However, it does not help to clarify the molecular mechanisms of toxic effects induced by nongenotoxic AhR ligands, such as TCDD, which is not metabolized. In vivo studies in two genetically different rat strains indicate that AhR-driven CYP1A1 induction and tumor promotion can be uncoupled from each other supporting the idea of additional AhR-triggered pathways [4]. This evidence concerns the gene AHR and neoplasm.