KLK3 and liver cancer: Currently, alpha-fetoprotein (AFP) for liver cancer (Liu et al., 2017), prostate-specific antigen (PSA) for prostate cancer (Wilt and Dahm, 2015), and carcinoembryonic antigen (CEA) for colon cancer (Konishi et al., 2018) are all glycosylated proteins that have been used as biomarkers in clinical application.