AHR and neoplasm: Although some of the AhR ligands, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), exert procarcinogenic properties [34,35], and the biological effects of the activation of some AhR-target genes may suggest the involvement of this receptor in tumor progression [36], a specific role of AhR in carcinogenesis has not been fully elucidated.