KLK3 and cancer: Nowadays, several biomarkers are available for the early detection and progressive stages of different types of cancer using blood samples, including total the prostate-specific antigen (TPSA) for the diagnosis of PCa, the carcinoembryonic antigen (CEA) for gastrointestinal, breast and lung cancer, the cancer antigen 125 (CA 125) for ovarian cancer, the carbohydrate antigen 19-9 (CA 19-9) for CRC and pancreatic cancer, and the CA 15-3 for BC (Diamandis, 2014).