Clinically, it has been observed that CDK9 is overexpressed in many cancer types, such as pancreatic cancer, osteosarcoma, synovial sarcoma, and endometrial cancer [23,24,25,27,28], and that a high CDK9 expression correlates with poor patient prognosis [23,24,25,27]. This evidence concerns the gene CDK9 and osteosarcoma.