The co-inhibitory receptor, TIGIT, blocks the direct interaction of NK cells with tumor cells by binding to the ligands CD155 and CD112, which are highly expressed in antigen-presenting cells (APCs) and tumor cells, diminishing their killing ability and further inhibiting cytokine secretion by NK cells, such as TNF-α and IFN-γ (83, 84). This evidence concerns the gene TIGIT and neoplasm.