MicroRNA-224 promotes tumor progression in non-small cell lung cancer

Lung cancer is the leading cause of cancer-related deaths worldwide. Despite advancements and improvements in surgical and medical treatments, the survival rate of lung cancer patients remains frustratingly poor. Local control for early stage non-small cell lung cancer (NSCLC) has dramatically improved over the last decades for both operable and inoperable patients. However, the molecular mechanisms of NSCLC invasion leading to regional and distant disease spread remain poorly understood. Here we identify miR-224 to be significantly up-regulated in NSCLC tissues, in particular in resected NSCLC metastasis. Increased miR-224 expression promotes cell migration, invasion and proliferation by directly targeting the tumor suppressors, TNFAIP1 and SMAD4. In concordance with in vitro studies, mouse xenograft studies validated that miR-224 function as a potent oncomiR in NSCLC in vivo. Moreover, we found promoter hypomethylation and activated ERK signaling to be involved in the regulation of miR-224 expression in NSCLC. Up-regulated mir-224 thus facilitates tumor progression by shifting the equilibrium of the partially antagonist functions of SMAD4 and TNFAIP1 towards enhanced invasion and growth in NSCLC. Our findings indicate that targeting miR-224 could be effective in the treatment of certain lung cancer patients Oncogenic role of miR-224 in lung cancer