KLK3 and prostate cancer: While digital rectal examination of the prostate gland may fail to detect cancer at an early stage, routine screening in blood for the prostate-specific antigen (PSA), a 28.4 kD serine protease secreted by the epithelial lining of the periurethral glands and the prostatic epithelium, has increased the diagnostic efficiency of prostate cancer from 8% to 18% in less than three decades [3].