IDO1 and colonic neoplasm: Furthermore, evidence from studies conducted on the tumor cell lines H22 (hepatocellular carcinoma) and CT26 (colon cancer) suggests that the IFN-γ/JAK/STAT1/IDO1 pathway not only aids tumor cells in immune escape by affecting T cell function but also inhibits tumor cell apoptosis by inducing tumor-repopulating cells to enter immunologic dormancy through a downstream signaling mechanism involving IDO1/Kyn/AhR/p27 pathway (40).