TGF-β (Transforming Growth Factor Beta) might serve as an example by working as a tumor suppressor in early-stage of cancer, inhibiting uncontrolled cell growth and proliferation, and as a tumor promoter and immune suppressor in the late-stages of cancer by weakening NK cells’ tumor-killing ability, downregulating NKG2D expression and impairing their expertise in immunorecognition of tumor cells [32]. This evidence concerns the gene KLRK1 and cancer.