KLK3 and prostate cancer: For instance, kallikrein-related peptidase 3 (also known as prostate-specific antigen, PSA) is the best characterized AR target, which is used in the clinic to monitor prostate cancer development and progression.4, 5 In addition, AR gene amplification and mutation are associated with prostate cancer development and the progression from androgen-dependent prostate cancer to castrate-resistant prostate cancer, which renders the cancer incurable.6, 7, 8