MDM2 (HDM2 in humans), a E3 ubiquitin ligase, is a key regulator of p53 function through its role in proteasomal degradation of p53.[1, 2] Small molecule inhibitors of MDM2 that can restore wild type p53 activity in a non-genotoxic manner and thereby activate apoptotic cell death, are in clinical development as treatment of cancers including leukemias and have shown early clinical activity.[3, 4] Nutlin 3a and its analogs are first-in-class MDM2 inhibitors [3]. This evidence concerns the gene TP53 and cancer.