Nodularin-R Synergistically Enhances Abiraterone Against Castrate- Resistant Prostate Cancer via PPP1CA Inhibition.

Clinically, most prostate cancer (PCa) patients inevitably progress to castration-resistant prostate cancer (CRPC) with poor prognosis after androgen deprivation therapy (ADT), including abiraterone, the drug of choice for ADT. Therefore, it is necessary to explore the resistance mechanism of abiraterone in depth. Genome-wide CRISPR/Cas9 knockout technology was used to screen CRPC cell line 22Rv1 for abiraterone-resistant genes. Combined with bioinformatics, a key gene with high expression and poor prognosis in CRPC patients was screened. Then, the effects of target gene on abiraterone-resistant 22Rv1 cell function were explored by silencing and overexpression. Further, a natural product with potential targeting effect was identified and validated by molecular docking and protein expression. Molecular dynamics simulations revealed potential mechanism for the natural product affecting target protein expression. Finally, the combined anti-CRPC effects of the natural product and abiraterone were validated by cellular and in vivo experiments. Five common resistance genes (KCNJ3, COL2A1, PPP1CA, MDH2 and EXOSC5) were identified successfully, among which high PPP1CA expression had the worst prognosis for disease-free survival. Moreover, PPP1CA was highly expressed in abiraterone-resistant 22Rv1 cells. Silencing PPP1CA increased cell sensitivity to abiraterone while promoting apoptosis and inhibiting clone formation. Overexpressing PPP1CA exerted the opposite effects. Molecular docking revealed the binding mode of the natural product nodularin-R to PPP1CA with a dose-dependent manner for inhibition. Mechanistically, nodularin-R attenuates the interaction between PPP1CA and USP11 (deubiquitinating enzyme), potentially promoting PPP1CA degradation. Additionally, combination of 2.72 μM nodularin-R and 54.5 μM abiraterone synergistically inhibited the resistant 22Rv1 cell function. In vivo experiments also revealed that combination therapy significantly inhibited tumour growth and reduced inducible expression of PPP1CA. PPP1CA is a key driver for abiraterone resistance, and nodularin-R enhances the anti-CRPC effects of abiraterone by inhibiting PPP1CA.