Histone deacetylase inhibitors (HDACIs) are involved in cell growth, apoptosis and differentiation. This study aimed to investigate the effects of HDACI scriptaid on histone modification, demethylation, cell growth, cell cycle and apoptosis in the RKO colorectal cancer cell line and screening for scriptaid-induced genes. RKO cells were treated with 5-aza-2'-deoxycytidine (5-aza-dC), trichostatin A (TSA) or scriptaid at different concentrations. Histone modification and methylation status of a silenced p16 gene were analyzed using chromatin immunoprecipitation and methylation-specific PCR, respectively. Flow cytometry was performed for the analysis of cell cycle and apoptosis. Scriptaid-induced expression was analyzed using Human OneArray™ chip. Scriptaid resulted in the demethylation and re-expression of a hypermethylated p16 gene along with 5-aza-dC synergistically in the RKO cells, but not alone. Scriptaid induced modifications of core histone tails important in euchromatin structure: increases in acetyl-H3-K9 and dimethyl-H3-K4 and a decrease in dimethyl-H3-K9. Cell growth was inhibited by scriptaid in a dose-dependent manner. Cell cycle analysis showed that scriptaid induced G1 arrest at 0.5 and 1.0 µM concentrations and G1 and G2/M arrest at 2.0 µM. Scriptaid did not have a significant effect on apoptosis in RKO cells. An altered expression of 278 genes was observed in RKO cells in response to scriptaid treatment. In conclusion, the present study suggests that scriptaid may be effective in growth suppression and cell cycle arrest and in the reversal of repressive chromatin marks at the promoter region of a hypermethylated p16 gene in colorectal cancer.

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