The authors proposed that tryptophan oxidation through the kynurenine pathway was a significant mechanism underlying tumour immunoresistance and suggested that this phenomenon could be attributed to the upregulation of kynurenine pathway enzymes, namely kynurenine monooxygenase, and kynureninase, resulting in enhanced production of immunosuppressive metabolites, such as anthranilic acid and 3-hydroxy anthranilic acid. The gene discussed is KYNU; the disease is neoplasm.