Effect of Retinole Acid and Phorbol-12-myristate-13-acetate on Glycosyltransferase Activities in Normal and Transformed Cells1

Retinole acid was found to increase the activity of cytidine monophosphosialic acid:lactosylceramide sialyltransferase activity in a nontransformed clonal hamster cell line, NIL 8, and a virally transformed clone, NIL 8-HSV. The potent tumor promoter phorbol-12-myristate-13-acetate (I'M A) had no significant effect on sialyltransferase activity in NIL 8 cells but stimulated this activity almost 6-fold when added to NIL 8HSV cells. There was a synergistically additive effect on sialyltransferase activity when I'M A was added to NIL 8 cells in concert with retinole acid. On the other hand neither I'M A nor retinole acid had an appreciable effect on two other glycosyltransferases measured, uridine diphosphoA/-acetylgalactosamine:globotriaosylceramide /V-acetylgalactosaminyltransferase and uridine diphosphogalactose:asialoagalactofetuin galactosyltransferase. Examination of sialyltransferase activity in a human epidermoid carcinoma cell line showed a large increase in enzyme activity in response to retinole acid administration. Two nontransformed hamster cell lines had less basal sialyltransferase activity but also showed marked elevations after retinole acid treatment. It is proposed that one of the molecular mechanisms underlying the biological effects of retinole acid and I'M A may be an increase in sialyltransferase activity. Possible regulatory mechanisms are discussed.