The treatment of IOMM-Lee cells with CEP-1347 resulted in a concentration-dependent decrease in MDM4 protein but not mRNA expression levels and also a reciprocal increase in p53 protein expression levels (Figure 4A,B), which is consistent with our previous findings on cell lines established from retinoblastoma and glioblastoma [19,20], cancer types associated with low incidence of p53 mutation [27,28]. This evidence concerns the gene MDM4 and cancer.