IDO1 and neoplasm: The tumorigenic effects of IDO1 are mediated through multiple mechanisms, including the shaping of a tumor-favorable immune microenvironment due to tryptophan shortages and the accumulation of tryptophan catabolites [2, 7, 8], as well as activation of pro-tumorigenic signaling pathways such as PI3K/AKT signaling and the translocation of β-catenin from the cytoplasm into the nucleus [9, 10].