A secreted mucin carrying Sialyl‐Lewis a from colon carcinoma cells binds to E‐selectin and inhibits HL‐60 cell adhesion

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Abstract
Sialyl‐Lewis × and a are known as ligands for E‐selectin (ELAM‐I) involved in leukocyte‐endothelial adhesion. L‐Canag (light cancer antigen), secreted by a colon carcinoma cell line COLO 205, is a soluble mucin‐type glycoprotein expressing sialyl‐Lewis a antigens. L‐Canag was purified from spent culture medium by trichloracetic acid precipitation and Superose 6 gel filtration. With a monoclonal antibody against E‐selectin (BBAI) as a positive control, the purified L‐Canag was shown to bind to E‐selectin‐Fc coated into plastic microtiter wells and to the surface of transiently E‐selectin‐transfected COS‐I cells in a Ca2+‐dependent way. Immunofluorescent double labelling showed that both BBAI and L‐Canag stained the same cells and morphological co‐localization on E‐selectin‐transfected COS‐I cells. Like BBAI, L‐Canag can inhibit leukocyte HL‐60 cell adhesion to E‐selectin‐transfected COS‐I cells, and this inhibition can be blocked by a F(ab')2 fragment directed against the sialyl‐Lewis a epitope.