PSA (KLK3) - Marker for normal prostate and prostate cancer

The prostate-specific antigen (PSA) is encoded by the KLK3 gene and is a member of the kallikrein-related peptidase family. PSA is specifically expressed in glandular cells of the prostate and is secreted into the semen, where it is important for maintaining sperm motility. Traditionally, elevated serum levels of PSA has been used to indicate prostate cancer, and due to the high specificity of PSA for prostate, antibodies against PSA are commonly used to diagnose metastases from prostate cancer.