Type-3 metabotropic glutamate receptors negatively modulate bone morphogenetic protein receptor signaling and support the tumourigenic potential of glioma-initiating cells

Neuropharmacology. 2008 Sep;55(4):568-76. doi: 10.1016/j.neuropharm.2008.06.064. Epub 2008 Jul 8.


Targeted-therapies enhancing differentiation of glioma-initiating cells (GICs) are potential innovative approaches to the treatment of malignant gliomas. These cells support tumour growth and recurrence and are resistant to radiotherapy and chemotherapy. We have found that GICs express mGlu3 metabotropic glutamate receptors. Activation of these receptors sustained the undifferentiated state of GICs in culture by negatively modulating the action of bone morphogenetic proteins, which physiologically signal through the phosphorylation of the transcription factors, Smads. The cross-talk between mGlu3 receptors and BMP receptors was mediated by the activation of the mitogen-activated protein kinase pathway. Remarkably, pharmacological blockade of mGlu3 receptors stimulated the differentiation of cultured GICs into astrocytes, an effect that appeared to be long lasting, independent of the growth conditions, and irreversible. In in vivo experiments, a 3-month treatment with the brain-permeant mGlu receptor antagonist, LY341495 limited the growth of infiltrating brain tumours originating from GICs implanted into the brain parenchyma of nude mice. While clusters of tumour cells were consistently found in the brain of control mice, they were virtually absent in a large proportion of mice treated with LY341495. These findings pave the way to a new non-cytotoxic treatment of malignant gliomas based on the use of mGlu3 receptor antagonists.

MeSH terms

  • Amino Acids / pharmacology
  • Animals
  • Bone Morphogenetic Protein Receptors / metabolism*
  • Brain Neoplasms / drug therapy
  • Brain Neoplasms / metabolism*
  • Brain Neoplasms / pathology
  • Brain Neoplasms / physiopathology
  • Bridged Bicyclo Compounds, Heterocyclic / pharmacology
  • Cell Differentiation / drug effects
  • Cell Line, Tumor
  • Disease Models, Animal
  • Enzyme Inhibitors / pharmacology
  • Excitatory Amino Acid Agonists / pharmacology
  • Excitatory Amino Acid Antagonists / pharmacology
  • Glioma / drug therapy
  • Glioma / metabolism*
  • Glioma / pathology
  • Glioma / physiopathology
  • Humans
  • Magnetic Resonance Imaging
  • Mice
  • Mitogen-Activated Protein Kinases / metabolism
  • Nerve Tissue Proteins / metabolism
  • Phosphorylation / drug effects
  • Receptors, Metabotropic Glutamate / antagonists & inhibitors
  • Receptors, Metabotropic Glutamate / physiology*
  • Signal Transduction / drug effects
  • Signal Transduction / physiology*
  • Xanthenes / pharmacology


  • Amino Acids
  • Bridged Bicyclo Compounds, Heterocyclic
  • Enzyme Inhibitors
  • Excitatory Amino Acid Agonists
  • Excitatory Amino Acid Antagonists
  • LY 341495
  • LY 379268
  • Nerve Tissue Proteins
  • Receptors, Metabotropic Glutamate
  • Xanthenes
  • metabotropic glutamate receptor 3
  • Mitogen-Activated Protein Kinases
  • Bone Morphogenetic Protein Receptors