Defining DNA damage repair deficiency and replication stress in pancreatic cancer.

2019 ◽  
Vol 37 (4_suppl) ◽  
pp. 285-285 ◽  
Author(s):  
Stephan Dreyer ◽  
Viola Paulus-Hock ◽  
Rosie Upstill-Goddard ◽  
Eirini Lampraki ◽  
Nigel Jamieson ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Pancreatic Cancer ◽  
Dna Damage ◽  
Checkpoint Inhibitors ◽  
Replication Stress ◽  
Parp Inhibitors ◽  
Cell Cycle Checkpoint ◽  
Cell Cycle Checkpoints ◽  
Cell Cycle Inhibitors

285 Background: Integrated multi-omic analyses revealed 24% of pancreatic cancer (PC) harbor defects in DNA damage response (DDR) and a subgroup demonstrate upregulation in replication stress pathways. DDR defective tumors preferentially respond to DNA damaging agents, and clinical responses to cell cycle inhibitors are seen in undefined subgroups, representing novel therapeutic strategies for PC. The aim of this study is to define and refine therapeutic segments for agents targeting DDR and replication stress in PC. Methods: We performed whole genome and RNA sequencing (RNAseq) on 48 patient-derived cell lines (PDCL) generated and characterized as part of the International Cancer Genome Initiative (ICGC). This identified increased replication stress in a sub-group of tumours, correlating with previously defined molecular subtypes of PC, irrespective of DDR status. Cytotoxic viability assays were performed using agents targeting the DDR pathway and cell cycle checkpoints, including Cisplatin, and inhibitors of PARP, ATR, WEE1, CHK1, CDK4/6 and PLK4. Subcutaneous patient derived xenografts (PDX) were generated to test therapeutic regimens in vivo. Results: DDR defective models, as defined by signatures of homologous recombination deficiency (HRD) were highly sensitive to Cisplatin and PARP inhibitors. Replication stress predicted differential responses to cell cycle inhibitors of WEE1, CHK1, CDK4/6 and PLK4. A novel mRNA signature of ATR inhibitor sensitivity was generated and correlated with response. Response to cell cycle checkpoint inhibitors were independent of DDR status, but strongly associated with replication stress. Conclusions: This proof of concept data demonstrates DDR deficiency and increased Replication Stress to be attractive targets in PC. Therapeutic vulnerabilities extend beyond platinum chemotherapy and can be targeted with novel small molecule inhibitors, with independent biomarkers predicting response to agents targeting either DDR or cell cycle checkpoints. This has led to the design and development of several personalized medicine trials via the Precision Panc platform targeting DDR and Replication stress, and will allow clinical testing of signatures of HRD and replication stress.

scholarly journals Acceleration or Brakes: Which Is Rational for Cell Cycle-Targeting Neuroblastoma Therapy?

Biomolecules ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 750
Author(s):  
Kiyohiro Ando ◽  
Akira Nakagawara
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Cycle Progression ◽  
Parp Inhibitors ◽  
Cell Cycle Checkpoint ◽  
Mitotic Catastrophe ◽  
Malignant Neoplasms ◽  
Checkpoint Kinases ◽  
Molecular Features ◽  
Cycle Checkpoint

Unrestrained proliferation is a common feature of malignant neoplasms. Targeting the cell cycle is a therapeutic strategy to prevent unlimited cell division. Recently developed rationales for these selective inhibitors can be subdivided into two categories with antithetical functionality. One applies a “brake” to the cell cycle to halt cell proliferation, such as with inhibitors of cell cycle kinases. The other “accelerates” the cell cycle to initiate replication/mitotic catastrophe, such as with inhibitors of cell cycle checkpoint kinases. The fate of cell cycle progression or arrest is tightly regulated by the presence of tolerable or excessive DNA damage, respectively. This suggests that there is compatibility between inhibitors of DNA repair kinases, such as PARP inhibitors, and inhibitors of cell cycle checkpoint kinases. In the present review, we explore alterations to the cell cycle that are concomitant with altered DNA damage repair machinery in unfavorable neuroblastomas, with respect to their unique genomic and molecular features. We highlight the vulnerabilities of these alterations that are attributable to the features of each. Based on the assessment, we offer possible therapeutic approaches for personalized medicine, which are seemingly antithetical, but both are promising strategies for targeting the altered cell cycle in unfavorable neuroblastomas.

scholarly journals PARP Inhibitor Upregulates PD-L1 Expression and Provides a New Combination Therapy in Pancreatic Cancer

2021 ◽  
Vol 12 ◽  
Author(s):  
Yali Wang ◽  
Kun Zheng ◽  
Hua Xiong ◽  
Yongbiao Huang ◽  
Xiuqiong Chen ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
T Cells ◽  
Combination Therapy ◽  
Checkpoint Inhibitors ◽  
Parp Inhibitors ◽  
New Combination ◽  
Treatment Modalities ◽  
Pancreatic Cancer Cells ◽  
Programmed Death

Despite recent improvements in treatment modalities, pancreatic cancer remains a highly lethal tumor with mortality rate increasing every year. Poly (ADP-ribose) polymerase (PARP) inhibitors are now used in pancreatic cancer as a breakthrough in targeted therapy. This study focused on whether PARP inhibitors (PARPis) can affect programmed death ligand-1 (PD-L1) expression in pancreatic cancer and whether immune checkpoint inhibitors of PD-L1/programmed death 1 (PD-1) can enhance the anti-tumor effects of PARPis. Here we found that PARPi, pamiparib, up-regulated PD-L1 expression on the surface of pancreatic cancer cells in vitro and in vivo. Mechanistically, pamiparib induced PD-L1 expression via JAK2/STAT3 pathway, at least partially, in pancreatic cancer. Importantly, pamiparib attenuated tumor growth; while co-administration of pamiparib with PD-L1 blockers significantly improved the therapeutic efficacy in vivo compared with monotherapy. Combination therapy resulted in an altered tumor immune microenvironment with a significant increase in windiness of CD8+ T cells, suggesting a potential role of CD8+ T cells in the combination therapy. Together, this study provides evidence for the clinical application of PARPis with anti-PD-L1/PD-1 drugs in the treatment of pancreatic cancer.

scholarly journals A kinetochore-based ATM/ATR-independent DNA damage checkpoint maintains genomic integrity in trypanosomes

2019 ◽  
Vol 47 (15) ◽  
pp. 7973-7988 ◽  
Author(s):  
Qing Zhou ◽  
Kieu T M Pham ◽  
Huiqing Hu ◽  
Yasuhiro Kurasawa ◽  
Ziyin Li
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Spindle Assembly Checkpoint ◽  
Cell Cycle Checkpoint ◽  
Cell Cycle Checkpoints ◽  
Genomic Integrity ◽  
Metaphase Arrest ◽  
M Cell ◽  
Independent Manner ◽  
Mitotic Cyclin

Abstract DNA damage-induced cell cycle checkpoints serve as surveillance mechanisms to maintain genomic stability, and are regulated by ATM/ATR-mediated signaling pathways that are conserved from yeast to humans. Trypanosoma brucei, an early divergent microbial eukaryote, lacks key components of the conventional DNA damage-induced G2/M cell cycle checkpoint and the spindle assembly checkpoint, and nothing is known about how T. brucei controls its cell cycle checkpoints. Here we discover a kinetochore-based, DNA damage-induced metaphase checkpoint in T. brucei. MMS-induced DNA damage triggers a metaphase arrest by modulating the abundance of the outer kinetochore protein KKIP5 in an Aurora B kinase- and kinetochore-dependent, but ATM/ATR-independent manner. Overexpression of KKIP5 arrests cells at metaphase through stabilizing the mitotic cyclin CYC6 and the cohesin subunit SCC1, mimicking DNA damage-induced metaphase arrest, whereas depletion of KKIP5 alleviates the DNA damage-induced metaphase arrest and causes chromosome mis-segregation and aneuploidy. These findings suggest that trypanosomes employ a novel DNA damage-induced metaphase checkpoint to maintain genomic integrity.

scholarly journals New Insights into p53 Signaling and Cancer Cell Response to DNA Damage: Implications for Cancer Therapy

2012 ◽  
Vol 2012 ◽  
pp. 1-16 ◽  
Author(s):  
Razmik Mirzayans ◽  
Bonnie Andrais ◽  
April Scott ◽  
David Murray
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Apoptotic Cell ◽  
Cell Types ◽  
Cell Cycle Checkpoint ◽  
Cell Cycle Checkpoints ◽  
Cancer Therapies ◽  
Wild Type ◽  
P53 Signaling ◽  
Upstream Kinase

Activation of the p53 signaling pathway by DNA-damaging agents was originally proposed to result either in cell cycle checkpoint activation to promote survival or in apoptotic cell death. This model provided the impetus for numerous studies focusing on the development of p53-based cancer therapies. According to recent evidence, however, most p53 wild-type human cell types respond to ionizing radiation by undergoing stress-induced premature senescence (SIPS) and not apoptosis. SIPS is a sustained growth-arrested state in which cells remain viable and secrete factors that may promote cancer growth and progression. Thep21WAF1(hereafter p21) protein has emerged as a key player in the p53 pathway. In addition to its well-studied role in cell cycle checkpoints, p21 regulates p53 and its upstream kinase (ATM), controls gene expression, suppresses apoptosis, and induces SIPS. Herein, we review these and related findings with human solid tumor-derived cell lines, report new data demonstrating dynamic behaviors of p53 and p21 in the DNA damage response, and examine the gain-of-function properties of cancer-associated p53 mutations. We point out obstacles in cancer-therapeutic strategies that are aimed at reactivating the wild-type p53 function and highlight some alternative approaches that target the apoptotic threshold in cancer cells with differing p53 status.

scholarly journals Impact of Replication Stress in Human Papillomavirus Pathogenesis

2018 ◽  
Vol 93 (2) ◽  
Author(s):  
Cary A. Moody
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Human Papillomavirus ◽  
Genomic Instability ◽  
Viral Persistence ◽  
Replication Stress ◽  
Cell Cycle Checkpoints ◽  
Premalignant Lesions ◽  
Associated Lesions ◽  
Novel Approach

ABSTRACTThe inactivation of critical cell cycle checkpoints by the human papillomavirus (HPV) oncoprotein E7 results in replication stress (RS) that leads to genomic instability in premalignant lesions. Intriguingly, RS tolerance is achieved through several mechanisms, enabling HPV to exploit the cellular RS response for viral replication and to facilitate viral persistence in the presence of DNA damage. As such, inhibitors of the RS response pathway may provide a novel approach to target HPV-associated lesions and cancers.

scholarly journals Inactivation of mouse Hus1 results in genomic instability and impaired responses to genotoxic stress

2000 ◽  
Vol 14 (15) ◽  
pp. 1886-1898 ◽  
Author(s):  
Robert S. Weiss ◽  
Tamar Enoch ◽  
Philip Leder
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Replication ◽  
Chromosomal Abnormalities ◽  
Genotoxic Stress ◽  
Eukaryotic Cell ◽  
Cell Cycle Checkpoint ◽  
Cell Cycle Checkpoints ◽  
Genome Damage

The eukaryotic cell cycle is overseen by regulatory mechanisms, termed checkpoints, that respond to DNA damage, mitotic spindle defects, and errors in the ordering of cell cycle events. The DNA replication and DNA damage cell cycle checkpoints of the fission yeastSchizosaccharomyces pombe require the hus1+(hydroxyurea sensitive) gene. To determine the role of the mouse homolog of hus1+ in murine development and cell cycle checkpoint function, we produced a targeted disruption of mouse Hus1. Inactivation of Hus1results in mid-gestational embryonic lethality due to widespread apoptosis and defective development of essential extra-embryonic tissues. DNA damage-inducible genes are up-regulated inHus1-deficient embryos, and primary cells fromHus1-null embryos contain increased spontaneous chromosomal abnormalities, suggesting that loss of Hus1 leads to an accumulation of genome damage. Embryonic fibroblasts lackingHus1 fail to proliferate in vitro, but inactivation ofp21 allows for the continued growth of Hus1-deficient cells.Hus1−/−p21−/−cells display a unique profile of significantly heightened sensitivity to hydroxyurea, a DNA replication inhibitor, and ultraviolet light, but only slightly increased sensitivity to ionizing radiation. Taken together, these results indicate that mouse Hus1 functions in the maintenance of genomic stability and additionally identify an evolutionarily-conserved role for Hus1 in mediating cellular responses to genotoxins.

An intimate alliance of DNA-damage response network with cell-cycle checkpoints amid events of uncontrolled cellular proliferation- a minireview

2020 ◽  
Vol 20 ◽  
Author(s):  
Aroni Chatterjee ◽  
Keshav Rajarshi ◽  
Rajni Khan ◽  
Hiya Ghosh ◽  
Sonia Kapoor ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Dna Damage Response ◽  
Cellular Proliferation ◽  
Cell Senescence ◽  
Cell Cycle Checkpoint ◽  
Effector Proteins ◽  
Cell Cycle Checkpoints ◽  
Response Network ◽  
Damage Response

: There is close interdependence between cell survival, cell senescence, events of the cell cycle, apoptosis, malignancy development, and tumor responses to cancer treatment. Intensive studies and elaborate researches have been conducted on the functional aspects of oncogenes, tumor suppressor genes, apoptotic genes, and members guiding cell cycle regulation. These disquisitions have put forward the existence of a highly organized response pathway termed as a DNAdamage response network. The pathways detecting DNA damage and signaling are intensively linked to the events of cellcycle arrest, cell proliferation, apoptosis, and cell senescence. DNA damage responses are complex systems that incorporate specific "sensor" and "transducer" proteins, for assessment of damage and signal transmission, respectively. These signals are thereafter relayed upon various "effector" proteins involved in different cellular pathways. It may include those governing cell-cycle checkpoints, participating in DNA repair, cell senescence, and apoptosis. This review discusses about the role of tumour suppressor gene, oncogenes, cell cycle checkpoint regulators during DNA damage response and regulation.

Imaging with FLT-PET demonstrates that PF-477736, an inhibitor of CHK1 kinase, overcomes a cell cycle checkpoint induced by gemcitabine in PC-3 xenografts

2006 ◽  
Vol 24 (18_suppl) ◽  
pp. 3045-3045 ◽  
Author(s):  
G. A. McArthur ◽  
J. Raleigh ◽  
A. Blasina ◽  
C. Cullinane ◽  
D. Dorow ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Fold Increase ◽  
Cell Cycle Checkpoint ◽  
Flt Pet ◽  
Cycle Arrest ◽  
Cycle Checkpoint ◽  
A Cell ◽  
Chk1 Inhibitor

3045 Background: The development of strategies to monitor the molecular and cellular response to novel agents that target the cell cycle is vital to provide proof of mechanism and biological activity of these compounds. The protein kinase CHK1 is activated following DNA damage in the S and G2-phases of the cell cycle and mediates cell cycle arrest. In vitro studies demonstrate that inhibition of CHK1 can overcome cell cycle arrest induced by DNA damage and enhance cytotoxic activity of DNA damaging agents. In vivo studies show that combining DNA damaging agents with a CHK1 inhibitor potentiates antitumor activity. We hypothesize that functional imaging with 18F-fluorine-L-thymidine (FLT), a PET-tracer where tumor uptake is maximal in the S and G2 phases of the cell cycle can be used to non-invasively monitor the induction and therapeutic inhibition of a cell cycle checkpoint in vivo. Methods: Nude mice harbouring PC-3 xenografts were treated with vehicle controls, gemcitabine, the CHK1-inhibitor PF-477736 or gemcitabine + PF-477736. FLT-PET scans were performed and tumors harvested for ex-vivo biomarkers to assess S-phase, M-phase and DNA-repair. Results: Gemcitabine induced a 8.3 ±0.8 fold increase in tumoral uptake of FLT at 21 hours that correlated with a 3.3 ±0.2-fold increase in thymidine kinase activity and S-phase arrest as demonstrated by BrdU incorporation and elevated expression of cyclin-A. Treatment with PF-477736 at 17 hours after gemcitabine abrogated the early FLT-flare at 21 hours by 82% (p<0.001). This was associated with both an increased fraction of cells in mitosis and G1-phase of the cell cycle as determined by phos-histone H3 and flow cytometry. Furthermore, the combination of gemcitabine and PF-477736 enhanced DNA damage as measured by phos-gamma-H2AX and significantly delayed tumor growth when compared to tumors treated with gemcitabine alone. Conclusion: These data clearly indicate that the CHK1-inhibitor PF-477736 can overcome the cell cycle checkpoint induced by gemcitabine and increase associated DNA damage in tumors in-vivo. The PET studies indicate that functional imaging with FLT-PET is a promising strategy to monitor responses to therapeutic agents that target cell cycle checkpoints. [Table: see text]

scholarly journals UBE2T-regulated H2AX monoubiquitination induces hepatocellular carcinoma radioresistance by facilitating CHK1 activation

2020 ◽  
Vol 39 (1) ◽  
Author(s):  
Jingyuan Sun ◽  
Zhenru Zhu ◽  
Wenwen Li ◽  
Mengying Shen ◽  
Chuanhui Cao ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Cell Cycle ◽  
Dna Repair ◽  
Clinical Data ◽  
Underlying Mechanism ◽  
Cell Cycle Checkpoint ◽  
Cell Cycle Checkpoints

Abstract Background Radioresistance is the major obstacle in radiation therapy (RT) for hepatocellular carcinoma (HCC). Dysregulation of DNA damage response (DDR), which includes DNA repair and cell cycle checkpoints activation, leads to radioresistance and limits radiotherapy efficacy in HCC patients. However, the underlying mechanism have not been clearly understood. Methods We obtained 7 pairs of HCC tissues and corresponding non-tumor tissues, and UBE2T was identified as one of the most upregulated genes. The radioresistant role of UBE2T was examined by colony formation assays in vitro and xenograft tumor models in vivo. Comet assay, cell cycle flow cytometry and γH2AX foci measurement were used to investigate the mechanism by which UBE2T mediating DDR. Chromatin fractionation and immunofluorescence staining were used to assess cell cycle checkpoint kinase 1(CHK1) activation. Finally, we analyzed clinical data from HCC patients to verify the function of UBE2T. Results Here, we found that ubiquitin-conjugating enzyme E2T (UBE2T) was upregulated in HCC tissues, and the HCC patients with higher UBE2T levels exhibited poorer outcomes. Functional studies indicated that UBE2T increased HCC radioresistance in vitro and in vivo. Mechanistically, UBE2T-RNF8, was identified as the E2-E3 pair, physically bonded with and monoubiquitinated histone variant H2AX/γH2AX upon radiation exposure. UBE2T-regulated H2AX/γH2AX monoubiquitination facilitated phosphorylation of CHK1 for activation and CHK1 release from the chromatin to cytosol for degradation. The interruption of UBE2T-mediated monoubiquitination on H2AX/γH2AX, including E2-enzyme-deficient mutation (C86A) of UBE2T and monoubiquitination-site-deficient mutation (K119/120R) of H2AX, cannot effectively activate CHK1. Moreover, genetical and pharmacological inhibition of CHK1 impaired the radioresistant role of UBE2T in HCC. Furthermore, clinical data suggested that the HCC patients with higher UBE2T levels exhibited worse response to radiotherapy. Conclusion Our results revealed a novel role of UBE2T-mediated H2AX/γH2AX monoubiquitination on facilitating cell cycle arrest activation to provide sufficient time for radiation-induced DNA repair, thus conferring HCC radioresistance. This study indicated that disrupting UBE2T-H2AX-CHK1 pathway maybe a promising potential strategy to overcome HCC radioresistance.

scholarly journals The Human G2 Checkpoint Control Protein hRAD9 Is a Nuclear Phosphoprotein That Forms Complexes with hRAD1 and hHUS1

1999 ◽  
Vol 10 (6) ◽  
pp. 1985-1995 ◽  
Author(s):  
Robert P. St. Onge ◽  
Christian M. Udell ◽  
Richard Casselman ◽  
Scott Davey
Keyword(s):  
Cell Cycle ◽  
Signal Transduction ◽  
Dna Damage ◽  
Signal Transduction Pathway ◽  
Cell Cycle Checkpoints ◽  
Checkpoint Control ◽  
Culture Cells ◽  
Replication Intermediates ◽  
Control Protein

Eukaryotic cells actively block entry into mitosis in the presence of DNA damage or incompletely replicated DNA. This response is mediated by signal transduction cascades called cell cycle checkpoints. We show here that the human checkpoint control protein hRAD9 physically associates with two other checkpoint control proteins, hRAD1 and hHUS1. Furthermore, hRAD1 and hHUS1 themselves interact, analogously to their fission yeast homologues Rad1 and Hus1. We also show that hRAD9 is present in multiple phosphorylation forms in vivo. These phosphorylated forms are present in tissue culture cells that have not been exposed to exogenous sources of DNA damage, but it remains possible that endogenous damage or naturally occurring replication intermediates cause the observed phosphorylation. Finally, we show that hRAD9 is a nuclear protein, indicating that in this signal transduction pathway, hRAD9 is physically proximal to the upstream (DNA damage) signal rather than to the downstream, cytoplasmic, cell cycle machinery.

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