Shedding of gangliosides from tumor cells depends on cell density.
The ganglioside composition of mouse ascites hepatoma ( MAH ) cells, the ascites fluid and cell-conditioned media were determined and found to be qualitatively identical, but quantitatively different. The ganglioside content of the ascites fluid and the medium conditioned by MAH -cells at the native cell concentration (10(8) cells/ml) comprised respectively 74.9% and 23% of the cell-associated gangliosides. When incubated at lower cell-density (10(6) cells/ml) the cells were found to be release about three-times higher amounts of ganglioside per cell than during incubation at the native concentration. Centrifugation of the dense-cell-conditioned medium revealed the major part of the released gangliosides to be associated with a 150000 X g pellet that probably contains shed plasma membrane fragments. In the 150000 X g pellet of the extracellular fluids the relative content of the most polar cell ganglioside corresponding chromatographically to GT1b was about ten-times higher than in the cells. The possibility is raised that the more intense shedding of gangliosides from less crowded MAH cells may play a role in the self protection of the tumor from host immune rejection during initial stages of growth.
D000818:Animals; D001202:Ascitic Fluid / Q000378:metabolism; D002452:Cell Count; D005732:Gangliosides / Q000378:metabolism*; D008055:Lipids / Q000032:analysis; D008114:Liver Neoplasms, Experimental / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D019158:N-Acetylneuraminic Acid; D012794:Sialic Acids / Q000032:analysis
D005732:Gangliosides; D008055:Lipids; D012794:Sialic Acids; D019158:N-Acetylneuraminic Acid