Enhancement of adhesive property of epithelial cell line Mm2T by culture in the presence of methylated vitamin B12.

: A thymic epithelial cell line Mm2T was cultured in a medium containing a high concentration (100 micrograms/ml) of methylated vitamin B12 (CH3-B12). After 19 days, cells were found to have a flat phenotype, to have lost the floating cells which were observed in the control cells at the confluent stage, and to have acquired a resistance to trypsin. However, treatment of the CH3-B12-treated cells with EDTA resulted in a dissociation of cell-to-cell contact and reaggregation was achieved by addition of Ca2+, indicating the involvement of Ca2+ ion in cell-to-cell contact. Electron microscopic analyses revealed that the CH3-B12-treated cells were nearly square in their vertical section, which was in contrast to the dome-shaped feature of the control cells, and their cell-to-cell contact area was significantly widespread, as compared to those of the control, indicating that Mm2T cells acquires an adhesive property by treatment with CH3-B12. Biochemical analyses of both cells indicated that the concentration of glucosylceramide in the CH3-B12-treated cells was higher than that of the control. Free glucose characteristically inhibited the reattachment of cells dissociated with EDTA, suggesting the involvement of glucose in the cell-to-cell adhesion of CH3-B12-treated cells. In addition, WGA-binding glycoconjugates were intensely observed in the boundary region of CH3-B12-treated cells by immunohistochemical staining, but not in that of the control cells. It is suggested that CH3-B12 may affect the morphological alteration of Mm2T by enhancing cell adhesion through elevated expression of the C-type lectin.