TCDD up-regulated epithelial Cyp1b1 expression and decreased Comt expression in pubertal mammary glands from mammary gland cohort mice fed HFD, indicating a role of the E2 metabolism genotoxicity pathway in cancer etiology (Figure 5), consistent with studies showing a role for maternal COMT and CYP1B1 in breast cancer risk of exposed daughters (Inoue et al. 1980; Sata et al. 2006). This evidence concerns the gene CYP1B1 and breast cancer.