PDCD1 and head and neck squamous cell carcinoma: ICB therapy is effective for HNSCC, so we collected seven immune checkpoint target genes (CD247, CD274, PDCD1, TNFRSF9, TNFRSF4, CTLA4, and TLR9) reported in previous studies (Ramos-Casals et al., 2020; van de Donk et al., 2021).