Background: The expression of a distinct alpha-3/4-monofucosylated polylactosaminoglycan epitope, which is detected by monoclonal antibody FW6, was investigated by comparative immunohistochemical analysis of colorectal tissue specimens exhibiting different grades of premalignant and malignant transformation. The presence of this peculiar epitope was compared with different lewis type 2 blood group antigens.
Methods: Paraffin embedded specimens from 8 hyperplastic polyps, 46 adenomas, 27 colorectal carcinomas, and 10 corresponding liver metastases were studied. Staining reactions included monoclonal antibodies FW6, AM-3 (anti-sialosyl-Le(x)), LeuM1 (anti-Le(x)), and 12-4LE (anti-Le(y)) in a standard peroxidase-antiperoxidase method.
Results: Hyperplastic polyps were not reactive with FW6 or LeuM1, but showed a slight binding of AM-3 and 12-4LE in some cases. Approximately two-thirds of the adenomatous polyps displayed a pronounced staining activity by AM-3, and approximately half of them revealed FW6, LeuM1, and 12-4LE binding. Only the expression of the FW6 (P < 0.005) epitope correlated with the presence of severe dysplasia. All antibodies were more or less reactive with colorectal carcinomas and their liver metastases, and some showed correlating binding patterns.
Conclusions: FW6 revealed a high specificity for adenomas with areas of severe epithelial dysplasia. Because this monoclonal antibody also detects the great majority of carcinomas, it is reasonable to postulate that the alpha-3/4-monofucosylated polylactosaminoglycan epitope is an important marker for malignant transformation in the colorectal adenoma-carcinoma sequence.