New diagnostic applications and physiological functions of prostate specific antigen.

Prostate specific antigen was, until recently, thought to be a highly specific biochemical marker of prostatic epithelial cells. Using highly sensitive techniques, we have recently found that PSA is present in 30-40% of breast tumors and at a lower percentage in other tumors including lung, colon, ovary, liver, kidney, adrenal and parotid tumors. Others have found PSA in skin and salivary gland tumors and in normal endometrium. We found PSA in normal breast, milk of lactating women and in amniotic fluid. The physiological role of PSA in these tissues and tumors is currently unknown. It appears that PSA is either a growth factor or a growth factor regulator and that it may play a role in fetal development. A substrate for PSA in these tissues has not as yet been identified.