Such a finding would likely have a global impact on p53 gene expression signatures in ERα-positive cells, as we have herein demonstrated that MDM4 and MDM2 are highly expressed in ERα-positive tumors, and Bailey et al. have demonstrated in a genome-wide breast cancer study that ERα antagonizes the expression of approximately 150 putative p53-regulated transcripts [114]. This evidence concerns the gene MDM4 and breast cancer.