NK cells from non-invasive and invasive cancers were shown to decrease expression of activating receptors (such as NKp30 and NKG2D) and increase expression of inhibitory receptors (such as NKG2A), induced by multiple immunosuppressive cytokines (e.g. TGF-β and IDO) in the tumor microenvironment [46]. Here, IDO1 is linked to neoplasm.