| Research Abstract |
Upon malignant transformation of cells, highly branching of N-linked oligosaccharides is induced by activation of N-acetylglucosaminyltransferase V. However, no significant change in β-1, 4-GalT activities was found during this biological event. When gene expression levels of the β-1, 4-GalT family members were examined between malignantly transformed cells and their normal counterparts, those of β-1, 4-GalT II decreased while those of β-1, 4-GalT V increased without significant changes in those of other β-1, 4-GalTs. When B16-F10 mouse melanoma cells were transfected with human β-1, 4-GalT II sense CDNA or β-1, 4-GalT V anti-sense cDNA, and transplanted subcutaneously in C57B/L6 mouse, tumor formation was suppressed in the gene-transfected cells. In order to investigate how tumor suppression was induced by them, the cells were cultured on fibronectin (FN)-coated plates without serum. The mock-transfected B16-F10 cells stayed in a round shape while both gene-transfected cells showed cell spreading aligned with actin filament as revealed with phalloidin staining. Lectin blot analysis of membrane glycoproteins from the tumors and cultured cells using RCA-I which interacts with oligosaccharides terminated with β-1, 4-linked galactose and L-PHA which binds to highly branched oligosaccharides showed that reactivities to these lectins are changed upon transfection of the β-1, 4-GalT genes. These results indicate that the altered galactosylation induced to the membrane glycoproteins including fibronectin receptor affects adhesiveness of the cells to fibronectin substrate, thus leading to the suppression of the tumor formation.
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