The crosstalk between HNSCC cells and macrophages involves a paracrine angiogenic loop in which MCP-1 and TGF-β1 from HNSCC cells attract and activate macrophages to secrete TNF-α and IL-1, stimulating tumour cells to secrete more VEGF and IL-8 (39). Here, CCL2 is linked to head and neck squamous cell carcinoma.