XIST negatively regulates the expression of miR-137 in OS cells by sponging. (A) The luciferase reporter plasmid containing the WT or MT miR-137 binding sites in XIST were constructed. (B) Saos-2 and (C) U2OS cells were used for the luciferase reporter gene assay, and transfection with miR-137 mimic significantly inhibited the luciferase activity of WT XIST in OS cells but did not significantly affect the luciferase activity of MT XIST. **P<0.01 vs. miR-NC. (D) Saos-2 and (E) U2OS cells were transfected with XIST siRNA or NC siRNA, and RT-qPCR was conducted to examine the expression of XIST and miR-137. **P<0.01 vs. NC siRNA. (F) Saos-2 and (G) U2OS were transfected with a XIST plasmid or blank vector, and RT-qPCR was conducted to examine the expression of XIST and miR-137. **P<0.01 vs. Blank. XIST, X inactive-specific transcript; miR, microRNA; OS, osteosarcoma; WT, wild-type; MT, mutant type; NC, negative control; siRNA, small interfering RNA; RT-qPCR, reverse transcription-quantitative polymerase chain reaction.