesis of metabolites. Here, we provide evidence that an alternative mitochondrial complex II (CII) assembly, designated as CII low , serves as a checkpoint for metabolite biosynthesis under bioenergetic stress, with cells suppressing their energy utilization by modulating DNA synthesis and cell cycle progression. Depletion of CII low leads to an imbalance in energy utilization and metabolite synthesis, as evidenced by recovery of the de novo pyrimidine pathway and unlocking cell cycle arrest from the S-phase. In vitro experiments are further corroborated by analysis of paraganglioma tissues from patients with sporadic, SDHA and SDHB mutations. These findings suggest that CII low is a core complex inside mitochondria that provides homeostatic control of cellular metabolism depending on the availability of energy.

Inhibition of the B7-H3 immune checkpoint limits tumor growth by enhancing cytotoxic lymphocyte function.

PubMed

Lee, Young-Hee; Martin-Orozco, Natalia; Zheng, Peilin; Li, Jing; Zhang, Peng; Tan, Haidong; Park, Hyun Jung; Jeong, Mira; Chang, Seon Hee; Kim, Byung-Seok; Xiong, Wei; Zang, Wenjuan; Guo, Li; Liu, Yang; Dong, Zhong-Jun; Overwijk, Willem W; Hwu, Patrick; Yi, Qing; Kwak, Larry; Yang, Zhiying; Mak, Tak W; Li, Wei; Radvanyi, Laszlo G; Ni, Ling; Liu, Dongfang; Dong, Chen

2017-08-01

The interaction between tumor and the immune system is still poorly understood. Significant clinical responses have been achieved in cancer patients treated with antibodies against the CTLA4 and PD-1/PD-L1 checkpoints; however, only a small portion of patients responded to the therapies, indicating a need to explore additional co-inhibitory molecules for cancer treatment. B7-H3, a member of the B7 superfamily, was previously shown by us to inhibit T-cell activation and autoimmunity. In this study, we have analyzed the function of B7-H3 in tumor immunity. Expression of B7-H3 was found in multiple tumor lines, tumor-infiltrating dendritic cells, and macrophages. B7-H3-deficient mice or mice treated with an antagonistic antibody to B7-H3 showed reduced growth of multiple tumors, which depended on NK and CD8 + T cells. With a putative receptor expressed by cytotoxic lymphocytes, B7-H3 inhibited their activation, and its deficiency resulted in increased cytotoxic lymphocyte function in tumor-bearing mice. Combining blockades of B7-H3 and PD-1 resulted in further enhanced therapeutic control of late-stage tumors. Taken together, our results indicate that the B7-H3 checkpoint may serve as a novel target for immunotherapy against cancer.

Alterations of the spindle checkpoint pathway in clinicopathologically aggressive CpG island methylator phenotype clear cell renal cell carcinomas.

PubMed

Arai, Eri; Gotoh, Masahiro; Tian, Ying; Sakamoto, Hiromi; Ono, Masaya; Matsuda, Akio; Takahashi, Yoriko; Miyata, Sayaka; Totsuka, Hirohiko; Chiku, Suenori; Komiyama, Motokiyo; Fujimoto, Hiroyuki; Matsumoto, Kenji; Yamada, Tesshi; Yoshida, Teruhiko; Kanai, Yae

2015-12-01

CpG-island methylator phenotype (CIMP)-positive clear cell renal cell carcinomas (RCCs) are characterized by accumulation of DNA hypermethylation of CpG islands, clinicopathological aggressiveness and poor patient outcome. The aim of this study was to clarify the molecular pathways participating in CIMP-positive renal carcinogenesis. Genome (whole-exome and copy number), transcriptome and proteome (two-dimensional image converted analysis of liquid chromatography-mass spectrometry) analyses were performed using tissue specimens of 87 CIMP-negative and 14 CIMP-positive clear cell RCCs and corresponding specimens of non-cancerous renal cortex. Genes encoding microtubule-associated proteins, such as DNAH2, DNAH5, DNAH10, RP1 and HAUS8, showed a 10% or higher incidence of genetic aberrations (non-synonymous single-nucleotide mutations and insertions/deletions) in CIMP-positive RCCs, whereas CIMP-negative RCCs lacked distinct genetic characteristics. MetaCore pathway analysis of CIMP-positive RCCs revealed that alterations of mRNA or protein expression were significantly accumulated in six pathways, all participating in the spindle checkpoint, including the "The metaphase checkpoint (p = 1.427 × 10(-6))," "Role of Anaphase Promoting Complex in cell cycle regulation (p = 7.444 × 10(-6))" and "Spindle assembly and chromosome separation (p = 9.260 × 10(-6))" pathways. Quantitative RT-PCR analysis revealed that mRNA expression levels for genes included in such pathways, i.e., AURKA, AURKB, BIRC5, BUB1, CDC20, NEK2 and SPC25, were significantly higher in CIMP-positive than in CIMP-negative RCCs. All CIMP-positive RCCs showed overexpression of Aurora kinases, AURKA and AURKB, and this overexpression was mainly attributable to increased copy number. These data suggest that abnormalities of the spindle checkpoint pathway participate in CIMP-positive renal carcinogenesis, and that AURKA and AURKB may be potential therapeutic targets in more aggressive CIMP-positive RCCs. �

Alterations of the spindle checkpoint pathway in clinicopathologically aggressive CpG island methylator phenotype clear cell renal cell carcinomas

PubMed Central

Arai, Eri; Gotoh, Masahiro; Tian, Ying; Sakamoto, Hiromi; Ono, Masaya; Matsuda, Akio; Takahashi, Yoriko; Miyata, Sayaka; Totsuka, Hirohiko; Chiku, Suenori; Komiyama, Motokiyo; Fujimoto, Hiroyuki; Matsumoto, Kenji; Yamada, Tesshi; Yoshida, Teruhiko

2015-01-01

CpG‐island methylator phenotype (CIMP)‐positive clear cell renal cell carcinomas (RCCs) are characterized by accumulation of DNA hypermethylation of CpG islands, clinicopathological aggressiveness and poor patient outcome. The aim of this study was to clarify the molecular pathways participating in CIMP‐positive renal carcinogenesis. Genome (whole‐exome and copy number), transcriptome and proteome (two‐dimensional image converted analysis of liquid chromatography‐mass spectrometry) analyses were performed using tissue specimens of 87 CIMP‐negative and 14 CIMP‐positive clear cell RCCs and corresponding specimens of non‐cancerous renal cortex. Genes encoding microtubule‐associated proteins, such as DNAH2, DNAH5, DNAH10, RP1 and HAUS8, showed a 10% or higher incidence of genetic aberrations (non‐synonymous single‐nucleotide mutations and insertions/deletions) in CIMP‐positive RCCs, whereas CIMP‐negative RCCs lacked distinct genetic characteristics. MetaCore pathway analysis of CIMP‐positive RCCs revealed that alterations of mRNA or protein expression were significantly accumulated in six pathways, all participating in the spindle checkpoint, including the “The metaphase checkpoint (p = 1.427 × 10−6),” “Role of Anaphase Promoting Complex in cell cycle regulation (p = 7.444 × 10−6)” and “Spindle assembly and chromosome separation (p = 9.260 × 10−6)” pathways. Quantitative RT‐PCR analysis revealed that mRNA expression levels for genes included in such pathways, i.e., AURKA, AURKB, BIRC5, BUB1, CDC20, NEK2 and SPC25, were significantly higher in CIMP‐positive than in CIMP‐negative RCCs. All CIMP‐positive RCCs showed overexpression of Aurora kinases, AURKA and AURKB, and this overexpression was mainly attributable to increased copy number. These data suggest that abnormalities of the spindle checkpoint pathway participate in CIMP‐positive renal carcinogenesis, and that AURKA and AURKB may be potential

Potent activity of nobiletin-rich Citrus reticulata peel extract to facilitate cAMP/PKA/ERK/CREB signaling associated with learning and memory in cultured hippocampal neurons: identification of the substances responsible for the pharmacological action.

PubMed

Kawahata, Ichiro; Yoshida, Masaaki; Sun, Wen; Nakajima, Akira; Lai, Yanxin; Osaka, Naoya; Matsuzaki, Kentaro; Yokosuka, Akihito; Mimaki, Yoshihiro; Naganuma, Akira; Tomioka, Yoshihisa; Yamakuni, Tohru

2013-10-01

cAMP/PKA/ERK/CREB signaling linked to CRE-mediated transcription is crucial for learning and memory. We originally found nobiletin as a natural compound that stimulates this intracellular signaling and exhibits anti-dementia action in animals. Citrus reticulata or C. unshiu peels are employed as "chinpi" and include a small amount of nobiletin. We here provide the first evidence for beneficial pharmacological actions on the cAMP/PKA/ERK/CREB cascade of extracts from nobiletin-rich C.reticulata peels designated as Nchinpi, the nobiletin content of which was 0.83 ± 0.13% of the dry weight or 16-fold higher than that of standard chinpi extracts. Nchinpi extracts potently facilitated CRE-mediated transcription in cultured hippocampal neurons, whereas the standard chinpi extracts showed no such activity. Also, the Nchinpi extract, but not the standard chinpi extract, stimulated PKA/ERK/CREB signaling. Interestingly, treatment with the Nchinpi extract at the concentration corresponding to approximately 5 μM nobiletin more potently facilitated CRE-mediated transcriptional activity than did 30 μM nobiletin alone. Consistently, sinensetin, tangeretin, 6-demethoxynobiletin, and 6-demethoxytangeretin were also identified as bioactive substances in Nchinpi that facilitated the CRE-mediated transcription. Purified sinensetin enhanced the transcription to a greater degree than nobiletin. Furthermore, samples reconstituted with the four purified compounds and nobiletin in the ratio of each constituent's content in the extract showed activity almost equal to that of the Nchinpi extract to stimulate CRE-mediated transcription. These findings suggest that above four compounds and nobiletin in the Nchinpi extract mainly cooperated to facilitate potently CRE-mediated transcription linked to the upstream cAMP/PKA/ERK/CREB pathway in hippocampal neurons.

The DNA damage checkpoint protein RAD9A is essential for male meiosis in the mouse

PubMed Central

Vasileva, Ana; Hopkins, Kevin M.; Wang, Xiangyuan; Weisbach, Melissa M.; Friedman, Richard A.; Wolgemuth, Debra J.; Lieberman, Howard B.

2013-01-01

Summary In mitotic cells, RAD9A functions in repairing DNA double-strand breaks (DSBs) by homologous recombination and facilitates the process by cell cycle checkpoint control in response to DNA damage. DSBs occur naturally in the germline during meiosis but whether RAD9A participates in repairing such breaks is not known. In this study, we determined that RAD9A is indeed expressed in the male germ line with a peak of expression in late pachytene and diplotene stages, and the protein was found associated with the XY body. As complete loss of RAD9A is embryonic lethal, we constructed and characterized a mouse strain with Stra8-Cre driven germ cell-specific ablation of Rad9a beginning in undifferentiated spermatogonia in order to assess its role in spermatogenesis. Adult mutant male mice were infertile or sub-fertile due to massive loss of spermatogenic cells. The onset of this loss occurs during meiotic prophase, and there was an increase in the numbers of apoptotic spermatocytes as determined by TUNEL. Spermatocytes lacking RAD9A usually arrested in meiotic prophase, specifically in pachytene. The incidence of unrepaired DNA breaks increased, as detected by accumulation of γH2AX and DMC1 foci on the axes of autosomal chromosomes in pachytene spermatocytes. The DNA topoisomerase IIβ-binding protein 1 (TOPBP1) was still localized to the sex body, albeit with lower intensity, suggesting that RAD9A may be dispensable for sex body formation. We therefore show for the first time that RAD9A is essential for male fertility and for repair of DNA DSBs during meiotic prophase I. PMID:23788429

Proteinase-Activated Receptor 2 May Drive Cancer Progression by Facilitating TGF-β Signaling

PubMed Central

Ungefroren, Hendrik; Witte, David; Settmacher, Utz; Lehnert, Hendrik; Kaufmann, Roland

2017-01-01

The G protein-coupled receptor proteinase-activated receptor 2 (PAR2) has been implicated in various aspects of cellular physiology including inflammation, obesity and cancer. In cancer, it usually acts as a driver of cancer progression in various tumor types by promoting invasion and metastasis in response to activation by serine proteinases. Recently, we discovered another mode through which PAR2 may enhance tumorigenesis: crosstalk with transforming growth factor-β (TGF-β) signaling to promote TGF-β1-induced cell migration/invasion and invasion-associated gene expression in ductal pancreatic adenocarcinoma (PDAC) cells. In this chapter, we review what is known about the cellular TGF-β responses and signaling pathways affected by PAR2 expression, the signaling activities of PAR2 required for promoting TGF-β signaling, and the potential molecular mechanism(s) that underlie(s) the TGF-β signaling–promoting effect. Since PAR2 is activated through various serine proteinases and biased agonists, it may couple TGF-β signaling to a diverse range of other physiological processes that may or may not predispose cells to cancer development such as local inflammation, systemic coagulation and pathogen infection. PMID:29165389

P38 Mitogen-activated Protein Kinase Activity Is Required during Mitosis for Timely Satisfaction of the Mitotic Checkpoint But Not for the Fidelity of Chromosome Segregation

PubMed Central

Lee, Kyunghee; Kenny, Alison E.

2010-01-01

Although p38 activity is reported to be required as cells enter mitosis for proper spindle assembly and checkpoint function, its role during the division process remains controversial in lieu of direct data. We therefore conducted live cell studies to determine the effect on mitosis of inhibiting or depleting p38. We found that in the absence of p38 activity the duration of mitosis is prolonged by ∼40% in nontransformed human RPE-1, ∼80% in PtK2 (rat kangaroo), and ∼25% in mouse cells, and this prolongation leads to an elevated mitotic index. However, under this condition chromatid segregation and cytokinesis are normal. Using Mad2/YFP-expressing cells, we show the prolongation of mitosis in the absence of p38 activity is directly due to a delay in satisfying the mitotic checkpoint. Inhibiting p38 did not affect the rate of chromosome motion; however, it did lead to the formation of significantly (10%) longer metaphase spindles. From these data we conclude that normal p38 activity is required for the timely stable attachment of all kinetochores to spindle microtubules, but not for the fidelity of the mitotic process. We speculate that p38 activity promotes timely checkpoint satisfaction by indirectly influencing those motor proteins (e.g., Klp10, Klp67A) involved in regulating the dynamics of kinetochore microtubule ends. PMID:20462950

Signaling cascades modulate the speed of signal propagation through space.

PubMed

Govern, Christopher C; Chakraborty, Arup K

2009-01-01

Cells are not mixed bags of signaling molecules. As a consequence, signals must travel from their origin to distal locations. Much is understood about the purely diffusive propagation of signals through space. Many signals, however, propagate via signaling cascades. Here, we show that, depending on their kinetics, cascades speed up or slow down the propagation of signals through space, relative to pure diffusion. We modeled simple cascades operating under different limits of Michaelis-Menten kinetics using deterministic reaction-diffusion equations. Cascades operating far from enzyme saturation speed up signal propagation; the second mobile species moves more quickly than the first through space, on average. The enhanced speed is due to more efficient serial activation of a downstream signaling module (by the signaling molecule immediately upstream in the cascade) at points distal from the signaling origin, compared to locations closer to the source. Conversely, cascades operating under saturated kinetics, which exhibit zero-order ultrasensitivity, can slow down signals, ultimately localizing them to regions around the origin. Signal speed modulation may be a fundamental function of cascades, affecting the ability of signals to penetrate within a cell, to cross-react with other signals, and to activate distant targets. In particular, enhanced speeds provide a way to increase signal penetration into a cell without needing to flood the cell with large numbers of active signaling molecules; conversely, diminished speeds in zero-order ultrasensitive cascades facilitate strong, but localized, signaling.

The Checkpoint Kinase 1 Inhibitor Prexasertib Induces Regression of Preclinical Models of Human Neuroblastoma.

PubMed

Lowery, Caitlin D; VanWye, Alle B; Dowless, Michele; Blosser, Wayne; Falcon, Beverly L; Stewart, Julie; Stephens, Jennifer; Beckmann, Richard P; Bence Lin, Aimee; Stancato, Louis F

2017-08-01

Purpose: Checkpoint kinase 1 (CHK1) is a key regulator of the DNA damage response and a mediator of replication stress through modulation of replication fork licensing and activation of S and G 2 -M cell-cycle checkpoints. We evaluated prexasertib (LY2606368), a small-molecule CHK1 inhibitor currently in clinical testing, in multiple preclinical models of pediatric cancer. Following an initial assessment of prexasertib activity, this study focused on the preclinical models of neuroblastoma. Experimental Design: We evaluated the antiproliferative activity of prexasertib in a panel of cancer cell lines; neuroblastoma cell lines were among the most sensitive. Subsequent Western blot and immunofluorescence analyses measured DNA damage and DNA repair protein activation. Prexasertib was investigated in several cell line-derived xenograft mouse models of neuroblastoma. Results: Within 24 hours, single-agent prexasertib promoted γH2AX-positive double-strand DNA breaks and phosphorylation of DNA damage sensors ATM and DNA-PKcs, leading to neuroblastoma cell death. Knockdown of CHK1 and/or CHK2 by siRNA verified that the double-strand DNA breaks and cell death elicited by prexasertib were due to specific CHK1 inhibition. Neuroblastoma xenografts rapidly regressed following prexasertib administration, independent of starting tumor volume. Decreased Ki67 and increased immunostaining of endothelial and pericyte markers were observed in xenografts after only 6 days of exposure to prexasertib, potentially indicating a swift reduction in tumor volume and/or a direct effect on tumor vasculature. Conclusions: Overall, these data demonstrate that prexasertib is a specific inhibitor of CHK1 in neuroblastoma and leads to DNA damage and cell death in preclinical models of this devastating pediatric malignancy. Clin Cancer Res; 23(15); 4354-63. ©2017 AACR . ©2017 American Association for Cancer Research.

Adenovirus Core Protein VII Protects the Viral Genome from a DNA Damage Response at Early Times after Infection▿

PubMed Central

Karen, Kasey A.; Hearing, Patrick

2011-01-01

Adenovirus has a linear, double-stranded DNA genome that is perceived by the cellular Mre11-Rad50-Nbs1 (MRN) DNA repair complex as a double-strand break. If unabated, MRN elicits a double-strand break repair response that blocks viral DNA replication and ligates the viral genomes into concatemers. There are two sets of early viral proteins that inhibit the MRN complex. The E1B-55K/E4-ORF6 complex recruits an E3 ubiquitin ligase and targets MRN proteins for proteasome-dependent degradation. The E4-ORF3 protein inhibits MRN through sequestration. The mechanism that prevents MRN recognition of the viral genome prior to the expression of these early proteins was previously unknown. Here we show a temporal correlation between the loss of viral core protein VII from the adenovirus genome and a gain of checkpoint signaling due to the double-strand break repair response. While checkpoint signaling corresponds to the recognition of the viral genome, core protein VII binding to and checkpoint signaling at viral genomes are largely mutually exclusive. Transcription is known to release protein VII from the genome, and the inhibition of transcription shows a decrease in checkpoint signaling. Finally, we show that the nuclease activity of Mre11 is dispensable for the inhibition of viral DNA replication during a DNA damage response. These results support a model involving the protection of the incoming viral genome from checkpoint signaling by core protein VII and suggest that the induction of an MRN-dependent DNA damage response may inhibit adenovirus replication by physically masking the origins of DNA replication rather than altering their integrity. PMID:21345950

Neural substrates of social facilitation effects on incentive-based performance

PubMed Central

Chib, Vikram S; Adachi, Ryo; O’Doherty, John P

2018-01-01

Abstract Throughout our lives we must perform tasks while being observed by others. Previous studies have shown that the presence of an audience can cause increases in an individual’s performance as compared to when they are not being observed—a phenomenon called ‘social facilitation’. However, the neural mechanisms underlying this effect, in the context of skilled-task performance for monetary incentives, are not well understood. We used functional magnetic resonance imaging to monitor brain activity while healthy human participants performed a skilled-task during conditions in which they were paid based on their performance and observed and not observed by an audience. We found that during social facilitation, social signals represented in the dorsomedial prefrontal cortex (dmPFC) enhanced reward value computations in ventromedial prefrontal cortex (vmPFC). We also found that functional connectivity between dmPFC and ventral striatum was enhanced when participants exhibited social facilitation effects, indicative of a means by which social signals serve to modulate brain regions involved in regulating behavioral motivation. These findings illustrate how neural processing of social judgments gives rise to the enhanced motivational state that results in social facilitation of incentive-based performance. PMID:29648653

Characterization of a Putative Spindle Assembly Checkpoint Kinase Mps1, Suggests Its Involvement in Cell Division, Morphogenesis and Oxidative Stress Tolerance in Candida albicans

PubMed Central

Ruhela, Deepa; Kamthan, Ayushi; Maiti, Protiti; Datta, Asis

2014-01-01

In Saccharomyces cerevisiae MPS1 is one of the major protein kinase that governs the spindle checkpoint pathway. The S. cerevisiae structural homolog of opportunistic pathogen Candida albicans CaMPS1, is indispensable for the cell viability. The essentiality of Mps1 was confirmed by Homozygote Trisome test. To determine its biological function in this pathogen conditional mutant was generated through regulatable MET3 promoter. Examination of heterozygous and conditional (+Met/Cys) mps1 mutants revealed a mitosis specific arrest phenotype, where mutants showed large buds with undivided nuclei. Flowcytometry analysis revealed abnormal ploidy levels in mps1mutant. In presence of anti-microtubule drug Nocodazole, mps1 mutant showed a dramatic loss of viability suggesting a role of Mps1 in Spindle Assembly Checkpoint (SAC) activation. These mutants were also defective in microtubule organization. Moreover, heterozygous mutant showed defective in-vitro yeast to hyphae morphological transition. Growth defect in heterozygous mutant suggest haploinsufficiency of this gene. qRT PCR analysis showed around 3 fold upregulation of MPS1 in presence of serum. This expression of MPS1 is dependent on Efg1and is independent of other hyphal regulators like Ras1 and Tpk2. Furthermore, mps1 mutants were also sensitive to oxidative stress. Heterozygous mps1 mutant did not undergo morphological transition and showed 5-Fold reduction in colony forming units in response to macrophage. Thus, the vital checkpoint kinase, Mps1 besides cell division also has a role in morphogenesis and oxidative stress tolerance, in this pathogenic fungus. PMID:25025778

Characterization of a putative spindle assembly checkpoint kinase Mps1, suggests its involvement in cell division, morphogenesis and oxidative stress tolerance in Candida albicans.

PubMed

Kamthan, Mohan; Nalla, Vijaya Kumar; Ruhela, Deepa; Kamthan, Ayushi; Maiti, Protiti; Datta, Asis

2014-01-01

In Saccharomyces cerevisiae MPS1 is one of the major protein kinase that governs the spindle checkpoint pathway. The S. cerevisiae structural homolog of opportunistic pathogen Candida albicans CaMPS1, is indispensable for the cell viability. The essentiality of Mps1 was confirmed by Homozygote Trisome test. To determine its biological function in this pathogen conditional mutant was generated through regulatable MET3 promoter. Examination of heterozygous and conditional (+Met/Cys) mps1 mutants revealed a mitosis specific arrest phenotype, where mutants showed large buds with undivided nuclei. Flowcytometry analysis revealed abnormal ploidy levels in mps1 mutant. In presence of anti-microtubule drug Nocodazole, mps1 mutant showed a dramatic loss of viability suggesting a role of Mps1 in Spindle Assembly Checkpoint (SAC) activation. These mutants were also defective in microtubule organization. Moreover, heterozygous mutant showed defective in-vitro yeast to hyphae morphological transition. Growth defect in heterozygous mutant suggest haploinsufficiency of this gene. qRT PCR analysis showed around 3 fold upregulation of MPS1 in presence of serum. This expression of MPS1 is dependent on Efg1 and is independent of other hyphal regulators like Ras1 and Tpk2. Furthermore, mps1 mutants were also sensitive to oxidative stress. Heterozygous mps1 mutant did not undergo morphological transition and showed 5-Fold reduction in colony forming units in response to macrophage. Thus, the vital checkpoint kinase, Mps1 besides cell division also has a role in morphogenesis and oxidative stress tolerance, in this pathogenic fungus.

An Archaeosome-Adjuvanted Vaccine and Checkpoint Inhibitor Therapy Combination Significantly Enhances Protection from Murine Melanoma

PubMed Central

Stark, Felicity C.; Weeratna, Risini D.; Deschatelets, Lise; Gurnani, Komal; Dudani, Renu; Krishnan, Lakshmi

2017-01-01

Archaeosomes constitute archaeal lipid vesicle vaccine adjuvants that evoke a strong CD8+ T cell response to antigenic cargo. Therapeutic treatment of murine B16-ovalbumin (B16-OVA) melanoma with archaeosome-OVA eliminates small subcutaneous solid tumors; however, they eventually resurge despite an increased frequency of circulating and tumor infiltrating OVA-CD8+ T cells. Herein, a number of different approaches were evaluated to improve responses, including dose number, interval, and the combination of vaccine with checkpoint inhibitors. Firstly, we found that tumor protection could not be enhanced by repetitive and/or delayed boosting to maximize the CD8+ T cell number and/or phenotype. The in vivo cytotoxicity of vaccine-induced OVA-CD8+ T cells was impaired in tumor-bearing mice. Additionally, tumor-infiltrating OVA-CD8+ T cells had an increased expression of programmed cell death protein-1 (PD-1) compared to other organ compartments, suggesting impaired function. Combination therapy of tumor-bearing mice with the vaccine archaeosome-OVA, and α-CTLA-4 administered concurrently as well as α-PD-1 and an α-PD-L1 antibody administered starting 9 days after tumor challenge given on a Q3Dx4 schedule (days 9, 12, 15 and 18), significantly enhanced survival. Following multi-combination therapy ~70% of mice had rapid tumor recession, with no detectable tumor mass after >80 days in comparison to a median survival of 17–22 days for untreated or experimental groups receiving single therapies. Overall, archaeosomes offer a powerful platform for delivering cancer antigens when used in combination with checkpoint inhibitor immunotherapies. PMID:29072624

PCP-B class pollen coat proteins are key regulators of the hydration checkpoint in Arabidopsis thaliana pollen-stigma interactions.

PubMed

Wang, Ludi; Clarke, Lisa A; Eason, Russell J; Parker, Christopher C; Qi, Baoxiu; Scott, Rod J; Doughty, James

2017-01-01

The establishment of pollen-pistil compatibility is strictly regulated by factors derived from both male and female reproductive structures. Highly diverse small cysteine-rich proteins (CRPs) have been found to play multiple roles in plant reproduction, including the earliest stages of the pollen-stigma interaction. Secreted CRPs found in the pollen coat of members of the Brassicaceae, the pollen coat proteins (PCPs), are emerging as important signalling molecules that regulate the pollen-stigma interaction. Using a combination of protein characterization, expression and phylogenetic analyses we identified a novel class of Arabidopsis thaliana pollen-borne CRPs, the PCP-Bs (for pollen coat protein B-class) that are related to embryo surrounding factor (ESF1) developmental regulators. Single and multiple PCP-B mutant lines were utilized in bioassays to assess effects on pollen hydration, adhesion and pollen tube growth. Our results revealed that pollen hydration is severely impaired when multiple PCP-Bs are lost from the pollen coat. The hydration defect also resulted in reduced pollen adhesion and delayed pollen tube growth in all mutants studied. These results demonstrate that AtPCP-Bs are key regulators of the hydration 'checkpoint' in establishment of pollen-stigma compatibility. In addition, we propose that interspecies diversity of PCP-Bs may contribute to reproductive barriers in the Brassicaceae. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Chemokine Signaling during Midline Epithelial Seam Disintegration Facilitates Palatal Fusion

PubMed Central

Suttorp, Christiaan M.; Cremers, Niels A.; van Rheden, René; Regan, Raymond F.; Helmich, Pia; van Kempen, Sven; Kuijpers-Jagtman, Anne M.; Wagener, Frank A.D.T.G.

2017-01-01

Disintegration of the midline epithelial seam (MES) is crucial for palatal fusion, and failure results in cleft palate. Palatal fusion and wound repair share many common signaling pathways related to epithelial-mesenchymal cross-talk. We postulate that chemokine CXCL11, its receptor CXCR3, and the cytoprotective enzyme heme oxygenase (HO), which are crucial during wound repair, also play a decisive role in MES disintegration. Fetal growth restriction and craniofacial abnormalities were present in HO-2 knockout (KO) mice without effects on palatal fusion. CXCL11 and CXCR3 were highly expressed in the disintegrating MES in both wild-type and HO-2 KO animals. Multiple apoptotic DNA fragments were present within the disintegrating MES and phagocytized by recruited CXCR3-positive wt and HO-2 KO macrophages. Macrophages located near the MES were HO-1-positive, and more HO-1-positive cells were present in HO-2 KO mice compared to wild-type. This study of embryonic and palatal development provided evidence that supports the hypothesis that the MES itself plays a prominent role in palatal fusion by orchestrating epithelial apoptosis and macrophage recruitment via CXCL11-CXCR3 signaling. PMID:29164113

Coordinate action of distinct sequence elements localizes checkpoint kinase Hsl1 to the septin collar at the bud neck in Saccharomyces cerevisiae

PubMed Central

Finnigan, Gregory C.; Sterling, Sarah M.; Duvalyan, Angela; Liao, Elizabeth N.; Sargsyan, Aspram; Garcia, Galo; Nogales, Eva; Thorner, Jeremy

2016-01-01

Passage through the eukaryotic cell cycle requires processes that are tightly regulated both spatially and temporally. Surveillance mechanisms (checkpoints) exert quality control and impose order on the timing and organization of downstream events by impeding cell cycle progression until the necessary components are available and undamaged and have acted in the proper sequence. In budding yeast, a checkpoint exists that does not allow timely execution of the G2/M transition unless and until a collar of septin filaments has properly assembled at the bud neck, which is the site where subsequent cytokinesis will occur. An essential component of this checkpoint is the large (1518-residue) protein kinase Hsl1, which localizes to the bud neck only if the septin collar has been correctly formed. Hsl1 reportedly interacts with particular septins; however, the precise molecular determinants in Hsl1 responsible for its recruitment to this cellular location during G2 have not been elucidated. We performed a comprehensive mutational dissection and accompanying image analysis to identify the sequence elements within Hsl1 responsible for its localization to the septins at the bud neck. Unexpectedly, we found that this targeting is multipartite. A segment of the central region of Hsl1 (residues 611–950), composed of two tandem, semiredundant but distinct septin-associating elements, is necessary and sufficient for binding to septin filaments both in vitro and in vivo. However, in addition to 611–950, efficient localization of Hsl1 to the septin collar in the cell obligatorily requires generalized targeting to the cytosolic face of the plasma membrane, a function normally provided by the C-terminal phosphatidylserine-binding KA1 domain (residues 1379–1518) in Hsl1 but that can be replaced by other, heterologous phosphatidylserine-binding sequences. PMID:27193302

SCFFBXW7α modulates the intra-S-phase DNA-damage checkpoint by regulating Polo like kinase-1 stability

PubMed Central

Giráldez, Servando; Herrero-Ruiz, Joaquín; Mora-Santos, Mar; Japón, Miguel Á.; Tortolero, Maria; Romero, Francisco

2014-01-01

The intra-S-checkpoint is essential to control cell progression through S phase under normal conditions and in response to replication stress. When DNA lesions are detected, replication fork progression is blocked allowing time for repair to avoid genomic instability and the risk of cancer. DNA replication initiates at many origins of replication in eukaryotic cells, where a series of proteins form pre-replicative complexes (pre-RCs) that are activated to become pre-initiation complexes and ensure a single round of replication in each cell cycle. PLK1 plays an important role in the regulation of DNA replication, contributing to the regulation of pre-RCs formation by phosphorylating several proteins, under both normal and stress conditions. Here we report that PLK1 is ubiquitinated and degraded by SCFFBXW7α/proteasome. Moreover, we identified a new Cdc4 phosphodegron in PLK1, conserved from yeast to humans, whose mutation prevents PLK1 destruction. We established that endogenous SCFFBXW7α degrades PLK1 in the G1 and S phases of an unperturbed cell cycle and in S phase following UV irradiation. Furthermore, we showed that FBXW7α overexpression or UV irradiation prevented the loading of proteins onto chromatin to form pre-RCs and, accordingly, reduced cell proliferation. We conclude that PLK1 degradation mediated by SCFFBXW7α modulates the intra-S-phase checkpoint. PMID:24970797

MC1R and cAMP signaling inhibit cdc25B activity and delay cell cycle progression in melanoma cells

PubMed Central

Lyons, Jesse; Bastian, Boris C.; McCormick, Frank

2013-01-01

The melanocortin 1 receptor (MC1R) mediates the tanning response through induction of cAMP and downstream pigmentary enzymes. Diminished function alleles of MC1R are associated with decreased tanning and increased melanoma risk, which has been attributed to increased rates of mutation. We have found that MC1R or cAMP signaling also directly decreases proliferation in melanoma cell lines. MC1R overexpression, treatment with the MC1R ligand, or treatment with small-molecule activators of cAMP signaling causes delayed progression from G2 into mitosis. This delay is caused by phosphorylation and inhibition of cdc25B, a cyclin dependent kinase 1-activating phosphatase, and is rescued by expression of a cdc25B mutant that cannot be phosphorylated at the serine 323 residue. These results show that MC1R and cAMP signaling can directly inhibit melanoma growth through regulation of the G2/M checkpoint. PMID:23908401

Gas1 extends the range of Hedgehog action by facilitating its signaling

PubMed Central

Martinelli, David C.; Fan, Chen-Ming

2007-01-01

Cellular signaling initiated by Hedgehog binding to Patched1 has profound importance in mammalian embryogenesis, genetic disease, and cancer. Hedgehog acts as a morphogen to specify distinctive cell fates using different concentration thresholds, but our knowledge of how the concentration gradient is interpreted into the activity gradient is incomplete. The membrane protein Growth Arrest-Specific Gene 1 (GAS1) was thought to be a negative regulator of the Hedgehog concentration gradient. Here, we report unexpected genetic evidence that Gas1 positively regulates Hedgehog signaling in multiple developmental contexts, an effect particularly noticeable at regions where Hedgehog acts at low concentration. Using a combination of in vitro cell culture and in ovo electroporation assays, we demonstrate that GAS1 acts cooperatively with Patched1 for Hedgehog binding and enhances signaling activity in a cell-autonomous manner. Our data support a model in which GAS1 helps transform the Hedgehog protein gradient into the observed activity gradient. We propose that Gas1 is an evolutionarily novel, vertebrate-specific Hedgehog pathway regulator. PMID:17504940

Regulation of Facilitative Glucose Transporters and AKT/MAPK/PRKAA Signaling via Estradiol and Progesterone in the Mouse Uterine Epithelium1

PubMed Central

Kim, Sung Tae; Moley, Kelle H.

2009-01-01

Adequate uterine glucose metabolism is an essential part of embryo implantation and the development of an adequate utero-fetal environment. However, expression of facilitative glucose transporters (GLUTs [solute transporter family SLC2A]) and AKT/MAPK/PRKAA (PRKAA) signaling has not been described in the mouse uterine cells, to our knowledge. The objective of this study was to determine the hormonal regulation of SLC2A protein expression and AKT/MAPK/PRKAA signaling in the mouse uterine epithelial cells during estrous cycles and peri-implantation periods. SLC2As 1, 4, 8, and 9B were highly expressed in the luminal and glandular epithelia of estrous stage. In metestrous and diestrous stages, expression of SLC2As 1, 4, 8, and 9B was lower than that in proestrous stage. Levels of activated phospho-AKT (p-AKT), p-MAPK3, and p-MAPK1 also varied during the estrous cycle. Estrogen and progesterone injection in an ovariectomized mouse (delayed implantation model) resulted in a decrease and an increase, respectively, in expression of GLUTs in the luminal epithelial cells of the uterus. The expression of SLC2A1, SLC2A8, SLC2A9B, p-AKT, p-MAPK3/1, and p-PRKAA was increased in the decidual region of the implantation sites and was significantly increased in the uterus of activated implantation. Using an artificial decidualization mouse model, it was also demonstrated that expression of the same GLUTs, p-MAPK3/1, and p-PRKAA was dramatically higher in the decidualized uteri than that in the control uteri. These results suggest that steroid hormones regulate expression of uterine epithelial GLUTs possibly through AKT/MAPK/PRKAA signaling pathways and that glucose utilization may have an important role in decidualization and possibly in the maintenance of pregnancy. PMID:19208550

Sustained Mps1 activity is required in mitosis to recruit O-Mad2 to the Mad1-C-Mad2 core complex.

PubMed

Hewitt, Laura; Tighe, Anthony; Santaguida, Stefano; White, Anne M; Jones, Clifford D; Musacchio, Andrea; Green, Stephen; Taylor, Stephen S

2010-07-12

Mps1 is an essential component of the spindle assembly checkpoint. In this study, we describe a novel Mps1 inhibitor, AZ3146, and use it to probe the role of Mps1's catalytic activity during mitosis. When Mps1 is inhibited before mitotic entry, subsequent recruitment of Mad1 and Mad2 to kinetochores is abolished. However, if Mps1 is inhibited after mitotic entry, the Mad1-C-Mad2 core complex remains kinetochore bound, but O-Mad2 is not recruited to the core. Although inhibiting Mps1 also interferes with chromosome alignment, we see no obvious effect on aurora B activity. In contrast, kinetochore recruitment of centromere protein E (CENP-E), a kinesin-related motor protein, is severely impaired. Strikingly, inhibition of Mps1 significantly increases its own abundance at kinetochores. Furthermore, we show that Mps1 can dimerize and transphosphorylate in cells. We propose a model whereby Mps1 transphosphorylation results in its release from kinetochores, thus facilitating recruitment of O-Mad2 and CENP-E and thereby simultaneously promoting checkpoint signaling and chromosome congression.

Development of NTCIP-based portable traffic signal evaluation system.

DOT National Transportation Integrated Search

2014-10-01

The objective of this project was to develop a custom toolbox for monitoring and troubleshooting operational : issues and faults at signalized intersections and diamond interchanges, and for providing a mechanism to : facilitate signal timing optimiz...

Fission yeast strains with circular chromosomes require the 9-1-1 checkpoint complex for the viability in response to the anti-cancer drug 5-fluorodeoxyuridine.

PubMed

Shamim, Hossain Mohammad; Minami, Yukako; Tanaka, Daiki; Ukimori, Shinobu; Murray, Johanne M; Ueno, Masaru

2017-01-01

Thymidine kinase converts 5-fluorodeoxyuridine to 5-fluorodeoxyuridine monophosphate, which causes disruption of deoxynucleotide triphosphate ratios. The fission yeast Schizosaccharomyces pombe does not express endogenous thymidine kinase but 5-fluorodeoxyuridine inhibits growth when exogenous thymidine kinase is expressed. Unexpectedly, we found that 5-fluorodeoxyuridine causes S phase arrest even without thymidine kinase expression. DNA damage checkpoint proteins such as the 9-1-1 complex were required for viability in the presence of 5-fluorodeoxyuridine. We also found that strains with circular chromosomes, due to loss of pot1+, which have higher levels of replication stress, were more sensitive to loss of the 9-1-1 complex in the presence of 5-fluorodeoxyuridine. Thus, our results suggest that strains carrying circular chromosomes exhibit a greater dependence on DNA damage checkpoints to ensure viability in the presence of 5-fluorodeoxyuridine compared to stains that have linear chromosomes.

The role of hearing ability and speech distortion in the facilitation of articulatory motor cortex.

PubMed

Nuttall, Helen E; Kennedy-Higgins, Daniel; Devlin, Joseph T; Adank, Patti

2017-01-08

Excitability of articulatory motor cortex is facilitated when listening to speech in challenging conditions. Beyond this, however, we have little knowledge of what listener-specific and speech-specific factors engage articulatory facilitation during speech perception. For example, it is unknown whether speech motor activity is independent or dependent on the form of distortion in the speech signal. It is also unknown if speech motor facilitation is moderated by hearing ability. We investigated these questions in two experiments. We applied transcranial magnetic stimulation (TMS) to the lip area of primary motor cortex (M1) in young, normally hearing participants to test if lip M1 is sensitive to the quality (Experiment 1) or quantity (Experiment 2) of distortion in the speech signal, and if lip M1 facilitation relates to the hearing ability of the listener. Experiment 1 found that lip motor evoked potentials (MEPs) were larger during perception of motor-distorted speech that had been produced using a tongue depressor, and during perception of speech presented in background noise, relative to natural speech in quiet. Experiment 2 did not find evidence of motor system facilitation when speech was presented in noise at signal-to-noise ratios where speech intelligibility was at 50% or 75%, which were significantly less severe noise levels than used in Experiment 1. However, there was a significant interaction between noise condition and hearing ability, which indicated that when speech stimuli were correctly classified at 50%, speech motor facilitation was observed in individuals with better hearing, whereas individuals with relatively worse but still normal hearing showed more activation during perception of clear speech. These findings indicate that the motor system may be sensitive to the quantity, but not quality, of degradation in the speech signal. Data support the notion that motor cortex complements auditory cortex during speech perception, and point to a role

Fanconi anemia and the cell cycle: new perspectives on aneuploidy

PubMed Central

2014-01-01

Fanconi anemia (FA) is a complex heterogenic disorder of genomic instability, bone marrow failure, cancer predisposition, and congenital malformations. The FA signaling network orchestrates the DNA damage recognition and repair in interphase as well as proper execution of mitosis. Loss of FA signaling causes chromosome instability by weakening the spindle assembly checkpoint, disrupting centrosome maintenance, disturbing resolution of ultrafine anaphase bridges, and dysregulating cytokinesis. Thus, the FA genes function as guardians of genome stability throughout the cell cycle. This review discusses recent advances in diagnosis and clinical management of Fanconi anemia and presents the new insights into the origins of genomic instability in FA. These new discoveries may facilitate the development of rational therapeutic strategies for FA and for FA-deficient malignancies in the general population. PMID:24765528

Development of Novel PD1/PD-L1 Antagonists Using Circular Cys-Knotted Micro Proteins

DTIC Science & Technology

2017-06-01

positive bacte- ria.[67] Similar antibacterial activities have been found in cyclo- tides isolated from Hedyota biflora (Rubiaceae family)[68] and C...immune control. Hence, reversing the inhibition of the adaptive immunity can lead to the activation of a patient’s immunity. For example, inhibition of...receptor and PD-L1, to block immune checkpoints, and facilitate antitumor activity . These checkpoint-blocking antibodies have demonstrated clinical

Facilitating adverse drug event detection in pharmacovigilance databases using molecular structure similarity: application to rhabdomyolysis

PubMed Central

Vilar, Santiago; Harpaz, Rave; Chase, Herbert S; Costanzi, Stefano; Rabadan, Raul

2011-01-01

Background Adverse drug events (ADE) cause considerable harm to patients, and consequently their detection is critical for patient safety. The US Food and Drug Administration maintains an adverse event reporting system (AERS) to facilitate the detection of ADE in drugs. Various data mining approaches have been developed that use AERS to detect signals identifying associations between drugs and ADE. The signals must then be monitored further by domain experts, which is a time-consuming task. Objective To develop a new methodology that combines existing data mining algorithms with chemical information by analysis of molecular fingerprints to enhance initial ADE signals generated from AERS, and to provide a decision support mechanism to facilitate the identification of novel adverse events. Results The method achieved a significant improvement in precision in identifying known ADE, and a more than twofold signal enhancement when applied to the ADE rhabdomyolysis. The simplicity of the method assists in highlighting the etiology of the ADE by identifying structurally similar drugs. A set of drugs with strong evidence from both AERS and molecular fingerprint-based modeling is constructed for further analysis. Conclusion The results demonstrate that the proposed methodology could be used as a pharmacovigilance decision support tool to facilitate ADE detection. PMID:21946238

Growth Coordination During Drosophila melanogaster Imaginal Disc Regeneration Is Mediated by Signaling Through the Relaxin Receptor Lgr3 in the Prothoracic Gland.

PubMed

Jaszczak, Jacob S; Wolpe, Jacob B; Bhandari, Rajan; Jaszczak, Rebecca G; Halme, Adrian

2016-10-01

Damage to Drosophila melanogaster imaginal discs activates a regeneration checkpoint that (1) extends larval development and (2) coordinates the regeneration of the damaged disc with the growth of undamaged discs. These two systemic responses to damage are both mediated by Dilp8, a member of the insulin/insulin-like growth factor/relaxin family of peptide hormones, which is released by regenerating imaginal discs. Growth coordination between regenerating and undamaged imaginal discs is dependent on Dilp8 activation of nitric oxide synthase (NOS) in the prothoracic gland (PG), which slows the growth of undamaged discs by limiting ecdysone synthesis. Here we demonstrate that the Drosophila relaxin receptor homolog Lgr3, a leucine-rich repeat-containing G-protein-coupled receptor, is required for Dilp8-dependent growth coordination and developmental delay during the regeneration checkpoint. Lgr3 regulates these responses to damage via distinct mechanisms in different tissues. Using tissue-specific RNA-interference disruption of Lgr3 expression, we show that Lgr3 functions in the PG upstream of NOS, and is necessary for NOS activation and growth coordination during the regeneration checkpoint. When Lgr3 is depleted from neurons, imaginal disc damage no longer produces either developmental delay or growth inhibition. To reconcile these discrete tissue requirements for Lgr3 during regenerative growth coordination, we demonstrate that Lgr3 activity in both the CNS and PG is necessary for NOS activation in the PG following damage. Together, these results identify new roles for a relaxin receptor in mediating damage signaling to regulate growth and developmental timing. Copyright © 2016 by the Genetics Society of America.

Withaferin A modulates the Spindle assembly checkpoint by degradation of Mad2-Cdc20 complex in colorectal cancer cell lines.

PubMed

Das, Tania; Roy, Kumar Singha; Chakrabarti, Tulika; Mukhopadhyay, Sibabrata; Roychoudhury, Susanta

2014-09-01

Withania somnifera L. Dunal (Ashwagandha) is used over centuries in the ayurvedic medicines in India. Withaferin A, a withanolide, is the major compound present in leaf extract of the plant which shows anticancer activity against leukemia, breast cancer and colorectal cancer. It arrests the ovarian cancer cells in the G2/M phase in dose dependent manner. In the current study we show the effect of Withaferin A on cell cycle regulation of colorectal cancer cell lines HCT116 and SW480 and its effect on cell fate. Treatment of these cells with this compound leads to apoptosis in a dose dependent manner. It causes the G2/M arrest in both the cell lines. We show that Withaferin A (WA) causes mitotic delay by blocking Spindle assembly checkpoint (SAC) function. Apoptosis induced by Withaferin A is associated with proteasomal degradation of Mad2 and Cdc20, an important constituent of the Spindle Checkpoint Complex. Further overexpression of Mad2 partially rescues the deleterious effect of WA by restoring proper anaphase initiation and keeping more number of cells viable. We hypothesize that Withaferin A kills cancer cells by delaying the mitotic exit followed by inducing chromosome instability. Copyright © 2014 Elsevier Inc. All rights reserved.

Herpes simplex virus type 2 glycoprotein H interacts with integrin αvβ3 to facilitate viral entry and calcium signaling in human genital tract epithelial cells.

PubMed

Cheshenko, Natalia; Trepanier, Janie B; González, Pablo A; Eugenin, Eliseo A; Jacobs, William R; Herold, Betsy C

2014-09-01

Herpes simplex virus (HSV) entry requires multiple interactions at the cell surface and activation of a complex calcium signaling cascade. Previous studies demonstrated that integrins participate in this process, but their precise role has not been determined. These studies were designed to test the hypothesis that integrin αvβ3 signaling promotes the release of intracellular calcium (Ca2+) stores and contributes to viral entry and cell-to-cell spread. Transfection of cells with small interfering RNA (siRNA) targeting integrin αvβ3, but not other integrin subunits, or treatment with cilengitide, an Arg-Gly-Asp (RGD) mimetic, impaired HSV-induced Ca2+ release, viral entry, plaque formation, and cell-to-cell spread of HSV-1 and HSV-2 in human cervical and primary genital tract epithelial cells. Coimmunoprecipitation studies and proximity ligation assays indicated that integrin αvβ3 interacts with glycoprotein H (gH). An HSV-2 gH-null virus was engineered to further assess the role of gH in the virus-induced signaling cascade. The gH-2-null virus bound to cells and activated Akt to induce a small Ca2+ response at the plasma membrane, but it failed to trigger the release of cytoplasmic Ca2+ stores and was impaired for entry and cell-to-cell spread. Silencing of integrin αvβ3 and deletion of gH prevented phosphorylation of focal adhesion kinase (FAK) and the transport of viral capsids to the nuclear pore. Together, these findings demonstrate that integrin signaling is activated downstream of virus-induced Akt signaling and facilitates viral entry through interactions with gH by activating the release of intracellular Ca2+ and FAK phosphorylation. These findings suggest a new target for HSV treatment and suppression. Herpes simplex viruses are the leading cause of genital disease worldwide, the most common infection associated with neonatal encephalitis, and a major cofactor for HIV acquisition and transmission. There is no effective vaccine. These

Multicenter Evaluation of the Tolerability of Combined Treatment With PD-1 and CTLA-4 Immune Checkpoint Inhibitors and Palliative Radiation Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bang, Andrew; Division of Radiation Oncology, University of Ottawa, Ottawa, Ontario; Wilhite, Tyler J.

Purpose: To analyze immune-related adverse events (ir-AEs) in patients treated with radiation and immune checkpoint blockade. Methods and Materials: We retrospectively reviewed records from patients with metastatic non-small cell lung cancer, melanoma, or renal cell cancer who received at least 1 cycle of a CTLA-4 or PD-1 inhibitor and radiation. Immune-related adverse events, defined using Common Terminology Criteria for Adverse Events version 4.0, were tabulated in relation to treatment variables, and associations with sequencing and timing were assessed. Results: We identified 133 patients, of whom 28 received a CTLA-4 inhibitor alone, 88 received a PD-1 inhibitor alone, and 17 received bothmore » classes of inhibitors either sequentially (n=13) or concurrently (n=4). Fifty-six patients received radiation within 14 days of an immune checkpoint inhibitor. Forty-six patients experienced at least 1 ir-AE (34.6%). Patients receiving both CTLA-4 and PD-1 inhibitors experienced more any-grade ir-AEs as compared with either individually (71% vs 29%, P=.0008). Any-grade ir-AEs occurred in 39% of patients in whom radiation was administered within 14 days of immunotherapy, compared with 23% of other patients (P=.06) and more often in patients who received higher equivalent dose in 2-Gy fractions (EQD2) EQD2 (P=.01). However, most toxicities were mild. There were no associations between site irradiated and specific ir-AEs. Conclusions: Our data suggest the combination of focal palliative radiation and CTLA-4 and/or PD-1 inhibitors is well tolerated, with manageable ir-AEs that did not seem to be associated with the particular site irradiated. Although conclusions are limited by the heterogeneity of patients and treatments, and future confirmatory studies are needed, this information can help guide clinical practice for patients receiving immune checkpoint therapy who require palliative radiation therapy.« less

Checkpoint suppressor 1 suppresses transcriptional activity of ERα and breast cancer cell proliferation via deacetylase SIRT1.

PubMed

Xu, Zhaowei; Yang, Yangyang; Li, Bowen; Li, Yanan; Xia, Kangkai; Yang, Yuxi; Li, Xiahui; Wang, Miao; Li, Shujing; Wu, Huijian

2018-05-11

Breast cancer is a highly heterogeneous carcinoma in women worldwide, but the underlying mechanisms that account for breast cancer initiation and development have not been fully established. Mounting evidence indicates that Checkpoint suppressor 1 (CHES1) is tightly associated with tumorigenesis and prognosis in many types of cancer. However, the definitive function of CHES1 in breast cancer remains to be explored. Here we showed that CHES1 had a physical interaction with estrogen receptor-α (ERα) and repressed the transactivation of ERα in breast cancer cells. Mechanistically, the interaction between CHES1 and ERα enhanced the recruitment of nicotinamide adenine dinucleotide (NAD+) deacetylase Sirtuin 1 (SIRT1), and it further induced SIRT1-mediated ERα deacetylation and repression on the promoter-binding enrichment of ERα. In addition, we also found that the expression of CHES1 was repressed by estrogen-ERα signaling and the expression level of CHES1 was significantly downregulated in ERα-positive breast cancer. The detailed mechanism was that ERα may directly bind to CHES1 potential promoter via recognizing the conserved estrogen response element (ERE) motif in response to estrogen stimulation. Functionally, CHES1 inhibited ERα-mediated proliferation and tumorigenesis of breast cancer cells in vivo and in vitro. Totally, these results identified a negative cross-regulatory loop between ERα and CHES1 that was required for growth of breast cancer cells, it might uncover novel insight into molecular mechanism of CHES1 involved in breast cancer and provide new avenues for molecular-targeted therapy in hormone-regulated breast cancer.

Identifying and managing the adverse effects of immune checkpoint blockade

PubMed Central

Winer, Arthur; Bodor, J. Nicholas

2018-01-01

Immunotherapy has revolutionized the field of oncology. By inhibiting the cytotoxic T-lymphocyte-associated protein (CTLA-4) and programmed death-1 (PD-1) immune checkpoint pathways, multiple studies have demonstrated greatly improved survival in locally advanced and metastatic cancers including melanoma, renal, lung, gastric, and hepatocellular carcinoma. Trials in other malignancies are ongoing, and undoubtedly the number of drugs in this space will grow beyond the six currently approved by the Food and Drug Administration. However, by altering the immune response to fight cancer, a new class of side effects has emerged known as immune-related adverse events (irAEs). These adverse events are due to overactivation of the immune system in almost any organ of the body, and can occur at any point along a patient’s treatment course. irAEs such as endocrinopathies (thyroiditis), colitis, and pneumonitis may occur more commonly. However, other organs such as the liver, heart, or brain may also be affected by immune overactivation and any of these side effects may become life threatening. This review presents an approach to promptly recognize and manage these toxicities, to hopefully minimize morbidity and mortality from irAEs. PMID:29593893

DW-MRI as a Predictive Biomarker of Radiosensitization of GBM through Targeted Inhibition of Checkpoint Kinases.

PubMed

Williams, Terence M; Galbán, Stefanie; Li, Fei; Heist, Kevin A; Galbán, Craig J; Lawrence, Theodore S; Holland, Eric C; Thomae, Tami L; Chenevert, Thomas L; Rehemtulla, Alnawaz; Ross, Brian D

2013-04-01

The inherent treatment resistance of glioblastoma (GBM) can involve multiple mechanisms including checkpoint kinase (Chk1/2)-mediated increased DNA repair capability, which can attenuate the effects of genotoxic chemotherapies and radiation. The goal of this study was to evaluate diffusion-weighted magnetic resonance imaging (DW-MRI) as a biomarker for Chk1/2 inhibitors in combination with radiation for enhancement of treatment efficacy in GBM. We evaluated a specific small molecule inhibitor of Chk1/2, AZD7762, in combination with radiation using in vitro human cell lines and in vivo using a genetically engineered GBM mouse model. DW-MRI and T1-contrast MRI were used to follow treatment effects on intracranial tumor cellularity and growth rates, respectively. AZD7762 inhibited clonal proliferation in a panel of GBM cell lines and increased radiosensitivity in p53-mutated GBM cell lines to a greater extent compared to p53 wild-type cells. In vivo efficacy of AZD7762 demonstrated a dose-dependent inhibitory effect on GBM tumor growth rate and a reduction in tumor cellularity based on DW-MRI scans along with enhancement of radiation efficacy. DW-MRI was found to be a useful imaging biomarker for the detection of radiosensitization through inhibition of checkpoint kinases. Chk1/2 inhibition resulted in antiproliferative activity, prevention of DNA damage-induced repair, and radiosensitization in preclinical GBM tumor models, both in vitro and in vivo. The effects were found to be maximal in p53-mutated GBM cells. These results provide the rationale for integration of DW-MRI in clinical translation of Chk1/2 inhibition with radiation for the treatment of GBM.

SCF(FBXW7α) modulates the intra-S-phase DNA-damage checkpoint by regulating Polo like kinase-1 stability.

PubMed

Giráldez, Servando; Herrero-Ruiz, Joaquín; Mora-Santos, Mar; Japón, Miguel Á; Tortolero, Maria; Romero, Francisco

2014-06-30

The intra-S-checkpoint is essential to control cell progression through S phase under normal conditions and in response to replication stress. When DNA lesions are detected, replication fork progression is blocked allowing time for repair to avoid genomic instability and the risk of cancer. DNA replication initiates at many origins of replication in eukaryotic cells, where a series of proteins form pre-replicative complexes (pre-RCs) that are activated to become pre-initiation complexes and ensure a single round of replication in each cell cycle. PLK1 plays an important role in the regulation of DNA replication, contributing to the regulation of pre-RCs formation by phosphorylating several proteins, under both normal and stress conditions. Here we report that PLK1 is ubiquitinated and degraded by SCFFBXW7α/proteasome. Moreover, we identified a new Cdc4 phosphodegron in PLK1, conserved from yeast to humans, whose mutation prevents PLK1 destruction. We established that endogenous SCFFBXW7α degrades PLK1 in the G1 and S phases of an unperturbed cell cycle and in S phase following UV irradiation. Furthermore, we showed that FBXW7α overexpression or UV irradiation prevented the loading of proteins onto chromatin to form pre-RCs and, accordingly, reduced cell proliferation. We conclude that PLK1 degradation mediated by SCFFBXW7α modulates the intra-S-phase checkpoint.

Cancer immunogenomic approach to neoantigen discovery in a checkpoint blockade responsive murine model of oral cavity squamous cell carcinoma

PubMed Central

Zolkind, Paul; Przybylski, Dariusz; Marjanovic, Nemanja; Nguyen, Lan; Lin, Tianxiang; Johanns, Tanner; Alexandrov, Anton; Zhou, Liye; Allen, Clint T.; Miceli, Alexander P.; Schreiber, Robert D.; Artyomov, Maxim; Dunn, Gavin P.; Uppaluri, Ravindra

2018-01-01

Head and neck squamous cell carcinomas (HNSCC) are an ideal immunotherapy target due to their high mutation burden and frequent infiltration with lymphocytes. Preclinical models to investigate targeted and combination therapies as well as defining biomarkers to guide treatment represent an important need in the field. Immunogenomics approaches have illuminated the role of mutation-derived tumor neoantigens as potential biomarkers of response to checkpoint blockade as well as representing therapeutic vaccines. Here, we aimed to define a platform for checkpoint and other immunotherapy studies using syngeneic HNSCC cell line models (MOC2 and MOC22), and evaluated the association between mutation burden, predicted neoantigen landscape, infiltrating T cell populations and responsiveness of tumors to anti-PD1 therapy. We defined dramatic hematopoietic cell transcriptomic alterations in the MOC22 anti-PD1 responsive model in both tumor and draining lymph nodes. Using a cancer immunogenomics pipeline and validation with ELISPOT and tetramer analysis, we identified the H-2Kb-restricted ICAM1P315L (mICAM1) as a neoantigen in MOC22. Finally, we demonstrated that mICAM1 vaccination was able to protect against MOC22 tumor development defining mICAM1 as a bona fide neoantigen. Together these data define a pre-clinical HNSCC model system that provides a foundation for future investigations into combination and novel therapeutics. PMID:29423108

Less Efficient G2-M Checkpoint Is Associated with an Increased Risk of Lung Cancer in African Americans

PubMed Central

Zheng, Yun-Ling; Loffredo, Christopher A.; Alberg, Anthony J.; Yu, Zhipeng; Jones, Raymond T.; Perlmutter, Donna; Enewold, Lindsey; Krasna, Mark J.; Yung, Rex; Shields, Peter G.; Harris, Curtis C.

2006-01-01

Cell cycle checkpoints play critical roles in the maintenance of genomic integrity. The inactivation of checkpoint genes by genetic and epigenetic mechanisms is frequent in all cancer types, as a less-efficient cell cycle control can lead to genetic instability and tumorigenesis. In an on-going case-control study consisting of 216 patients with non–small cell lung cancer, 226 population-based controls, and 114 hospital-based controls, we investigated the relationship of γ-radiation-induced G2-M arrest and lung cancer risk. Peripheral blood lymphocytes were cultured for 90 hours, exposed to 1.0 Gy γ-radiation, and harvested at 3 hours after γ-radiation treatment. γ-Radiation-induced G2-M arrest was measured as the percentage of mitotic cells in untreated cultures minus the percentage of mitotic cells in γ-radiation-treated cultures from the same subject. The mean percentage of γ-radiation-induced G2-M arrest was significantly lower in cases than in population controls (1.18 versus 1.44, P < 0.01) and hospital controls (1.18 versus 1.40, P = 0.01). When dichotomized at the 50th percentile value in combined controls (population and hospital controls), a lower level of γ-radiation-induced G2-M arrest was associated with an increased risk of lung cancer among African Americans after adjusting for baseline mitotic index, age, gender, and pack-years of smoking [adjusted odd ratio (OR), 2.25; 95% confidence interval (95% CI), 0.97–5.20]. A significant trend of an increased risk of lung cancer with a decreased level of G2-M arrest was observed (Ptrend = 0.02) among African Americans, with a lowest-versus-highest quartile adjusted OR of 3.74 (95% CI, 0.98–14.3). This trend was most apparent among African American females (Ptrend < 0.01), with a lowest-versus-highest quartile adjusted OR of 11.75 (95% CI, 1.47–94.04). The results suggest that a less-efficient DNA damage–induced G2-M checkpoint is associated with an increased risk of lung cancer among African

Development of Inhibitors of Salicylic Acid Signaling.

PubMed

Jiang, Kai; Kurimoto, Tetsuya; Seo, Eun-kyung; Miyazaki, Sho; Nakajima, Masatoshi; Nakamura, Hidemitsu; Asami, Tadao

2015-08-19

Salicylic acid (SA) plays important roles in the induction of systemic acquired resistance (SAR) in plants. Determining the mechanism of SAR will extend our understanding of plant defenses against pathogens. We recently reported that PAMD is an inhibitor of SA signaling, which suppresses the expression of the pathogenesis-related PR genes and is expected to facilitate the understanding of SA signaling. However, PAMD strongly inhibits plant growth. To minimize the side effects of PAMD, we synthesized a number of PAMD derivatives, and identified compound 4 that strongly suppresses the expression of the PR genes with fewer adverse effects on plant growth than PAMD. We further showed that the adverse effects on plant growth were partially caused the stabilization of DELLA, which is also related to the pathogen responses. These results indicate that compound 4 would facilitate our understanding of SA signaling and its cross talk with other plant hormones.

Clonal neoantigens elicit T cell immunoreactivity and sensitivity to immune checkpoint blockade

PubMed Central

McGranahan, Nicholas; Furness, Andrew J. S.; Rosenthal, Rachel; Ramskov, Sofie; Lyngaa, Rikke; Saini, Sunil Kumar; Jamal-Hanjani, Mariam; Wilson, Gareth A.; Birkbak, Nicolai J.; Hiley, Crispin T.; Watkins, Thomas B. K.; Shafi, Seema; Murugaesu, Nirupa; Mitter, Richard; Akarca, Ayse U.; Linares, Joseph; Marafioti, Teresa; Henry, Jake Y.; Van Allen, Eliezer M.; Miao, Diana; Schilling, Bastian; Schadendorf, Dirk; Garraway, Levi A.; Makarov, Vladimir; Rizvi, Naiyer A.; Snyder, Alexandra; Hellmann, Matthew D.; Merghoub, Taha; Wolchok, Jedd D.; Shukla, Sachet A.; Wu, Catherine J.; Peggs, Karl S.; Chan, Timothy A.; Hadrup, Sine R.; Quezada, Sergio A.; Swanton, Charles

2016-01-01

As tumors grow, they acquire mutations, some of which create neoantigens that influence the response of patients to immune checkpoint inhibitors. We explored the impact of neoantigen intratumor heterogeneity (ITH) on antitumor immunity. Through integrated analysis of ITH and neoantigen burden, we demonstrate a relationship between clonal neoantigen burden and overall survival in primary lung adenocarcinomas. CD8+ tumor-infiltrating lymphocytes reactive to clonal neoantigens were identified in early-stage non–small cell lung cancer and expressed high levels of PD-1. Sensitivity to PD-1 and CTLA-4 blockade in patients with advanced NSCLC and melanoma was enhanced in tumors enriched for clonal neoantigens. T cells recognizing clonal neoantigens were detectable in patients with durable clinical benefit. Cytotoxic chemotherapy–induced subclonal neoantigens, contributing to an increased mutational load, were enriched in certain poor responders. These data suggest that neoantigen heterogeneity may influence immune surveillance and support therapeutic developments targeting clonal neoantigens. PMID:26940869

Modeling combination therapy for breast cancer with BET and immune checkpoint inhibitors.

PubMed

Lai, Xiulan; Stiff, Andrew; Duggan, Megan; Wesolowski, Robert; Carson, William E; Friedman, Avner

2018-05-07

CTLA-4 is an immune checkpoint expressed on active anticancer T cells. When it combines with its ligand B7 on dendritic cells, it inhibits the activity of the T cells. The Bromo- and Extra-Terminal (BET) protein family includes proteins that regulate the expression of key oncogenes and antiapoptotic proteins. BET inhibitor (BETi) has been shown to reduce the expression of MYC by suppressing its transcription factors and to down-regulate the hypoxic transcriptome response to VEGF-A. This paper develops a mathematical model of the treatment of cancer by combination therapy of BETi and CTLA-4 inhibitor. The model shows that the two drugs are positively correlated in the sense that the tumor volume decreases as the dose of each of the drugs is increased. The model also considers the effect of the combined therapy on levels of myeloid-derived suppressor cells (MDSCs) and the overexpression of TNF-[Formula: see text], which may predict gastrointestinal side effects of the combination.

The role of temporal speech cues in facilitating the fluency of adults who stutter.

PubMed

Park, Jin; Logan, Kenneth J

2015-12-01

Adults who stutter speak more fluently during choral speech contexts than they do during solo speech contexts. The underlying mechanisms for this effect remain unclear, however. In this study, we examined the extent to which the choral speech effect depended on presentation of intact temporal speech cues. We also examined whether speakers who stutter followed choral signals more closely than typical speakers did. 8 adults who stuttered and 8 adults who did not stutter read 60 sentences aloud during a solo speaking condition and three choral speaking conditions (240 total sentences), two of which featured either temporally altered or indeterminate word duration patterns. Effects of these manipulations on speech fluency, rate, and temporal entrainment with the choral speech signal were assessed. Adults who stutter spoke more fluently in all choral speaking conditions than they did when speaking solo. They also spoke slower and exhibited closer temporal entrainment with the choral signal during the mid- to late-stages of sentence production than the adults who did not stutter. Both groups entrained more closely with unaltered choral signals than they did with altered choral signals. Findings suggest that adults who stutter make greater use of speech-related information in choral signals when talking than adults with typical fluency do. The presence of fluency facilitation during temporally altered choral speech and conversation babble, however, suggests that temporal/gestural cueing alone cannot account for fluency facilitation in speakers who stutter. Other potential fluency enhancing mechanisms are discussed. The reader will be able to (a) summarize competing views on stuttering as a speech timing disorder, (b) describe the extent to which adults who stutter depend on an accurate rendering of temporal information in order to benefit from choral speech, and (c) discuss possible explanations for fluency facilitation in the presence of inaccurate or indeterminate

Timing of CSF-1/CSF-1R signaling blockade is critical to improving responses to CTLA-4 based immunotherapy

PubMed Central

Holmgaard, Rikke B.; Brachfeld, Alexandra; Gasmi, Billel; Jones, David R.; Mattar, Marissa; Doman, Thompson; Murphy, Mary; Schaer, David; Wolchok, Jedd D.; Merghoub, Taha

2016-01-01

ABSTRACT Colony stimulating factor-1 (CSF-1) is produced by a variety of cancers and recruits myeloid cells that suppress antitumor immunity, including myeloid-derived suppressor cells (MDSCs.) Here, we show that both CSF-1 and its receptor (CSF-1R) are frequently expressed in tumors from cancer patients, and that this expression correlates with tumor-infiltration of MDSCs. Furthermore, we demonstrate that these tumor-infiltrating MDSCs are highly immunosuppressive but can be reprogrammed toward an antitumor phenotype in vitro upon CSF-1/CSF-1R signaling blockade. Supporting these findings, we show that inhibition of CSF-1/CSF-1R signaling using an anti-CSF-1R antibody can regulate both the number and the function of MDSCs in murine tumors in vivo. We further find that treatment with anti-CSF-1R antibody induces antitumor T-cell responses and tumor regression in multiple tumor models when combined with CTLA-4 blockade therapy. However, this occurs only when administered after or concurrent with CTLA-4 blockade, indicating that timing of each therapeutic intervention is critical for optimal antitumor responses. Importantly, MDSCs present within murine tumors after CTLA-4 blockade showed increased expression of CSF-1R and were capable of suppressing T cell proliferation, and CSF-1/CSF-1R expression in the human tumors was not reduced after treatment with CTLA-4 blockade immunotherapy. Taken together, our findings suggest that CSF-1R-expressing MDSCs can be targeted to modulate the tumor microenvironment and that timing of CSF-1/CSF-1R signaling blockade is critical to improving responses to checkpoint based immunotherapy. Significance: Infiltration by immunosuppressive myeloid cells contributes to tumor immune escape and can render patients resistant or less responsive to therapeutic intervention with checkpoint blocking antibodies. Our data demonstrate that blocking CSF-1/CSF-1R signaling using a monoclonal antibody directed to CSF-1R can regulate both the number

Toward Small-Molecule Inhibition of Protein-Protein Interactions: General Aspects and Recent Progress in Targeting Costimulatory and Coinhibitory (Immune Checkpoint) Interactions.

PubMed

Bojadzic, Damir; Buchwald, Peter

2018-05-30

Protein-protein interactions (PPIs) that are part of the costimulatory and coinhibitory (immune checkpoint) signaling are critical for adequate T cell response and are important therapeutic targets for immunomodulation. Biologics targeting them have already achieved considerable clinical success in the treatment of autoimmune diseases or transplant recipients (e.g., abatacept, belatacept, and belimumab) as well as cancer (e.g., ipilimumab, nivolumab, pembrolizumab, atezolizumab, durvalumab, and avelumab). In view of such progress, there have been only relatively limited efforts toward developing small-molecule PPI inhibitors (SMPPIIs) targeting these cosignaling interactions, possibly because they, as all other PPIs, are difficult to target by small molecules and were not considered druggable. Nevertheless, substantial progress has been achieved during the last decade. SMPPIIs proving the feasibility of such approaches have been identified through various strategies for a number of cosignaling interactions including CD40-CD40L, OX40-OX40L, BAFFR-BAFF, CD80-CD28, and PD-1-PD-L1s. Here, after an overview of the general aspects and challenges of SMPPII-focused drug discovery, we review them briefly together with relevant structural, immune-signaling, physicochemical, and medicinal chemistry aspects. While so far only a few of these SMPPIIs have shown activity in animal models (DRI-C21045 for CD40-D40L, KR33426 for BAFFR-BAFF) or reached clinical development (RhuDex for CD80-CD28, CA-170 for PD-1-PD-L1), there is proof-of-principle evidence for the feasibility of such approaches in immunomodulation. They can result in products that are easier to develop/manufacture and are less likely to be immunogenic or encounter postmarket safety events than corresponding biologics, and, contrary to them, can even become orally bioavailable. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

The inhibitory HVEM-BTLA pathway counter regulates lymphotoxin receptor signaling to achieve homeostasis of dendritic cells.

PubMed

De Trez, Carl; Schneider, Kirsten; Potter, Karen; Droin, Nathalie; Fulton, James; Norris, Paula S; Ha, Suk-won; Fu, Yang-Xin; Murphy, Theresa; Murphy, Kenneth M; Pfeffer, Klaus; Benedict, Chris A; Ware, Carl F

2008-01-01

Proliferation of dendritic cells (DC) in the spleen is regulated by positive growth signals through the lymphotoxin (LT)-beta receptor; however, the countering inhibitory signals that achieve homeostatic control are unresolved. Mice deficient in LTalpha, LTbeta, LTbetaR, and the NFkappaB inducing kinase show a specific loss of CD8- DC subsets. In contrast, the CD8alpha- DC subsets were overpopulated in mice deficient in the herpesvirus entry mediator (HVEM) or B and T lymphocyte attenuator (BTLA). HVEM- and BTLA-deficient DC subsets displayed a specific growth advantage in repopulating the spleen in competitive replacement bone marrow chimeric mice. Expression of HVEM and BTLA were required in DC and in the surrounding microenvironment, although DC expression of LTbetaR was necessary to maintain homeostasis. Moreover, enforced activation of the LTbetaR with an agonist Ab drove expansion of CD8alpha- DC subsets, overriding regulation by the HVEM-BTLA pathway. These results indicate the HVEM-BTLA pathway provides an inhibitory checkpoint for DC homeostasis in lymphoid tissue. Together, the LTbetaR and HVEM-BTLA pathways form an integrated signaling network regulating DC homeostasis.

Synaptic unreliability facilitates information transmission in balanced cortical populations

NASA Astrophysics Data System (ADS)

Gatys, Leon A.; Ecker, Alexander S.; Tchumatchenko, Tatjana; Bethge, Matthias

2015-06-01

Synaptic unreliability is one of the major sources of biophysical noise in the brain. In the context of neural information processing, it is a central question how neural systems can afford this unreliability. Here we examine how synaptic noise affects signal transmission in cortical circuits, where excitation and inhibition are thought to be tightly balanced. Surprisingly, we find that in this balanced state synaptic response variability actually facilitates information transmission, rather than impairing it. In particular, the transmission of fast-varying signals benefits from synaptic noise, as it instantaneously increases the amount of information shared between presynaptic signal and postsynaptic current. Furthermore we show that the beneficial effect of noise is based on a very general mechanism which contrary to stochastic resonance does not reach an optimum at a finite noise level.

Facilitating Facilitators: Enhancing PBL through a Structured Facilitator Development Program

ERIC Educational Resources Information Center

Salinitri, Francine D.; Wilhelm, Sheila M.; Crabtree, Brian L.

2015-01-01

With increasing adoption of the problem-based learning (PBL) model, creative approaches to enhancing facilitator training and optimizing resources to maintain effective learning in small groups is essential. We describe a theoretical framework for the development of a PBL facilitator training program that uses the constructivist approach as the…

Auditory display of knee-joint vibration signals

NASA Astrophysics Data System (ADS)

Krishnan, Sridhar; Rangayyan, Rangaraj M.; Bell, G. Douglas; Frank, Cyril B.

2001-12-01

Sounds generated due to rubbing of knee-joint surfaces may lead to a potential tool for noninvasive assessment of articular cartilage degeneration. In the work reported in the present paper, an attempt is made to perform computer-assisted auscultation of knee joints by auditory display (AD) of vibration signals (also known as vibroarthrographic or VAG signals) emitted during active movement of the leg. Two types of AD methods are considered: audification and sonification. In audification, the VAG signals are scaled in time and frequency using a time-frequency distribution to facilitate aural analysis. In sonification, the instantaneous mean frequency and envelope of the VAG signals are derived and used to synthesize sounds that are expected to facilitate more accurate diagnosis than the original signals by improving their aural quality. Auditory classification experiments were performed by two orthopedic surgeons with 37 VAG signals including 19 normal and 18 abnormal cases. Sensitivity values (correct detection of abnormality) of 31%, 44%, and 83%, and overall classification accuracies of 53%, 40%, and 57% were obtained with the direct playback, audification, and sonification methods, respectively. The corresponding d' scores were estimated to be 1.10, -0.36, and 0.55. The high sensitivity of the sonification method indicates that the technique could lead to improved detection of knee-joint abnormalities; however, additional work is required to improve its specificity and achieve better overall performance.

Coordinate action of distinct sequence elements localizes checkpoint kinase Hsl1 to the septin collar at the bud neck in Saccharomyces cerevisiae.

PubMed

Finnigan, Gregory C; Sterling, Sarah M; Duvalyan, Angela; Liao, Elizabeth N; Sargsyan, Aspram; Garcia, Galo; Nogales, Eva; Thorner, Jeremy

2016-07-15

Passage through the eukaryotic cell cycle requires processes that are tightly regulated both spatially and temporally. Surveillance mechanisms (checkpoints) exert quality control and impose order on the timing and organization of downstream events by impeding cell cycle progression until the necessary components are available and undamaged and have acted in the proper sequence. In budding yeast, a checkpoint exists that does not allow timely execution of the G2/M transition unless and until a collar of septin filaments has properly assembled at the bud neck, which is the site where subsequent cytokinesis will occur. An essential component of this checkpoint is the large (1518-residue) protein kinase Hsl1, which localizes to the bud neck only if the septin collar has been correctly formed. Hsl1 reportedly interacts with particular septins; however, the precise molecular determinants in Hsl1 responsible for its recruitment to this cellular location during G2 have not been elucidated. We performed a comprehensive mutational dissection and accompanying image analysis to identify the sequence elements within Hsl1 responsible for its localization to the septins at the bud neck. Unexpectedly, we found that this targeting is multipartite. A segment of the central region of Hsl1 (residues 611-950), composed of two tandem, semiredundant but distinct septin-associating elements, is necessary and sufficient for binding to septin filaments both in vitro and in vivo. However, in addition to 611-950, efficient localization of Hsl1 to the septin collar in the cell obligatorily requires generalized targeting to the cytosolic face of the plasma membrane, a function normally provided by the C-terminal phosphatidylserine-binding KA1 domain (residues 1379-1518) in Hsl1 but that can be replaced by other, heterologous phosphatidylserine-binding sequences. © 2016 Finnigan et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two

Structural and functional insights into the role of the N-terminal Mps1 TPR domain in the SAC (spindle assembly checkpoint).