SPP1 and neoplasm: CAFs can activate tumor cell proliferation and growth, tumor invasion, and metastasis (Table 1) and influence other TME cells by producing a variety of growth factors and cytokines, such as hepatocyte growth factor (HGF), fibroblast growth factors FGF2 and 7, TGF-β, PDGF, osteopontin (OPN), SFRP2 (secreted frizzled-related protein 2), SDF-1 (stromal cell-derived factor 1), VEGFA, IL-6, IL-8, and many others [96,109,110,111].