In a previous study, we have analyzed the expression of these genes located on chromosome 12q13-15, in osteosarcoma (OS) of the jaws; their high expression supported the notion that p53-MDM2 and Rb-cyclin D–CDK4 pathways play a role in the pathogenesis of these gnathic tumors (9). This evidence concerns the gene MDM2 and osteosarcoma.