INFLUENCE OF GROWTH ENVIRONMENT ON THE GANGLIOSIDE COMPOSITION OF AN EXPERIMENTAL MOUSE-BRAIN TUMOR

Ganglioside composition was examined in an experimental mouse brain tu mor growing as a solid tumor in vivo and as a cultured cell line in vi tro. Gangliosides were also studied in the solid tmor rederived from t he cultured tumor cell line. Although GM3-NeuAc was the major ganglios ide in both the solid tumor and cultured tumor cells, several ganglios ides expressed in the solid tumors (e.g., GM2-NeuGc, GM1, and GM1b) we re not expressed in the cultured tumor cells. These gangliosides, howe ver, are major components of mouse macrophages. Furthermore, significa nt amounts of gangliosides containing N-glycolylneuraminic acid (NeuGc ) were found in the solid tumor growing in vivo, but only trace amount s were present in the cultured tumor cells. NeuGc is a common ganglios ide sialic acid in mouse nonneural cells, whereas N-acetylneuraminic ( NeuAc) is the predominant sialic acid in mouse brain. The trace amount s of NeuGc in the cultured cells are attributed to contamination from the fetal bovine serum. Radiolabeling of the cultured tumor cell gangl iosides with [C-14]galactose revealed that GM3-NeuAc was the only gang lioside synthesized by the tumor cells. The results suggest that nontu mor-infiltrating cells, e.g., macrophages, lymphocytes, and endothelia l cells, may contribute significantly to the total ganglioside composi tion of solid tumors growing in vivo.