Moreover, the expression level of TIGIT on the surface of tumor-infiltrating T cells was discovered to increase fourfold than that on peripheral blood mononuclear cells (PBMC), and further studies reveal that only the expression of TIGIT in CD8+ T cell exhaustion increased significantly, and changed synchronously with that of PD-1 (5), indicating that TIGIT and PD1/PD-Ll pathway had a synergistic inhibitory effect on tumor-infiltrating T cells. This evidence concerns the gene PDCD1 and neoplasm.