Although there are several circulating protein biomarkers currently in use to diagnose cancer, such as CA-125 for diagnosis of ovarian cancer, CA19-9 for pancreatic cancer, and prostate specific antigen (PSA) for prostate cancer, these traditional biomarkers are limited by low sensitivity and the inability to distinguish between aggressive and indolent forms of disease [23]. The gene discussed is KLK3; the disease is prostate cancer.