KLK3 and prostate cancer: Today, most of the biomarkers detected in cancer patients are proteins, such as prostate specific antigen (PSA) for prostate cancer, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) for hepatocellular carcinoma, etc. However, the protein assay procedure is not always easy to apply in clinical diagnosis and remains labor-intensive.