miR-19a-3p inhibitor enhances chemosensitivity of OS cells. A Cisplatin-resistant cell line was constructed, and Cisplatin-resistant cells were transfected with miR-19a-3p mimics or inhibitor. Cisplatin treatment of cisplatin-resistant cells was used as a control. (A) Cell proliferation was measured by CCK-8 assay. (B) Expression of Ki67 and PCNA protein was detected through western blotting. (C) Quantification of the protein expression of Ki67 and PCNA. (D) Apoptosis was detected by flow cytometric analysis. (E) Quantification of cell apoptotic rate. (F) Expression of Bax and Bcl-2 protein was detected through western blotting. (G) Quantification of Bax and Bcl-2 protein expression. The error bars represent means ± standard deviation of three independent experiments. #P<0.05, ##P<0.01 compared with Cisplatin group. miR, microRNA; OS, osteosarcoma; CCK-8, Cell Counting Kit-8; PCNA, proliferating cell nuclear antigen; Bax, BCL2 associated X, apoptosis regulator.