CTLA4 and head and neck squamous cell carcinoma: In particular, the advent of ICI, that block PD-1, PD-L1 and CTLA-4, significantly improved treatment for a number of solid tumors, such as metastatic melanoma (83), non-small-cell lung cancer (84), merkel cell carcinoma (85), colon carcinoma (86), head-and-neck squamous cell carcinoma (HNSCC) (87) and others (88, 89).