g(m2)-ganglioside and Necrosis

The frequently occurring alteration of ganglioside expression in tumor cells has been implicated to play a role in the uncontrolled growth of these cells; antibodies to such gangliosides might affect tumor cell growth. We have studied the effect of IgM monoclonal antibodies to two glioma-associated gangliosides, GD3 and GM2, on cell proliferation of four human glioma cell lines and one renal tumor cell line. Of the two anti-ganglioside antibodies tested, only the anti-GD3 antibody resulted in a significant (p<0.005) inhibition of cell proliferation as measured by thymidine incorporation and Brd-U labeling, after 24h incubation. The effect was not dependent on any serum factor and no increased cell death was observed. All cell lines contained higher or similar amounts of GM2 than GD3, and both antigens were shown to be expressed on the cell surface and accessible to antibodies. The selective effect of anti-GD3 antibodies as contrasted to the inactivity of anti-GM2 antibodies suggests a possible role for ganglioside GD3 in tumor cell proliferation.

Topics: Antibodies, Monoclonal; Cell Division; Central Nervous System Neoplasms; Drug Screening Assays, Antitumor; G(M2) Ganglioside; Gangliosides; Glioma; Humans; Necrosis; Thymidine; Tumor Cells, Cultured

The effects of four anti-GM2 monoclonal antibodies (DMAb-1, DMAb-2, DMAb-3, and DMAb-5) were studied on spheroid cultures from a human glioma cell line (D-54 MG) that is known to express high levels of GM2. The spheroids developed central necrosis 48 h after antibody exposures at concentrations greater than 6 micrograms/ml. No necrosis was found with antibodies that had been absorbed with GM2 prior to exposure or with unrelated cytotoxic antibodies. Immunohistochemistry showed that the necrosis started shortly after the antibodies were evenly distributed throughout the spheroids. Light and transmission electron microscopy revealed that a small portion of the cells, mainly in the periphery of the spheroids, was unaffected by antibody exposure. New monolayer cultures established from antibody-treated cells expressed a 50% lower GM2 content as shown by flow cytometry and determination of ganglioside content throughout at least 12 passages. Thus, the GM2-rich D-54 MG cell line has subpopulations of cells with lower GM2 content. Spheroids obtained from this subpopulation developed only minor necrosis after antibody treatment. These results show that GM2 antibodies cause severe necrosis of GM2-containing glioma cells in vitro, but the effect depends on the concentration of antigen, and a threshold number of GM2 molecules is required.

Topics: Antibodies, Monoclonal; Cell Survival; G(M2) Ganglioside; Glioma; Humans; Microscopy, Electron; Microscopy, Fluorescence; Necrosis; Tumor Cells, Cultured