Prostate-specific antigen: a cancer fighter and a valuable messenger?

Background: Prostate-specific antigen (PSA) is a valuable prostatic cancer biomarker that is now widely used for population screening, diagnosis, and monitoring of patients with prostate cancer. Despite the voluminous literat ure on this biomarker, relatively few reports have addressed the issue of i ts physiological function and its connection to the pathogenesis and progre ssion of prostate and other cancers. Approach: I here review literature dealing with PSA physiology and pathobio logy and discuss reports that either suggest that PSA is a beneficial molec ule with tumor suppressor activity or that PSA has deleterious effects in p rostate, breast, and possibly other cancers. Content: The present scientific literature on PSA physiology and pathobiolo gy is confusing. A group of reports have suggested that PSA may act as a tu mor suppressor, a negative regulator of cell growth, and an apoptotic molec ule, whereas others suggest that PSA may, through its chymotrypsin-like act ivity, promote tumor progression and metastasis. Summary: The physiological function of PSA is still not well understood. Be cause PSA is just one member of the human kallikrein gene family, it is pos sible that its biological functions are related to the activity of other re lated kallikreins. Only when the physiological functions of PSA and other k allikreins are elucidated will we be able to explain the currently apparent ly conflicting experimental data. (C) 2000 American Association for Clinica l Chemistry.