Using the glioma C6-dioxin response elements (DRE)-luciferase cell-based assay of AHR agonist activities (Fig. 2c), in which AHR activation can be quantified by DRE-induced luciferase expression, the AHR agonist 6-formylindolo(3,2-b)carbazole (FICZ) significantly increased AHR activity compared with the control. This evidence concerns the gene AHR and central nervous system cancer.