CD274 and head and neck squamous cell carcinoma: Recently, a considerable number of ICIs for different checkpoints have been FDA-approved for many cancers, including melanoma, non-small cell lung cancer (NSCLC), head and neck squamous cell carcinoma (HNSCC), triple-negative breast cancer (TNBC), Renal Cell Carcinoma (RCC), etc. These drugs include Pembrolizumab and Nivolumab targeting PD-1, Ipilimumab targeting CTLA-4, and Atezolizumab targeting PD-L1 [57,58].