title: Inhibition of Notch signaling alters the phenotype of orthotopic tumors formed from glioblastoma multiforme neurosphere cells but does not hamper intracranial tumor growth regardless of endogene Notch pathway signature.
abstract: BACKGROUND
  Brain cancer stem-like cells (bCSC) are cancer cells with neural stem cell (NSC)-like properties found in the devastating brain tumor glioblastoma multiforme (GBM). bCSC are proposed a central role in tumor initiation, progression, treatment resistance and relapse and as such present a promising target in GBM research. The Notch signaling pathway is often deregulated in GBM and we have previously characterized GBM-derived bCSC cultures based on their expression of the Notch-1 receptor and found that it could be used as predictive marker for the effect of Notch inhibition. The aim of the present project was therefore to further elucidate the significance of Notch pathway activity for the tumorigenic properties of GBM-derived bCSC.
  
  
  METHODS
  Human-derived GBM xenograft cells previously established as NSC-like neurosphere cultures were used. Notch inhibition was accomplished by exposing the cells to the gamma-secretase inhibitor DAPT prior to gene expression analysis and intracranial injection into immunocompromised mice.
  
  
  RESULTS
  By analyzing the expression of several Notch pathway components, we found that the cultures indeed displayed different Notch pathway signatures. However, when DAPT-treated neurosphere cells were injected into the brain of immunocompromised mice, no increase in survival was obtained regardless of Notch pathway signature and Notch inhibition. We did however observe a decrease in the expression of the stem cell marker Nestin, an increase in the proliferative marker Ki-67 and an increased number of abnormal vessels in tumors formed from DAPT-treated, high Notch-1 expressing cultures, when compared with the control.
  
  
  CONCLUSIONS
  Based on the presented results we propose that Notch inhibition partly induces differentiation of bCSC, and selects for a cell type that more strongly induces angiogenesis if the treatment is not sustained. However, this more differentiated cell type might prove to be more sensitive to conventional therapies.
authors.affiliation: Department of Radiation Biology; The Finsen Center; Copenhagen University Hospital; Copenhagen, Denmark.
authors.forename: Karina
authors.initials: K
authors.lastname: Kristoffersen
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging; Copenhagen University Hospital and University of Copenhagen; Copenhagen, Denmark.
authors.forename: Mette Kjølhede
authors.initials: MK
authors.lastname: Nedergaard
authors.affiliation: Department of Radiation Biology; The Finsen Center; Copenhagen University Hospital; Copenhagen, Denmark.
authors.forename: Mette
authors.initials: M
authors.lastname: Villingshøj
authors.affiliation: Center for Genomic Medicine; Copenhagen University Hospital; Copenhagen, Denmark.
authors.forename: Rehannah
authors.initials: R
authors.lastname: Borup
authors.affiliation: Department of Neuropathology; The Diagnostic Center; Copenhagen University Hospital; Copenhagen, Denmark.
authors.forename: Helle
authors.initials: H
authors.lastname: Broholm
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine & PET and Cluster for Molecular Imaging; Copenhagen University Hospital and University of Copenhagen; Copenhagen, Denmark.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kjær
authors.affiliation: Department of Radiation Biology; The Finsen Center; Copenhagen University Hospital; Copenhagen, Denmark.
authors.forename: Hans Skovgaard
authors.initials: HS
authors.lastname: Poulsen
authors.affiliation: Department of Radiation Biology; The Finsen Center; Copenhagen University Hospital; Copenhagen, Denmark.
authors.forename: Marie-Thérése
authors.initials: MT
authors.lastname: Stockhausen
mesh_terms: D000818:Animals; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology*; D049109:Cell Proliferation / Q000187:drug effects*; D002470:Cell Survival; D004151:Dipeptides / Q000494:pharmacology; D005260:Female; D015870:Gene Expression; D005909:Glioblastoma / Q000378:metabolism / Q000473:pathology*; D064593:Heterografts; D006801:Humans; D016513:Mice, SCID; D009368:Neoplasm Transplantation; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology; D051880:Receptors, Notch / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D004151:Dipeptides; C419410:N-(N-(3,5-difluorophenacetyl)alanyl)phenylglycine tert-butyl ester; D051880:Receptors, Notch
keywords: DAPT; Notch activity; Notch signaling; brain cancer stem-like cells; glioblastoma multiforme; neurosphere culture; orthotopic xenograft
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