Abstract 2005: ZDHHC7 contributes to ferroptosis resistance through YAP localization in ovarian clear cell carcinoma

Abstract

Abstract [Objective] Ovarian clear cell carcinoma (CCC) shows unique clinical features including an association with benign endometriosis which contains iron-rich fluid, and poor prognosis because of resistance to chemotherapy. Therefore, elucidating the basic mechanism as well as new treatment strategy of ovarian CCC is urgently needed. Recently, ferroptosis, which is characterized by the iron-dependent accumulation of lipid ROS, was reported to affect the malignant behaviors. Also, some reports showed ferroptosis regulation by Hippo signaling. ZDHHC7 is reported as the molecule regulating yes-associated protein (YAP), a key molecule of Hippo signature and is one of the ovarian CCC gene signature which we previously identified. We explored the impact of ferroptosis in ovarian CCC by investigating YAP localization.[Methods] We performed immunohistochemistry (IHC) of malondialdehyde (MDA; a marker of lipid reactive oxygen species, ROS) and 8-Oxo-2'-deoxyguanosine (8-OHdG, a marker of oxidative stress DNA damage) to analyze the status of lipid ROS with ovarian cancer patients. We also performed IHC of YAP and ZDHHC7 to evaluate them in clinical status. We calculated IC50 values of erastin (ferroptosis inducer) with seventeen ovarian cancer cell lines. Functional annotation clustering of microarray expression data was performed using Metascape. ZDHHC7 knockdown and YAP-5SA mutant, or YAP-activated form of ovarian CCC cell lines were generated and applied for in vitro assays.[Results] IHC analysis indicated higher MDA expression (p=0.0354) and 8-OHdG (p<0.0001) in CCC compared to high-grade serous carcinoma (HGSC), suggesting higher lipid ROS as well as oxidative stress status in ovarian CCC. IC50 values of erastin were significantly higher in CCC than in other types of ovarian cancer (p<0.01). Categorical analysis revealed that genes related to Hippo signaling were enriched in erastin-resistant cell lines. IHC analyses indicated low nuclear expression of YAP and high expression of ZDHHC7 in CCC samples (p=0.0010). The cases with low expression of nuclear YAP showed significantly poorer prognosis compared to high expression cases (p=0.0075) in ovarian CCC. YAP-5SA mutant (YAP-active-mutant) CCC cells showed higher sensitivity to erastin and ML210 (ferroptosis inducer) than control in ovarian CCC cell lines. ZDHHC7 knockdown of CCC cells induced nuclear localization of YAP and showed decreased IC50 values of erastin and ML210 compared to control cells.[Conclusion] Although lipid ROS is accumulated in ovarian CCC, ovarian CCC showed ferroptosis resistance through YAP localization regulated by ZDHHC7. Citation Format: Yoko Furutake, Ken Yamaguchi, Masayo Ukita, Mana Taki, Koji Yamanoi, Junzo Hamanishi, Takashi Kobayashi, Masaki Mandai. ZDHHC7 contributes to ferroptosis resistance through YAP localization in ovarian clear cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2005.