circUBAP2 promotes OS cell proliferation, migration and invasion, and inhibits OS cell apoptosis by sponging miR-204-3p. (A) Transfection efficiency of miR-203-3p mimic. (B) Cell Counting Kit-8 assays were performed to examine the effect of circUBAP2 and miR-204-3p on HOS and SaOS-2 cell proliferation. (C) Transwell assays were performed to assess the effect of circUBAP2 and miR-204-3p on HOS and SaOS-2 cell (C) migration and (D) invasion (scale bar, 500 µm). (E) Flow cytometry was performed to assess the effect of circUBAP2 and miR-204-3p on HOS and SaOS-2 cell apoptosis. *P<0.05 and **P<0.01. circ, circular RNA; UBAP2, ubiquitin associated protein 2; OS, osteosarcoma; miR, microRNA; NC, negative control; si, small interfering RNA; OD, optical density.