Abstract 3495: A kinome-wide CRISPR screen identifies CK1α as a novel target to overcome enzalutamide resistance of prostate cancer

Abstract Background: Androgen deprivation therapy is the first line of therapy for localized prostate cancer (PCa), but most patients will eventually develop castration-resistant PCa (CRPC). Enzalutamide (ENZA), a second-generation androgen receptor (AR) antagonist, has significantly increased CRPC patient survival. However, resistance remains a prominent obstacle in treatment, illustrating the urgent need to develop new approaches to increase ENZA efficacy. Methods: A Kinome-wide CRISPR-Cas9 screen was used to identify the targets related to ENZA response. In vitro cell viability and in vivo cell line or patient-derived xenografts were used to verify inhibiting CK1α overcoming ENZA resistance. RNA sequencing was used to address the functions of CK1α in ENZA resistance. In vitro kinase assay was used to study ATM phosphorylation by CK1α. Immunohistochemistry, immunofluorescence, immunoblot and immunoprecipitation assays were used to study the functions of CK1α in regulation of ATM and DNA damage response signaling. Bioinformatics analysis was used to confirm these findings with clinical patients’ database. Results: Utilizing a kinome-wide CRISPR-Cas9 knockout screen, we identified casein kinase 1 alpha (CK1α) as a novel therapeutic target to overcome ENZA resistance. Depletion or pharmacologic inhibition of CK1α with a novel compound in clinical trial significantly enhanced EZNA efficacy in ENZA resistant cell lines and patient-derived xenografts. Mechanistically, CK1α phosphorylates the serine residue S1270 and modulates the protein abundance of ataxia-telangiectasia mutated (ATM), which is a primary initiator of DNA double-strand break (DSB)-response signaling, and is compromised in ENZA-resistant cells and patients. Inhibition of CK1α stabilizes ATM, resulting in the restoration of DSB-response signaling, and thus increases ENZA-induced cell death and growth arrest in an ATM-dependent manner. Conclusions: Our study details an innovative therapeutic approach for ENZA-resistant PCa and characterizes a novel perspective for the function of CK1α in the regulation of DNA damage response signaling through phosphorylation of ATM S1270. Citation Format: Jinghui Liu, Yue Zhao, Derek Allison, Daheng He, Lang Li, Xiaoqi Liu. A kinome-wide CRISPR screen identifies CK1α as a novel target to overcome enzalutamide resistance of 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 3495.