Lung cancer is the leading cause of cancer-related deaths in the world, and non-small cell lung carcinomas (NSCLC) account for 85 % of lung cancer cases. Despite enormous achievement in the treatment of NSCLC, the molecular mechanisms underlying the pathogenesis are largely unknown. The current study was designed to evaluate the role of miR-155 in NSCLC cell proliferation and to explore the possible molecular mechanisms. We found that miR-155 expression was increased in NSCLC tissues and cell lines. The increase of miR-155 significantly increased A549 cell proliferation, decreased S phase cell population and increased G2/M phase cell population. Decrease of miR-155 expression markedly inhibited cell proliferation, increased S phase cell population, and decreased G2/M phase cell population. Increase of miR-155 significantly decreased forkhead box protein O1 (FoxO1) 3'UTR luciferase activity and expression and decrease of miR-155 notably increased FoxO1 expression. Overexpression of FoxO1 significantly inhibited miR-155-exerted increase of cell proliferation and G2/M cell population. Downregulation of FoxO1 by siRNAs significantly promoted cell proliferation, decreased S phase cell numbers, and increased G2/M cell population. Downregulation of FoxO1 markedly increased ROS level, as reflected by increased DHE staining. Moreover, when N-acetylcysteine was present, increase of cell proliferation induced by downregulation of FoxO1, and upregulation of miR-155 was significantly inhibited. In conclusion, we found that miR-155 promoted NSCLC cell proliferation through inhibition of FoxO1 and the subsequent increase of ROS generation. Our findings highlight miR-155/FoxO1/ROS axis as a novel therapeutic target for the inhibition of NSCLC growth.
Keywords: Cell proliferation; Forkhead box protein O1; Non-small cell lung carcinomas; Reactive oxygen species; miR-155.