Altered ganglioside biosynthesis in mouse cell cultures following transformation with chemical carcinogens and x-irradiation.

Chemicaly and x-ray-transformed subclones of BALB/c 3T3 mouse embryo cells were found to have reduced amounts of the mono- and disialogangliosides galactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosylceramide (Gm1) and N-acetylneuraminylgalactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosylceramide (Gd1a), and increased amounts of N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosylceramide (Gm2). The activity of the enzyme UDP-Gal:Gm2 galactosyltransferase was reduced to between 2.7 and 14.3% of normal in the transformed clones. Other ganglioside glycosyltransferase activities were unaffected. This enzymatic change was consistent with the observed alteration in ganglioside pattern in the transformed cells. The residual galactosyltransferase activity in the transformed cells was kinetically similar to the normal enzyme, suggesting that transformation alters ganglioside biosynthesis by blocking enzyme synthesis at the translational or transcriptional levels.