CTLA4 and neoplasm: Apart from modulating the expression of activating receptors on NK cells, tumor cells also evade NK-mediated immunosurveillance by enhancing inhibitory signalings, including inhibitory receptors KIRs and NKG2A, as well as immune checkpoints programmed cell death 1 (PD-1), lymphocyte-activation gene 3 (LAG-3), CD96 (also known as TACTILE), T cell immunoglobulin and ITIM domain (TIGIT), T cell immunoglobulin and mucin-domain containing-3 (TIM3), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and Interleukin-1 receptor 8 (IL1R8) [66,93] (Figure 2).