Neutrophils in non-small cell lung cancer and immunotherapy with PD-1/PD-L1 inhibitors

Neutrophils, which represent about 50-70% of circulating leukocytes in humans, have been viewed as short-lived effector cells of the innate immune system with a primary role in the clearance of pathogens and taking part in inflammatory processes. More recent evidence shows that neutrophils make up a significant portion of the inflammatory cell infiltration in many types of cancer, including non-small cell lung cancer (NSCLC). These tumor-associated neutrophils (TANs) can be divided into protumorigenic and antitumorigenic phenotypes. The biological features and functions of these TANs are under the influence of the tumor microenvironment. TANs also play a role in determining the responsiveness of NSCLC to immunotherapies targeting the programmed cell death-1 (PD-1)/programmed death ligand 1 (PD-L1) axis. This review aimed to summarize recent findings regarding the role of TANs in NSCLC progression and PD-1/PD-L1 targeted immunotherapy.