Cancer-associated fibroblasts (CAFs) express and secrete signalling proteins which stimulate cancer cell proliferation, including insulin-like growth factor-1 (IGF-1), hepatocyte growth factor (HGF), stromal-cell-derived factor-1 (CXCL12), and a range of fibroblast growth factors (FGFs) [44]. The gene discussed is HGF; the disease is cancer.