DNA Repair In Cancer Cells Research Articles

Lactobacillus, Bifidobacterium and Streptococcus, Probiotic Bacteria Supplements, Induce DNA Repair of Local Breast Cancer Cell Line AMJ13

General Background: Breast cancer is the most prevalent cancer affecting women, with increasing incidence worldwide. Specific Background: Recent research has focused on the role of epigenetic changes in DNA damage, repair mechanisms, and the potential therapeutic effects of probiotics. Probiotics have shown promise in promoting tissue regeneration and DNA repair. Knowledge Gap: However, the precise impact of probiotics on DNA repair in cancer cells, specifically breast cancer cells, remains underexplored. Aims: This study aimed to evaluate the effects of probiotics on DNA damage repair in AMJ13 Iraqi breast cancer cells and assess the cytotoxic effects of probiotics on these cells. Results: Using the comet assay, we found significant increases in DNA damage repair in AMJ13 cells treated with Lactobacillus plantarum (T1) and a combination of eight probiotic strains (T2). Exposure to T1 for 48 hours resulted in significant increases in tail DNA (P≤0.001), head DNA (P≤0.001), and tail moment (P<0.001), while T2 showed similar significant increases at 72 hours (P<0.05). Image analysis further supported the DNA repair potential of probiotics, as indicated by a small tail curve for treated cells. Novelty: This study provides novel insights into the therapeutic potential of probiotics in breast cancer treatment by demonstrating their capacity to enhance DNA repair mechanisms in cancer cells. Implications: The findings suggest that probiotic therapy may be a promising adjunct treatment in breast cancer, offering a new avenue for cancer management through the enhancement of DNA repair and reduction of DNA damage. Highlights: Probiotics significantly repaired DNA damage in breast cancer cells. T1 and T2 enhanced DNA repair within 48-72 hours. Probiotics offer potential as breast cancer adjunct therapy. Keywords: Breast cancer, probiotics, DNA repair, AMJ13 cells, cytotoxicity

An Insight into the Effect of Schiff Base and their d and f Block Metal Complexes on Various Cancer Cell Lines as Anticancer Agents: A Review.

Over the last few decades, an alarming rise in the percentage of individuals with cancer and those with multi-resistant illnesses has forced researchers to explore possibilities for novel therapeutic approaches. Numerous medications currently exist to treat various disorders, and the development of small molecules as anticancer agents has considerable potential. However, the widespread prevalence of resistance to multiple drugs in cancer indicates that it is necessary to discover novel and promising compounds with ideal characteristics that could overcome the multidrug resistance issue. The utilisation of metallo-drugs has served as a productive anticancer chemotherapeutic method, and this approach may be implemented for combating multi-resistant tumours more successfully. Schiff bases have been receiving a lot of attention as a group of compounds due to their adaptable metal chelating abilities, innate biologic properties, and versatility to tweak the structure to optimise it for a specific biological purpose. The biological relevance of Schiff base and related complexes, notably their anticancer effects, has increased in their popularity as bio-inorganic chemistry has progressed. As a result of learning about Schiff bases antitumor efficacy against multiple cancer cell lines and their complexes, researchers are motivated to develop novel, side-effect-free anticancer treatments. According to study reports from the past ten years, we are still seeking a powerful anticancer contender. This study highlights the potential of Schiff bases, a broad class of chemical molecules, as potent anticancer agents. In combination with other anticancer strategies, they enhance the efficacy of treatment by elevating the cytotoxicity of chemotherapy, surmounting drug resistance, and promoting targeted therapy. Schiff bases also cause cancer cell DNA repair, improve immunotherapy, prevent angiogenesis, cause apoptosis, and lessen the side effects of chemotherapy. The present review explores the development of potential Schiff base and their d and f block metal complexes as anticancer agents against various cancer cell lines.

Abstract 7112: Preclinical profile of novel and potent small molecule inhibitors of PARG

Abstract Poly(ADP-ribose) glycohydrolase (PARG) is primary enzyme involved in the dePARylation process of DNA repair, specifically in the single strand break repair (SSBRs). PARG is a macrodomain protein with exo- and endo-glycohydrolase activity that liberates free ADP-ribose and PAR chains, respectively. It interacts with various Poly(ADP-ribose) polymerase (PARP) proteins to facilitate appropriate and timely DNA repair. The balance between PARP and PARG activity is essential for efficient DDR. Inhibition of PARG lead to altered DNA repair in cancer cells. We have identified highly potent PARG inhibitors with picomolar IC50 in. PARG is the primary enzyme for dePARylation and accounts for 90% of dePARylation activity. Treatment of HCC-1806 cells with PARG inhibitors showed dose dependent increase of PARylation signature, with sub micromolar IC50. Compounds also demonstrate significant functional, anti-proliferative activity in ovarian and breast cancer cell lines besides a favourable ADME profile. Further pharmacokinetic and pharmacodynamic characterization of the identified hits is currently in progress. Citation Format: Sukanya Patra, Manoj Pothuganti, Githavani Kummari, Venu Sankeshi, Jyothipriya Kapaka, Navnath Karche, Ramamohan Mekala, Srikant Viswanadha. Preclinical profile of novel and potent small molecule inhibitors of PARG [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7112.

Targeting WEE1 Kinase in Gynecological Malignancies.

WEE1 kinase is involved in the G2/M cell cycle checkpoint control and DNA damage repair. A functional G2/M checkpoint is crucial for DNA repair in cancer cells with p53 mutations since they lack a functional G1/S checkpoint. Targeted inhibition of WEE1 kinase may cause tumor cell apoptosis, primarily, in the p53-deficient tumor, via bypassing the G2/M checkpoint without properly repairing DNA damage, resulting in genome instability and chromosomal deletion. This review aims to provide a comprehensive overview of the biological role of WEE1 kinase and the potential of WEE1 inhibitor (WEE1i) for treating gynecological malignancies. We conducted a thorough literature search from 2001 to September 2023 in prominent databases such as PubMed, Scopus, and Cochrane, utilizing appropriate keywords of WEE1i and gynecologic oncology. WEE1i has been shown to inhibit tumor activity and enhance the sensitivity of chemotherapy or radiotherapy in preclinical models, particularly in p53-mutated gynecologic cancer models, although not exclusively. Recently, WEE1i alone or combined with genotoxic agents has confirmed its efficacy and safety in Phase I/II gynecological malignancies clinical trials. Furthermore, it has become increasingly clear that other inhibitors of DNA damage pathways show synthetic lethality with WEE1i, and WEE1 modulates therapeutic immune responses, providing a rationale for the combination of WEE1i and immune checkpoint blockade. In this review, we summarize the biological function of WEE1 kinase, development of WEE1i, and outline the preclinical and clinical data available on the investigation of WEE1i for treating gynecologic malignancies.

DNA Damage and Its Role in Cancer Therapeutics.

DNA damage is a double-edged sword in cancer cells. On the one hand, DNA damage exacerbates gene mutation frequency and cancer risk. Mutations in key DNA repair genes, such as breast cancer 1 (BRCA1) and/or breast cancer 2 (BRCA2), induce genomic instability and promote tumorigenesis. On the other hand, the induction of DNA damage using chemical reagents or radiation kills cancer cells effectively. Cancer-burdening mutations in key DNA repair-related genes imply relatively high sensitivity to chemotherapy or radiotherapy because of reduced DNA repair efficiency. Therefore, designing specific inhibitors targeting key enzymes in the DNA repair pathway is an effective way to induce synthetic lethality with chemotherapy or radiotherapy in cancer therapeutics. This study reviews the general pathways involved in DNA repair in cancer cells and the potential proteins that could be targeted for cancer therapeutics.

Abstract 812: High RAD51 gene expression is associated with aggressive biology and with poor survival in breast cancer

Abstract INTRODUCTION: Homologous recombination deficiency (HRD) is involved in breast cancer carcinogenesis, however, activation of DNA repair in cancer cells may promote its survival and progression. RAD51 plays an essential role in homologous recombination with BRCA2. Recently, RAD51 has been highlighted to play a role in resistance to DNA-damaging chemotherapy or PARP inhibitors. We hypothesized that RAD51 as a prognostic and predictive biomarker of drug sensitivity in breast cancer. MATERIALS AND METHODS: Total of 4500 primary breast cancer patients from three independent cohorts were examined. High and low expression of RAD51 were divided by median RNA expression. Response to treatments were assessed in total of 3000 patients across 11 independent cohorts of breast cancer patients that received neoadjuvant chemotherapy. RESULTS: RAD51 was upregulated in cancer compared to normal tissues in the TCGA cohort and was positively correlated with HRD. Cancer with high RAD51 group enriched DNA repair gene set in gene set enrichment analysis (GSEA) in all cohorts and had high expression of HRD-related genes including BRCA1 and BRCA2. Histological grade and Ki67 expression were positively correlated with RAD51, and all cancer proliferation gene sets from Hallmark (E2F target, G2M checkpoint, Myc Targets v1 and v2, and Mitotic Spindle) were strongly enriched in the high RAD51 expression breast cancer in all cohorts. In TCGA, tumor mutation burden and neoantigen were also higher in tumor with high RAD51 expression, but RAD51 expression was not elevated in BRCA1 or BRCA2 mutant tumors. Cytolytic activity score, a marker of cancer immunity, was elevated high RAD51 group in two cohorts, and the immune cell fraction calculated by the xCell algorithm showed increase in immune cell infiltration, including CD4 memory T cells, Th1 cells, M1 macrophages and activated dendritic cells, in all cohorts, suggesting a certain level of activation of cancer immunity in this RAD51 high breast cancer group. However, contrary to previous reports, RAD51 expression in breast cancer cell lines did not show any association between sensitivity to chemotherapy or PARP inhibitors. Neither for the breast cancer NAC cohort, RAD51 expression was not increased in the residual burden group, but conversely increase in RAD51expression was observed in pathological complete response group in some cohorts. Surprisingly, RAD51 was significantly associated with worse overall survival in all three large cohorts included in this analysis, and with worse disease-specific survival in two cohorts. CONCLUSIONS: RAD51 expression was significantly associated with worse survival, but did not with treatment-responsive, suggesting its usefulness as prognostic, but not predictive, biomarker. Citation Format: Rongrong Wu, Ankit Patel, Yoshihisa Tokumaru, Mariko Asaoka, Masanori Oshi, Li Yan, Takashi Ishikawa, Kazuaki Takabe. High RAD51 gene expression is associated with aggressive biology and with poor survival in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 812.

Brain Distribution of Berzosertib: An Ataxia Telangiectasia and Rad3-Related Protein Inhibitor for the Treatment of Glioblastoma.

The effective treatment of brain tumors is a considerable challenge in part because of the presence of the blood-brain barrier (BBB) that limits drug delivery. Glioblastoma multiforme (GBM) is an aggressive and infiltrative primary brain tumor with an extremely poor prognosis after standard-of-care therapy with surgery, radiotherapy (RT), and chemotherapy. DNA damage response (DDR) pathways play a critical role in DNA repair in cancer cells, and inhibition of these pathways can potentially augment RT and chemotherapy tumor cell toxicity. The ataxia telangiectasia and Rad3-related protein (ATR) kinase is a key regulator of the DDR network and is potently and selectively inhibited by the ATR inhibitor berzosertib. Although in vitro studies demonstrate a synergistic effect of berzosertib in combination with temozolomide, in vivo efficacy studies have yet to recapitulate this observation using intracranial tumor models. In the current study, we demonstrate that delivery of berzosertib to the brain is restricted by efflux at the BBB. Berzosertib has a high binding affinity to brain tissue compared with plasma, thereby leading to low free drug concentrations in the brain. Berzosertib distribution is heterogenous within the tumor, wherein concentrations are substantially lower in normal brain and invasive tumor rim (wherein the BBB is intact) when compared with those in the tumor core (wherein the BBB is leaky). These results demonstrate that high tissue binding and limited and heterogenous brain distribution of berzosertib may be important factors that influence the efficacy of berzosertib therapy in GBM. SIGNIFICANCE STATEMENT: This study examined the brain delivery and efficacy of berzosertib in patient-derived xenograft models of glioblastoma multiforme (GBM). Berzosertib is actively effluxed at the blood-brain barrier and is highly bound to brain tissue, leading to low free drug concentrations in the brain. Berzosertib is heterogeneously distributed into different regions of the brain and tumor and, in this study, was not efficacious in vivo when combined with temozolomide. These factors inform the future clinical utility of berzosertib for GBM.

Protein Found That Aids DNA Repair in Cancer Cells

Protein Found That Aids DNA Repair in Cancer Cells

Discovery of pyrano[2,3-d]pyrimidine-2,4-dione derivatives as novel PARP-1 inhibitors: design, synthesis and antitumor activity.

Poly(ADP-ribose) polymerases-1 (PARP-1) are involved in DNA repair damage and so PARP-1 inhibitors have been used as potentiators in combination with DNA damaging cytotoxic agents to compromise the cancer cell DNA repair mechanism, resulting in genomic dysfunction and cell death. In this study, we report the synthesis of a novel series of pyrano[2,3-d]pyrimidine-2,4-dione analogues as potential inhibitors against PARP-1. All the newly synthesized compounds were evaluated for their inhibitory activity towards PARP-1 and examined for their anti-proliferative activity against MCF-7 and HCT116 human cancer cell lines. The synthesized compounds showed promising activity where compounds S2 and S7 emerged as the most potent PARP-1 inhibitors with an IC50 value of 4.06 ± 0.18 and 3.61 ± 0.15 nM, respectively compared to that of Olaparib 5.77 nM and high cytotoxicity against MCF-7 with IC50 2.65 ± 0.05 and 1.28 ± 1.12 μM, respectively (Staurosporine 7.258 μM). Compound S8 remarkably showed the highest cell growth inhibition against MCF-7 and HCT116 with an IC50 value of 0.66 ± 0.05 and 2.76 ± 0.06 μM, respectively. Furthermore, molecular docking of the compounds into the PARP-1 active site was performed to explore the probable binding mode. Finally, most of the synthesized compounds were predicted to have good pharmacokinetics properties in a theoretical kinetic study.

KIAA0101 and UbcH10 interact to regulate non-small cell lung cancer cell proliferation by disrupting the function of the spindle assembly checkpoint

BackgroundChromosome mis-segregation caused by spindle assembly checkpoint (SAC) dysfunction during mitosis is an important pathogenic factor in cancer, and modulating SAC function has emerged as a potential novel therapy for non-small cell lung cancer (NSCLC). UbcH10 is considered to be associated with SAC function and the pathological types and clinical grades of NSCLC. KIAA0101, which contains a highly conserved proliferating cell nuclear antigen (PCNA)-binding motif that is involved in DNA repair in cancer cells, plays an important role in the regulation of SAC function in NSCLC cells, and bioinformatics predictions showed that this regulatory role is related to UbcH10. We hypothesized KIAA0101 and UbcH10 interact to mediate SAC dysfunction and neoplastic transformation during the development of USCLC.MethodsNSCLC cell lines were used to investigate the spatial-temporal correlation between UbcH10 and KIAA0101 expression and the downstream effects of modulating their expression were evaluated. Further immunoprecipitation assays were used to investigate the possible mechanism underlying the correlation between UbcH10 and KIAA0101. Eventually, the effect of modulating UbcH10 and KIAA010 on tumor growth and its possible mechanisms were explored through in vivo tumor-bearing models.ResultsIn this study, we demonstrated that both UbcH10 and KIAA0101 were upregulated in NSCLC tissues and cells and that their expression levels were correlated in a spatial and temporal manner. Importantly, UbcH10 and KIAA0101 coordinated to mediate the premature degradation of various SAC components to cause further SAC dysfunction and neoplastic proliferation. Moreover, tumor growth in vivo was significantly inhibited by silencing UbcH10 and KIAA0101 expression.ConclusionsKIAA0101 and UbcH10 interact to cause SAC dysfunction, chromosomal instability and malignant proliferation in NSCLC, suggesting that UbcH10 and KIAA0101 are potential therapeutic targets for the treatment of NSCLC by ameliorating SAC function.

The lipogenic LXR-SREBF1 signaling pathway controls cancer cell DNA repair and apoptosis and is a vulnerable point of malignant tumors for cancer therapy.

Cancer cells are defective in DNA repair, so they experience increased DNA strand breaks, genome instability, gene mutagenesis, and tumorigenicity; however, multiple classic DNA repair genes and pathways are strongly activated in malignant tumor cells to compensate for the DNA repair deficiency and gain an apoptosis resistance. The mechanisms underlying this phenomenon in cancer are unclear. We speculate that a key DNA repair gene or signaling pathway in cancer has not yet been recognized. Here, we show that the lipogenic liver X receptor (LXR)-sterol response element binding factor-1 (SREBF1) axis controls the transcription of a key DNA repair gene polynucleotide kinase/phosphatase (PNKP), thereby governing cancer cell DNA repair and apoptosis. Notably, the PNKP levels were significantly reduced in 95% of human pancreatic cancer (PC) patients, particularly deep reduction for sixfold in all of the advanced-stage PC cases. PNKP is also deficient in three other types of cancer that we examined. In addition, the expression of LXRs and SREBF1 was significantly reduced in the tumor tissues from human PC patients compared with the adjacent normal tissues. The newly identified LXR-SREBF1-PNKP signaling pathway is deficient in PC, and the defect in the pathway contributes to the DNA repair deficiency in the cancer. Strikingly, further diminution of the vulnerable LXR-SREBF1-PNKP signaling pathway using a small molecule triptonide, a new LXR antagonist identified in this investigation, at a concentration of 8 nM robustly activated tumor-suppressor p53 and readily elevated cancer cell DNA strand breaks over an apoptotic threshold, and selectively induced PC cell apoptosis, resulting in almost complete elimination of tumors in xenograft mice without obvious complications. Our findings provide new insight into DNA repair and apoptosis in cancer, and offer a new platform for developing novel anticancer therapeutics.

An Emerging Regulatory Role for the Tumor Microenvironment in the DNA Damage Response to Double-Strand Breaks.

Radiation, alkylating agents, and platinum-based chemotherapy treatments eliminate cancer cells through the induction of excessive DNA damage. The resultant DNA damage challenges the cancer cell's DNA repair capacity. Among the different types of DNA damage induced in cells, double-strand breaks (DSB) are the most lethal if left unrepaired. Unrepaired DSBs in tumor cells exacerbate existing gene deletions, chromosome losses and rearrangements, and aberrant features that characteristically enable tumor progression, metastasis, and drug resistance. Tumor microenvironmental factors like hypoxia, inflammation, cellular metabolism, and the immune system profoundly influence DSB repair mechanisms. Here, we put into context the role of the microenvironment in governing DSB repair mechanisms.

Identification and validation of non-histone protein acetylation regulated by the DNA damage response

Event Abstract Back to Event Identification and validation of non-histone protein acetylation regulated by the DNA damage response Judith Nicholson1, Junetha Syed Jabarulla1, Iolanda Vendrell1, 2, Xin Ying Yeo1, Roman Fischer2, Benedikt M. Kessler2 and Anne Kiltie1* 1 Department of Oncology, Medical Sciences Division, University of Oxford, United Kingdom 2 Nuffield Department of Medicine, Medical Sciences Division, University of Oxford, United Kingdom Background: The DNA Damage Response (DDR) is an attractive target for developing radiosensitising drugs, which can downregulate the efficiency of DNA repair in cancer cells induced by ionising radiation. Post-translational modifications of DNA repair proteins tightly coordinate the DDR events, among which lysine acetylation plays an important role in regulating histone and non-histone proteins in the DDR process. Our previous work on modulating acetylation with histone deacetylase inhibitor (HDACi) panobinostat in bladder cancer cell lines has shown to increase radiosensitivity by targeting DDR without any side effects to the normal tissue. In this study, we identified acetylation of DDR-associated non-histone proteins after treatment with panobinostat with the long-term goal of finding effective radiosensitisers with less systemic toxicity. Methods: Tandem mass spectrometry was used to identify potential DDR candidates that become acetylated following irradiation +/- panobinostat treatment. Acetylated protein enrichment was achieved by Immunoprecipitation. Radiosensitisation was determined by clonogenic assay, gamma H2AX levels by western blotting and interacting partners of the protein of interest by APEX-mediated proximity labelling. Results: In total, 228 proteins harbouring 657 unique acetylation sites with a subset related to DNA repair functions were identified. The acetylation of two hit DDR candidates sMEK1 and THRAP3 was validated. The clonogenic survival assay and the pattern of H2AX phosphorylation with acetyl-mimic and acetyl-dead constructs indicated the important role of the identified acetylation site in THRAP3 for radiosensitivity. Conclusion: Several non-histone proteins are regulated on a post-translational level by acetylation during the DNA damage response. The acetylated proteins identified in this dataset represent a complex sample of non-histone proteins, THRAP3 is one of which we validated as having a role in radiosensitisation via a specific acetyl site. Identifying the interacting partners of acetylated THRAP3 would help in understanding the biological significance of identified acetylation site with respect to DDR. Keywords: DNA repair protein, Proteomics, Acetylation, HDACi, THRAP3 Conference: Bladder Cancer Translational Research Meeting, London, United Kingdom, 29 Mar - 29 Mar, 2019. Presentation Type: Poster Topic: Optimisation of diagnostic pathways Citation: Nicholson J, Syed Jabarulla J, Vendrell I, Yeo X, Fischer R, Kessler BM and Kiltie A (2019). Identification and validation of non-histone protein acetylation regulated by the DNA damage response. Front. Oncol. Conference Abstract: Bladder Cancer Translational Research Meeting. doi: 10.3389/conf.fonc.2019.01.00017 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 01 Mar 2019; Published Online: 27 Sep 2019. * Correspondence: Prof. Anne Kiltie, Department of Oncology, Medical Sciences Division, University of Oxford, Oxford, England, OX3 7DQ, United Kingdom, anne.kiltie@oncology.ox.ac.uk Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Judith Nicholson Junetha Syed Jabarulla Iolanda Vendrell Xin Ying Yeo Roman Fischer Benedikt M Kessler Anne Kiltie Google Judith Nicholson Junetha Syed Jabarulla Iolanda Vendrell Xin Ying Yeo Roman Fischer Benedikt M Kessler Anne Kiltie Google Scholar Judith Nicholson Junetha Syed Jabarulla Iolanda Vendrell Xin Ying Yeo Roman Fischer Benedikt M Kessler Anne Kiltie PubMed Judith Nicholson Junetha Syed Jabarulla Iolanda Vendrell Xin Ying Yeo Roman Fischer Benedikt M Kessler Anne Kiltie Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Development of Potent Pyrazolopyrimidinone-Based WEE1 Inhibitors with Limited Single-Agent Cytotoxicity for Cancer Therapy.

WEE1 kinase regulates the G2 /M cell-cycle checkpoint, a critical mechanism for DNA repair in cancer cells that can confer resistance to DNA-damaging agents. We previously reported a series of pyrazolopyrimidinones based on AZD1775, a known WEE1 inhibitor, as an initial investigation into the structural requirements for WEE1 inhibition. Our lead inhibitor demonstrated WEE1 inhibition in the same nanomolar range as AZD1775, and potentiated the effects of cisplatin in medulloblastoma cells, but had reduced single-agent cytotoxicity. These results prompted the development of a more comprehensive series of WEE1 inhibitors. Herein we report a series of pyrazolopyrimidinones and identify a more potent WEE1 inhibitor than AZD1775 and additional compounds that demonstrate that WEE1 inhibition can be achieved with reduced single-agent cytotoxicity. These studies support that WEE1 inhibition can be uncoupled from the potent cytotoxic effects observed with AZD1775, and this may have important ramifications in the clinical setting where WEE1 inhibitors are used as chemosensitizers for DNA-targeted chemotherapy.

Application of synthetic lethality in the precise oncology

Cancer is a leading cause of death in both developed and developing countries. Most cancers occur as a result of somatically acquired alternations in the genomes of normal cells. The somatic alterations presented in a cancer genome can reach about ten thousands. However, a few such alterations that are able to drive initiation and progression of cancer are defined as “driver” mutations, while all other mutations are assumed to be randomly acquired and termed as “passenger” mutations. Driver mutations confer growth advantage on the cells carrying them and have been positively selected during the evolution of the cancer. Accumulating driver mutations in a cell genome likely result in multi-step mutations of encoded proteins or non-coding transcripts, which change their biological functions of the proteins and transcripts. Driver mutations potentially have been classified into two categories: “oncogenes” that are likely resulted from gain-of-function mutations and “tumor suppressor genes” that may be due to loss-of-function mutations. Together these two types of mutations drive cancer initiation and development. Targeting driver gene mutations have been successfully applied to the treatment of various cancers in humans. In this review, we introduce the concept of driver and passenger mutations, and theory of synthetic lethality (SL). Furthermore, we address the application of SL by targeting synthetic lethal partner of these “driver” genes and the clinical trial that can be designed based on the theory of SL. Synthetic lethal interactions arise when the perturbation of more than one genes simultaneously results in the loss of viability, whereas a deficiency in only one of these genes does not. SL might be extended to synthetic sickness, which is referred to the sickness but not lethality in cells resulting from mutations of those genes, and synthetic dosage lethality by targeting its partner to kill cells with overexpression of one gene. This theory has been applied to genetic studies to determine functional interactions among different genes for decades and has been exploited for the development of new genotype-selective anticancer agents in engineered human tumor cells. In precision oncology, the theory of SL provides greater promise in specifically targeting cancer cells with genetic mutations but not in normal cells. For example, targeting both of the breast-cancer susceptibility genes 1 and 2( BRCA1 and BRCA2 ) deficiencies dramatically sensitized cells to poly(ADP-ribose) polymerase (PARP) inhibitors due to associated defective homologous recombination, which leads to dysfunction of DNA repair in cancer cells. Moreover, oncogenic drivers such as RAS, P53 are not “druggable”, but recently these oncogenic drivers have been studied in successfully screening for their synthetic lethal partners or agents. If a synthetic lethal agent can be combined with conventionally chemotherapy, this will probably benefit cancer patients. Therefore, the application of the SL in cancer researches and clinical trials might represent one of the most important technological breakthrough in the treatment of cancer in the era of precision oncology.

Disruption of DNA repair in cancer cells by ubiquitination of a destabilising dimerization domain of nucleotide excision repair protein ERCC1.

DNA repair pathways present in all cells serve to preserve genome stability, but in cancer cells they also act reduce the efficacy of chemotherapy. The endonuclease ERCC1-XPF has an important role in the repair of DNA damage caused by a variety of chemotherapeutic agents and there has been intense interest in the use of ERCC1 as a predictive marker of therapeutic response in non-small cell lung carcinoma, squamous cell carcinoma and ovarian cancer. We have previously validated ERCC1 as a therapeutic target in melanoma, but all small molecule ERCC1-XPF inhibitors reported to date have lacked sufficient potency and specificity for clinical use. In an alternative approach to prevent the repair activity of ERCC1-XPF, we investigated the mechanism of ERCC1 ubiquitination and found that the key region was the C-terminal (HhH)2 domain which heterodimerizes with XPF. This ERCC1 region was modified by non-conventional lysine-independent, but proteasome-dependent polyubiquitination, involving Lys33 of ubiquitin and a linear ubiquitin chain. XPF was not polyubiquitinated and its expression was dependent on presence of ERCC1, but not vice versa. To our surprise we found that ERCC1 can also homodimerize through its C-terminal (HhH)2 domain. We exploited the ability of a peptide containing this C-terminal domain to destabilise both endogenous ERCC1 and XPF in human melanoma cells and fibroblasts, resulting in reductions of up to 85% in nucleotide excision repair and near two-fold increased sensitivity to DNA damaging agents. We suggest that the ERCC1 (HhH)2 domain could be used in an alternative strategy to treat cancer.

Shutting down the power supply for DNA repair in cancer cells.

Phosphoglycerate mutase 1 (PGAM1) functions in glycolysis. In this issue, Qu et al. (2017. J. Cell Biol. https://doi.org/10.1083/jcb.201607008) show that PGAM1 inactivation leads to nucleotide depletion, which causes defective homologous recombination-mediated DNA repair, suggesting that targeting metabolic enzymes increases cancer cell susceptibility to DNA damaging agents.

Biomarkers of Response and Resistance to DNA Repair Targeted Therapies.

Drugs targeting DNA damage repair (DDR) pathways are exciting new agents in cancer therapy. Many of these drugs exhibit synthetic lethality with defects in DNA repair in cancer cells. For example, ovarian cancers with impaired homologous recombination DNA repair show increased sensitivity to poly(ADP-ribose) polymerase (PARP) inhibitors. Understanding the activity of different DNA repair pathways in individual tumors, and the correlations between DNA repair function and drug response, will be critical to patient selection for DNA repair targeted agents. Genomic and functional assays of DNA repair pathway activity are being investigated as potential biomarkers of response to targeted therapies. Furthermore, alterations in DNA repair function generate resistance to DNA repair targeted agents, and DNA repair states may predict intrinsic or acquired drug resistance. In this review, we provide an overview of DNA repair targeted agents currently in clinical trials and the emerging biomarkers of response and resistance to these agents: genetic and genomic analysis of DDR pathways, genomic signatures of mutational processes, expression of DNA repair proteins, and functional assays for DNA repair capacity. We review biomarkers that may predict response to selected DNA repair targeted agents, including PARP inhibitors, inhibitors of the DNA damage sensors ATM and ATR, and inhibitors of nonhomologous end joining. Finally, we introduce emerging categories of drugs targeting DDR and new strategies for integrating DNA repair targeted therapies into clinical practice, including combination regimens. Generating and validating robust biomarkers will optimize the efficacy of DNA repair targeted therapies and maximize their impact on cancer treatment. Clin Cancer Res; 22(23); 5651-60. ©2016 AACR.

Inhibiting Mitochondrial DNA Ligase IIIα Activates Caspase 1-Dependent Apoptosis in Cancer Cells.

Elevated levels of DNA ligase IIIα (LigIIIα) have been identified as a biomarker of an alteration in DNA repair in cancer cells that confers hypersensitivity to a LigIIIα inhibitor, L67, in combination with a poly (ADP-ribose) polymerase inhibitor. Because LigIIIα functions in the nucleus and mitochondria, we examined the effect of L67 on these organelles. Here, we show that, although the DNA ligase inhibitor selectively targets mitochondria, cancer and nonmalignant cells respond differently to disruption of mitochondrial DNA metabolism. Inhibition of mitochondrial LigIIIα in cancer cells resulted in abnormal mitochondrial morphology, reduced levels of mitochondrial DNA, and increased levels of mitochondrially generated reactive oxygen species that caused nuclear DNA damage. In contrast, these effects did not occur in nonmalignant cells. Furthermore, inhibition of mitochondrial LigIIIα activated a caspase 1-dependent apoptotic pathway, which is known to be part of inflammatory responses induced by pathogenic microorganisms in cancer, but not nonmalignant cells. These results demonstrate that the disruption of mitochondrial DNA metabolism elicits different responses in nonmalignant and cancer cells and suggests that the abnormal response in cancer cells may be exploited in the development of novel therapeutic strategies that selectively target cancer cells. Cancer Res; 76(18); 5431-41. ©2016 AACR.

3'-hydroxy-3,4,5,4'-tetramethoxystilbene, the metabolite of resveratrol analogue DMU-212, inhibits ovarian cancer cell growth in vitro and in a mice xenograft model.

In screening studies, the cytotoxic activity of four metabolites of resveratrol analogue 3,4,5,4′-tetramethoxystilbene (DMU-212) against A-2780 and SKOV-3 ovarian cancer cells was investigated. The most active metabolite, 3′-hydroxy-3,4,5,4′-tetramethoxystilbene (DMU-214), was chosen for further studies. The cytotoxicity of DMU-214 was shown to be higher than that of the parent compound, DMU-212, in both cell lines tested. Since DMU-212 was supposed to undergo metabolic activation through its conversion to DMU-214, an attempt was made to elucidate the mechanism of its anti-proliferative activity. We found that in SKOV-3 cells lacking p53, DMU-214 induced receptor-mediated apoptosis. In A-2780 cell line with expression of wild-type p53, DMU-214 modulated the expression pattern of p53-target genes driving intrinsic and extrinsic apoptosis pathways, as well as DNA repair and damage prevention. Regardless of the up-regulation of p48, p53R2, sestrins and Gaad45 genes involved in cancer cell DNA repair, we demonstrated the stronger anti-proliferative and pro-apoptotic effects of DMU-214 in A-2780 cells when compared to those in SKOV-3. Hence we verified DMU-214 activity in the xenograft model using SCID mice injected with A-2780 cells. The strong anti-proliferative activity of DMU-214 in the in vivo model allowed to suggest the tested compound as a potential therapeutic in ovarian cancer treatment.