HGF and cancer: The CAF express and secrete α-smooth muscle actin, platelet-derived growth factor (PDGF) which promotes cell proliferation and fibrosis, transforming growth factor beta (TGF-β), hepatocyte growth factor (HGF), insulin growth factor 1⁄2 (IGF), chemokines such as interleukin 1 (IL-1) and monocyte chemotactic protein 1 that facilitate the proliferation of cancer cells.