Human Melanoma Cell Lines Deficient in GD3 Ganglioside Expression Exhibit Altered Growth and Tumorigenic Characteristics

We have selected GD3-deficient human melanoma cell lines, in order to investigate the function of GD3 ganglioside. This was done by treating SK-MEL-28 cells with anti-GD3 antibody (R24) and rabbit complement and subsequent subcloning of the surviving cells, resulting in the derivation of two cell lines deficient in the cell surface expression of GD3. Neither cell line (designated SK-MEL-28-N1 and SK-MEL-28-N2) had detectable cell surface expression of GD3 as analyzed with monoclonal antibody R24, and no GD3 was detectable in either cell line by glycolipid isolation, thin-layer chromatography, or resorcinol-HCl spray, but thin-layer chromatography immuno-staining with monoclonal antibody R24 showed the presence of low amounts of GD3 in both N1 and N2 (1/40 of the amount in the parent cell line in N1 and 1/500 in N2.) In SK-MEL-28-N1, the residual GD3 was shown by immunofluorescence assays on permeabilized cells to be present in discrete intracellular organelles, suggesting that these cells have a defect in the transport of GD3 as well as in its synthesis. Both SK-MEL-28-N1 and -N2 had an increase in detectable GD3 expression. The mutant cell lines had altered cell morphology in comparison to the parent cell line and both had slower growth rates in vitro and lower tumorgenicty in nu/nu mice. These results indicate that GD3ganglioside plays an important role in proliferation and growth of melanoma cells.