Association of Sialyl-Lewisa and Sialyl-Lewis* with MUC-1 Apomucin in a Pancreatic Cancer Cell Line1

We have shown previously that the mucins of the human pancreatic cancer cell line, SVV1990, have both sialyl-Lewis" and sialyl-Lewis* car bohydrate ligands that are implicated in tumor cell metastasis. In the present study, we undertook to identify the protein core of these mucins. SW1990 mucins that carry sialyl-Lewis" and sialyl-Lewis" bound to the MIO peptide-specific m Vb 139H2. Removal of most of the sialic acids from SW1990 mucins by neuraminidase greatly enhanced binding of two other MICI peptide specific antibodies, HMFG-2 and SM-3. After re moval of sialic acids, most of the mucins rich in sialyl-Lewis" and sialylLewis'1 oligosaccharides no longer bound to a DEAE-cellulose column at pH 8.O. These results indicate that at least part of the sialyl-Lewis" and sialyl-Lewis" in SW1990 cells is associated with the MICI polypeptide. Moreover, sialic acids play an important role in determining the net negative charge of sialyl-Lewis" and sialyl-Lewis* rich mucins and in obscuring MICI peptide regions.