CCR2+ T cells were nearly absent in FoxP3+CD4+ T cell fractions, indicating that HNSCC-circulating aTreg cells may be recruited to the tumor microenvironment by endogenous MCP-1 via binding to CCR4 but not CCR2 (Figure 5A, 5B). This evidence concerns the gene CCL2 and head and neck squamous cell carcinoma.