title: Motility of glioblastoma cells is driven by netrin-1 induced gain of stemness.
abstract: Glioblastoma is an untreatable brain cancer. The tumors contain a population of stem-like cells which are highly invasive and resistant to therapies. These cells are the main reason for the lethality of glioblastoma. Extracellular guidance molecule netrin-1 promotes the invasiveness and survival of various cancer cell types. We have previously found that netrin-1 activates Notch signaling, and Notch signaling associates with cell stemness. Therefore, we have here investigated the effects of netrin-1 on glioblastoma pathogenesis and glioblastoma cell stemness.
  
  
  
  Glioma tissue microarrays were stained with immunohistochemistry and the results were used to evaluate the association between netrin-1 and survival of glioma patients. The localization of netrin-1 was analyzed utilizing fresh frozen glioblastoma tissues. The glioma cell invasion was investigated using ex vivo glioma tissue cultures and newly established primary cell cultures in 3D in vitro invasion assays. Intracranial mouse xenograft models were utilized to investigate the effects of netrin-1 on glioblastoma growth and invasion in vivo.
  
  
  
  Netrin-1 expression associated with poor patient prognosis in grade II-III gliomas. In addition, its expression correlated with the stem-like cell marker nestin. Netrin-1 overexpression in cultured cells led to increased formation of stem-like cell spheroids. In glioblastoma tumor biopsies netrin-1 localized to hypoxic tumor areas known to be rich in the stem-like cells. In xenograft mouse models netrin-1 expression altered the phenotype of non-invasive glioblastoma cells into diffusively invading and increased the expression of glioma stem-like cell markers. Furthermore, a distinct invasion pattern where netrin-1 positive cells were following the invasive stem-like cells was detected both in mouse models and ex vivo human glioblastoma tissue cultures. Inhibition of netrin-1 signaling targeted especially the stem-like cells and inhibited their infiltrative growth.
  
  
  
  Our findings describe netrin-1 as an important regulator of glioblastoma cell stemness and motility. Netrin-1 activates Notch signaling in glioblastoma cells resulting in subsequent gain of stemness and enhanced invasiveness of these cells. Moreover, inhibition of netrin-1 signaling may offer a way to target stem-like cells.
authors.affiliation: Translational Cancer Biology Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.|The Hospital District of Helsinki and Uusimaa, Helsinki, Finland.
authors.forename: Irene
authors.initials: I
authors.lastname: Ylivinkka
authors.affiliation: Translational Cancer Biology Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
authors.forename: Harri
authors.initials: H
authors.lastname: Sihto
authors.affiliation: Department of Pathology, Haartman Institute, University of Helsinki and HUSLAB, Helsinki, Finland.
authors.forename: Olli
authors.initials: O
authors.lastname: Tynninen
authors.affiliation: Translational Cancer Biology Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
authors.forename: Yizhou
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Department of Neurosurgery, Helsinki University Hospital and Clinical Neurosciences, Neurosurgery, University of Helsinki, Helsinki, Finland.
authors.forename: Aki
authors.initials: A
authors.lastname: Laakso
authors.affiliation: Department of Neurosurgery, Helsinki University Hospital and Clinical Neurosciences, Neurosurgery, University of Helsinki, Helsinki, Finland.
authors.forename: Riku
authors.initials: R
authors.lastname: Kivisaari
authors.affiliation: Translational Cancer Biology Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
authors.forename: Pirjo
authors.initials: P
authors.lastname: Laakkonen
authors.affiliation: Translational Cancer Biology Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.|The Hospital District of Helsinki and Uusimaa, Helsinki, Finland.
authors.forename: Jorma
authors.initials: J
authors.lastname: Keski-Oja
authors.affiliation: Translational Cancer Biology Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland. marko.hyytiainen@helsinki.fi.|Translational Cancer Biology Research Program, Biomedicum, University of Helsinki, B530b2, PL 63 (Haartmaninkatu 8), 00014, Helsinki, Finland. marko.hyytiainen@helsinki.fi.
authors.forename: Marko
authors.identifier: 0000-0002-3017-6862
authors.initials: M
authors.lastname: Hyytiäinen
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D015972:Gene Expression Regulation, Neoplastic; D005909:Glioblastoma / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D051379:Mice; D060787:Neoplasm Grading; D009361:Neoplasm Invasiveness; D009368:Neoplasm Transplantation; D014411:Neoplastic Stem Cells / Q000378:metabolism*; D000075388:Netrin-1 / Q000378:metabolism*; D011379:Prognosis; D051880:Receptors, Notch / Q000378:metabolism*; D015398:Signal Transduction; D016019:Survival Analysis; D046888:Tissue Array Analysis
chemical_list: C000617351:NTN1 protein, human; D051880:Receptors, Notch; D000075388:Netrin-1
keywords: Cancer stem cell; Cell invasion; Glioblastoma; Glioblastoma stem-like cell; Glioma; Netrin; Notch signalling