Dual mTORC1/2 blockade inhibits glioblastoma brain tumor initiating cells in vitro and in vivo and synergizes with temozolomide to increase orthotopic xenograft survival

H Artee Luchman; Owen D M Stechishin; Stephanie A Nguyen; Xueqing Q Lun; J Gregory Cairncross; Samuel Weiss

doi:10.1158/1078-0432.CCR-13-3389

Dual mTORC1/2 blockade inhibits glioblastoma brain tumor initiating cells in vitro and in vivo and synergizes with temozolomide to increase orthotopic xenograft survival

Clin Cancer Res. 2014 Nov 15;20(22):5756-67. doi: 10.1158/1078-0432.CCR-13-3389. Epub 2014 Oct 14.

Authors

H Artee Luchman¹, Owen D M Stechishin¹, Stephanie A Nguyen¹, Xueqing Q Lun², J Gregory Cairncross³, Samuel Weiss⁴

Affiliations

¹ Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada. Department of Cell Biology and Anatomy, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada.
² Clark Smith Brain Tumour Research Centre, Southern Alberta Cancer Research Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada. Department of Oncology, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada.
³ Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada. Clark Smith Brain Tumour Research Centre, Southern Alberta Cancer Research Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada. Department of Clinical Neurosciences, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada.
⁴ Hotchkiss Brain Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada. Department of Cell Biology and Anatomy, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada. Clark Smith Brain Tumour Research Centre, Southern Alberta Cancer Research Institute, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada. weiss@ucalgary.ca.

PMID: 25316808
DOI: 10.1158/1078-0432.CCR-13-3389

Abstract

Purpose: The EGFR and PI3K/mTORC1/2 pathways are frequently altered in glioblastoma (GBM), but pharmacologic targeting of EGFR and PI3K signaling has failed to demonstrate efficacy in clinical trials. Lack of relevant models has rendered it difficult to assess whether targeting these pathways might be effective in molecularly defined subgroups of GBMs. Here, human brain tumor-initiating cell (BTIC) lines with different combinations of endogenous EGFR wild-type, EGFRvIII, and PTEN mutations were used to investigate response to the EGFR inhibitor gefitinib, mTORC1 inhibitor rapamycin, and dual mTORC1/2 inhibitor AZD8055 alone and in combination with temozolomide (TMZ) EXPERIMENTAL DESIGN: In vitro growth inhibition and cell death induced by gefitinib, rapamycin, AZD8055, and TMZ or combinations in human BTICs were assessed by alamarBlue, neurosphere, and Western blotting assays. The in vivo efficacy of AZD8055 was assessed in subcutaneous and intracranial BTIC xenografts. Kaplan-Meier survival studies were performed with AZD8055 and in combination with TMZ.

Results: We confirm that gefitinib and rapamycin have modest effects in most BTIC lines, but AZD8055 was highly effective at inhibiting Akt/mTORC2 activity and dramatically reduced the viability of BTICs regardless of their EGFR and PTEN mutational status. Systemic administration of AZD8055 effectively inhibited tumor growth in subcutaneous BTIC xenografts and mTORC1/2 signaling in orthotopic BTIC xenografts. AZD8055 was synergistic with the alkylating agent TMZ and significantly prolonged animal survival.

Conclusion: These data suggest that dual inhibition of mTORC1/2 may be of benefit in GBM, including the subset of TMZ-resistant GBMs.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Antineoplastic Agents / administration & dosage
Antineoplastic Agents / pharmacology
Apoptosis / drug effects
Apoptosis / genetics
Brain Neoplasms / drug therapy
Brain Neoplasms / genetics
Brain Neoplasms / metabolism*
Brain Neoplasms / mortality
Brain Neoplasms / pathology
Cell Line, Tumor
Cell Proliferation / drug effects
Cell Survival / drug effects
Cell Survival / genetics
DNA Methylation
DNA Modification Methylases / genetics
DNA Modification Methylases / metabolism
DNA Repair Enzymes / genetics
DNA Repair Enzymes / metabolism
Dacarbazine / administration & dosage
Dacarbazine / analogs & derivatives*
Dacarbazine / pharmacology
Disease Models, Animal
Drug Synergism
ErbB Receptors / antagonists & inhibitors
ErbB Receptors / genetics
Glioblastoma / drug therapy
Glioblastoma / genetics
Glioblastoma / metabolism*
Glioblastoma / mortality
Glioblastoma / pathology
Humans
Mechanistic Target of Rapamycin Complex 1
Mechanistic Target of Rapamycin Complex 2
Mice
Multiprotein Complexes / antagonists & inhibitors*
Mutation
Neoplastic Stem Cells / drug effects*
Neoplastic Stem Cells / metabolism*
PTEN Phosphohydrolase / genetics
Promoter Regions, Genetic
Protein Kinase Inhibitors / administration & dosage
Protein Kinase Inhibitors / pharmacology*
Signal Transduction / drug effects
TOR Serine-Threonine Kinases / antagonists & inhibitors*
Temozolomide
Tumor Burden / drug effects
Tumor Burden / genetics
Tumor Suppressor Proteins / genetics
Tumor Suppressor Proteins / metabolism
Xenograft Model Antitumor Assays

Substances

Antineoplastic Agents
Multiprotein Complexes
Protein Kinase Inhibitors
Tumor Suppressor Proteins
Dacarbazine
DNA Modification Methylases
MGMT protein, human
ErbB Receptors
Mechanistic Target of Rapamycin Complex 1
Mechanistic Target of Rapamycin Complex 2
TOR Serine-Threonine Kinases
PTEN Phosphohydrolase
DNA Repair Enzymes
Temozolomide