Enhanced antitumor efficacy by combining afatinib with MDV3100 in castration-resistant prostate cancer

Background: Patients with prostate cancer often develop resistance to androgen deprivation therapy, a condition called castration-resistant prostate cancer (CRPC). Enzalutamide (MDV3100) can prolong the survival of patients with CRPC after chemotherapy, but ∼50% of patients eventually relapse and develop resistance to MDV3100. Thus, it is necessary to explore new treatment methods to improve the therapeutic effect of MDV3100. Tyrosine kinases play an essential role in the pathogenesis of CRPC. Methods: MTT assay was used to detect the inhibitory effects of MDV3100 and tyrosine kinase inhibitor on prostate cancer cells. CompuSyn version 1.0 was used to calculate the combination index (CI) values using the Chou-Talalay method. Clone formation and EdU assay were used to detect the effect of afatinib combined with MDV3100 on the proliferation of 22Rv1 cells. RT-qPCR and Western blot were used to explore the mechanism of drug combination. The aim of the present study was to determine the effects of several tyrosine kinase inhibitors (TKIs) when used in combination with MDV3100 in vitro. Results: The results demonstrated that TKIs combined with MDV3100 exerted a synergistic effect on a variety of PCa cells. Afatinib combined with MDV3100 could suppress the proliferation and migration of 22RV1 cells, as well as cause their cell cycle arrest and apoptosis. Mechanistically, afatinib effectively reduced the protein expression levels of HER2 and HER3 and inhibited EGFR phosphorylation, thereby enhancing the effect of MDV3100 and suppressing CRPC. Conclusions: These findings suggested that afatinib treatment improved the effect of MDV3100 on 22RV1 cells, highlighting this drug as a potential therapeutic strategy for patients with CRPC.