Expression of the monoclonal antibody-defined CAR-3 epitope on neoplastic and preneoplastic lesions of the colon mucosa.

The AR-3 monoclonal antibody, which defines the tumor-associated antigen CAR-3, was previously found to be able to discriminate between neoplastic cells in gastric, pancreatic, colonic, ovarian and endometrial carcinomas and their normal counterparts. In fact, it strongly reacts with carcinomatous cells at the level of both the glycocalix and the cytoplasm, while its reactivity with normal tissues is restricted to the glycocalix of few mucin-producing epithelial cells. We have now investigated the reactivity of this antibody with immunohistochemical techniques on a series of formalin-fixed paraffin-embedded specimens, from precancerous and cancerous lesions of the large bowel which were classified as adenomas with mild, moderate or severe dysplasia, adenomas with cancer and adenocarcinomas, respectively. It was found that the intensity and extent of the staining correlated with the degree of dysplasia and that the highest expression of the CAR-3 epitope was detectable in adenocarcinomas. Also the localization of the staining in the lesions displayed an increasingly complex pattern, going from linear in adenomas with mild dysplasia to a very strong intracytoplasmic and/or intraluminal expression in adenomas with severe dysplasia or adenocarcinomas.