We also investigated the possibility that the dual-target MDM2/MDMX inhibitory protein might reverse DOX resistance in human breast cancer through the activation of the transforming growth factor β-activated kinase 1 (TAK1)-binding protein 1 (TAB1) /TAK1/p38 mitogen-activated protein kinase (MAPK) signaling pathway. This evidence concerns the gene MDM4 and breast cancer.