Abstract: Objective To explore the mechanism of miR-296-5p induced autophagy and inhibition of epithelial-mesenchymal transition ( EMT) in osteosarcoma (OS) cells. Methods The expression level of miR-296-5p in OS cells was detected by qRT-PCR. The target gene of miR-296- 5p was predicted by bioinformatic method. The direct binding relationship of miR-296-5p with its target gene PLK1 was verified. Cell lines overexpressed or silenced of miR-296-5p were constructed through cell transfection method. The effect of miR-296-5p on cell proliferation, invasion, apoptosis, autophagy, EMT, and the expression level of PTBP1 in U2OS cells were detected by CCK-8, colony formation assay, transwell chamber assay, flow cytometry, and Western blotting. Results The expression level of miR-296-5p was decreased in OS, while the expression level of PLK1 was increased when compared to the control group (P < 0. 05). The colony formation rate, the number of invasive cells, and the expression levels of PTBP1, p62, N-cadherin, Vimentin, p-PI3K/ PI3K and p-AKT / AKT were decreased in mimic group, while the apoptosis rate, the expression levels of Beclin-1, LC3-Ⅱ/ Ⅰ and E-cadherin were increased when compared to the miR-NC group (P< 0. 05). The colony formation rate, the number of invasive cells, the expression levels of PTBP1, p62, N-cadherin, Vimentin, p-PI3K/ PI3K and p-AKT / AKT were decreased in PLK1 + mimic group, while the apoptosis rate, the expression levels of Beclin-1, LC3-Ⅱ/ Ⅰ and E-cadherin were increased in PLK1 + mimic group when compared to the PLK1 group (P< 0. 05). Conclusion miR-296-5p may induce autophagy in OS cells and inhibit EMT through regulation of PI3K/ AKT pathways by targeting PLK1.

Key words: osteosarcoma, miR-296-5p, PLK1, PI3K/ AKT pathway, autophagy, epithelial-mesenchymal transition