PDCD1 and neoplasm: Mechanically, PD-1 inhibitors block signal transduction between the immunosuppressive molecule PD-L1 on the surface of tumor cells and the receptor PD-1 on the surface of immune cells by competitively combining with PD-L1, thereby reactivating T cells and their immune monitoring effects.[8] In 2015, the Food and Drug Administration approved the first immune checkpoint inhibitor, nivolumab, as a therapy for patients with advanced NSCLC, meaning that immunological therapy could become a new type of therapeutic method after chemoradiotherapy and targeted therapy.[9]