DIRECT DEMONSTRATION OF INCREASED EXPRESSION OF THOMSEN-FRIEDENREICH (TF) ANTIGEN IN COLONIC ADENOCARCINOMA AND ULCERATIVE-COLITIS MUCIN AND ITS CONCEALMENT IN NORMAL MUCIN

Increased binding of the lectin peanut agglutinin is a common feature in epithelial malignancy and hyperplasia. This may have considerable f unctional importance in the intestine by allowing interaction between the epithelium and mitogenic lectins of dietary or microbial origin. P eanut agglutinin binds the disaccharide Thomsen-Friedenreich (TF,T or core 1) blood group antigen, Gal beta(1-3)GalNAc alpha-, but is not to tally specific for this site. Consequently, there has been controversy about the presence of this structure in colon cancer; studies with an ti-TF monoclonal antibodies have failed to detect it. We have examined the presence of TF antigen in colonic mucus glycoprotein (mucin) usin g endo-alpha-N-acetylgalactosaminidase (O-Glycanase(R)), which specifi cally catalyzes the hydrolysis of TF antigen from glycoconjugates. Sam ples of adenocarcinoma, inflammatory bowel disease (ulcerative colitis ), and normal mucin were treated with O-glycanase, the liberated disac charide was separated from the glycoprotein and analyzed using dual Ca rboPac PA-100 column high performance anion-exchange chromatography co upled with pulsed amperometric detection. O-Glycanase treatment releas ed increased amounts of TF antigen from both colonic adenocarcinoma (8 .0+/-3.9 ng/mu g protein, n = 11; P < 0.0001 ANOVA) and ulcerative col itis mucin (3.3+/-0.3 ng/mu g protein, n = 5; P = 0.04) compared with mucin samples from histologically normal mucosa distant from carcinoma (1.5+/-1.1 ng/mu g protein, n = 9). However, after mild acid treatmen t to remove sialic acids and fucose, releasable TF antigen was increas ed in all nine of these histologically normal mucin samples (5.5+/-2.6 ng/mu g protein, P < 0.0002). We conclude that TF antigen is an oncof etal antigen which is expressed in colon cancer, but is concealed by f urther glycosylation (sialylation and/or fucosylation) in the normal c olonic mucosa.