title: TGF-β is an inducer of ZEB1-dependent mesenchymal transdifferentiation in glioblastoma that is associated with tumor invasion.
abstract: Different molecular subtypes of glioblastoma (GBM) have been recently identified, of which the mesenchymal subtype is associated with worst prognoses. Here, we report that transforming growth factor-β (TGF-β) is able to induce a mesenchymal phenotype in GBM that involves activation of SMAD2 and ZEB1, a known transcriptional inducer of mesenchymal transition in epithelial cancers. TGF-β exposure of established and newly generated GBM cell lines was associated with morphological changes, enhanced mesenchymal marker expression, migration and invasion in vitro and in an orthotopic mouse model. TGF-β-induced mesenchymal differentiation and invasive behavior was prevented by chemical inhibition of TGF-β signaling as well as small interfering RNA (siRNA)-dependent silencing of ZEB1. Furthermore, TGF-β-responding and -nonresponding GBM neurospheres were identified in vitro. Interestingly, nonresponding cells displayed already high levels of pSMAD2 and ZEB1 that could not be suppressed by inhibition of TGF-β signaling, suggesting the involvement of yet unknown mechanisms. These different GBM neurospheres formed invasive tumors in mice as well as revealed mesenchymal marker expression in immunohistochemical analyses. Moreover, we also detected distinct zones with overlapping pSMAD2, elevated ZEB1 and mesenchymal marker expression in GBM patient material, suggestive of the induction of local, microenvironment-dependent mesenchymal differentiation. Overall, our findings indicate that GBM cells can acquire mesenchymal features associated with enhanced invasive potential following stimulation by secretory cytokines, such as TGF-β. This property of GBM contributes to heterogeneity in this tumor type and may blur the boundaries between the proposed transcriptional subtypes. Targeting TGF-β or downstream targets like ZEB1 might be of potential benefit in reducing the invasive phenotype of GBM in a subpopulation of patients.
authors.affiliation: Department of Medical Oncology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: J V
authors.initials: JV
authors.lastname: Joseph
authors.affiliation: Department of Pathology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Conroy
authors.affiliation: Department of Gynecologic Oncology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: T
authors.initials: T
authors.lastname: Tomar
authors.affiliation: Department of Neuroscience, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Eggens-Meijer
authors.affiliation: Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: K
authors.initials: K
authors.lastname: Bhat
authors.affiliation: Department of Neuroscience, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Copray
authors.affiliation: Department of Medical Oncology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: A M E
authors.initials: AM
authors.lastname: Walenkamp
authors.affiliation: Department of Neuroscience, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Boddeke
authors.affiliation: Department of Neuroscience, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: V
authors.initials: V
authors.lastname: Balasubramanyian
authors.affiliation: Department of Neuro-surgery, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 Groningen, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Wagemakers
authors.affiliation: Department of Pathology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: W F A
authors.initials: WF
authors.lastname: den Dunnen
authors.affiliation: Department of Medical Oncology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: F A E
authors.initials: FA
authors.lastname: Kruyt
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002465:Cell Movement; D058750:Epithelial-Mesenchymal Transition; D005909:Glioblastoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D009361:Neoplasm Invasiveness; D015398:Signal Transduction; D051899:Smad2 Protein / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D000071799:Zinc Finger E-box-Binding Homeobox 1
chemical_list: D018398:Homeodomain Proteins; C497782:SMAD2 protein, human; D051899:Smad2 Protein; C508960:TGFB1 protein, human; D014157:Transcription Factors; D053773:Transforming Growth Factor beta1; C486307:ZEB1 protein, human; D000071799:Zinc Finger E-box-Binding Homeobox 1