Abstract 1761: Dual inhibition of HSP27 and FAO as a novel therapeutic strategy for cisplatin-resistant ovarian cancer

Abstract Cisplatin is the most commonly employed chemotherapeutic drug for ovarian cancer treatment. However, most ovarian cancer patients experience recurrent cisplatin-resistant cancer, for which treatment options are limited. We have previously shown that inhibition of heat shock protein 27 (HSP27) or fatty acid oxidation (FAO) sensitizes cisplatin-resistant ovarian cancer cells to cisplatin. However, it is unknown if HSP27 and FAO pathways interact to promote cisplatin resistance in ovarian cancer cells. Therefore, we tested whether cisplatin-resistant ovarian cancer cells are sensitive to concurrent HSP27 and FAO inhibition. Strikingly, dual inhibition of HSP27 and FAO, with the clinically employed drugs ivermectin and perhexiline respectively, dramatically decreased the viability of A2780CIS, a cisplatin-resistant ovarian cancer cell line. We also found that HSP27 knockdown cancer cells are more sensitive to cisplatin and perhexiline dual treatment. Thus, we sought to test the hypothesis that cisplatin-resistant ovarian cancer cells rely on FAO upon HSP27 inhibition to maintain cisplatin resistance. To test if FAO is affected by HSP27 inhibition, we measured AMPK activity and CPT1A expression, an inducer of FAO and the rate limiting enzyme of FAO respectively. We found that AMPK is activated and CPT1A is upregulated in HSP27 knockdown cancer cells. It has been shown that cisplatin induces reactive oxygen species (ROS) and that HSP27 is a negative regulator of ROS. Thus, we treated HSP27 knockdown cancer cells with cisplatin and measured the levels of mitochondrial and cellular ROS, oxidized/reduced lipids, and reduced thiols using MitoSOX, CellROX, Image -iT Lipid Peroxidation, and ThiolTracker fluorescent dyes, respectively. Our data demonstrates that HSP27 inhibition increases mitochondrial ROS, cellular ROS, and the ratio of oxidized to reduced lipids in cisplatin-treated cells. Additionally, HSP27 inhibition decreases levels of reduced thiols in this context. Our preliminary data also suggests that cisplatin-treated HSP27 knockdown cells have decreased expression of glucose-6-phosphate dehydrogenase (G6PD) and glutathione reductase (GSR), key enzymes that facilitate the reduction of glutathione into its reduced form (GSH). Additionally, we demonstrate that attenuation of cisplatin-induced ROS with N-Acetyl cysteine (NAC) prevented cisplatin-induced apoptosis and ferroptosis. NAC also attenuated cisplatin-mediated induction of HSP27 and FAO gene expression in cisplatin-resistant ovarian cancer cells. Collectively, our results demonstrate that HSP27 and FAO are two parallel pathways that promote cisplatin resistance in ovarian cancer cells by attenuating cisplatin-induced ROS. Future studies will determine the in vivo efficacy of this combination therapy and if dual inhibition leads to synergistic cell death through a ROS based mechanism. Citation Format: James P. Heiserman, Zenab Minhas, Dong-Joo Cheon. Dual inhibition of HSP27 and FAO as a novel therapeutic strategy for cisplatin-resistant ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1761.