Tenascin-C is a novel RBPJkappa-induced target gene for Notch signaling in gliomas.
Tenascin-C (TNC) expression is known to correlate with malignancy in glioblastoma (GBM), a highly invasive and aggressive brain tumor that shows limited response to conventional therapies. In these malignant gliomas as well as in GBM cell lines, we found Notch2 protein to be strongly expressed. In a GBM tumor tissue microarray, RBPJk protein, a Notch2 cofactor for transcription, was found to be significantly coexpressed with TNC. We show that the TNC gene is transactivated by Notch2 in an RBPJk-dependent manner mediated by an RBPJk binding element in the TNC promoter. The transactivation is abrogated by a Notch2 mutation, which we detected in the glioma cell line Hs683 that does not express TNC. This L1711M mutation resides in the RAM domain, the site of interaction between Notch2 and RBPJk. In addition, transfection of constructs encoding activated Notch2 or Notch1 increased endogenous TNC expression identifying TNC as a novel Notch target gene. Overexpression of a dominant negative form of the transcriptional coactivator MAML1 or knocking down RBPJk in LN319 cells led to a dramatic decrease in TNC protein levels accompanied by a significant reduction of cell migration. Because addition of purified TNC stimulated glioma cell migration, this represents a mechanism for the invasive properties of glioma cells controlled by Notch signaling and defines a novel oncogenic pathway in gliomagenesis that may be targeted for therapeutic intervention in GBM patients.
Sivasankaran
Balasubramanian
B
Department of Research, Laboratory of Molecular Neuro-Oncology, University Hospital, Basel, Switzerland.
Degen
Martin
M
Ghaffari
Anthony
A
Hegi
Monika E
ME
Hamou
Marie-France
MF
Ionescu
Mihai-Constantin S
MC
Zweifel
Christian
C
Tolnay
Markus
M
Wasner
Morten
M
Mergenthaler
Susanne
S
Miserez
André R
AR
Kiss
Robert
R
Lino
Maddalena M
MM
Merlo
Adrian
A
Chiquet-Ehrismann
Ruth
R
Boulay
Jean-Louis
JL
D000595:Amino Acid Sequence; D001483:Base Sequence; D001932:Brain Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002465:Cell Movement / Q000502:physiology; D005909:Glioblastoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D006801:Humans; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein / Q000096:biosynthesis* / Q000235:genetics; D007150:Immunohistochemistry; D008969:Molecular Sequence Data; D009837:Oligodendroglioma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D011401:Promoter Regions, Genetic; D051883:Receptor, Notch2 / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D020218:Response Elements; D015398:Signal Transduction; D019063:Tenascin / Q000096:biosynthesis / Q000235:genetics*; D015533:Transcriptional Activation
D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; C497764:NOTCH2 protein, human; C497570:RBPJ protein, human; D051883:Receptor, Notch2; D019063:Tenascin