Effect of sodium butyrate on alpha-fetoprotein gene expression in rat hepatoma cells in vitro.

Sodium butyrate has been reported to induce cellular differentiation and reduce the tumorigenicity of certain tumor cells. We have examined the effects of butyrate on alpha-fetoprotein (AFP) gene expression in 7777 and McA-RH8994 rat hepatoma cells and have found that nontoxic concentrations of the drug decrease AFP mRNA levels in both cell lines. However, McA-RH8994 requires a 10-fold lower concentration (0.5 mM) of butyrate to affect a 50% reduction in AFP mRNA levels within 48 h. At 2 mM, sodium butyrate reduces AFP mRNA levels in McA-RH8994 cells by at least 90% after 48 h, while having little effect on the expression of either the 7S RNA or Harvey-ras genes. Time-course studies show that the effect of butyrate on McA-RH8994 AFP mRNA levels is immediate and is accompanied by an accumulation of cells in the G1/G0 phase of the cell cycle. Sodium butyrate was found to reduce AFP mRNA levels in both dexamethasone-treated 7777 and McA-RH8994 cells; dexamethasone decreases AFP mRNA levels in the former cell line and increases AFP mRNA levels in the latter. Therefore, it is unlikely that butyrate acts simply by reducing the dexamethasone receptor concentration in 7777 cells.