Abstract 377: Anti-tumor effects in combination with PARP inhibitor and DNMT inhibitor in ovarian cancer
Authors: Lee Jeong-Won , Jeong Soo Young , Ryu Ji Yoon , Lee Yoo-Young , Paik ESUN 
Published: August 2019

Objective: Olaparib is one of the first PARP inhibitors and has been used for maintenance therapy in BRCA-mutant patients with platinum-sensitive, recurrent, high-grade serous ovarian cancer. However, there are some results of failure to show impressive clinical benefit with PARP inhibitor only. So, new strategies to maximize the efficacy for using these agents were developed. DNA-demethylating agents, inhibitors of DNA methylation and DNA methyltransferases(DNMTs), increase PARP1 tightly bound into chromatin in acute myeloid leukemia (AML) and breast cancer cells. The purpose of this study is to investigate the anti-cancer effect of combination therapy, olaparib with DNA demethylating agents(5-azacytidine) in ovarian cancer cell models including in vitro and in vivo - cell line xenografts and patient-derived tumor xenografts (PDX) - experiments.

Methods: In vitro experiments, we treated olaparib only, 5-azacytidine only, and combination with olaparib and 5-azacytidine in ovarian cancer cell lines (A2780, SKOV3ip1, HeyA8) to evaluate the effect on cell proliferation using MTT assay. To check the human active caspase3, MMP2, and MMP9 level and the apoptosis according to each treatment, we performed the Western blot, ELISA, and apoptosis assay in ovarian cancer cell line. With wound-healing assay and migration assay, invasive ability of cancer cell was evaluated and compared after few hours of treatment with inhibitors. In addition, in vivo therapy experiments for this co-treatment in established cell line xenografts and PDX models of epithelial ovarian cancer were done. For cell line xenografts, A2780 were injected into the peritoneal cavity of mice. For the PDX model, surgical patient tumor specimens (less than 2-3mm) implanted into the subrenal capsule of left kidney and propagated by serial transplantation. We recorded body weight, tumor weight, and number of tumor nodules.

Results: Both olaparib and 5-azacytidine inhibited the cell survival and increased the apoptosis in ovarian cancer cells. In this study, combination treatment of cells with olaparib and 5-azacytidine significantly inhibited the cell growth and increased the apoptosis compared to the single agent treatment in ovarian cancer cells. In in vivo experiments, combination treatment with olaparib and 5-azacytidine significantly decreased weight and nodule numbers of tumor in cell-line xenograft models with A2780 cells and PDX model compared with control, olaparib alone, or 5-azacytidine alone group.

Conclusions: We found that combination treatment with olaparib and DNA-demethylating agent (5-azacytidine) has synergetic effect to attack ovarian cancer cells compared with control or single agent treatment through in vitro and in vivo tests.

Citation Format: Jeong-Won Lee, Soo Young Jeong, Ji Yoon Ryu, Yoo-Young Lee, ESUN Paik. Anti-tumor effects in combination with PARP inhibitor and DNMT inhibitor in ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 377.