The expression of DDB2 was assessed in both the ER-negative (MDA-MB231 and SKBR3) and ER-positive (MCF-7 and T47D) breast cancer cells and was compared to that in the normal human mammary epithelial cells (HMEC), at both the transcriptional and the translational levels (Figure 1). This evidence concerns the gene ESR1 and breast carcinoma.