IDO1/2 and TDO overexpression in tumor cells promotes tryptophan depletion in the microenvironment, resulting in suppression of the T-cell mediated immune response. IDO1/2 and TDO catalyze the breakdown of tryptophan into kynurenine, and subsequently KYNU cleaves kynurenine into anthranilic acid, a precursor of tryptophan. High levels of KYNU have been found in lymphoma, breast, liver, pancreas, and urothelial cancers, and is thought to promote tumor aggressiveness and metastasis. KYNU levels are also elevated in many chronic inflammatory skin diseases such as psoriasis and atopic dermatitis inflammatory, making KYNU attractive as a potential therapeutic and prognostic target.