Comparative studies on glycoproteins expressing polylactosamine-type N-glycans in cancer cells.

In the series of our previous reports, we showed that some cancer cell lines specifically express polylactosamine-type N-glycans and such glycans were often modified with fucose and sulfate residues. To confirm the proteins expressing these glycans, glycopeptide mixture obtained by digestion of whole protein fractions with trypsin was captured by a polylactosamine-specific lectin, Datura strasmonium agglutinin (DSA). And the peptides and glycans of the captured glycopeptides after digestion with N-glycoamidase F were extensively analyzed by HPLC and MS techniques. We found that some glycoproteins such as CD107a and CD107b commonly contained polylactosamine-type glycans in all the examined cancer cells. But integrin-α5 (CD49e) and carcinoembryonic antigen-related cell adhesion molecule 5 (CD66e) having these glycans were specifically found in U937 (human T-lymphoma) and MKN45 (human gastric cancer) cells, respectively. These data clearly indicate that specific glycans attached to specific proteins will be promising markers for specific tumors with high accuracy.