miR-16 mimics inhibit TGF-β1-induced epithelial-to-mesenchymal transition via activation of autophagy in non-small cell lung carcinoma cells

Autophagy is critical for the metastasis of cancer cells through induction of epithelial-to-mesenchymal transition (EMT). Activation of TGF-beta signaling plays a key role in regulating autophagy. miR-16 may be associated with non-small cell lung carcinoma (NSCLC) progression. However, the role of miR-16 in NSCLC cell autophagy in the presence of TGF-beta and the underlying mechanism are still unclear. To test whether miR-16 targets ATG3 which is involved in autophagy of NSCLC cells, we studied the expression levels of miR-16 and ATG3 in NSCLC patients, verified the targeting of ATG3 by miR-16 by luciferase reporter gene system, and investigated the role of miR-16 in the autophagy of NSCLC cells. Results revealed that miR-16 was significantly downregulated, and ATG3 was significantly upregulated in NSCLC patient tissue samples. ATG3 was found to be a direct target of miR-16. TGF-beta 1 significantly downregulated the expression of miR-16 and ATG3 mRNA. Using transmission electron microscopy, we observed that TGF-beta 1 treatment reduced autophagosomes in the A549 cells, and miR-16 mimics increased the autophagosomes in the presence of TGF-beta 1. Acridine orange (AO) staining and expression of LC3B II/I and p62 confirmed the inhibition of autophagy by TGF-beta 1, and the recovery of TGF-beta 1-mediated inhibition of autophagy by miR-16 mimics. Finally, miR-16 mimics inhibited TGF-beta 1-induced EMT, and this effect was attenuated by autophagy inhibitor 3-MA. Taken together, miR-16 mimics inhibited TGF-beta 1-induced EMT via activation of autophagy.