Biphasic effect of cell surface sialic acids on pancreatic cancer cell adhesiveness.

Partial removal of cell surface sialic acids, by enzymatic hydrolysis or by reducing sialylation, increased both adhesion to Matrigel and cellular aggregation in the pancreatic cancer cell line, SW1990. In contrast, a greater reduction in cell surface sialic acids decreased cellular adhesiveness below that of untreated cells. Cellular adhesion and homotypic cellular aggregation were enhanced by reducing O-linked glycosylation. Addition of purified SW1990 mucins reversed the effect of the inhibition of O-glycosylation. Both adhesion to extracellular matrix proteins and cellular aggregation were generally unaffected or decreased by inhibition of N-linked glycosylation. These results suggest that although certain sialic acids are required for the adhesion, sialic acids on oligosaccharides O-linked to surface glycoproteins inhibit SW1990 cellular aggregation and adhesion to the substratum.