The c-myb gene is induced by activation of ERs in breast cancer cell lines such as MCF-7 [6-8] and c-Myb protein has been implicated in the regulation of several genes important in breast cancer development and progression, including BRCA1 [9], CXCL12 [10], Mdm2 and p53 [11]. This evidence concerns the gene MDM2 and breast cancer.