Expression of gangliosides GM3 (NeuAc) and GM3 (NeuGc) in myelomas and hybridomas of mouse, rat, and human origin.

In this study gangliosides from various myelomas and hybridomas of mouse, rat, and human origin were characterized by thin-layer and high-performance liquid chromatography, immunological methods (overlay technique) and fast atom bombardment mass spectrometry. Exclusively GM3 substituted with C24:1- and C16:0-fatty acid, was found in all B cell-derived cell lines. C18 sphingosine was the single long chain base in each GM3 ceramide portion. The mouse myeloma (NS-1) and all hybridomas, obtained by fusion of mouse, rat, or human B lymphocytes with murine myelomas, showed high GM3 (NeuGc) content (> 75%) and low GM3 (NeuAc) expression. Absolute amounts of GM3 ranged from 0.2 up to 0.8 mg x 10(-9) cells. Normally, human cells do not express NeuGc, and an Epstein-Barr virus-transformed human B lymphocyte line analyzed in this study retained this sialylation status, expressing exclusively GM3 (NeuAc) (100%). The fusion of human B lymphocytes with mouse myelomas led to high GM3 (NeuGc) expression (average about 85%) in all mouse/human heterohybridomas examined. Our results indicate the chromosomal gene "transfer" and/or the activation of enzymes involved in NeuGc-biosynthesis due to the somatic cell fusion process, which might explain the mouse dominance in the manifestation of the NeuGc-phenotype in hybridomas of human origin.