HGF and neoplasm: When triggered by extracellular molecules (such as TGF-β, hepatocyte growth factor (HGF) and insulin-like growth factor (IGF)) and tumor microenvironment stimuli (such as hypoxia), EMT transforms tumor cells from an epithelial state to a mesenchymal state and endows tumor cells with greater invasion ability and greater metastatic potential, thereby inducing intravasation and shedding of tumor cells.