The inhibitory action of sodium butyrate on the growth of KB, MMT and RPMI cells.

Three tumor cell lines (KB, MMT and RPMI) established from epithelial tissues were treated for 24 h with sodium butyrate (BU), the BU concentrations giving rise to 50% inhibition of [3H]thymidine incorporation were 2.0, 0.3, 0.2 mmol/L, respectively, for the KB, MMT and RPMI cell lines. Studies with [14C]BU have shown that, at similar degrees of inhibition of [3H]thymidine incorporation, the intracellular concentrations of BU are very close for all three cell types, despite the dissimilarity of the extracellular BU concentrations. These results imply that the BU sensitivity of the cells does not depend on the inhibition of thymidine incorporation, but on their BU uptake. The [3H]thymidine incorporation of MMT cells exposed to 5 mmol/L BU for 72 h returned to normal within the next 48 h. The same treatment accounted for about an 80-90% decrease in the cloning efficiency and tumourigenicity of MMT cells. These findings indicate that BU pretreatment inhibits DNA synthesis temporarily, while other parameters related to the cell growth, such as cloning efficiency and tumourigenicity, are durably influenced by BU pretreatment.