In order to investigate GM2 expression in gliomas, the GM2-positive human glioma cell line (HGL) D-54 MG, which contains 0.6 nmol GM2/mg protein, representing 77% of the total monosialoganglioside fraction, was used as an immunogen for the production of anti-GM2 monoclonal antibodies. For ganglioside designations, see IUPAC-IUB (Eur. J. Biochem., 79: 11–21, 1977) and Svennerholm (J. Neurochem., 10: 613–623, 1963). Five IgM monoclonal antibodies (DMAb-1 through DMAb-5) specifically recognizing the GalNAcβ1-4(NeuAcα2-3)Gal-terminal epitope common to GM2 and GalNAc-GD1a are reported. The antibodies did not react with GM1, GM3, GD2, GD3, GD1a, GD1b, GT1b, and GQ1b. Purified anti-GM2 MAbs were used to define the expression of the “GM2” terminal epitope by cultured human malignant and normal cells by radioimmunoassay and membrane immunofluorescence. Among neuroectodermal tissue-derived cell lines, DMAb-3, at an optimal concentration of 5 µg/ml, showed high reactivity (radioimmunoassay binding ratios > 20) with 9 of 19 HGLs, 3 of 5 medulloblastoma, 4 of 5 neuroblastoma, and 1 of 3 melanoma lines. Moderate reactivity (binding ratio, 10–20) was exhibited by 3 HGL, 2 medulloblastoma, and 1 neuroblastoma lines and low reactivity (binding ratio, 3–10) by 5 HGL lines; no reactivity was detected with 2 HGL and 2 melanoma lines. Densitometric evaluation of monosi-aloganglioside extracts from human glioma and medulloblastoma cell lines in conjunction with immunostaining on thin-layer chromatograms showed that GM2 represents the major monosialoganglioside in 8 of 10 HGL and in 3 of 4 Med lines. In these lines the amount of GM2 ranged from <0.1 to 0.6 nmol/mg protein. These results indicate that GM2 represents a proportionally increased ganglioside of most glioma, medulloblastoma, and neuroblastoma cells in vitro.
This work was supported by NIH Grants R37 CA11898, NS 20023, and CA32672 and by grants from the Swedish Medical Research Council (Project 03X-627), Swedish Cancer Society (Project 2260-B88-01X), and the National Swedish Board for Technical Development (Project 84-4667).