scholarly journals Characterization of environmental chemicals with potential for DNA damage using isogenic DNA repair-deficient chicken DT40 cell lines

2011 ◽  
Vol 52 (7) ◽  
pp. 547-561 ◽  
Author(s):  
Kimiyo N. Yamamoto ◽  
Kouji Hirota ◽  
Koichi Kono ◽  
Shunichi Takeda ◽  
Srilatha Sakamuru ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Cell Lines ◽  
Environmental Chemicals ◽  
Dt40 Cell ◽  
Chicken Dt40 Cell

scholarly journals A Novel Approach Using DNA-Repair–Deficient Chicken DT40 Cell Lines for Screening and Characterizing the Genotoxicity of Environmental Contaminants

2009 ◽  
Vol 117 (11) ◽  
pp. 1737-1744 ◽  
Author(s):  
Kyunghee Ji ◽  
Toshiaki Kogame ◽  
Kyungho Choi ◽  
Xin Wang ◽  
Jinyoung Lee ◽  
...  
Keyword(s):  
Dna Repair ◽  
Cell Lines ◽  
Environmental Contaminants ◽  
Dt40 Cell ◽  
Novel Approach ◽  
Chicken Dt40 Cell

scholarly journals Impact of DNA repair pathways on the cytotoxicity of piperlongumine in chicken DT40 cell-lines.

2014 ◽  
Vol 5 (7-8) ◽  
pp. 285-292 ◽  
Author(s):  
Saki Okamoto ◽  
Takeo Narita ◽  
Hiroyuki Sasanuma ◽  
Shunichi Takeda ◽  
Shin-ichiro Masunaga ◽  
...  
Keyword(s):  
Dna Repair ◽  
Cell Lines ◽  
Dt40 Cell ◽  
Repair Pathways ◽  
Chicken Dt40 Cell

scholarly journals 900 Depleting non-canonical, cell-intrinsic PD-L1 signals induces synthetic lethality to small molecule DNA damage response inhibitors in an immune independent and dependent manner

2021 ◽  
Vol 9 (Suppl 3) ◽  
pp. A944-A944
Author(s):  
Anand Kornepati ◽  
Clare Murray ◽  
Barbara Avalos ◽  
Cody Rogers ◽  
Kavya Ramkumar ◽  
...  
Keyword(s):  
Ovarian Cancer ◽  
Dna Damage ◽  
Dna Repair ◽  
Cell Lines ◽  
Dna Damage Response ◽  
Small Molecule ◽  
Treatment Resistance ◽  
Programmed Death ◽  
Damage Response ◽  
Response Biomarker

BackgroundTumor surface-expressed programmed death-ligand 1 (PD-L1) suppresses immunity when it engages programmed death-1 (PD-1) on anti-tumor immune cells in canonical PD-L1/PD-1.1 Non-canonical, tumour-intrinsic PD-L1 signals can mediate treatment resistance2–6 but mechanisms remain incompletely understood. Targeting non-canonical, cell-intrinsic PD-L1 signals, especially modulation of the DNA damage response (DDR), remains largely untapped.MethodsWe made PD-L1 knockout (PD-L1 KO) murine transplantable and human cell lines representing melanoma, bladder, and breast histologies. We used biochemical, genetic, and cell-biology techniques for mechanistic insights into tumor-intrinsic PD-L1 control of specific DDR and DNA repair pathways. We generated a novel inducible melanoma GEMM lacking PD-L1 only in melanocytes to corroborate DDR alterations observed in PD-L1 KO of established tumors.ResultsGenetic tumor PD-L1 depletion destabilized Chk2 and impaired ATM/Chk2, but not ATR/Chk1 DDR. PD-L1KO increased DNA damage (γH2AX) and impaired homologous recombination DNA repair (p-RPA32, BRCA1, RAD51 nuclear foci) and function (DR-GFP reporter). PD-L1 KO cells were significantly more sensitive versus controls to DDR inhibitors (DDRi) against ATR, Chk1, and PARP but not ATM in multiple human and mouse tumor models in vitro and in vivo in NSG mice. PD-1 independent, intracellular, not surface PD-L1 stabilized Chk2 protein with minimal Chek2 mRNA effect. Mechanistically, PD-L1 could directly complex with Chk2, protecting it from PIRH2-mediated polyubiquitination. PD-L1 N-terminal domains Ig-V and Ig-C but not the PD-L1 C-terminal tail co-IP’d with Chk2 and restored Chk1 inhibitor (Chk1i) treatment resistance. Tumor PD-L1 expression correlated with Chk1i sensitivity in 44 primary human small cell lung cancer cell lines, implicating tumor-intrinsic PD-L1 as a DDRi response biomarker. In WT mice, genetic PD-L1 depletion but not surface PD-L1 blockade with αPD-L1, sensitized immunotherapy-resistant, BRCA1-WT 4T1 tumors to PARP inhibitor (PARPi). PARPi effects were reduced on PD-L1 KO tumors in RAG2KO mice indicating immune-dependent DDRi efficacy. Tumor PD-L1 depletion, likely due to impaired DDR, enhanced PARPi induced tumor-intrinsic STING activation (e.g., p-TBK1, CCL5) suggesting potential to augment immunotherapies.ConclusionsWe challenge the prevailing surface PD-L1 paradigm and establish a novel mechanism for cell-intrinsic PD-L1 control of the DDR and gene product expression. We identify therapeutic vulnerabilities from tumor PD-L1 depletion utilizing small molecule DDRi currently being tested in clinical trials. Data could explain αPD-L1/DDRi treatment resistance. Intracellular PD-L1 could be a pharmacologically targetable treatment target and/or response biomarker for selective DDRi alone plus other immunotherapies.ReferencesTopalian SL, Taube JM, Anders RA, Pardoll DM. Mechanism-driven biomarkers to guide immune checkpoint blockade in cancer therapy. Nat Rev Cancer 16:275–287, doi:10.1038/nrc.2016.36 (2016).Clark CA, et al. Tumor-intrinsic PD-L1 signals regulate cell growth, pathogenesis and autophagy in ovarian cancer and melanoma. Canres 0258.2016 (2016).Gupta HB et al. Tumor cell-intrinsic PD-L1 promotes tumor-initiating cell generation and functions in melanoma and ovarian cancer. 1, 16030 (2016).Zhu H, et al. BET bromodomain inhibition promotes anti-tumor immunity by suppressing PD-L1 expression. Cell Rep 16:2829–2837, doi:10.1016/j.celrep.2016.08.032 (2016)Wu B, et al. Adipose PD-L1 modulates PD-1/PD-L1 checkpoint blockade immunotherapy efficacy in breast cancer. Oncoimmunology 7:e1500107, doi:10.1080/2162402X.2018.1500107 (2018)Liang J, et al. Verteporfin inhibits PD-L1 through autophagy and the STAT1-IRF1-TRIM28 signaling axis, exerting antitumor efficacy. Cancer Immunol Res 8:952–965, doi:10.1158/2326-6066.CIR-19-0159 (2020)

scholarly journals Databases and Bioinformatics Tools for the Study of DNA Repair

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Kaja Milanowska ◽  
Kristian Rother ◽  
Janusz M. Bujnicki
Keyword(s):  
Dna Damage ◽  
Dna Repair ◽  
Excision Repair ◽  
Uv Light ◽  
Dna Lesions ◽  
Environmental Chemicals ◽  
Nonhomologous End Joining ◽  
End Joining ◽  
Repair Mechanisms ◽  
Base Excision

DNA is continuously exposed to many different damaging agents such as environmental chemicals, UV light, ionizing radiation, and reactive cellular metabolites. DNA lesions can result in different phenotypical consequences ranging from a number of diseases, including cancer, to cellular malfunction, cell death, or aging. To counteract the deleterious effects of DNA damage, cells have developed various repair systems, including biochemical pathways responsible for the removal of single-strand lesions such as base excision repair (BER) and nucleotide excision repair (NER) or specialized polymerases temporarily taking over lesion-arrested DNA polymerases during the S phase in translesion synthesis (TLS). There are also other mechanisms of DNA repair such as homologous recombination repair (HRR), nonhomologous end-joining repair (NHEJ), or DNA damage response system (DDR). This paper reviews bioinformatics resources specialized in disseminating information about DNA repair pathways, proteins involved in repair mechanisms, damaging agents, and DNA lesions.

The mTOR Inhibitor Everolimus Overcomes CXCR4-Mediated Resistance to HDAC Inhibitor Panobinostat through Inhibition of p21 and Mitosis Regulators, Sensitizing MM Cells to DNA-Damaged Induced Apoptosis

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 891-891
Author(s):  
Katia Beider ◽  
Valeria Voevoda ◽  
Hanna Bitner ◽  
Evgenia Rosenberg ◽  
Hila Magen ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Death ◽  
Dna Repair ◽  
Cell Lines ◽  
Hdac Inhibitor ◽  
Mtor Inhibitor ◽  
Mtor Inhibition ◽  
Induced Apoptosis

Abstract Introduction: Multiple myeloma (MM) is a neoplastic disorder that is characterized by clonal proliferation of plasma cells in the bone marrow (BM). Despite the initial efficacious treatment, MM patients often become refractory to common anti-MM drugs, therefore novel therapies are in need. Pan-histone deacetylase (HDAC) inhibitor panobinostat exerts multiple cytotoxic actions in MM cells in vitro, and was approved for the treatment of relapsed/refractory MM in combination with bortezomib and dexamethasone. Although having promising anti-MM properties, panobinostat lacks therapeutic activity as monotherapy. The aim of the current study was to elucidate the mechanisms underlying MM resistance to panobinostat and to define strategies to overcome it. Results: Panobinostat at the low concentrations (IC50 5-30 nM) suppressed the viability in MM cell lines (n=7) and primary CD138+ cells from MM patients (n=8) in vitro. Sensitivity to panobinostat correlated with reduced expression of chemokine receptor CXCR4, while overexpression of CXCR4 or its ligand CXCL12 in RPMI8226 and CAG MM cell lines significantly (p<0.001) increased their resistance to panobinostat, pointing to the role of the CXCR4 axis in HDACi response. Notably, similar expression levels of class I HDACs (HDAC1-3) were detected in MM cells with either low or high CXCR4. Interaction with BM stromal cells that represent the source of CXCL12 also protected MM cells from panobinostat-induced apoptosis, further strengthening a role for CXCR4 downstream pathway. Decreased sensitivity to cytotoxic effect was concomitant with reduced histone (H3K9 and H4K8) acetylation in response to panobinostat treatment. In addition, resistance to HDACi was associated with the reversible G0/G1 cell growth arrest, whereas sensitivity was characterized by apoptotic cell death. Analysis of intra-cellular signaling mediators involved in CXCR4-mediated HDACi resistance revealed the pro-survival AKT/mTOR pathway to be regulated by both CXCR4 over-expression and interaction with BMSCs. Combining panobinostat with mTOR inhibitor everolimus abrogated the resistance and induced synergistic cell death of MM cell lines and primary MM cells, but not of normal mononuclear cells (CI<0.4). This effect was concurrent with the increase in DNA double strand breaks, histone H2AX phosphorylation, loss of Dψm, cytochrome c release, caspase 3 activation and PARP cleavage. The increase in DNA damage upon combinational treatment was not secondary to the apoptotic DNA fragmentation, as it occurred similarly when apoptosis onset was blocked by caspase inhibitor z-VAD-fmk. Kinetics studies also confirmed that panobinostat-induced DNA damage preceded apoptosis induction. Strikingly, combined panobinostat/everolimus treatment resulted in sustained DNA damage and irreversible suppression of MM cell proliferation accompanied by robust apoptosis, in contrast to the modest effects induced by single agent. Gene expression analysis revealed distinct genetic profiles of single versus combined exposures. Whereas panobinostat increased the expression of cell cycle inhibitors GADD45G and p21, co-treatment with everolimus abrogated the increase in p21 and synergistically downregulated DNA repair genes, including RAD21, Ku70, Ku80 and DNA-PKcs. Furthermore, combined treatment markedly decreased both mRNA and protein expression of anti-apoptotic factors survivin and BCL-XL, checkpoint regulator CHK1, and G2/M-specific factors PLK1, CDK1 and cyclin B1, therefore suppressing the DNA damage repair and inhibiting mitotic progression. Given the anti-apoptotic role of p21, the synergistic lethal effect of everolimus could be attributed to its ability to suppress p21 induction by panobinostat ensuing the shift in the DNA damage response toward apoptosis. Conclusions: Collectively, our findings indicate that CXCR4/CXCL12 activity promotes the resistance of MM cells to HDACi with panobinostat through mTOR activation. Inhibition of mTOR by everolimus synergizes with panobinostat by simultaneous suppression of p21, G2/M mitotic factors and DNA repair machinery, rendering MM cells incapable of repairing accumulated DNA damage and promoting their apoptosis. Our results unravel the mechanism responsible for strong synergistic anti-MM activity of dual HDAC and mTOR inhibition and provide the rationale for a novel therapeutic strategy to eradicate MM. Disclosures No relevant conflicts of interest to declare.

DNA Repair Studies: Experimental Evidence in Support of Chicken DT40 Cell Line as a Unique Model

2001 ◽  
Vol 20 (4) ◽  
pp. 11 ◽  
Author(s):  
Pawan Kumar Dhar ◽  
Eiichiro Sonoda ◽  
Akira Fujimori ◽  
Yukiko M. Yamashita ◽  
Shunichi Takeda
Keyword(s):  
Dna Repair ◽  
Experimental Evidence ◽  
Cell Line ◽  
Dt40 Cell ◽  
Unique Model ◽  
Chicken Dt40 Cell

Compromised Nuclear Sirtuins Activity Sensitizes BRCA-Proficient multiple Myeloma Cells to DNA Damage Agents

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 723-723
Author(s):  
Michele Cea ◽  
Antonia Cagnetta ◽  
Aditya Munshi ◽  
Yu-Tzu Tai ◽  
Teru Hideshima ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Dna Damage ◽  
Dna Repair ◽  
Cell Lines ◽  
Plasma Cells ◽  
Dsb Repair ◽  
Dna Repair Mechanisms ◽  
Dna Damaging Agents ◽  
Normal Plasma ◽  
Repair Mechanisms

Abstract Abstract 723 Background: Multiple myeloma (MM) is a clonal malignancy of plasma cells with hallmark genetic instability resulting in large-scale changes at diagnosis, as well as further evolution contributing to disease progression. Inhibition of DNA repair mechanisms leads to significant reduction in acquisition of new genetic changes and associated progression of MM. Mammalian sirtuins are class III NAD+-dependent deacetylases emerging as innovative proteins involved in multiple pathways, including genome maintenance. Methods: A panel of 18 MM cell lines, both sensitive and resistant to conventional and novel anti-MM therapies, was used in the study. The antitumor effect of a pan-sirtuins inhibitor, Nicotinamide (Nam), alone and combined with DNA-damaging agents, was investigated by CTG assay and Annexin-V/propidium iodide staining. Mechanistic studies were performed with thymidine incorporation, Western-blotting, lentivirus-mediated shRNAs and immunofluorescence assay. Analysis of DNA DSB repair was done using chromosomally integrated reporter constructs, followed by cytometer analysis. Results: We analyzed an Affymetrix GeneChip (GSE6477) array of patient MM cells (n=162) compared with normal plasma cells, and found that transcript levels of two nuclear sirtuins (SIRT6 and SIRT7) were significantly higher in monoclonal gammopathy of undetermined significance (MGUS), smoldering MM, active MM, and relapsed MM compared with normal plasma cells. Importantly, protein analysis confirmed increased nuclear levels of these deacetylases in MM cell lines, including those resistant to DNA-damaging agents (MM.1R, LR-5, Dox40), as well as in patient CD138+ MM cells compared to PBMCs from healthy donors. Next we evaluated the functional role of these Sirtuins in MM cells by using loss of function approaches with RNAi. SIRT6 and SIRT7 silencing by knockdown reduced MM cell proliferation compared with control scrambled cells, with only a modest induction of cytotoxicity. We also examined the effects of Nam on DNA-damage response signaling triggered by conventional anti-MM agents melphalan and doxorubicin. Nam treatment did not appreciably affect MM cell viability; however, pretreatment with Nam impaired DNA double-strand breaks (DSBs) repair as well as DNA repair mechanisms triggered by conventional DNA damaging agents, evidenced by γH2AX and RPA phosphorylation, respectively. Consistent with these findings, Nam-pretreated MM cells formed fewer RAD51 foci in response to Doxorubicin and Melphalan, thereby conferring sensitivity to these agents. Importantly, this sensitizing effect was also observed in MM cells resistant to doxorubicin (RPMI-Doxo40) or melphalan (LR5), indicating that Nam increases chemosensitivity in both drug-sensitive and –resistant MM cells. Similarly, lentivirus-mediated shRNA knockdown of SIRT-6 and −7 sensitized MM cells to melphalan and doxorubicin. Finally, both chemical and genetic approaches improved the efficiency of DNA DSB repair mechanisms (Homologous and non-Homologous end-joining Recombination) in MM cell lines containing chromosomally integrated green fluorescent protein-based reporter constructs. Ongoing in vivo experiments are assessing how the chemical susceptibility of SIRT6 and/or 7-deficient cells can be exploited therapeutically. Conclusion: Our study demonstrates a link between nuclear sirtuins and DNA instability in MM cells, providing the basis for incorporation of inhibitors of these SIRTs into innovative anti-MM therapeutic approaches. Disclosures: Munshi: Celgene: Consultancy; Millenium: Consultancy; Merck: Consultancy; Onyx: Consultancy.

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