Oncogenic EGFR signaling activates an mTORC2-NF-κB pathway that promotes chemotherapy resistance

Cancer Discov. 2011 Nov;1(6):524-38. doi: 10.1158/2159-8290.CD-11-0124. Epub 2011 Sep 13.

Abstract

Although it is known that mTOR complex 2 (mTORC2) functions upstream of Akt, the role of this protein kinase complex in cancer is not well understood. Through an integrated analysis of cell lines, in vivo models, and clinical samples, we demonstrate that mTORC2 is frequently activated in glioblastoma (GBM), the most common malignant primary brain tumor of adults. We show that the common activating epidermal growth factor receptor (EGFR) mutation (EGFRvIII) stimulates mTORC2 kinase activity, which is partially suppressed by PTEN. mTORC2 signaling promotes GBM growth and survival and activates NF-κB. Importantly, this mTORC2-NF-κB pathway renders GBM cells and tumors resistant to chemotherapy in a manner independent of Akt. These results highlight the critical role of mTORC2 in the pathogenesis of GBM, including through the activation of NF-κB downstream of mutant EGFR, leading to a previously unrecognized function in cancer chemotherapy resistance. These findings suggest that therapeutic strategies targeting mTORC2, alone or in combination with chemotherapy, will be effective in the treatment of cancer.

Significance: This study demonstrates that EGFRvIII-activated mTORC2 signaling promotes GBM proliferation, survival, and chemotherapy resistance through Akt-independent activation of NF-κB. These results highlight the role of mTORC2 as an integrator of two canonical signaling networks that are commonly altered in cancer, EGFR/phosphoinositide-3 kinase (PI3K) and NF-κB. These results also validate the importance of mTORC2 as a cancer target and provide new insights into its role in mediating chemotherapy resistance, suggesting new treatment strategies.

Keywords: EGFRvIII; NF-κB; Rictor; and chomotherapy resistance; mTORC2.

Publication types

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

MeSH terms

  • Brain Neoplasms / drug therapy
  • Brain Neoplasms / genetics
  • Brain Neoplasms / metabolism*
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Cell Survival / physiology
  • Cisplatin / pharmacology
  • Drug Resistance, Neoplasm
  • ErbB Receptors / genetics
  • ErbB Receptors / metabolism*
  • Glioblastoma / drug therapy
  • Glioblastoma / genetics
  • Glioblastoma / metabolism*
  • Humans
  • NF-kappa B / genetics
  • NF-kappa B / metabolism*
  • PTEN Phosphohydrolase / genetics
  • PTEN Phosphohydrolase / metabolism
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / metabolism
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • Signal Transduction
  • TOR Serine-Threonine Kinases / metabolism*

Substances

  • NF-kappa B
  • epidermal growth factor receptor VIII
  • ErbB Receptors
  • Proto-Oncogene Proteins c-akt
  • TOR Serine-Threonine Kinases
  • PTEN Phosphohydrolase
  • PTEN protein, human
  • Cisplatin