The induction of vimentin gene expression by sodium butyrate in human promonocytic leukemia U937 cells

The administration of 1 mM sodium butyrate induced the phenotypic differentiation of human promonocytic leukemia U937 cells, as judged by the expression of cD11b and cD11c antigens, two differentiation-specific surface markers. At the same time, butyrate greatly induced the expression at the mRNA level of the vimentin gene. The increase in the level of this RNA started at 6 h of treatment and reached the maximum at Hour 24. Such an increase was caused at least in part by a stimulation in the rate of gene transcription, as suggested by transcription assays in isolated nuclei. Experiments in the presence of cycloheximide suggested that vimentin induction is probably a direct response to the action of butyrate, not mediated by the prior induction of other gene products. Unlike the case of vimentin, the levels of other RNAs, namely beta-actin, ornithine decarboxylase, and c-myc, were not enhanced, but they decreased at different times of treatment with butyrate. Finally, we observed that butyrate induced also the differentiation of HL60 cells, another human myeloid cell type. Nevertheless, the drug failed to stimulate the expression of vimentin in this cell line.