A microRNA contribution to aberrant Ras activation in gastric cancer.

Oncogenic Ras mutations are rare in gastric cancer, indicating that other mechanisms may be responsible for aberrant Ras activation in this type of cancer. Ezrin is critical to Ras activation by remodeling cortical actin cy-toskeleton. In this study, we aimed to illustrate the relevance and regulation of ezrin in gastric cancer. Ezrin was upregulated in gastric cancer cells. Ezrin siRNA inhibited Ras activation, cell growth and cell migration. Ezrin overex-pression was correlated with a poor outcome of gastric cancer patients (n=150, p<0.01). Cox regression analysis revealed a significant value of ezrin expression in prognosis prediction of gastric cancer (relative risk: 2.37, 95% confidence interval: 1.24-4.56, p<0.01). MiR-204, which was predicted to target ezrin, was downregulated in gastric cancer cells and gastric carcinomas (n=22, p<0.01). MiR-204 inhibited ezrin expression, Ras activation, cell growth and cell migration. Importantly, miR-204 suppressed the expression of luciferase controlled by wild-type but not mutated ezrin 3'-UTR. In conclusion, ezrin is important to Ras activation in gastric cancer. Its upregulation is an independent prognosis prediction factor for gastric cancer. By contributing to ezrin upregulation, miR-204 downregulation represents a novel mechanism for aberrant Ras activation in gastric carcinogenesis.