Breast Cancer Research and Treatment

, Volume 106, Issue 3, pp 319–331 | Cite as

Decreased levels of hypoxic cells in gefitinib treated ER+ HER-2 overexpressing MCF-7 breast cancer tumors are associated with hyperactivation of the mTOR pathway: therapeutic implications for combination therapy with rapamycin

  • Wieslawa H. Dragowska
  • Maïté Verreault
  • Donald T. T. Yapp
  • Corinna Warburton
  • Lincoln Edwards
  • Euan C. Ramsay
  • Lynsey A. Huxham
  • Andrew I. Minchinton
  • Karen Gelmon
  • Marcel B. Bally
Preclinical Study


Developing novel synergistic and more effective combination treatments is necessary for better management of breast cancer in the clinic. It is established that HER-2 overexpressing breast cancers are sensitive to the HER-1 (epidermal growth factor receptor (EGFR)) inhibitor gefitinib, but that this targeted agent produces only moderate therapeutic effects in vivo. Here, we use a model of ER+ HER-2 overexpressing MCF-7 breast cancer (MCF-7HER-2) to identify, as broadly as possible, the in vivo microenvironmental and molecular therapeutic responses to gefitinib to predict a therapeutically viable target for gefitinib-based combination treatment. Our data show a link between in vivo reductions in tumor hypoxia (3-fold decrease, P = 0.002) and elevated activity of the mTOR pathway (3.8-fold increase in phospho-p70-S6K protein, P = 0.006) in gefitinib treated MCF-7HER-2 tumors. Despite decreased levels of phosphorylated EGFR, HER-2 and Erk1/2 (P = 0.081, 0.005 and 0.034, respectively) the expression of phospho-AKT was not reduced in MCF-7HER-2 tumors after gefitinib treatment. Levels of ERα receptor were, however, 1.8-fold higher in gefitinib treated compared to control tumors (P = 0.008). Based on these results we predict that gefitinib activity against ER+ HER-2 overexpressing EGFR co-expressing breast cancers should be enhanced if used with agents that target the mTOR pathway. In vitro studies using MCF-7HER-2 and BT474 breast cancer cells exposed to gefitinib and rapamycin in combination show that this combination produced significantly greater growth inhibitory effects than either of the drugs alone. Chou and Talalay analysis of the data suggested that combination of gefitinib and rapamycin was synergistic (CI < 1) at a number of selected drug ratios and over a broad range of effective doses.


Breast cancer Gefitinib HER-2 mTOR Tumor microenvironment 



The authors thank Drs. Sandra Dunn, Sylvia Ng, Dawn Waterhouse, Ghania Chikh and members of the Advanced Therapeutics Laboratory for helpful comments. We also thank Dr. Gerry Krystal and Dr. Sandra Dunn for sharing their antibody stock. We greatly appreciate the help of Tom Oliver with western blotting, Hong Yan with cytotoxicity assays and Dana Masin, Rebecca Ng, and Maryam Osooly with animal work.


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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Wieslawa H. Dragowska
    • 1
  • Maïté Verreault
    • 1
  • Donald T. T. Yapp
    • 1
    • 3
  • Corinna Warburton
    • 1
  • Lincoln Edwards
    • 1
  • Euan C. Ramsay
    • 1
  • Lynsey A. Huxham
    • 2
  • Andrew I. Minchinton
    • 2
    • 4
  • Karen Gelmon
    • 6
  • Marcel B. Bally
    • 1
    • 4
    • 5
  1. 1.Department of Advanced TherapeuticsBritish Columbia Cancer AgencyVancouverCanada
  2. 2.Department of Medical BiophysicsBritish Columbia Cancer Research CentreVancouverCanada
  3. 3.Faculty of Pharmaceutical Sciences ,The Division of Pharmaceutics and BiopharmaceuticsUniversity of British ColumbiaVancouverCanada
  4. 4.Department of Pathology and Laboratory MedicineUniversity of British ColumbiaVancouverCanada
  5. 5.Faculty of Pharmaceutical SciencesUniversity of British ColumbiaVancouverCanada
  6. 6.Medical OncologyBritish Columbia Cancer AgencyVancouverCanada

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