The mTORC1/mTORC2 inhibitor AZD2014 enhances the radiosensitivity of glioblastoma stem-like cells

Neuro Oncol. 2014 Jan;16(1):29-37. doi: 10.1093/neuonc/not139. Epub 2013 Dec 4.

Abstract

Background: The mammalian target of rapamycin (mTOR) has been suggested as a target for radiosensitization. Given that radiotherapy is a primary treatment modality for glioblastoma (GBM) and that mTOR is often dysregulated in GBM, the goal of this study was to determine the effects of AZD2014, a dual mTORC1/2 inhibitor, on the radiosensitivity of GBM stem-like cells (GSCs).

Methods: mTORC1 and mTORC2 activities were defined by immunoblot analysis. The effects of this mTOR inhibitor on the in vitro radiosensitivity of GSCs were determined using a clonogenic assay. DNA double strand breaks were evaluated according to γH2AX foci. Orthotopic xenografts initiated from GSCs were used to define the in vivo response to AZD2014 and radiation.

Results: Exposure of GSCs to AZD2014 resulted in the inhibition of mTORC1 and 2 activities. Based on clonogenic survival analysis, addition of AZD2014 to culture media 1 hour before irradiation enhanced the radiosensitivity of CD133+ and CD15+ GSC cell lines. Whereas AZD2014 treatment had no effect on the initial level of γH2AX foci, the dispersal of radiation-induced γH2AX foci was significantly delayed. Finally, the combination of AZD2014 and radiation delivered to mice bearing GSC-initiated orthotopic xenografts significantly prolonged survival as compared with the individual treatments.

Conclusions: These data indicate that AZD2014 enhances the radiosensitivity of GSCs both in vitro and under orthotopic in vivo conditions and suggest that this effect involves an inhibition of DNA repair. Moreover, these results suggest that this dual mTORC1/2 inhibitor may be a radiosensitizer applicable to GBM therapy.

Keywords: AZD2014; Radiation; glioblastoma; mTOR; orthotopic xenograft; tumor stem cell.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis / radiation effects
  • Benzamides
  • Brain Neoplasms / drug therapy*
  • Brain Neoplasms / pathology
  • Brain Neoplasms / radiotherapy
  • Cell Cycle / drug effects
  • Cell Cycle / radiation effects
  • Cell Proliferation / drug effects
  • Cell Proliferation / radiation effects
  • DNA Breaks, Double-Stranded / drug effects
  • DNA Breaks, Double-Stranded / radiation effects
  • DNA Repair / drug effects
  • DNA Repair / radiation effects
  • Female
  • Fluorescent Antibody Technique
  • Glioblastoma / drug therapy*
  • Glioblastoma / pathology
  • Glioblastoma / radiotherapy
  • Histones / metabolism
  • Humans
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2
  • Mice
  • Mice, Nude
  • Morpholines / pharmacology*
  • Multiprotein Complexes / antagonists & inhibitors*
  • Neoplastic Stem Cells / drug effects
  • Neoplastic Stem Cells / pathology*
  • Neoplastic Stem Cells / radiation effects
  • Protein Kinase Inhibitors / pharmacology
  • Pyrimidines
  • Radiation-Sensitizing Agents / pharmacology*
  • TOR Serine-Threonine Kinases / antagonists & inhibitors*
  • Tumor Cells, Cultured
  • X-Ray Therapy
  • Xenograft Model Antitumor Assays

Substances

  • Benzamides
  • Histones
  • Morpholines
  • Multiprotein Complexes
  • Protein Kinase Inhibitors
  • Pyrimidines
  • Radiation-Sensitizing Agents
  • gamma-H2AX protein, mouse
  • vistusertib
  • TOR Serine-Threonine Kinases
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2