CD274 and viral infectious disease: The binding of PD-1 to PD-L1 on tumor cells helps these cells evade immune surveillance.32 The expression of PD-L1 on both cancer cells and immune cells is associated with survival outcomes and responses to immune checkpoint inhibitors.17,35 The regulation of PD-L1 in oropharyngeal tumor cells is considered an adaptive immune response in chronic diseases associated with viral infection.14 In some studies, high immunoexpression of PD-L1 is observed in HPV-associated cancers.35