Gangliosides of normal and neoplastic human melanocytes

The major ganglioside component isolated from diploid human melanocytes is sialosyllactosylceramide (G_M3 86-91% of total sialic acid). The corresponding disialo derivative (G_D3) is found as a minor component (2-6% of total sialic acid) in the membranes of these cells. In human melanoma cells, grown in tissue culture, G_D3 is the predominant ganglioside component (48-63% of total sialic acid). Withdrawal of TPA from the culture medium of normal melanocytes or addition of TPA to the medium of melanoma cells had no significant effect on G_M3 G_D3 ratios. We conclude that the difference between the composition of gangliosides is related to the normal vs transformed phenotypes of melanocytes.