Abstract 1077: Porcupine inhibition enhances enzalutamide efficacy in drug resistant prostate cancer

Abstract Androgen receptor (AR) signaling continues to participate as a vital component of castration-resistant prostate cancer (CRPC). Subsequently, this has led to the development of Androgen Signaling Inhibitors (ASI), specifically Enzalutamide (ENZ), which is a direct inhibitor of AR, to clinically manage CRPC. Inevitably, ENZ treatment only provides improvement for approximately two months before advancing to an incurable form, ENZ-resistant CRPC. With PCa ranking as the second leading cause of cancer-related deaths in USA males, there is an urgency and necessity for the discovery and development of novel therapeutic approaches for CRPC. Wnt signaling has been extensively documented in its involvement in PCa and the tumor microenvironment (TME), however the mechanism of how the Wnt signaling cascades contribute to ENZ resistance is still ambiguous. Recently we have published that the activation of the canonical Wnt pathway contributes to the progression of ENZ resistance in CRPC and using a combination of β-catenin inhibitor with ENZ resulted in the synergistic inhibition of patient derived xenograft (PDX) tumor growth. Regarding the non-canonical Wnt pathway, we confirmed its contribution to invasion and migration which leads to metastasis in ENZ-resistant CRPC, and when the downstream effector ROCK is depleted or depleted ROCK cells are treated with ENZ, there is a significant hindering of cell migration and invasion. Also, utilizing a combination therapy of ROCK inhibitor with ENZ synergistically inhibited the growth of PDX tumors. Hence the reasoning that by simultaneously inhibiting both the canonical and non-canonical Wnt signaling cascade will result in the inhibition of cell proliferation, migration, and invasion. The goal of this study was to define the mechanism of PORCN in ENZ-resistant CRPC and develop a therapeutic approach to combat this disease. My research has determined that Porcupine (PORCN) is associated with CRPC progression to ENZ-resistance, and that an inhibition or loss of PORCN has resulted in the regain of ENZ sensitivity in ENZ-resistant models. This model has also demonstrated that PORCN and Wnt signaling engage in a paramount role contributing to AR activation, promoting CRPC progression, and the development of ENZ resistance. Citation Format: Katelyn Makayla Jones, Xiaoqi Liu. Porcupine inhibition enhances enzalutamide efficacy in drug resistant prostate 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 1077.