SPP1 and head and neck squamous cell carcinoma: MIHC staining revealed that SPP1 was substantially colocalized with CD68+ cells but barely colocalized with CD4+ T cells, CD8+ T cells or B cells and that SPP1 was more highly expressed in macrophages derived from HNSCC tumor tissues compared with those derived from adjacent normal tissues (Fig. 2D, E, Supplementary Fig. S2D).