Notable examples include prostate-specific antigen (PSA) for prostate cancer, carbohydrate antigen (CA) 19-9 for pancreatic cancer, CA125 for ovarian cancer, and carcinoembryonic antigen (CEA) for colorectal and other cancers [2,3,[52], [53], [54], [55]]. The gene discussed is KLK3; the disease is prostate cancer.