OBJECTIVES: To determine whether the tumor-associated neovasculature of metastatic prostate and metastatic conventional (clear cell) renal carcinoma express prostate-specific membrane antigen (PSMA). PSMA is a type II integral membrane glycoprotein highly expressed in prostate cancer cells and also recently discovered to be expressed in the neovasculature of non-prostatic primary malignancies. METHODS: We examined metastatic prostate carcinoma (22 patients) and metastatic conventional (clear cell) renal carcinoma (20 patients) in various anatomic sites, including bone, lymph nodes, liver, lung, and soft tissue. Using the biotin-streptavidin method, we performed immunohistochemical reactions with the anti-PSMA monoclonal antibodies (mAbs) 7E11 and PM2J004.5 and with the anti-endothelial cell mAb CD34. RESULTS: Metastatic conventional (clear cell) renal carcinoma consistently expressed PSMA. The PM2J004.5 mAb was positive in 20 of 20 specimens, and the 7E11 mAb was positive in 15 of 20. The anti-PSMA immunoreactions with the neovasculature were confirmed by similar staining by the anti-CD34 mAb (20 of 20). Although the metastatic prostatic cancer cells expressed PSMA in all the specimens, only 2 of 22 had neovasculature PSMA expression. CONCLUSIONS: As in primary prostatic adenocarcinomas, the neovasculature of metastatic prostate cancer, regardless of site, rarely express PSMA. The neovascular endothelial cells of metastatic clear cell renal carcinoma, however, express PSMA. This expression may make PSMA an effective target for mAb-based antineovasculature therapy in metastatic renal carcinoma.
