TP53 and retinoblastoma: Our subsequent examination of its effects particularly on non-stem cancer cells, unexpectedly revealed that MDM4-expressing retinoblastoma cells with wild-type p53 were selectively sensitive to the growth inhibitory effects of CEP-1347 and also that CEP-1347 down-regulated MDM4 protein expression and activated the p53 pathway to suppress the growth of these cells [19].