Abstract: Programmed death ligand-1 (PD-L1) is highly expressed on most tumor cells, and it interacts with programmed death-1 (PD-1) on the surface of immune cells, which mainly inhibits T cell proliferation and plays an important role in tumor immune escape. The studies find that PD1/PDL1 pathway can promote tumor cell glycolysis and epithelialmesenchymal transition, and can induce PDL1 expression on macrophages and enhance immunosuppression in tumor microenvironment. Therefore, PD-1/PD-L1 is considered to be an important immunoassay point, and a series of antiPD-1 and PD-L1 antibodies, such as pembrolizumab, nivolumab, atezolizumab, durvalumab and avelumab, have clinically shown good effects. Further understanding of its mechanism may provide new ideas for the treatment of malignant tumors such as lung tumors.

Key words: Tumor escape, Immunotherapy, PD-1/PD-L1