title: Role of hepatocyte growth factor activator (HGF activator) in invasive growth of human glioblastoma cells in vivo.
abstract: Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional growth factor that is involved in invasive growth of tumor cells via its receptor MET, a protein product of c-met proto-oncogene. HGF activator (HGFA) is a serine proteinase responsible for the activation of proform of HGF/SF (proHGF/SF). In our study, we examined the effects of engineered expression of HGFA on 2 human glioblastoma cell lines (YKG-1 and U251). Both cells expressed MET, while only YKG-1 expressed endogenous proHGF/SF. Enhanced MET phosphorylation and increased migratory activity were induced by the expression of HGFA in YKG-1 cells in vitro in the presence of thrombin, which is a known activator of proHGFA. In contrast, MET phosphorylation was consistently observed in U251 that lacked endogenous HGF/SF, suggesting ligand-independent activation of MET in this cell line. Consequently, the expression of HGFA in U251 did not enhance the MET phosphorylation and following cellular response even with the thrombin treatment. However, addition of exogenous proHGF/SF resulted in enhanced migratory activity of HGFA-expressing U251 cells in the presence of thrombin in vitro. The engineered HGFA expression resulted in significantly enhanced tumor growth with increased vascular density in vivo when YKG-1 cells were implanted in nude mouse brain. This effect was not observed in U251 lacking endogenous proHGF/SF. These results indicate the possible existence of multiple mechanisms of MET activation in glioblastomas and that the activation system of proHGF/SF is important in progression of glioblastomas that express endogenous proHGF/SF and require ligand-dependent MET activation.
authors.affiliation: Second Department of Pathology, Faculty of Medicine, University of Miyazaki, Kiyotake, Miyazaki, Japan.
authors.forename: Shunro
authors.initials: S
authors.lastname: Uchinokura
authors.forename: Shiro
authors.initials: S
authors.lastname: Miyata
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Fukushima
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Itoh
authors.forename: Shinichi
authors.initials: S
authors.lastname: Nakano
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Wakisaka
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kataoka
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000378:metabolism* / Q000473:pathology*; D002465:Cell Movement; D049109:Cell Proliferation; D005909:Glioblastoma / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009154:Mutation / Q000235:genetics; D009361:Neoplasm Invasiveness / Q000473:pathology*; D010766:Phosphorylation; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019859:Proto-Oncogene Proteins c-met; D012333:RNA, Messenger; D017978:Receptors, Growth Factor / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012697:Serine Endopeptidases / Q000502:physiology*; D013917:Thrombin / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D017978:Receptors, Growth Factor; C491743:MET protein, human; D019859:Proto-Oncogene Proteins c-met; C081092:HGF activator; D012697:Serine Endopeptidases; D013917:Thrombin