Expression of the prostate-specific antigen gene by a primary ovarian carcinoma

We describe a patient with primary ovarian carcinoma that developed after liver transplantation whose tumor was highly positive for prostate-specific antigen (PSA). PSA in tumor tissue was characterized by two immunoassays, HPLC, immunohistochemistry, reverse transcription-PCR, Southern blotting, and DNA sequencing. PSA in the ovarian tumor was present as free, M(r) 33,000 protein (> 90%) and as PSA bound to alpha 1-antichymotrypsin (M(r) 100,000; < 10%). Immunohistochemistry localized PSA in the cytoplasm of epithelial cells of the tumor. Two separate reverse transcription-PCRs for PSA amplified the expected products which hybridized specifically to a PSA cDNA probe on Southern blots. Sequencing of the PCR products, representing the whole coding sequence of the PSA gene, revealed identity with the sequence of PSA cDNA from prostate tissue. These data suggest that the PSA produced by the ovarian tumor was identical in molecular weight and sequence to prostatic PSA. Based on data of tissue culture experiments with breast carcinoma cell lines, we speculate that the PSA gene in the tumor of this patient was up-regulated by the therapeutically administered glucocorticoids after liver transplantation.