Abstract NTOC-114: ARID1A DEFICIENCY IN OVARIAN CLEAR CELL CARCINOMAS UP–REGULATES OXIDATIVE STRESS AND SENSITIZES CELLS TO ROS–INDUCING AGENTS

Abstract

Abstract Inactivating mutations in AT-rich interaction domain 1A (ARID1A) are most frequently found in ovarian clear cell carcinomas (OCCC) and ovarian endometrioid carcinomas (OEC). The functional roles of ARID1A are not completely understood and there are limited therapeutic strategies that specifically target ARID1A-mutant cancers. Given that ARID1A expression is lost in cancer, ARID1A mutations cannot be targeted directly and novel therapeutic strategies are required to target ARID1A-mutant cancers. In this study, drug responses between ARID1A-wildtype and ARID1A-mutant cell lines were compared using the ‘Genomics of Drug Sensitivities in Cancer’ database. From this analysis, we found that ARID1A-mutant cell lines are more sensitive to elesclomol, which is a reactive oxygen species (ROS)-inducing agent. This finding was validated using a panel of well-characterized ovarian and endometrial cancer cell lines. ARID1A-mutant OCCC cell lines exhibited lower IC50 values and higher apoptotic rates when treated with elesclomol. Knockdown and re-expression of ARID1A in ovarian cancer cells showed that ARID1A is required to protect cancer cells from oxidative stress. In the absence of ARID1A, intracellular ROS levels were increased as determined by flow cytometry. Immunostaining of 4-hydroxy-2-nonenals (4-HNE), one of the products from lipid peroxidation induced by ROS, in OCCC patient samples indicated an up-regulation of oxidative stress in the tumor. We also found that ARID1A negatively regulates the expression of NRF2 which is the major regulator of the antioxidant response in the cell. Knockdown of NRF2 in ovarian cancer cell lines revealed that NRF2 expression may be preferentially required for protection from oxidative stress and cell proliferation in ARID1A-mutant cells. Analysis using The Cancer Genome Atlas (TCGA) UCEC dataset revealed that ARID1A-mutant tumor samples have higher expression of NRF2 and NRF2-target genes. In summary, this study revealed novel roles of ARID1A in protecting ovarian cancer cells against oxidative stress. In the absence of ARID1A, NRF2 is up-regulated and may be required to compensate for ARID1A deficiency. These findings suggest that ARID1A-mutant ovarian cancer cells may be targeted for treatment with ROS-inducing agents and NRF2 inhibitors. Citation Format: Suet-Yan Kwan, Xuanjin Cheng, Suet-Ying Kwan, Daisy I. Izaguirre, Yvonne T.M. Tsang, Jong-Sun Choi, Hoi-Shan Kwan, David M. Gershenson and Kwong-Kwok Wong. ARID1A DEFICIENCY IN OVARIAN CLEAR CELL CARCINOMAS UP–REGULATES OXIDATIVE STRESS AND SENSITIZES CELLS TO ROS–INDUCING AGENTS [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr NTOC-114.