MIF and osteosarcoma: In order to further verify the specific role of MIF/CDK9/c‐Myb axis in 4‐IPP inhibition effect in osteosarcoma, HOS cells were stably transfected with MIF knockout/MIF overexpression/CDK9 overexpression/c‐Myb overexpression plasmids to establish xenograft model in nude mice, and followed by PBS or 20 mg/kg 4‐IPP treatment.