Objective To investigate the effect of miRNA-199a-5p on cell proliferation and autophagy in osteosarcoma cell line U2OS and its possible mechanism.

Methods The expression of miRNA-199a-5p were detected by qRT-PCR after transfection with the miRNA-199a-5p mimics in U2OS cells in paraffin section and paired adjacent normal tissue from 32 patients with osteosarcoma. The proliferation were measured by CCK-8 assay and flow cytometry assay. The expression of cell cycle related protein (cyclinD1, P27, pRb) and autography related protein (Beclin 1, LC3Ⅱ/Ⅰ) were measured by Western blot assay.

Results MiRNA-199a-5p was lowly expressed in both osteosarcoma tissues and U2OS cells (P < 0.05). The expression level of miRNA-199a-5p was correlated with the tumor size, distant metastasis, Enneking stage and pathological grade stage (P < 0.05). Overexpression of miRNA-199a-5p suppressed U2OS cell proliferation (P < 0.05), and downregulated the expression of cyclinD1 and pRb, while upregulated the expression of P27, Beclin 1 and LC3Ⅱ/Ⅰ(P < 0.05).

Conclusion miRNA-199a-5p suppresses cell proliferation but induces cell autophagy. And its mechanism may be related to thedownregulation of cyclinD1 and upregulation of P27 protein expression, then supressed the phosphorylation of pRb, resulting in G₁/S arrest in human osteosarcoma cell line U2OS. It suggests that miRNA-199a-5p may be used as a potential new target for targeted therapy of osteosarcoma.