title: The mTORC1/mTORC2 inhibitor AZD2014 enhances the radiosensitivity of glioblastoma stem-like cells.
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.
authors: Corresponding author: Philip J. Tofilon, PhD, National Cancer Institute, 10 Center Drive-MSC 1002, Building 10, B3B69B, Bethesda, MD 20892. tofilonp@mail.nih.gov.
authors: Jenna
authors: J
authors: Kahn
authors: Thomas J
authors: TJ
authors: Hayman
authors: Muhammad
authors: M
authors: Jamal
authors: Barbara H
authors: BH
authors: Rath
authors: Tamalee
authors: T
authors: Kramp
authors: Kevin
authors: K
authors: Camphausen
authors: Philip J
authors: PJ
authors: Tofilon
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D001549:Benzamides; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects / Q000528:radiation effects; D004260:DNA Repair / Q000187:drug effects / Q000528:radiation effects; D005260:Female; D005455:Fluorescent Antibody Technique; D005909:Glioblastoma / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy; D006657:Histones / Q000378:metabolism; D006801:Humans; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D051379:Mice; D008819:Mice, Nude; D009025:Morpholines / Q000494:pharmacology*; D046912:Multiprotein Complexes / Q000037:antagonists & inhibitors*; D014411:Neoplastic Stem Cells / Q000187:drug effects / Q000473:pathology* / Q000528:radiation effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011743:Pyrimidines; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D014407:Tumor Cells, Cultured; D014964:X-Ray Therapy; D023041:Xenograft Model Antitumor Assays
chemical_list: D001549:Benzamides; D006657:Histones; D009025:Morpholines; D046912:Multiprotein Complexes; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; D011838:Radiation-Sensitizing Agents; C475961:gamma-H2AX protein, mouse; C585537:vistusertib; D000076222:Mechanistic Target of Rapamycin Complex 1; D000076225:Mechanistic Target of Rapamycin Complex 2; D058570:TOR Serine-Threonine Kinases
keywords: AZD2014; Radiation; glioblastoma; mTOR; orthotopic xenograft; tumor stem cell