MDM4 and cancer: Although GBM and MM are both cancer types that express wild-type p53 in the majority of cases [15,16,17], p53 is negatively regulated by MDM2 and MDM4 in wild-type p53 cancer [18,19], and methods to enhance the IR sensitivity of GBM cells, with the aim of promoting the activation of p53 by the combined use of MDM2/MDM4 inhibitors, are currently being evaluated [20,21].