Therefore, the T-cell receptor signaling pathway (hsa04660) was further analyzed, revealing that neither PDCD1 (PD-1) nor CTLA4, the ICIs target ligands, were upregulated in HNSCC, as also confirmed by ST (Fig. 4d, Online Resource 7) and SIN (data not shown) compared with NOM. The gene discussed is PDCD1; the disease is head and neck squamous cell carcinoma.