IDO1 and cancer: However, IDO1 is overexpressed in many cancers, such as, breast, colorectal, gastric, lung, and endometrial cancers, and IDO1 overexpression is also associated with poor survival rates (Uyttenhove et al., 2003; Dolusić et al., 2011; Heidari et al., 2020; Odunsi et al., 2022).