Charactrization of human colon cancer associated carbohydrate antigens.

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Monoclonal antibodies, which were raised against the carbohydrate moieties of glycoproteins and glycolipids on cancer cell surfaces, have proved useful in the detection of carcer associated antigens. We have produced many such monoclonal antibodies, using human colorectal cancer cell lines, LS180 and SWI116, as immunogens and immobilized glycopeptides as probes for screening hybridomas.One of the antibodies, called MLS102, reacted with the carcer associated sialyl-Tn antigen, and with ovine, bovine and porcine submaxillary mucins. The reactivity toward these mucins varied in parallel with the NeuAc alpha2 ->6 GalNAc alpha1 ->Ser/Thr(sialyl-Tn)content. The antigenic determinant was then identified as a cluster of sialyl-Tn residues on the polypeptide chain.Another monoclonal antibody, called MLS103, reacted with the carbohydrate chain in the normal mucin-type glycoproteins and glycolipids.The mucin antigens were isolated by immunoaffinity chromatography from cell lysates and spent mediu … More m of LS180 cells. The amino acid composition of the MLS102 antigen was typical of mucins, containing serine, threonine and proline as major amino acids. The carbohydrate analysis revealed that the MLS102 antigen was composed of 0-linked NeuAc alpha2 ->6 GalNAc(56%), N-acetylgalactosamine(25%), and uncharacterized sulfated oligosaccharides.The MLS103 antigen differed from the MLS102 antigen in both amino acid and carbohydrate compositions. Most of the 0-linked carbohydrate chains were larger than disaccharide. Immuniochemical and chemical analyses showed that the antigenic determinant of the MLS103 was Lewis A blood group antigen, and that the MLS103 antigen possessed several characteristic structures involving galactose linked to N-acetylgalactosamine residue in the core region.Immunostaining of LS180 cells using MLS102 and MLS103 revealed that the cells are heterogeneous with respect to the expression of both antigens.Above findings show that the expression of the MLS102 antigen may depend on the defective control of galactosyltransferase which transfers galactose residue to the core structure, or may be due to the acceralated modification of carbohydrate chains with sulfate, which results in the loss of large oligosaccharide chains on the molecule. Less