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Ganglioside composition of an experimental mouse brain tumor
Abstract:
The ganglioside composition of an experimental ependymoblastoma was examined in C57BL/6 mice. This tumor was produced by Dr. H. Zimmerman in 1949 from methylcholanthrene implantation in the brain and has been maintained in serial transplants through many generations. The influence of tumor environment on ganglioside composition was determined by studying the tumor growing intracerebrally and s.c. (over the skull and in the flank). The ganglioside composition of this tumor is markedly different from that of adult mouse brain. The total ganglioside sialic acid content (micrograms/100 mg dry weight) of the tumor growing in the cerebrum, s.c. over the skull, and in the flank was 70.4 +/- 3.8 (N = 3), 66.8 (N = 2), and 41.7 +/- 0.7 (N = 3), respectively. These values are about 10-fold lower than the ganglioside content of normal mouse cerebrum. This tumor contained a significant amount of N-glycolyneuraminic acid (NGNA). Histological analysis revealed two basically different cell types. The predominant cell type is densely packed and poorly defined in shape, whereas the minor cell type is less densely packed and fibroblastlike in shape. GM3, which migrates as double bands on thin-layer chromatography, is the predominant ganglioside of this tumor in all three regions of growth. Also present in all regions are gangliosides NGNA-GM3 and GM1. Significant amounts of GD1a, GD1b, GT1b, and GQ1b are present only in the cerebral tumor. These gangliosides therefore represent contaminants from normal brain tissue surrounding the tumor and are not native to the tumor. Ganglioside GD3, however, is a minor component of the tumor. Using a thin-layer chromatography-immunostaining method with anti-GA1 antibody, we found significant amounts of ganglioside with a GA1 oligosaccharide backbone migrating near GD3 and GD2. This tumor is similar to other neural tumors in having elevated amounts of GM3 and reduced amounts of total ganglioside and polysialogangliosides but is unique in having a high content of NGNA-containing gangliosides. The possible origin of the NGNA-containing gangliosides is discussed.