Recently, we have reported that the expression of both IDO1 and TDO was associated with advanced stage of disease and poor prognosis in patients with glioblastoma, which attributed to Kyn-AhR-AQP signaling pathway and an IDO1/TDO (IDO1 and TDO) dual inhibitor could exert anti-glioma effects in GL261 orthotopic glioma mice[122]. This evidence concerns the gene TDO2 and central nervous system cancer.