MDM2 and cancer: Indeed, several E3 ligases, such as Mdm2/Hdm2, Inhibitor of Apoptosis/ or Apoptosis inhibitor (IAPs) and Skp, Cullin, F-box containing complex (SCF), are over-expressed in many human cancers, and because evidence suggests that the inhibition of these enzymes may lead to growth suppression or apoptosis (19).