Based on its functions as a mediator of the cellular response to xenobiotics, initial human epidemiological studies alerted to health authorities about the pathological effects likely attributable to AhR-mediated activity including alterations in the immune system, lipid metabolism, epithelial integrity, porphyria, liver damage, thymic involution and cancer (Fingerhut et al., 1991; Flesch-Janys et al., 1995). This evidence concerns the gene AHR and cancer.