CD274 and head and neck squamous cell carcinoma: In addition, macrophages recruited to the immunosuppressive TME would transform into tumor-associated macrophages, which secrete the immunosuppressive cytokines, including IL-1beta, IL-6, IL-10, TGFB1, and the PD-L1 protein and other checkpoint ligands, which are correlated with unfavorable outcomes for patients with HNSCC (Marcus et al., 2004; Costa et al., 2013).