EXPRESSION OF THE PROSTATE-SPECIFIC ANTIGEN GENE BY LUNG-TISSUE

We describe a female patient with lung adenocarcinoma whose tumor extr act was highly positive for prostate specific antigen (PSA) immunoreac tivity. PSA was present in its M-r 33,000 free form. Using reverse tra nscription-PCR, we were able to amplify a 754-bp fragment that specifi cally hybridized to a PSA RNA probe on Southern blots. The PCR fragmen t was sequenced and found to represent PSA cDNA and not human glandula r kallikrein cDNA. PSA immunoreactivity in the lung tissue was localiz ed by immunohistochemistry to normal epithelial cells adjacent to the tumor which was completely negative for PSA. Tissue culture experiment s suggested that beclomethasone, a glucocorticoid used to treat the pa tient, was able to up-regulate PSA gene expression. This is the first report that unequivocally demonstrates PSA expression in lung tissue. We speculate that PSA expression was mediated by the exogenously admin istered steroid beclomethasone.