CCL18 and head and neck squamous cell carcinoma: CCL18 exerts its function via binding to the receptor Nir1 on cancer cell surface and then activates downstream signaling pathways, which include the mammalian target of rapamycin (mTOR) [47], NF-κB [41] and PI3K/Akt signaling pathways [48] etc. We have found that activation of CCL18/Nir1 signaling pathway can increase the expression of oncogene MTDH, which is important for the promotion of SCCHN metastasis in our previous studies (Data are prepared in another manuscript) [27, 28, 49].