Fig. 8

Schematic diagrams illustrating the mechanisms for tumor-suppression by IDO1 blockade and radiation. a Schematic model for IDO1-induced sequential activations of kynurenine-PI3K-Akt axis and Wnt/β-catenin pathway in tumor cells, b Presumable mechanisms for activation of antitumor immune response by IDO1 blockade and radiation therapy. 1-MT: 1-methyl tryptophan, RT: radiation, Trp: tryptophan, IDO1: indoleamine 2,3 dioxygenase 1, Kyn: kynurenine, KPM: kynurenine pathway metabolites, LAT1: L-amino acid transporter 1, CTLA-4: cytotoxic T lymphocyte-associated antigen-4, GCN2: general control non-depressive 2 kinase, AHR: aryl hydrocarbon receptor