title: Differential regulation of TGF-β-induced, ALK-5-mediated VEGF release by SMAD2/3 versus SMAD1/5/8 signaling in glioblastoma.
abstract: BACKGROUND
  The transforming growth factor (TGF)-β and vascular endothelial growth factor (VEGF) pathways have a major role in the pathogenesis of glioblastoma, notably immunosuppression, migration, and angiogenesis, but their interactions have remained poorly understood.
  
  
  METHODS
  We characterized TGF-β pathway activity in 9 long-term glioma cell lines (LTCs) and 4 glioma-initiating cell lines (GICs) in relation to constitutive and exogenous TGF-β-induced VEGF release. Results were validated using The Cancer Genome Atlas transcriptomics data.
  
  
  RESULTS
  Glioma cells exhibit heterogeneous patterns of constitutive TGF-β pathway activation reflected by phosphorylation not only of SMAD2 and SMAD3 but also of SMAD1/5/8. Constitutive TGF-β pathway activity depends on the type I TGF-β receptor, ALK-5, and accounts for up to 69% of constitutive VEGF release, which is positively regulated by SMAD2/3 and negatively regulated by SMAD1/5/8 signaling in a cell line-specific manner. Exogenous TGF-β induces VEGF release in most cell lines in a SMAD- and ALK-5-dependent manner. There is no correlation between the fold induction of VEGF secretion induced by TGF-β compared with hypoxia. The role of SMAD5 signaling is highly context and cell-line dependent with a VEGF inhibitory effect at low TGF-β and pSMAD2 levels and a stimulatory effect when TGF-β is abundant.
  
  
  CONCLUSIONS
  TGF-β regulates VEGF release by glioma cells in an ALK-5-dependent manner involving SMAD2, SMAD3, and SMAD1/5/8 signaling. This crosstalk between the TGF-β and VEGF pathways may open up new avenues of biomarker-driven exploratory clinical trials focusing on the microenvironment in glioblastoma.
authors.affiliation: Department of Neurology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Katharina
authors.initials: K
authors.lastname: Seystahl
authors.affiliation: Department of Neurology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Isabel
authors.initials: I
authors.lastname: Tritschler
authors.affiliation: Department of Neurology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Emese
authors.initials: E
authors.lastname: Szabo
authors.affiliation: Department of Neurology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Ghazaleh
authors.initials: G
authors.lastname: Tabatabai
authors.affiliation: Department of Neurology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Weller
mesh_terms: D001932:Brain Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D005786:Gene Expression Regulation; D005909:Glioblastoma / Q000378:metabolism*; D006801:Humans; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D015398:Signal Transduction; D051896:Smad Proteins, Receptor-Regulated / Q000378:metabolism*; D051898:Smad1 Protein / Q000378:metabolism; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D051902:Smad5 Protein / Q000378:metabolism; D051904:Smad8 Protein / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; C497399:SMAD1 protein, human; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C497797:SMAD5 protein, human; C107514:SMAD9 protein, human; D051896:Smad Proteins, Receptor-Regulated; D051898:Smad1 Protein; D051899:Smad2 Protein; D051900:Smad3 Protein; D051902:Smad5 Protein; D051904:Smad8 Protein; D016212:Transforming Growth Factor beta; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human
keywords: TGF-β; VEGF; angiogenesis; glioblastoma