The genes for
cytidine monophospho-
N-acetylneuraminic acid hydroxylase (NeuAc-H) and beta-1,4-N-acetylgalactosaminyl
transferase (GalNAc-T) were examined using reverse transcription-PCR in two experimental mouse
brain tumors, EPEN and CT-2A. NeuAc-H is required for the synthesis of
gangliosides containing
N-glycolylneuraminic acid, whereas GalNAc-T is required for the synthesis of
ganglioside GM2. The genes were analyzed in solid
tumors grown in vivo and in
tumor cells grown in vitro. NeuGc-containing
gangliosides are abundant in cells of the mouse immune system, including macrophages, but are undetectable in normal mouse brain. GM2 is expressed in both neural and nonneural mouse cells and tissues. The EPEN
tumor cells synthesize only
ganglioside GM3, whereas the CT-2A
tumor cells synthesize GM3, GM2, GM1, and GD1a. NeuAc-H gene expression was detected in both solid
tumors grown in vivo but was undetectable in either tumor cell line. The presence or absence of NeuAc-H gene expression in the
tumor tissues and cells correlates with the presence or absence, respectively, of NeuGc-containing
gangliosides. Differences in GalNAc-T gene expression between the solid
tumors and the cultured tumor cells correlate with the expression of
ganglioside GM2. The findings suggest that the differences in
ganglioside biosynthetic gene expression between
brain tumors grown in vivo and in vitro are associated with the presence or absence, respectively, of
tumor-infiltrating host cells.