Abstract 4861: Loss of YAP1 activates Wnt/beta-Catenin signaling in prostate cancer

Abstract

Abstract Prostate cancer (PCa) is the most common non-cutaneous cancer among American men. In 2019, 174,650 new patients will be diagnosed from this disease. Most patients with localized PCa could be treated successfully. However, when PCa develops into castrate-resistant prostate cancer (CRPCa), the five-year survival rate drops below 30%. Neuroendocrine prostate cancer (NEPCa) is an aggressive subtype of PCa observed in 20%-30% CRPCa patients. Understanding how NEPCa progressed from prostate adenocarcinoma could reveal novel therapeutic targets. Previous studies indicate that activation of Wnt/beta-Catenin signaling promotes the progression to CRPCa with an increased NE differentiation. Additionally, animal studies suggest that Wnt/beta-Catenin signaling is active in NEPCa. Here we explored the mechanisms that promote Wnt/beta-Catenin signaling in NEPCa. Using TRAMP mice, which develop NEPCa after castration, we assessed the expression of Wnt-related genes and found that after androgen deprivation, the expression of Wnt7A is increased in prostate derived from both wild type and TRAMP mice but the expression of DKK1, a Wnt inhibitor, is decreased in wild type prostate but not in TRAMP prostate. The elevated expression of Wnt7a in combination with the lack of induction of Dkk1 in TRAMP tumors provides a mechanism to activate Wnt/beta-Catenin signaling in these tumors. Furthermore, we found the expression of YES-associated Protein (YAP1), a key transcriptional coactivator of Hippo pathway, is lost in NEPCa, in contrast to the elevated expression of YAP1 in high-grade prostate adenocarcinoma. YAP1 knockdown activated Wnt/beta-Catenin activity in PCa PC3 and 22Rv1 cells, indicating that the loss of YAP1 expression provides another mechanism to activate Wnt/beta-Catenin signaling, promoting NEPCa phenotype in PCa cells. Funding: This study is supported by: FWCC/Foundation Legacy Funds, DOD New Investigator Award, The Office of Research SEED awards, NIH R01 AND R03. Citation Format: Siyuan Cheng, Shu Yang, Nestor Prieto-Dominguez, Zachary M. Connelly, Yingli Shi, Xiuping Yu. Loss of YAP1 activates Wnt/beta-Catenin signaling in prostate cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4861.