CCL2 and head and neck squamous cell carcinoma: It is reported that monocyte chemotactic protein (MCP)-1, a kind of cytokine associated with poor long-term survival of HNSCC patients (Ji et al., 2014), could be produced by fibroblasts infiltrating in TME to facilitate the recruitment of monocytes into the local inflammatory tissues and regulate their functions (Kondoh et al., 2019).