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Loss of E2F7 confers resistance to poly-ADP-ribose polymerase (PARP) inhibitors in BRCA2-deficient cells.

ABSTRACT: BRCA proteins are essential for homologous recombination (HR) DNA repair, and their germline or somatic inactivation is frequently observed in human tumors. Understanding the molecular mechanisms underlying the response of BRCA-deficient tumors to chemotherapy is paramount for developing improved personalized cancer therapies. While PARP inhibitors have been recently approved for treatment of BRCA-mutant breast and ovarian cancers, not all patients respond to this therapy, and resistance to these novel drugs remains a major clinical problem. Several mechanisms of chemoresistance in BRCA2-deficient cells have been identified. Rather than restoring normal recombination, these mechanisms result in stabilization of stalled replication forks, which can be subjected to degradation in BRCA2-mutated cells. Here, we show that the transcriptional repressor E2F7 modulates the chemosensitivity of BRCA2-deficient cells. We found that BRCA2-deficient cells are less sensitive to PARP inhibitor and cisplatin treatment after E2F7 depletion. Moreover, we show that the mechanism underlying this activity involves increased expression of RAD51, a target for E2F7-mediated transcriptional repression, which enhances both HR DNA repair, and replication fork stability in BRCA2-deficient cells. Our work describes a new mechanism of therapy resistance in BRCA2-deficient cells, and identifies E2F7 as a putative biomarker for tumor response to PARP inhibitor therapy.

SUBMITTER: Clements KE

PROVIDER: S-EPMC6158596 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Loss of E2F7 confers resistance to poly-ADP-ribose polymerase (PARP) inhibitors in BRCA2-deficient cells.

Clements Kristen E KE Thakar Tanay T Nicolae Claudia M CM Liang Xinwen X Wang Hong-Gang HG Moldovan George-Lucian GL

Nucleic acids research 20180901 17

BRCA proteins are essential for homologous recombination (HR) DNA repair, and their germline or somatic inactivation is frequently observed in human tumors. Understanding the molecular mechanisms underlying the response of BRCA-deficient tumors to chemotherapy is paramount for developing improved personalized cancer therapies. While PARP inhibitors have been recently approved for treatment of BRCA-mutant breast and ovarian cancers, not all patients respond to this therapy, and resistance to thes ...[more]

PMID: 30032296

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Project description:BackgroundOvarian cancer is the sixth most common cancer and seventh most common cause of cancer death in women world-wide. Three-quarters of women present when the disease has spread throughout the abdomen (stage III or IV) and treatment consists of a combination of debulking surgery and platinum-based chemotherapy. Although initial responses to chemotherapy are good, most women will relapse and require further chemotherapy and will eventually develop resistance to chemotherapy.PARP (poly (ADP-ribose) polymerase) inhibitors, are a novel type of medication that works by preventing cancer cells from repairing their DNA once they have been damaged by other chemotherapy agents. It is not clear how PARP inhibitors compare to conventional chemotherapy regimens for the treatment of ovarian cancer, with respect to survival, side effects and quality of life.ObjectivesTo determine the benefits and risks of PARP inhibitors for the treatment of epithelial ovarian cancer (EOC).Search methodsWe identified randomised controlled trials (RCTs) by searching the Cochrane Central Register of Controlled Trials (CENTRAL 2014, Issue 4), the Cochrane Gynaecological Cancer Group Trial Register, MEDLINE (1990 to May 2014), EMBASE (1990 to May 2014), ongoing trials on www.controlled-trials.com/rct, www.clinicaltrials.gov, www.cancer.gov/clinicaltrials and the National Research Register (NRR), the FDA database and pharmaceutical industry biomedical literature.Selection criteriaWomen with histologically proven EOC who were randomised to treatment groups in trials that either compared PARP inhibitors with no treatment, or PARP inhibitors versus conventional chemotherapy, or PARP inhibitors together with conventional chemotherapy versus conventional chemotherapy alone.Data collection and analysisWe used standard Cochrane methodology. Two review authors independently assessed whether studies met the inclusion criteria. We contacted investigators for additional data, where possible. Outcomes included survival, quality of life and toxicity.Main resultsWe included four RCTs involving 599 women with EOC. Data for veliparib were limited and of low quality, due to small numbers (75 women total). Olaparib, on average, improved progression-free survival (PFS) when added to conventional treatment and when used as maintenance treatment in women with platinum-sensitive disease compared with placebo (hazard ratio (HR) 0.42, 95% confidence interval (CI) 0.29 to 0.60; 426 participants ; two studies), but did not improve overall survival (OS) (HR 1.05, 95% CI 0.79 to 1.39; 426 participants; two studies). We graded this evidence as moderate quality using the GRADE approach. Olaparib was associated with more severe adverse events (G3/4) during the maintenance phase compared with controls (risk ratio (RR) 1.74, 95% CI 1.22 to 2.49; 385 participants, two studies; moderate quality evidence). Quality of life data were insufficient for meta-analysis. We identified four ongoing studies.Authors' conclusionsPARP inhibitors appear to improve PFS in women with recurrent platinum-sensitive disease. Ongoing studies are likely to provide more information about whether the improvement in PFS leads to any change in OS in this subgroup of women with EOC. More research is needed to determine whether PARP inhibitors have any role to play in platinum-resistant disease.

Dataset Information

Loss of E2F7 confers resistance to poly-ADP-ribose polymerase (PARP) inhibitors in BRCA2-deficient cells.

Publications

Loss of E2F7 confers resistance to poly-ADP-ribose polymerase (PARP) inhibitors in BRCA2-deficient cells.

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