SPOP mutations increase PARP inhibitor sensitivity via CK2/PIAS1/SPOP axis in prostate cancer

It is well documented that impaired DNA damage repair (DDR) induces genomic instability that can efficiently increase the sensitivity of prostate cancer (PCa) cells to PARP inhibitors; however, the underlying mechanism remains elusive. Here, we found profound genomic instability in PCa cells with SPOP gene mutations and confirmed the sensitivity of SPOP-mutated PCa cells to olaparib-induced apoptosis. Mechanistically, we identified olaparib-induced CK2-mediated phosphorylation of PIAS1-S468, which in turn mediated SUMOylation of SPOP, thus promoting its E3 ligase activity in the DDR. Moreover, an abnormal CK2/PIAS1/SPOP axis due to SPOP mutations or defects in CK2-mediated phosphorylation of PIAS1, as well as SPOP inhibitor treatment, led to impaired DDR, thus increasing olaparib-induced apoptosis of PCa cells and enhancing olaparib sensitivity in animal models and patient-derived organoids. This suggested that disruption of the CK2/PIAS1/SPOP signaling axis could serve as an indicator for targeted therapy of PCa using a PARP inhibitor.