Poly(ADP-ribose) polymerase (PARP) inhibitors exploit synthetic lethality to target epithelial ovarian cancer (EOC) with hereditary BRCA mutations and defects in homologous recombination repair (HRR). However, such an approach is limited to a small subset of EOC patients and compromised by restored HRR due to secondary mutations in BRCA genes. Here, it was demonstrated that triapine, a small molecule inhibitor of ribonucleotide reductase, enhances the sensitivity of BRCA wild-type EOC cells to the PARP inhibitor olaparib and the topoisomerase II inhibitor etoposide. Triapine abolishes olaparib-induced BRCA1 and Rad51 foci, and disrupts BRCA1 interaction with the Mre11-Rad50-Nbs1 (MRN) complex in BRCA1 wild-type EOC cells. It has been shown that phosphorylation of CtIP (RBBP8) is required for interaction with BRCA1 and with MRN to promote DNA double-strand break (DSB) resection during S- and G2-phases of the cell cycle. Mechanistic studies within reveal that triapine inhibits CDK activity and blocks olaparib-induced CtIP phosphorylation through Chk1 activation. Furthermore, triapine abrogates etoposide-induced CtIP phosphorylation and DSB resection as evidenced by marked attenuation of RPA32 phosphorylation. Concurrently, triapine obliterates etoposide-induced BRCA1 foci and sensitizes BRCA1 wild-type EOC cells to etoposide. Using a GFP-based HRR assay, it was determined that triapine suppresses HRR activity induced by an I-SceI-generated DSB. These results suggest that triapine augments the sensitivity of BRCA wild-type EOC cells to drug-induced DSBs by disrupting CtIP-mediated HRR.

Background: Platinum resistance may be attributable to inherent or acquired proficiency in homologous recombination repair (HRR) in epithelial ovarian cancer (EOC). The objective of this study was to evaluate the efficacy of the small molecule inhibitor triapine to disrupt HRR and sensitise BRCA wild-type EOC cells to platinum-based combination therapy in vitro and in vivo.

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Aims: To compare baseline risk factors for type 1 vs. 2 endometrial cancers and analyze these risk factors for association with overall survival and time to recurrence. Methods: Retrospective review of 816 consecutive endometrial cancer cases was conducted with diagnosis from January 2005 to December 2010 and clinical course until 2016. Risk factors, treatment, recurrence, and death were compared using 2 sample t tests, χ² test and Cox Regression models. Results: There were 550 cases of type 1 and 266 cases of type 2 cancer. Patients with type 2 disease were older (p < 0.001), less obese (p = 0.03), non-white (p < 0.001), and menopausal (p = 0.02). There was no difference in use of oral contraceptives, hormone replacement therapy (HRT), smoking, or major cardiovascular disease. Cox Regression models showed that type 2 disease (p < 0.001) and advanced stage (p = 0.001) were associated with recurrence. Conclusions: Consistent with previous literature, our analysis found that type 2 cancer is more common in non-white, older, and less obese patients and associated with higher mortality and recurrence. However, inconsistent with previous literature, we found no association between type 2 cancer and diabetes mellitus or use of HRT. These factors should be considered when approaching patients with endometrial cancer.