KLK3 and colorectal cancer: Modified proteins such as plasma glycoproteins including human epidermal growth factor receptor 2 (HER2) in breast cancer, prostate-specific antigen (PSA) in prostate cancer, carcinoembryonic antigen (CEA) in colorectal cancer, cancer antigen 125 (CA-125) in ovarian cancer, alpha-fetoprotein in hepatocellular carcinoma have been approved by the Food and Drug Administration (FDA) as a potential diagnostic biomarker of various cancers8.