Effects of exogenous G_M1 and G_D1a on S20Y neuroblastoma cells

The effects of exogenous G_M1 and G_D1a on S20Y murine neuroblastoma cells were assessed by monitoring morphology, tumorigenicity, mitotic index, and plating efficiency. S20Y cells were seeded at a density equivalent to 5 × 10⁴ cells per 35‐mm tissue culture dish; 38–42 hr after seeding (preconfluent stage) the cells were treated for 12 hr with 100 μg of ganglioside per ml of medium in which the serum content was reduced from 10% to 0.5%. Analysis of the cell lipids indicated that added ganglioside became tightly associated with the membrane during the 12‐hr exposure. G_M1 treatment resulted in increased projections on the cell surface and fine structures projecting from the cell processes. G_D1a treatment resulted in a reduction in the cellular mitotic index. Plating efficiency was reduced by both G_M1 and G_D1a. Neither ganglioside affected tumorigenicity of the S20Y cells. Twelve hours after removal of the added ganglioside and exposure of the cells to normal medium, the ganglioside composition of the membranes from treated cells approached that of the controls, and the ganglioside‐induced effects had been reversed. These results suggest that addition of specific gangliosides induces different cellular responses and that these changes are dependent upon the continued presence of the ganglioside.