Bioinformatic analysis demonstrates that indoleamine 2,3-dioxygenase 1 and 3-hydroxy-3-methylglutaryl coenzyme A reductase (key enzymes of kynurenine (Kyn) and cholesterol metabolism, respectively), are overexpressed in human colon adenocarcinoma tissues. Here, IDO1 is linked to colon adenocarcinoma.