CD274 and head and neck squamous cell carcinoma: Dasatinib, an indirect STAT3 inhibitor, significantly facilitated anti-CTLA-4 immunotherapy in head and neck squamous cell carcinoma (61), while the combined blockade of IL-6 and PD-L1 remarkably inhibited the growth of pancreatic ductal adenocarcinoma and hepatocellular carcinoma (62, 63).