Inhibition of human melanoma cell growth in vitro by monoclonal anti-GD3-ganglioside antibody.

Malignant melanoma cell growth in vitro was blocked by the monoclonal antibody R-24, which detects the disialoganglioside GD3 on melanoma cells. GD3 expression varies greatly in cultured human malignant melanoma cells. The level of ganglioside GD3 was measured by quantitative absorption tests. In our observations, six melanoma cell lines expressing high levels of GD3 on the cell surface showed growth inhibition and rounding up in the presence of R-24 antibody. Four melanoma cell lines with low levels of GD3 and seven nonmelanoma cell lines with no detectable GD3 remained unchanged in morphology and continued to grow. The data presented indicate that complement is not involved in the growth inhibition observed here. Because ganglioside GD3 was detected in all 16 tissue specimens of primary and metastatic human malignant melanoma examined by immunofluorescence tests, the possible relevance of this finding in vivo is discussed.