[Epithelial-mesenchymal transition (EMT) and its effect on microRNA expression in lung cancer]

To investigate the effect of epithelial-mesenchymal transition (EMT) on the expression of microRNAs (miRNAs) in lung cancer A549 cells.

Transforming growth factor beta-1 (TGF-beta 1) in different concentrations was used to induce EMT in lung cancer A549 cells. The morphological changes were observed under phase-contrast microscope. The changes of EMT-related proteins were analyzed by Western blot. The changes of miRNAs expression after EMT were detected by microRNA (miRNA) array. Real time quantitative RT-PCR was applied to verify the reliability of miRNA array results.

The lung cancer A549 cells became elongated and the cell-cell junction became loose after EMT. The epithelial protein marker E-cadherin was down-regulated and the mesenchymal protein markers vimentin and fibronectin up-regulated. There were 51 miRNAs showing statistically significant changes of expression more than double (P<0.05) after EMT. Among them 18 were up-regulated and 33 down-regulated. Of them, mir-33a was down-regulated by 92.8% and mir-193a-3p by 86.5%. Real time quantitative RT-PCR showed that mir-33a was down-regulated by 73.1% and mir-193a-3p by 56.6%.

Epithelial-mesenchymal transition has effects on the expression of miRNAs, and miRNAs may regulate the invasion and metastasis of lung cancer cells via EMT.