AHR and neuroblastoma: Human neuroblastoma M17 cells were differentiated for 7 days in 3% FBS media with 10 μM retinoic acid and treated for a further 7 days with vehicle, AHR agonist 6-formylindolo[3,2-b]carbazole (FICZ) or with agonist and antagonist; FICZ is a non-toxic, high-affinity AHR agonist and putative endogenous AHR ligand [30, 31].