PDCD1 and lung cancer: With the emergence of immune checkpoint inhibitors (ICIs), such as programmed cell death protein-1 (PD-1)/programmed cell death protein-1 ligand (PD-L1) and cytotoxic T lymphocyte-associated 4 (CTLA-4) inhibitors, immunotherapy has become one of the most promising treatment strategies for lung cancer, particularly for advanced and metastatic non-small cell lung cancers (NSCLC) with no epidermal growth factor receptor (EGFR) or anaplastic large cell kinase gene (ALK) alterations (NCCN Guidelines Version 3.2022 Non-Small Cell Lung Cancer, https://www.nccn.org/).