MEK-ERK Signaling Dictates DNA-Repair Gene MGMT Expression and Temozolomide Resistance of Stem-Like Glioblastoma Cells via the MDM2-p53 Axis§

Authors

  • Atsushi Sato,

    1. Department of Molecular Cancer Science, Yamagata University School of Medicine, Yamagata, Japan
    2. Department of Neurosurgery, Yamagata University School of Medicine, Yamagata, Japan
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  • Jun Sunayama,

    1. Department of Molecular Cancer Science, Yamagata University School of Medicine, Yamagata, Japan
    2. Oncology Research Center, Research Institute for Advanced Molecular Epidemiology, Yamagata University, Yamagata, Japan
    3. Global COE Program for Medical Sciences, Japan Society for the Promotion of Science, Tokyo, Japan
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  • Ken-ichiro Matsuda,

    1. Department of Molecular Cancer Science, Yamagata University School of Medicine, Yamagata, Japan
    2. Department of Neurosurgery, Yamagata University School of Medicine, Yamagata, Japan
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  • Shizuka Seino,

    1. Department of Molecular Cancer Science, Yamagata University School of Medicine, Yamagata, Japan
    2. Oncology Research Center, Research Institute for Advanced Molecular Epidemiology, Yamagata University, Yamagata, Japan
    3. Global COE Program for Medical Sciences, Japan Society for the Promotion of Science, Tokyo, Japan
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  • Kaori Suzuki,

    1. Department of Molecular Cancer Science, Yamagata University School of Medicine, Yamagata, Japan
    2. Oncology Research Center, Research Institute for Advanced Molecular Epidemiology, Yamagata University, Yamagata, Japan
    3. Global COE Program for Medical Sciences, Japan Society for the Promotion of Science, Tokyo, Japan
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  • Eriko Watanabe,

    1. Department of Molecular Cancer Science, Yamagata University School of Medicine, Yamagata, Japan
    2. Oncology Research Center, Research Institute for Advanced Molecular Epidemiology, Yamagata University, Yamagata, Japan
    3. Global COE Program for Medical Sciences, Japan Society for the Promotion of Science, Tokyo, Japan
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  • Ken Tachibana,

    1. Department of Molecular Cancer Science, Yamagata University School of Medicine, Yamagata, Japan
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  • Arata Tomiyama,

    1. Department of Molecular Cancer Science, Yamagata University School of Medicine, Yamagata, Japan
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  • Takamasa Kayama,

    1. Department of Neurosurgery, Yamagata University School of Medicine, Yamagata, Japan
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  • Chifumi Kitanaka

    Corresponding author
    1. Department of Molecular Cancer Science, Yamagata University School of Medicine, Yamagata, Japan
    2. Oncology Research Center, Research Institute for Advanced Molecular Epidemiology, Yamagata University, Yamagata, Japan
    3. Global COE Program for Medical Sciences, Japan Society for the Promotion of Science, Tokyo, Japan
    • Department of Molecular Cancer Science, Yamagata University School of Medicine, Yamagata 990-9585, Japan
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    • Telephone: +81-23-628-5212; Fax: +81-23-628-5215


  • Author contributions: A.S.: concept and design, collection and assembly of data, data analysis and interpretation, and manuscript writing; J.S.: concept and design and data analysis and interpretation; K.-i.M., S.S., K.T., and A.T: data analysis and interpretation; K.S.: provision of study material or patients; E.W.: collection and assembly of data; T.K.: provision of study material or patients and data analysis and interpretation; C.K.: concept and design, data analysis and interpretation, manuscript writing, and final approval of manuscript.

  • Disclosure of potential conflicts of interest is found at the end of this article.

  • §

    First published online in STEM CELLSEXPRESS September 28, 2011.

Abstract

Overcoming the resistance of glioblastoma cells against temozolomide, the first-line chemotherapeutic agent of choice for newly diagnosed glioblastoma, is a major therapeutic challenge in the management of this deadly brain tumor. The gene encoding O6-methylguanine DNA methyltransferase (MGMT), which removes the methyl group attached by temozolomide, is often silenced by promoter methylation in glioblastoma but is nevertheless expressed in a significant fraction of cases and is therefore regarded as one of the most clinically relevant mechanisms of resistance against temozolomide. However, to date, signaling pathways regulating MGMT in MGMT-expressing glioblastoma cells have been poorly delineated. Here in this study, we provide lines of evidence that the mitogen-activated protein/extracellular signal-regulated kinase kinase (MEK)–extracellular signal-regulated kinase (ERK)--murine double minute 2 (MDM2)-p53 pathway plays a critical role in the regulation of MGMT expression, using stem-like glioblastoma cells directly derived from patient tumor samples and maintained in the absence of serum, which not only possess stem-like properties but are also known to phenocopy the characteristics of the original tumors from which they are derived. We show that, in stem-like glioblastoma cells, MEK inhibition reduced MDM2 expression and that inhibition of either MEK or MDM2 resulted in p53 activation accompanied by p53-dependent downregulation of MGMT expression. MEK inhibition rendered otherwise resistant stem-like glioblastoma cells sensitive to temozolomide, and combination of MEK inhibitor and temozolomide treatments effectively deprived stem-like glioblastoma cells of their tumorigenic potential. Our findings suggest that targeting of the MEK-ERK-MDM2-p53 pathway in combination with temozolomide could be a novel and promising therapeutic strategy in the treatment of glioblastoma. STEM CELLS 2011;29:1942–1951.

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