Kynurenine (2922-83-0) is a tryptophan catabolite1. Endogenous tumor-promoting ligand of the human aryl hydrocarbon receptor (AhR). Constitutively generated by human tumor cells via the action of the tryptophan degrading enzyme, tryptophan-2,3-dioxygenase (TDO). Kynurenine suppresses antitumor immune responses and promotes tumor cell survival and motility2.
1) Ibana et al. (2011), Inhibition of indoleamine 2,3-dioxygenase activity by levo-1-methyl tryptophan blocks gamma interferon-induced Chlaydia trachomatis persistence in human epithelial cells; Infect. Immun., 79 4425
2) Opitz et al. (2011), An endogenous tumour-promoting ligand of the human aryl hydrocarbon receptor; Nature, 478 197