The expression of IDO1 in non small cell lung cancer cells has been already related to the constitutive activation of the IL-6/STAT3 signaling: kynurenine activates the transcription factor aryl hydrocarbon receptor, that in turn increases the autocrine synthesis of IL-6 and the subsequent activation of STAT3 [34]. The gene discussed is AHR; the disease is non-small cell lung carcinoma.