HGF and glioma: HGF and MET are expressed in vitro in glioblastoma multiforme cell lines as well as in normal human astrocyte (NHA) cells. HGF stimulates tyrosine phosphorylation of MET in both glioma cell lines and NHA cells, but only the glioma cell lines proliferate and become motile and invasive in response to HGF, whereas the NHA cells are nonresponsive, implicating autocrine/paracrine MET/HGF signaling in glioma tumorigenesis; HGF signaling through MET is negatively regulated in NHA cells [119].