KLK3 and prostate cancer: In the United States, for men aged 55 to 69 years old, a prostate-specific-antigen (PSA) test every two years with physician’s recommendation is recommended to screen for prostate cancer, per U.S. Preventive Services Task Force (USPSTF)’s recommendation and the Cluster Randomized Trial of PSA Testing for Prostate Cancer Group’s report [5, 6].