CTLA4 and neoplasm: Among them, different types of extrinsic and intrinsic immune inhibitory receptors such as KIRS (killer inhibitory receptors), CD96, TIGIT, PD-1, CTLA-4, TIM-3, VISTA, and LAG-3, also known as checkpoint receptors, are responsible to prevent the tumor-killing potentiality of NK cells through their upregulation on NK cell surface which is typically mediated by IL-10 and TGF-β [120].