Tumor-associated antigen expression of primary and metastatic colon carcinomas detected by monoclonal antibody 17-1A.

Murine monoclonal antibody (MAb) 17-1A has been used in radioimmunodetection and immunotherapy trials of intestinal adenocarcinoma in humans. Tumor heterogeneity of antigen expression has been recognized as a potential limiting factor in such studies. The authors report a study designed to evaluate the degree of heterogeneity of 17-1A antigen expression among primary and metastatic human colon carcinomas. All 141 specimens, including 74 primary or metastatic colonic adenocarcinomas, were evaluated with the use of an avidin-biotin complex immunoperoxidase technic on briefly fixed frozen tissue sections. All of these showed at least focal staining with MAb 17-1A. However, well- or moderately differentiated tumors generally showed diffuse cytoplasmic immunostaining, whereas poorly differentiated tumors showed minimal immunostaining with no detectable antigen in most areas. In 16 cases that had both primary and metastatic adenocarcinomas or multiple metastatic tumors, 17-1A antigen expression was similar among the tumor sites except for one case. This case showed variation in tumor differentiation and corresponding variation in 17-1A antigen expression. Of 36 additional malignant tumors that were not of colonic epithelial origin, adenocarcinomas of the stomach, duodenum, endometrium, ovary, and breast showed 17-1A antigen expression.