Differential expression of difucosyl type 2 chain (LeY) defined by monoclonal antibody AH6 in different locations of colonic epithelia, various histological types of colonic polyps, and adenocarcinomas.

The expression of LeY (Fuc alpha 1----2Gal beta 1----4 [Fuc alpha 1----3]GlcNAc beta 1----R) (in which Fuc is fucose, Gal is galactose, and GlcNAc is N-acetylglucosamine) defined by monoclonal antibody AH6 in various locations of human colonic epithelia, colonic polyps, and adenocarcinomas has been studied. In normal colonic mucosa, strong staining by AH6 was observed in the proximal regions such as the terminal ileum and cecum. The staining was, however, greatly reduced in the epithelia of the ascending colon and became very weak in the epithelia of transverse, descending, and sigmoidal colon as well as the rectum. Of 481 crypts in 40 biopsy samples of the epithelia of normal sigmoidal colon, 421 crypts did not show any staining, and only a weak staining of the lowest crypt area was observed in 60 crypts (12%); of 474 crypts in 40 biopsy samples of normal rectal epithelia, 110 crypts (26%) showed a weak staining. At the fetal stage, the LeY staining was much more intense in all locations of the colon than in corresponding locations of adult epithelia, and staining was observed in the epithelia of the sigmoidal colon and rectum. A strong staining was observed in 24 of 25 cases of colorectal adenocarcinomas, irrespective of their original location. The expression of LeY in polyps was correlated with histological type as well as the degree of dysplasia of the polyps. Of various adenomas examined, tubular adenomas, many of which showed mild or moderate dysplasia and less malignant potentials, displayed the least LeY expression. Tubulovillous and villous adenomas, which have higher malignant potential and showed a higher incidence of severe dysplasia, showed a greater area and intensity of LeY expression. No LeY was detectable in juvenile polyps, and only a very weak staining was observed in the dysplastic area of hyperplastic polyps. The extent and intensity of staining in various adenocarcinomas and adenomas could not be correlated with blood group ABO status of the hosts nor with location of the tumors. These results suggest that LeY in colonic adenocarcinomas and polyps at the distal region of the colon and rectum is a typical oncofetal antigen and is a useful marker for diagnosis of colonic cancer. Its expression in colonic polyps can be correlated with the degree of dysplasia and may indicate the degree of malignant potential of the polyp. Thus, LeY expression in polyps may have prognostic value.