| Summary: | The silencing of Bcl-xL in the non-small cell lung cancer (NSCLC) cell line, A549, downregulates miR-361-5p expression. This study aimed to determine the biological effects of miR-361-5p on NSCLC, and to elucidate the molecular mechanisms through which apoptosis is regulated. MicroRNA (miRNA or miR) functional analyses were performed via transfection of miR-361-5p mimics and inhibitors, demonstrating that the inhibition of miR-361-5p induced the apoptosis of NSCLC cells. To elucidate the function of miR-361-5p in vivo, cells transfected with miR-361-5p inhibitors were microinjected into zebrafish embryos, and immunostained using antibodies to detect the active form of caspase-3. Co-transfection with siBcl-xL and miR-361-5p mimics illustrated the association between Bcl-xL, miR-361-5p and apoptosis; miR-361-5p mimics blocked the apoptosis initiated by siBcl-xL. Luciferase reporter assays identified mothers against decapentaplegic homolog 2 (SMAD2) as a novel target of miR-361-5p and the reduction of its protein level was validated by western blot analysis. To confirm the molecular mechanisms through which apoptosis is regulated, gene rescue experiments revealed that the ectopic expression of SMAD2 attenuated the inhibitory effects on apoptosis induced by miR-361-5p. In this study, to the best of our knowledge, we provide the first evidence that miR-361-5p functions as an oncomiR in A549 and SK-LU-1 cells through the regulation of SMAD2, suggesting that miR-361-5p may be employed as a potential therapeutic target for the miRNA-based therapy of NSCLC.
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