GD2 x GM2(ganglioside M2) x GD3

Increased expression of gangliosides by different tumor types including renal cell carcinoma (RCC) is thought to contribute to the immune suppression observed in cancer patients. In this study, we report an increase in apoptotic T cells from RCC patients compared with T cells from normal donors that coincided with the detection of T cells staining positive for GM2 and that the apoptosis was predominantly observed in the GM2(+) but not the GM2(-) T cell population. Ganglioside shedding from tumor rather than endogenous production accounts for GM2(+) T cells since there was no detectable level of mRNA for GM2 synthase in RCC patient T cells and in T cells from normal healthy donors after incubation with either purified GM2 or supernatant from RCC cell lines despite their staining positive for GM2. Moreover, reactive oxygen species as well as activated caspase 3, 8, and 9 were predominantly elevated in GM2(+) but not GM2(-) T cells. Similarly, increased staining for GD2 and GD3 but not GD1a was detected with patient T cells with elevated levels of apoptosis in the GD2(+) and GD3(+) cells. These findings suggest that GM2, GD2, and GD3 play a significant role in immune dysfunction observed in RCC patient T cells.

Most human neuroblastoma tumors are characterized by the high expression of GD2 (or GD2 and/or GM2) gangliosides, whereas melanomas characteristically express GD3 ganglioside. The molecular basis for these patterns was investigated by examining the relationship between ganglioside levels, glycosyltransferase (GM2/GD2 synthase and GD3 synthase) activity, and corresponding mRNA levels in a panel of human neuroblastoma and melanoma cell lines. In general, the ganglioside patterns could be explained by the levels of the transferases and their mRNA, indicating control at the level of transcription. A key role was noted for GD3 synthase. Notably, it was found that neuroblastoma cell lines with high GD2 ganglioside levels had low levels of GD3, its synthase, and mRNA for the enzyme even though this step provides the substrate for GD2 synthesis. The key role for GD3 synthase was also examined by stably transfecting GD3 synthase cDNA into a neuroblastoma cell line (SH-SY5Y) not expressing GD3 and GD2. The resulting cell line had high levels of GD2 ganglioside and altered morphology and growth characteristics.

Ganglioside patterns were quantitated for brains of bullfrog (Rana catesbeiana) at three stages of metamorphosis and adult. At each stage nine gangliosides were identified by mobility on silica gel thin-layer chromatograms, and quantitated on the basis of sialic acid content. A single band with chromatographic mobility close to that of GD2, and doublets close to GT1b and GQ were quantitatively the major ones (over 16% each). Doublets close to GM1 and GD1b and a single band slightly behind GD1a made up 5-10% each. A doublet comigrating with GM3, and bands close to GM2 (trace) and GD3 were present in smaller amounts. The only developmental trend was a slight increase in the proportion of the band close to GD3 from 2.4% (early prometamorphic phase) to 9.1% (adult). This suggests that changes in the regenerative capacity of frog nervous tissues during metamorphosis are due to changes other than ganglioside composition.