Unbound MEDLINE

Gefitinib radiosensitizes stem-like glioma cells: inhibition of epidermal growth factor receptor-Akt-DNA-PK signaling, accompanied by inhibition of DNA double-strand break repair.

Abstract

PURPOSE
We compared radiosensitivity of brain tumor stem cells (BTSCs) with matched nonstem glioma cells, and determined whether gefitinib enhanced BTSC radiosensitivity by inhibiting epidermal growth factor receptor (EGFR)-Akt-DNA-dependent protein kinase (DNA-PK) signaling, followed by enhanced DNA double-stand breaks (DSBs) and inhibition of DSB repair.
METHODS AND MATERIALS
Radiosensitivity of stem-like gliomaspheres and nonstem glioma cells (obtained at patient neurosurgical resection) were evaluated by clonogenic assays, γ-H(2)AX immunostaining and cell cycle distribution. Survival of irradiated and nonirradiated NOD-SCID mice intracranially implanted with stem-like gliomaspheres were monitored. Glioma cells treated with gefitinib, irradiation, or both were assayed for clonogenic survival, γ-H(2)AX immunostaining, DNA-PKcs expression, and phosphorylation of EGFR and Akt.
RESULTS
Stem-like gliomaspheres displayed BTSC characteristics of self-renewal; differentiation into lineages of neurons, oligodendrocytes, and astrocytes; and initiation of glioma growth in NOD-SCID mice. Irradiation dose-dependently reduced clonogenic survival, induced G(2)/M arrest and increased γ-H(2)AX immunostaining of nonstem glioma cells, but not stem-like gliomaspheres. There was no difference in survival of irradiated and nonirradiated mice implanted with stem-like gliomaspheres. The addition of gefitinib significantly inhibited clonogenic survival, increased γ-H(2)AX immunostaining, and reduced DNA-PKcs expression of irradiated stem-like gliomaspheres, without affecting irradiated-nonstem glioma cells. Gefitinib alone, and when combined with irradiation, inhibited phosphorylation of EGFR (Y1068 and Y1045) and Akt (S473) in stem-like gliomaspheres. In nonstem glioma cells, gefitinib alone inhibited EGFR Y1068 phosphorylation, with further inhibition by combined gefitinib and irradiation.
CONCLUSIONS
Stem-like gliomaspheres are resistant to irradiation-induced cytotoxicity, G(2)/M arrest, and DNA DSBs, compared with nonstem glioma cells. Gefitinib differentially enhances radiosensitivity of stem-like gliomaspheres by reducing EGFR-Akt activation and DNA-PKcs expression, accompanied by enhanced irradiation-induced DNA DSBs and inhibition of DSB repair.

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  • Publisher Full Text

    • Authors

    Kang KB, Zhu C, Wong YL, Gao Q, Ty A, Wong MC

    Institution

    Brain Tumour Research Laboratory, Division of Medical Sciences, National Cancer Centre Singapore, Singapore.

    Source

    International journal of radiation oncology, biology, physics 83:1 2012 May 1 pg e43-52

    MeSH

    Animals
    Antineoplastic Agents
    Brain Neoplasms
    DNA Breaks, Double-Stranded
    DNA-Activated Protein Kinase
    Glioma
    Histones
    Mice
    Mice, Inbred NOD
    Mice, SCID
    Neoplastic Stem Cells
    Neuroglia
    Phosphorylation
    Quinazolines
    Radiation Tolerance
    Radiation-Sensitizing Agents
    Receptor, Epidermal Growth Factor
    Tumor Stem Cell Assay

    Pub Type(s)

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

    Language

    eng

    PubMed ID

    22516386