HGF and neoplasm: In time, these cells become active again, taking advantage of the factors that are secreted by resident cells such as interleukin (IL-6), insulin-like growth factor (IGF), hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), stromal cell-derived factor 1α (SDF1α) and a proliferation-induced ligand (APRIL), which provide crucial signals for tumour growth and survival [7, 12].