CTLA4 and head and neck squamous cell carcinoma: Immune checkpoint inhibitors (ICIs), including anti-programmed death-1 (anti-PD-1), anti-programmed death ligand-1 (anti-PD-L1), and anti-cytotoxic T-cell lymphocyte-associated antigen-4 (anti-CTLA-4) monoclonal antibodies, represent a breakthrough in cancer therapy and have shown great benefits in the treatment of multiple cancer types, besides melanoma, and especially in non-small cell lung cancer (NSCLC) and head and neck squamous cell carcinoma (HNSCC)1.