Griffonia simplicifolia Agglutinin‐2‐binding Glycoprotein as a Novel Carbohydrate Antigen of Human Colonic Carcinoma

Griffonia simplicifolia agglutinin‐2‐binding glycoprotein (GBG) in human colonic carcinoma was examined immunochemically and histochemically. GBG was extracted from colonic carcinoma as a serum‐type glycoprotein of 160 kilodaltons. GBG was not identical with carcinoembryonic antigen (CEA), since its molecular weight and localization in tissue sections were different from those of CEA. The non‐reducing terminals of GBG probably carry N‐acetylglucosamine, but not blood group determinants. Furthermore, GBG was released by phosphatidylinositol‐specific phospholipase C from cell membrane. GBG was suggested to be anchored to the membrane via linkage to a glycosyl‐phos‐phatidylinositol molecule. Among colonic carcinoma‐associated antigens, serum‐type glycoproteins having N‐acetylglucosamine at non‐reducing terminals have not previously been reported. GBG is a novel carbohydrate antigen of human colonic carcinoma.