Comparison of anti-prostate-specific membrane antigen antibodies and otherimmunomarkers in metastatic prostate carcinoma

Objectives. To compare the immunohistochemical properties of the 7E11 anti- prostate-specific membrane antigen (anti-PSMA) monoclonal antibody (mAb) wi th the recently developed anti-PSMA mAb, PM2J004.5, and with other common i mmunomarkers in metastatic prostate cancer. PSMA is a type II integral memb rane glycoprotein highly expressed in prostate cancer cells, The mAb 7E11 i s currently used in the radioisotopic evaluation of prostate cancer, and it s immunohistochemical properties have been examined in primary prostate can cer specimens. Methods. We examined 23 formalin-fixed, paraffin-embedded, metastatic prost ate carcinoma specimens from various anatomic sites, including bone, lymph node, liver, lung, and soft tissue. Using the biotin-streptavidin method, w e performed immunohistochemical reactions with the anti-PSMA mAbs 7E11 and PM2J004.5 and with antibodies to prostate-specific antigen and prostatic ac id phosphatase. The immunoreactions were scored by pathologists unaware of the clinical and pathologic data according to a staining intensity scale an d the percentage of cells stained. Results. All four mAbs consistently stained the metastatic prostate cancer specimens. in 2 (8.7%) of 23 cases, however, the prostate-specific antigen immunoreaction was negative but the anti-PSMA mAbs had positive staining. A lthough 7E11 and PM2J004.5 had a similar staining intensity and percentage of cells stained for most specimens, in 3 (13%) of 23 specimens, 7E11 had l ess intense staining. None of the specimens were negative for all four anti bodies. Conclusions. Anti-PSMA mAbs consistently immunoreacted with metastatic pros tate cancer specimens and were positive in instances when prostate-specific antigen staining was negative. The anti-PSMA mAbs demonstrated similar sta ining patterns; however, in select cases, the PM2J004.5 mAb did show more i ntense staining. The anti-PSMA mAbs 7E11 and PM2J004.5 are useful in the pa thologic evaluation of paraffin-embedded metastatic prostate cancer specime ns. UROLOGY 57: 1179-1183, 2001. (C) 2001, Elsevier Science Inc.