Tumor-derived HGF has been shown to facilitate microglia migration41 through paracrine signaling, as well as promote glioma invasion and chemoresistance through autocrine signaling.40,42 It is also possible that microglia are a source of HGF in the tumor environment, as TGFB isoforms induce microglia production of HGF.43 Importantly, therapeutic targeting of HGF or HGFR through antibodies or small-molecule inhibitors has shown efficacy in numerous preclinical studies, but the therapeutic benefit has failed to translate to human patients. This evidence concerns the gene MET and glioma.