Effects of sodium butyrate on proliferation of human gastric cancer cells and expression of p16 gene

OBJECTIVE: To investigate the effects of sodium butyrate (NaB), a histone deacetylase inhibitor (HDACI), on the proliferation of human gastric cancer cells and the expression of p16, an important negative-regulatory factor of the cell cycle G1. METHODS: Human gastric cancer cells of the lines SGC7901 and BGC823 were cultured in RPMI1640 medium and treated with NaB of different concentrations: 5 x10(-4), 1 x 10(-3), 3 x 10(-3), and 5 x 10(-3) mol/L for 24 h or 72 h. MTT assay, flow cytometry, and annexin V-fluorescein isothiocyanate staining were performed to analyze the cell proliferation activity, cell cycle, and apoptotic rate. RT- PCR, Western blotting, and methylation-specific PCR (MSP) were used to detect the e mRNA and protein expression and methylation state of p16 gene respectively. RESULTS: Exposure to different concentrations of NaB inhibited the growth of the SGC7901 and BGC823 cells. Treated with NaB of the concentrations of 1 x 10(-3), 3 x 10(-3), and 5 x 10(-3) mol/L respectively for 72 h, the numbers of the SGC7901 and BGC823 cells at G0/G1 stage increased significantly and those at S stage decreased significantly (all P <0.01), which showed that the cell cycle was blocked at G1 phase. The apoptosis rates of the SGC7901 and BGC823 cells treated with NaB of different concentrations for 72 h all increased significantly (all P <0.01). P16 was expressed in the SGC7901 and BGC823 cells at low levels, and hypermethylation was detected in its promoter region in both cells before the treatment of NaB. After treated with NaB the mRNA and protein expressions of p16 gene were increased in both cells. CONCLUSION: NaB inhibits the growth of human gastric cancer cells by blocking cell cycles, inducing apoptosis and upregulating the expression of p16 gene by increasing acetylation and reducing methylation.