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.