SPP1 and head and neck squamous cell carcinoma: SPP1 + Macs increase the secretion of TNF-α and IL-1β via the NF-kappa B pathway to promote HNSCC cell proliferation, and TNF-α and IL-1β in turn upregulate the expression of OPN in tumor cells and macrophages; thus, SPP1 + Macs may be a candidate target through which antitumor efficacy can be enhanced.