Knockdown of RhoA Expression Reverts Enzalutamide Resistance via the p38 MAPK Pathway in Castration-resistant Prostate Cancer

Background: Enzalutamide has been approved clinically for the treatment of castrationresistant prostate cancer (CRPC) but is limited by the emergence of resistance. RhoA has been shown to play a vital role in carcinogenesis, invasion, and metastasis. However, the role of RhoA in enzalutamide-resistant prostate cancer (PCa) remains unclear. Objectives: This study investigated the role of RhoA and the associated mechanisms of RhoA depletion in enzalutamide resistance in CRPC. Methods: Western blotting, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), and colony formation assays were used to assess protein expression, survival, and proliferation of PCa cells, respectively. Xenograft experiments and hematoxylin and eosin (H) staining were used to detect further effects of RhoA on enzalutamide resistance in vivo. Results: In the present study, the expression of RhoA, ROCK2, p38, p-p38, and AR was upregulated in enzalutamide-resistant PCa cells treated with enzalutamide, and silencing of RhoA or ROCK2 attenuated enzalutamide-resistant cell proliferation and colony formation. Furthermore, the deletion of RhoA dramatically increased the efficacy of enzalutamide in inhibiting 22RV1-derived xenograft tumor growth. Additionally, there was no significant change in ROCK1 expression in C4-2R cells treated with or without enzalutamide. Mechanistically, the knockdown of RhoA expression reverted the resistance to enzalutamide via RhoA/ROCK2/p38 rather than RhoA/ROCK1/p38. Conclusion: Our results suggested that RhoA is a promising therapeutic target. As the inhibition of RhoA reverted enzalutamide resistance, it may increase its effectiveness in CRPC.