Downregulation of miR-153 contributes to epithelial-mesenchymal transition and tumor metastasis in human epithelial cancer.

The epithelial-mesenchymal transition (EMT) is a crucial step in epithelial cancer invasion and metastasis. The aims of this study were to investigate and validate unidentified micro RNAs (miRNAs) that regulate EMT and to reveal their clinical relevance in epithelial cancer patients. By applying miRNA array screening in a natural epithelial-mesenchymal phenotype cell line pair and in a transforming growth factor β-induced EMT cell model, we found miR-153 was markedly downregulated in the cells that underwent an EMT. A close association was confirmed between inhibition of miR-153 and the EMT phenotype, as well as the invasive ability of epithelial cancer cells. Ectopic expression of miR-153 in mesenchymal-like cells resulted in an epithelial morphology change with decreased cellular invasive ability. On the contrary, transfection of a miR-153 inhibitor in epithelial-like cells led to a mesenchymal phenotype change. In vivo ectopic expression of miR-153 significantly inhibited tumor cell metastasis formation. Data from the dual-luciferase reporter gene assay showed, for the first time, that SNAI1 and ZEB2 were direct targets of miR-153. Inverse correlations were also observed between miR-153 and SNA1 and ZEB2 levels in oral cancer patients' samples. Furthermore, low expression level of miR-153 was found to be significantly related to metastasis and poor prognosis in oral cancer patients. These data demonstrate that miR-153 is a novel regulator of EMT by targeting SNAI1 and ZEB2 and indicate its potential therapeutic value for reducing cancer metastasis.