Prostate specific antigen--new applications in breast and other cancers.

Prostate specific antigen was, until recently, thought to be a highly specific biochemical marker of prostatic epithelial cells which is not produced by any female tissue. We have used immunological and molecular techniques to demonstrate the presence of PSA protein or mRNA in various non-prostatic tissues. 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 paroria tumors. Others have found PSA in skin and salivary gland tumors and in normal endometrium. We found PSA in the normal breast, the milk of lactating women, breast discharge fluid and in amniotic fluid. We developed a tissue culture system that reproduces the phenomenon of PSA production by breast tumors. Using this system, we showed that PSA regulation is under the control of steroid hormones and their receptors. PSA is produced by normal, hyperplastic and malignant breast tissue and is present in all breast secretions and some other tumors. The physiological role of PSA in these tissues, fluids and tumors is currently unknown. A substrate for PSA in these tissues has not as yet been identified.