But some clinical trials such as ‘CheckMate 141’ and ‘KEYNOTE-014’ indicated that only 15–20% of patients with platinum-refractory recurrent or metastatic HNSCC did respond to immunotherapy with programmed death-1 (PD-1)/programmed death-ligand-1 (PD-L1) immune-checkpoint inhibitors (ICIs) [9–12]. Here, PDCD1 is linked to head and neck squamous cell carcinoma.