Function and expression mechanism of cancer associated carbohydrate antigens

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Expression and strucutre of Tn antigen was investigated by using human glycophorin A and leulosialin. Glycophorin A was treated with glycoprotease and the digest was fractionated by various volumn chromatographies. Several glycopeptides tith a cluster and /or single structure on an O-glycan were obtained, which were certified by chemical and sequence analyzes. Tn antigenecty of these glycopeptoeds were examined by solid phasa radioimmunoassay after treatment with sialidase and-galactosidase. Essential structure of Tn antigenecity was found to be three consecutive glycosylated Ser/Thr residues. A large amount of leukosialin was also prepared form human T cell lymphoma, Jurkat cells and the digests with trypsin was applied to a immunoaffinity column of MLS128 (anti Tn antibody). Immunoreactive glycopeptides thus obtained were purified by reverse phase chromatography. Sequence analyzes revealed that all the glycopeptieds obtained contained three consequtive residues ofM-acetylgalactosamine-Ser/Thr. Novel gangliosides containing sialyl-Le^a were also found in a juman rectal adenocarcinoma. Oligosaccharides were released from the gangliosides of a human rectal adenocarcinoma with endoglycoceramidase and then purifies by affinity chromatography ona column of an immobilized monoclonal antibody, MSW113. Structural studies, involving 600-MHz-^1HNMR spectrometry indicated that umique lkigosaccharide chains containing the sialyl-Le^a-X antigen in linear and brached structures were found, which might be new potential tumar markers and/or ligands for selectin families.