CD274 and head and neck squamous cell carcinoma: Research on anti-PD-L1 antibodies has been conducted in a variety of tumors, including NSCLC, SCLC, melanoma, HCC, BC, head and neck squamous cell carcinoma, gastric and gastroesophageal junction cancer, OSCC, urothelial carcinoma (UC), renal cell carcinoma (RCC) [125].