Evidence for a labile intermediate in the butyrate induced reduction of the level of c-myc RNA in SW837 rectal carcinoma cells.

We have found that the differentiation inducer butyric acid causes the synthesis of a cellular protein(s) that mediates a rapid decline in the level of myc RNA in SW837, a cell line derived from a human adenocarcinoma of the rectum. This effect was dose-dependent and was maximal at 1 mM. Among the short chain fatty acids tested, butyric acid was found to be the most potent. Valeric acid was less effective, and acetic, propionic, isobutyric, and caproic acids did not cause a significant change in myc RNA level. Dimethylsulfoxide, another inducer of differentiation, also caused a marked diminution of myc RNA level, but was only tested at a relatively high dose (282 mM). The reduction in myc RNA level caused by butyrate was blocked by inhibitors of protein synthesis, and was rapidly reversed by removing the inducer. This suggests that butyrate causes the induction of a labile activity that has a negative effect on myc RNA abundance.