The aryl hydrocarbon receptor links integrin signaling to the TGF-β pathway.
Glioblastoma is the most common and aggressive form of intrinsic brain tumor. Transforming growth factor (TGF)-β represents a central mediator of the malignant phenotype of these tumors by promoting invasiveness and angiogenesis, maintaining tumor cell stemness and inducing profound immunosuppression. Integrins, which are highly expressed in glioma cells, interact with the TGF-β pathway. Furthermore, a link has been described between activity of the transcription factor aryl hydrocarbon receptor (AhR) and TGF-β expression. Here we demonstrate that integrin inhibition, using αv, β3 or β5 neutralizing antibodies, RNA interference-mediated integrin gene silencing or pharmacological inhibition by the cyclic RGD peptide EMD 121974 (cilengitide) or the non-peptidic molecule GLPG0187, inhibits AhR activity. These effects are independent of cell detachment or cell density. While AhR mRNA expression was not affected by integrin inhibition, AhR total and nuclear protein levels were reduced, suggesting that integrin inhibition-mediated regulation of AhR may occur at a post-transcriptional level. AhR-null astrocytes, AhR-null hepatocytes or glioblastoma cells with a transiently silenced AhR gene showed reduced sensitivity to integrin inhibition-mediated alterations in TGF-β signaling, indicating that AhR mediates integrin control of the TGF-β pathway. Accordingly, there was a significant correlation of αv integrin levels with nuclear AhR and pSmad2 levels as determined by immunohistochemistry in human glioblastoma in vivo. In summary, this study identifies a signaling network comprising integrins, AhR and TGF-β and validates integrin inhibition as a promising strategy not only to inhibit angiogenesis, but also to block AhR- and TGF-β-controlled features of malignancy in human glioblastoma.
Laboratory of Molecular Neuro-Oncology, Department of Neurology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
M
M
Silginer
Laboratory of Molecular Neuro-Oncology, Department of Neurology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
I
I
Burghardt
Laboratory of Molecular Neuro-Oncology, Department of Neurology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
D
D
Gramatzki
Department of Neurology, University Hospital Heidelberg, National Center for Tumor Diseases and German Cancer Consortium (DKTK) Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
L
L
Bunse
Institute of Neuropathology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
H
H
Leske
Institute of Neuropathology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
E J
EJ
Rushing
School of Biological Sciences, University of Adelaide, Adelaide, Australia.
N
N
Hao
Department of Neurology, University Hospital Heidelberg, National Center for Tumor Diseases and German Cancer Consortium (DKTK) Clinical Cooperation Unit Neuroimmunology and Brain Tumor Immunology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
M
M
Platten
Laboratory of Molecular Neuro-Oncology, Department of Neurology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
M
M
Weller
Laboratory of Molecular Neuro-Oncology, Department of Neurology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
P
P
Roth
D000818:Animals; D000831:Animals, Newborn; D057134:Antibodies, Neutralizing / Q000494:pharmacology; D001932:Brain Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D005909:Glioblastoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D016023:Integrins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009287:Naphthyridines / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D034622:RNA Interference; D018336:Receptors, Aryl Hydrocarbon / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D012910:Snake Venoms / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*
D057134:Antibodies, Neutralizing; C000612647:GLPG0187; D016023:Integrins; D009287:Naphthyridines; D010456:Peptides, Cyclic; D018336:Receptors, Aryl Hydrocarbon; D012910:Snake Venoms; D013449:Sulfonamides; D016212:Transforming Growth Factor beta; C507169:cyclic arginine-glycine-aspartic acid peptide; C422910:Cilengitide