To study the capability of the CYP17A1 inhibitor abiraterone acetate (AER) to antagonize the androgen receptor (AR) activation in human prostate cancer (PCa) cell lines. T877A-AR-LNCaP, WT-AR-VCaP, AR-negative DU145, and PC3 PCa cell lines were used by MTT and cell count to study the ability of AER and enzalutamide (ENZ) to modify cell viability. The role of ARs in LNCaP was demonstrated through a gene-silencing experiment. The mechanism of AER cytotoxicity in LNCaP cells was studied, as well as the ability of AER to modulate AR gene expression. The in silico docking approach was applied to study the interaction of AER and ENZ with T877A-AR. Through high-performance liquid chromatography, the production of the AER main metabolite Δ4A was studied. AER bound AR in an almost identical manner to that of dihydrotestosterone (DHT). The higher binding energy for AER in T877A-AR could explain the major cytotoxic effect observed in LNCaP cells. The capability of LNCaP cells to synthesize Δ4A could mediate, at least in part, this effect. AER cytotoxicity in LNCaP cells was mainly due to the activation of apoptosis. Further, AER induced modification of AR target gene expression, suggesting a direct effect on AR activity. AER-induced cytotoxicity on PCa cell lines seemed to be mediated by binding with AR. The higher affinity of AER for T877A-AR may suggest a potential role of AER in the management of CRPC carrying this mutation; however, T877A-AR expressing CRPC patients developed AER resistance, probably due to the increase of progesterone.
Keywords: Abiraterone acetate; Cell lines; Cytotoxicity; Prostate cancer.