MDM2 and osteosarcoma: Employing three osteosarcoma cell lines [U-2 OS (wt p53), SaOS2 (null p53), MG63 (mut-p53)], the authors deciphered that activation of the p53 pathway due to the disruption of p53-MDM2-interaction by nutlin-3a depends on the presence of wt-p53 [109].