Adhesion of human uroepithelial cells to E-selectin: possible involvement of sialosyl LewisA-ganglioside.

In a previous study we showed that tumorigenic and invasive human uroepithelial cell lines are characterized by the presence of sialosyl Le(a) (sLe(a)) ganglioside. Our data suggested that expression of this glycolipid correlated with acquisition of the malignant phenotype by human urothelial cells. To evaluate the postulated adhesion function of sLe(a) antigen, we studied the adherence of 6 human urothelial cell lines with different expressions of this carbohydrate structure to E-selectin-expressing CHO cells. The only cell line that bound specifically to E-selectin was Hu 1703He, which expressed the highest level of sLe(a) antigen. The involvement of carbohydrate-E-selectin interaction in the adhesion of Hu 1703He cells was indicated by the following facts: (i) anti-E-selectin monoclonal antibody (MAb) completely abolished binding to E-selectin-expressing CHO cells; (ii) removal of sialic acid from Hu 1703He cells highly decreased the adhesion. Adhesion correlated with the presence of several sLe(a)-carrying glycoproteins, which was shown by immunoblotting of Hu 1703He cell lysate with anti-sLe(a) MAb 19-9. The binding of antibody was abolished when cell lysate was treated with O-sialoglycoprotein endopeptidase, suggesting that sLe(a) is present on O-linked oligosaccharides. However, incubation of Hu 1703He cells with O-sialoglycoprotease had no effect on adhesion to E-selectin or on binding of 19-9 MAb to the cell surface. Our data suggest that (i) protein-bound sLe(a) oligosaccharides represent only a minor portion of whole sLe(a) antigen produced by uroepithelial cells; (ii) effective binding to E-selectin occurs when sLe(a) oligosaccharide present on cell-surface glycosphingolipids is expressed in high density since the cell lines with moderate expression of sLe(a) ganglioside did not bind to E-selectin-transfected CHO cells.