Many
cancer-associated
antigens are present on
mucin glycoproteins. These include peripheral
antigens such as sialyl Lea and
sialyl Lex and core region
carbohydrate antigens such as T, Tn, and Sialyl Tn. We have recently described an inhibitor of
mucin glycosylation,
benzyl-alpha-GalNAc. The purpose of this study was to determine its effect on expression of
mucin carbohydrate antigens. HM7
colon cancer cells were treated for 2 days in culture with 2 mM
benzyl-alpha-GalNAc. This treatment did not affect viability or doubling time, but inhibited synthesis of [3H]
glucosamine-labeled
mucins. There was also secretion of benzyl-
oligosaccharides and a decrease in the proportion of long
oligosaccharides on 3H-labeled
mucins.
Mucins were purified from spent media by gel filtration and assayed for binding of
monoclonal antibodies and
lectins.
Mucins from
benzyl-alpha-GalNAc-treated cells had increased binding of
peanut agglutinin (specific for
T antigen, Gal beta 3GalNAc) and
Vicia villosa agglutinin B4 (specific for
Tn antigen, GalNAc alpha-Thr/Ser), but decreased binding of
monoclonal antibodies 19-9, SNH3, and 91.9H (specific for sialyl Lea,
sialyl Lex, and
sulfomucin, respectively). Treatment of the cells with
benzyl-alpha-GalNAc also decreased their binding to
E-selectin (ELAM-1), which recognizes sialyl Lea and
sialyl Lex. Thus,
benzyl-alpha-GalNAc treatment, which decreases the level of peripheral
carbohydrate carbohydrate antigens on
mucins with accumulation of core region
antigens, may be useful in modifying the immunological and
biological properties of
colon cancer cells.