AHR and breast cancer: Strengthening our findings, previous studies support a role for AhR and breast tumor progression: (i) AhR expression levels were significantly up-regulated in human breast ductal carcinoma in situ and breast cancer tissues compared to normal/benign breast tissues (70, 71); (ii) an in vivo model of breast tumorigenesis suggests that AhR is constitutively activated at early stages of mammary tumorigenesis (72); (iii) the prognostic value of AhR seems to be dependent on the activation/inactivation of metastatic processes (73).