TAG-72 EXPRESSION IN PRIMARY, METASTATIC AND HORMONALLY TREATED PROSTATE-CANCER AS DEFINED BY MONOCLONAL-ANTIBODY CC49

Monoclonal antibodies CC49 and B72.3, which recognize a tumor associat ed glycoprotein (TAG-72) related to sialyted Tn antigen, have been use d in clinical trials for radionuclide imaging, and treatment of colon, breast and ovarian carcinoma. In addition, studies with CC49 in patie nts with metastatic hormone refractory prostate cancer have been initi ated based on the observed expression of TAG-72 in primary prostate ca ncer. We examined whether TAG-72 expression is a common feature of pri mary, metastatic and hormonally treated prostatic carcinoma. Immunohis tochemical analysis of 25 primary prostatic carcinomas confirmed previ ous data that 21 of 25 specimens (80%) were immunoreactive with CC49. CC49 staining was noted in all 6 well (Gleason score 2 to 4), 8 of 10 moderately (Gleason score 5 to 6) and 7 of 9 poorly (Gleason score 7 t o 9) differentiated tumors. CC49 immunoreactivity was noted in 10 of 2 0 hormonally treated prostate cancers and in 21 of 25 tumors without h ormonal therapy. Intense CC49 staining of prostatic intraepithelial ne oplasia was present in all 5 specimens examined. In contrast to the pr imary lesion, many metastatic prostate cancers lacked detectable CC49 immunoreactivity. Of 24 pelvic lymph node metastases from different pa tients only 4 (17%) had significant CC49 staining and 5 others had rar e CC49 positive cells. However, 6 of 12 bone metastases showed CC49 im mune staining. One specimen from an anaplastic locally recurrent tumor showed no reactivity. To our knowledge we present the first analysis of TAG-72 expression in a large series of patients with hormonally tre ated and metastatic prostate cancer, the most likely candidates for CC 49 immunotherapy. Our findings that lymph node and bone metastases fro m prostate cancer are less likely to express significant amounts of TA G-72 than primary prostate cancer suggest that pretreatment biopsy typ ing for TAG-72 may be necessary to optimize the results of ongoing CC4 9 imaging and therapy studies.