HGF and neoplasm: TAMs are important sources of epithelial growth factor within tumor tissue (141) and can also produce a variety of other cytokines, including platelet-derived growth factor, transforming growth factor beta-β, hepatocyte growth factor, and basic fibroblast growth factor (bFGF), thus promoting tumor cell proliferation and survival, acting as “signal transducers” in the interactions between tumors and neurons.