Epigenetic modification of RhoE expression in gastric cancer cells

RhoE is a unique member of Rho family of GTPases without detectable intrinsic GTPase activity. Our previous study showed that RhoE is a tumor suppressor gene and its expression is down-regulated in gastric cancer. However, the mechanism underlying the down-regulated expression of RhoE in gastric cancer has not been elucidated yet. In the present study, the effect of epigenetic modification on the RhoE expression in gastric cancer cells was investigated. The mRNA and protein expression of RhoE were detected by real-time RT-PCR and Western blotting, respectively. Results showed RhoE was significantly down-regulated in three gastric cancer cell lines. A promoter (2980 bp) of RhoE and its five truncated mutants were cloned into vector pGL-3Basic for the activity analysis by luciferase reporter assay. Treatment with trichostatin A, a histone deacetylation inhibitor, enhanced not only the activity of RhoE promoter, but also the mRNA and protein expression of RhoE in three gastric cancer cell lines, whereas treatment with 5-Aza-2'-deoxycytidine, a DNA methylation inhibitor, affected neither RhoE promoter activity nor RhoE expression. No synergistic effect was observed in cells treated with both drugs. Our results suggested that RhoE expression in gastric cancer cells was regulated by histone deacetylation, but not by DNA methylation, at the epigenetic level.