Interplay between ADP-Ribosylation and Androgen Receptor Function in Prostate Cancer

Androgen receptor (AR) signalling is central to both normal prostate physiology and prostate cancer (PCa) progression. Its activity is tightly regulated by localization, transcriptional control, and post-translational modifications. Among these, poly (ADP-ribose) polymerase (PARP) mediated ADP-ribosylation has emerged as a key regulator. Multisite cysteine mono-ADP-ribosylation of AR by PARP7 modulates its function. Molecular recognition of ADP-ribosyl-cysteine by PARP9/DTX3L influences AR-driven gene expression. Importantly, defects in homologous recombination repair (HRR) genes have made PARP inhibitors (PARPi) an effective treatment for BRCA (Breast cancer susceptibility genes 1 and 2)-mutated metastatic castration-resistant prostate cancer (mCRPC). Clinical trials such as TALAPRO-2 show that combining PARPi with AR signalling inhibitors can be effective; however, their benefit in tumours without HRR mutations remains unclear. PARP enzymes regulate AR via MARylation and PARylation, with inhibitors such as Olaparib, which disrupts AR-PARP crosstalk. In this review, we present current knowledge on the interplay between ADP-ribosylation and AR signalling in prostate cancer, emphasizing the roles of distinct PARP enzymes in shaping AR activity and therapeutic response. Herein, we focus on the combined contributions of MARylation and PARylation to prostate tumorigenesis. We also discuss how this complex regulatory network may contribute to the development of advanced prostate cancer therapies in the future. This could improve PARP inhibitor and AR signalling inhibitor combinations and allow more patients to benefit from them.