Abstract A022: Alternative polyadenylation as a therapeutic vulnerability in prostate cancer

Abstract Prostate cancer is the second leading cause of male cancer death in the United States. While localized disease can be cured by radiation or surgery, metastatic prostate cancer presents a clinical challenge. Metastatic prostate cancer can initially be controlled by endocrine therapies that target the androgen receptor (AR), however, these tumors will inevitably develop resistance. This stage of the disease, termed castration-resistant prostate cancer (CRPC), is responsible for the majority of prostate cancer-specific deaths. Current treatment options for CRPC patients are not curable and highlight the need to develop novel therapeutic options that will more effectively treat the disease. Spliced mRNA molecules undergo cleavage and polyadenylation ~25 base pair downstream from a canonical 5’AAUAAA poly(A) site located within the 3’ untranslated region (UTR). Shortening of mRNA 3’UTRs through alternative polyadenylation has been found in numerous cancers leading to downregulation of tumor suppressor genes and upregulation of oncogenes. To investigate the function of alternative polyadenylation in CRPC, we conducted a loss-of-function screen of mRNA polyadenylation factors in hormone-sensitive LNCaP cells and hormone-insensitive LNCaP95 and 22Rv1 cells. We found that knockdown of the cleavage and polyadenylation specificity factor (CPSF) component, CPSF1, inhibited growth of all cell lines. To define pathways that are regulated by CPSF1 in prostate cancer, we identified CPSF1-dependent gene expression using RNA-seq and CPSF1-dependent poly(A) sites using poly(A)-ClickSeq (PAC-Seq). Gene set enrichment analysis of RNA-seq data revealed the Glycolysis Hallmark and Hypoxia Hallmark gene sets were positively regulated by CPSF1. Analysis of PAC-seq data revealed global induction of poly(A) sites distal to 3’ UTRs upon CPSF1 knockdown. By integrating these RNA-seq and PAC-seq datasets, we have identified AR-independent pathways that may be attractive for therapeutic targeting in prostate cancer. This study has revealed post-transcriptional gene regulation by CPSF1 as an important pathway used in CRPC. Citation Format: Kiel T. Tietz, Braedan M. McClukey, Sarah A. Munro, Conor R. Miller, Scott M. Dehm. Alternative polyadenylation as a therapeutic vulnerability in prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A022.