EXPRESSION OF ALPHA-3 4-MONOFUCOSYLATED POLYLACTOSAMINOGLYCAN EPITOPE, AS DEFINED BY MONOCLONAL-ANTIBODY FW6, IS A MARKER OF THE COLORECTALADENOMA-CARCINOMA SEQUENCE/

Background. The expression of a distinct alpha-3/4-monofucosylated pol ylactosaminoglycan epitope, which is detected by monoclonal antibody F W6, was investigated by comparative immunohistochemical analysis of co lorectal tissue specimens exhibiting different grades of premalignant and malignant transformation. The presence of this peculiar epitope wa s compared with different Lewis type 2 blood group antigens. Methods. Paraffin embedded specimens from 8 hyperplastic polyps, 46 adenomas, 2 7 colorectal carcinomas, and 10 corresponding liver metastases were st udied. Staining reactions included monoclonal antibodies FW6, AM-3 (an ti-sialosyl-Lex), LeuM1 (anti-Lex), and 12-4LE (anti-Ley) in a standar d peroxidase-antiperoxidase method. Results. Hyperplastic polyps were not reactive with FW6 or LeuM1, but showed a slight binding of AM-3 an d 12-4LE in some cases. Approximately two-thirds of the adenomatous po lyps displayed a pronounced staining activity by AM-3, and approximate ly half of them revealed FW6, LeuM1 and 12-4LE binding. Only the expre ssion of the FW6 (P < 0.005) epitope correlated with the presence of s evere dysplasia. All antibodies were more or less reactive with colore ctal carcinomas and their liver metastases, and some showed correlatin g binding patterns. Conclusions. FW6 revealed a high specificity for a denomas with areas of severe dysplasia. Because this monoclonal antibo dy also detects the great majority of carcinomas, it is reasonable to postulate that the alpha-3/4-monofucosylated polylactosaminoglycan epi tope is an important marker for malignant transformation in the colore ctal adenoma-carcinoma sequence.