Autocrine VEGF-VEGFR2-Neuropilin-1 signaling promotes glioma stem-like cell viability and tumor growth

J Exp Med. 2012 Mar 12;209(3):507-20. doi: 10.1084/jem.20111424. Epub 2012 Mar 5.

Abstract

Although vascular endothelial growth factor (VEGF) receptor 2 (VEGFR2) is traditionally regarded as an endothelial cell protein, evidence suggests that VEGFRs may be expressed by cancer cells. Glioblastoma multiforme (GBM) is a lethal cancer characterized by florid vascularization and aberrantly elevated VEGF. Antiangiogenic therapy with the humanized VEGF antibody bevacizumab reduces GBM tumor growth; however, the clinical benefits are transient and invariably followed by tumor recurrence. In this study, we show that VEGFR2 is preferentially expressed on the cell surface of the CD133(+) human glioma stem-like cells (GSCs), whose viability, self-renewal, and tumorigenicity rely, at least in part, on signaling through the VEGF-VEGFR2-Neuropilin-1 (NRP1) axis. We find that the limited impact of bevacizumab-mediated VEGF blockage may reflect ongoing autocrine signaling through VEGF-VEGFR2-NRP1, which is associated with VEGFR2-NRP1 recycling and a pool of active VEGFR2 within a cytosolic compartment of a subset of human GBM cells. Whereas bevacizumab failed to inhibit prosurvival effects of VEGFR2-mediated signaling, GSC viability under unperturbed or radiation-evoked stress conditions was attenuated by direct inhibition of VEGFR2 tyrosine kinase activity and/or shRNA-mediated knockdown of VEGFR2 or NRP1. We propose that direct inhibition of VEGFR2 kinase may block the highly dynamic VEGF-VEGFR2-NRP1 pathway and inspire a GBM treatment strategy to complement the currently prevalent ligand neutralization approach.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Monoclonal, Humanized / pharmacology
  • Autocrine Communication
  • Bevacizumab
  • Cell Proliferation
  • Cell Survival
  • Endosomes / physiology
  • Glioblastoma / blood supply
  • Glioblastoma / pathology*
  • Glioblastoma / physiopathology*
  • Glioblastoma / therapy
  • Humans
  • In Vitro Techniques
  • Neoplastic Stem Cells / pathology*
  • Neoplastic Stem Cells / physiology*
  • Neovascularization, Pathologic
  • Neuropilin-1 / antagonists & inhibitors
  • Neuropilin-1 / genetics
  • Neuropilin-1 / physiology*
  • RNA, Small Interfering / genetics
  • Vascular Endothelial Growth Factor A / antagonists & inhibitors
  • Vascular Endothelial Growth Factor A / physiology*
  • Vascular Endothelial Growth Factor Receptor-2 / antagonists & inhibitors
  • Vascular Endothelial Growth Factor Receptor-2 / genetics
  • Vascular Endothelial Growth Factor Receptor-2 / physiology*

Substances

  • Antibodies, Monoclonal, Humanized
  • RNA, Small Interfering
  • VEGFA protein, human
  • Vascular Endothelial Growth Factor A
  • Neuropilin-1
  • Bevacizumab
  • Vascular Endothelial Growth Factor Receptor-2