title: Netrin-4 promotes glioblastoma cell proliferation through integrin β4 signaling.
abstract: Netrin-4 is a laminin-related secreted molecule originally found to have roles in neuronal axon migration. Recent studies have indicated that netrin-4 also participates in the development of nonneural tissues and modulates tumor cell proliferation and tumor metastasis. Here we have explored the functions and molecular mechanisms of netrin-4 in glioblastoma multiforme. The suppression of netrin-4 expression in glioblastoma cell lines significantly reduced cell proliferation and motility and increased serum deprivation-induced apoptosis. Using tandem affinity purification combined with protein identification by mass spectrometry, we found that integrin β(4) interacts with netrin-4 and that it mediates mitogenic effects as well as AKT and mammalian target of rapamycin phosphorylation induced by netrin-4. Interestingly, netrin-4 acted as an inhibitor of cell proliferation in integrin β(4)-silenced glioblastoma cells, and high concentrations of netrin-4 reduced cell proliferation. The negative effects of netrin-4 on proliferation were mediated by UNC5B. Analysis of more than 400 primary tumors from The Cancer Genome Atlas repository revealed that the expression of netrin-4 is significantly downregulated in glioblastoma and that the reduced expression is linked to poor patient survival time. The expression of integrin β(4) is increased in glioblastoma, and it predicts poor patient survival time. Current results illustrate a novel mechanism for glioma progression, where glioma cells reduce netrin-4 expression to decrease its inhibitory effects. In parallel, the expression of integrin β(4) is upregulated to sensitize the cells to low concentrations of netrin-4 for maintaining cell proliferation.
authors.affiliation: Department of Virology, The Haartman Institute, Molecular Cancer Biology Research Program and Helsinki University Hospital, University of Helsinki, Helsinki, Finland.
authors.forename: Yizhou
authors.initials: Y
authors.lastname: Hu
authors.forename: Irene
authors.initials: I
authors.lastname: Ylivinkka
authors.forename: Ping
authors.initials: P
authors.lastname: Chen
authors.forename: Li
authors.initials: L
authors.lastname: Li
authors.forename: Sampsa
authors.initials: S
authors.lastname: Hautaniemi
authors.forename: Tuula A
authors.initials: TA
authors.lastname: Nyman
authors.forename: Jorma
authors.initials: J
authors.lastname: Keski-Oja
authors.forename: Marko
authors.initials: M
authors.lastname: Hyytiäinen
mesh_terms: D002460:Cell Line; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation; D015972:Gene Expression Regulation, Neoplastic; D005909:Glioblastoma / Q000235:genetics / Q000378:metabolism* / Q000401:mortality; D006801:Humans; D039663:Integrin beta4 / Q000378:metabolism*; D009414:Nerve Growth Factors / Q000235:genetics / Q000378:metabolism*; D000075385:Netrins; D011485:Protein Binding; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: D039663:Integrin beta4; C498815:NTN4 protein, human; D009414:Nerve Growth Factors; D000075385:Netrins; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases