Immunoreactive prostate-specific antigen in lung tumors.

Prostate-specific antigen (PSA) is a glycoprotein produced by the epithelial cells of the prostate. PSA is currently used clinically to diagnose and monitor prostate carcinoma. In previous work we have demonstrated that 30% of breast tumors and, more rarely other tumors, contain significant amounts of PSA. PSA appears to be a favorable prognostic indicator in breast cancer. Here, using a sensitive assay, we demonstrated for the first time that lung adenocarcinomas and squamous cell carcinomas also contain PSA. PSA in lung tumor extracts was present mainly in its 33 KDa form (free PSA), at levels measurable by commercial methods. The presence of PSA was associated more closely with male patients and adenocarcinomas. The physiological role of PSA in lung tissue and the prognostic significance of PSA in lung cancer remain to be determined. These and our previous data as well as reports by other groups support the view that PSA is a ubiquitous biochemical marker of steroid hormone action.