MiR-340 impedes the progression of laryngeal squamous cell carcinoma by targeting EZH2.

Laryngeal squamous cell carcinoma (LSCC) is a common malignant tumor of the otolaryngeal region and accounts for 1-2% of all malignancies diagnosed worldwide. miR-340 down-regulation and EZH2 up-regulation have been frequently identified in multiple cancers, but the role of miR-340 and EZH2 in LSCC has not been explored. In this study, we investigated the regulative role of miR-340 in EZH2 expression and LSCC progression. The results showed that EZH2 was up-regulated and miR-340 was down-regulated in both Hep-2 cells and LSCC tissues. Molecularly, our results confirmed that miR-340 directly targeted EZH2 gene and inhibited EZH2 expression. MTT assay and BrdU assay showed that miR-340 transfection reduced the cell proliferation ability of Hep-2 cells. The transwell assay indicated that the invasion and migration ability of Hep-2 cells was dramatically inhibited by miR-340 transfection. In addition, miR-340 transfection induced cell apoptosis with concomitant enhancement of Bax, increase of Caspase-3 expression and activity, and reduction of Bcl-2 expression in Hep-2 cells. Both miR-340 transfection and EZH2 knockdown induced p27 expression and suppressed PI3K/Akt activation in Hep-2 cells. Strikingly, EZH2 knockdown reduced cell proliferation, and EZH2 overexpression significantly rescued the miR-340-mediated suppressive effect on cell proliferation. Moreover, miR-340 could obviously induce the inhibition of Hep-2 cell-derived tumor growth and EZH2/p27 expression ratio in vivo. Taken together, these data suggest that miR-340 impedes LSCC progression by targeting EZH2 with the possible mechanism to enhance the expression of anti-oncogene p27 and suppress PI3K/Akt activation, providing a novel target and a potential therapeutic pathway against LSCC.