While kynurenine is produced by the tryptophan catabolizing enzyme TDO in several types of cancer including glioma, hepatocellular carcinoma and melanoma to promote immune evasion [25, 42], we demonstrate here that IDO1 is equally capable of employing the AHR pathway in NSCLC and ovarian carcinoma cells. The gene discussed is IDO1; the disease is glioma.