Loss of butyrate-induced apoptosis in human hepatoma cell lines HCC-M and HCC-T having substantial Bcl-2 expression

We have demonstrated that sodium butyrate induces differentiation in human hepatoma cells; however, recent studies have shown that this agent causes apoptosis in some types of cancer cells. In this study, we examined whether sodium butyrate causes apoptosis in the human hepatoma cell lines, HCC-M and HCC-T. The growth of human hepatoma cells was dose-dependently reduced by sodium butyrate. Flow cytometric analysis showed cell-cycle arrest at the G₁ phase in the sodium butyrate-treated cells. Apoptotic change was never found in treated cells at concentration levels of less than 5 mmol/L. Sodium butyrate decreased p53 expression and increased p21(waf-1) expression in Hcc-t and Hcc-m cells having the wild-type p53 gene. Western blot analysis showed that Bcl-2 was expressed in the Hcc-t and Hcc-m cells, and its expression was increased after exposure to sodium butyrate. Antisense oligodeoxynucleotide against bcl-2 easily caused apoptosis. These results indicate that sodium butyrate hardly induces apoptotic change in the human hepatoma cell lines, HCC-T and HCC-M, with the increase of Bcl-2 expression. Cell-cycle arrest in the G₁ phase caused by sodium butyrate was suggested to be induced by the increase in p21(waf-1) expression, but this change did not link with the p53 increase.