EGFR tyrosine kinase inhibition radiosensitizes and induces apoptosis in malignant glioma and childhood ependymoma xenografts

Int J Cancer. 2008 Jul 1;123(1):209-16. doi: 10.1002/ijc.23488.


Malignant gliomas and childhood ependymomas have a high rate of treatment failure. Epidermal growth factor receptor (EGFR) activation has been implicated in the tumorigenesis and radioresistance of many cancers, including brain tumors. Therefore, combining EGFR targeting with irradiation is a potentially attractive therapeutic option. We evaluated the tyrosine kinase inhibitor gefitinib for its antitumor activity and potential to radio-sensitize in vivo in two xenograft models: an EGFR amplified glioma and an EGFR expressing ependymoma, both derived from primary tumors. When administered at 100 mg/kg for 5 consecutive days, gefitinib-induced partial tumor regression in all treated EGFR amplified IGRG88 glioma xenografts. The addition of 1 Gy of irradiation prior to gefitinib administration resulted in 5 complete and 4 partial regressions for the 9 treated tumors as well as a significant tumor growth delay of 33 days for the combined treatment compared to 19 days for each therapy alone, suggesting additive antitumor activity. Tumor regression was associated with inhibition of AKT and MAPK pathways by gefitinib. In contrast, the ependymoma IGREP83 was sensitive to irradiation, but remained resistant to gefitinib. Combined treatment was associated with inhibition of radiation-induced MAPK phosphorylation and significant induction of apoptotic cell death though radiation-induced AKT phosphorylation was maintained. Depending on the scheduling of both therapies, a trend towards superior antitumor activity was observed with combined treatment. Thus, EGFR targeting through tyrosine kinase inhibition appears to be a promising new approach in the treatment of EGFR-driven glioma, particularly in combination with radiation therapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacology*
  • Apoptosis* / drug effects
  • Apoptosis* / radiation effects
  • Blotting, Western
  • Brain Neoplasms / drug therapy
  • Brain Neoplasms / radiotherapy
  • Chemotherapy, Adjuvant
  • Child
  • Enzyme Activation / drug effects
  • Enzyme Activation / radiation effects
  • Ependymoma / drug therapy*
  • Ependymoma / pathology
  • Ependymoma / radiotherapy*
  • ErbB Receptors / antagonists & inhibitors*
  • ErbB Receptors / genetics
  • ErbB Receptors / metabolism*
  • Female
  • Flow Cytometry
  • G1 Phase / drug effects
  • Gefitinib
  • Gene Expression Regulation, Enzymologic / drug effects
  • Gene Expression Regulation, Enzymologic / radiation effects
  • Gene Expression Regulation, Neoplastic / drug effects
  • Gene Expression Regulation, Neoplastic / radiation effects
  • Glioma / drug therapy*
  • Glioma / pathology
  • Glioma / radiotherapy*
  • Humans
  • Immunohistochemistry
  • In Situ Hybridization, Fluorescence
  • In Situ Nick-End Labeling
  • Mice
  • Mice, Nude
  • Middle Aged
  • Mitogen-Activated Protein Kinase Kinases / drug effects
  • Mitogen-Activated Protein Kinase Kinases / metabolism
  • Phosphorylation / drug effects
  • Protein Kinase Inhibitors / pharmacology*
  • Proto-Oncogene Proteins c-akt / drug effects
  • Proto-Oncogene Proteins c-akt / metabolism
  • Quinazolines / pharmacology*
  • RNA, Messenger / metabolism
  • Radiation-Sensitizing Agents / pharmacology*
  • Radiotherapy, Adjuvant
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / drug effects
  • Time Factors
  • Xenograft Model Antitumor Assays


  • Antineoplastic Agents
  • Protein Kinase Inhibitors
  • Quinazolines
  • RNA, Messenger
  • Radiation-Sensitizing Agents
  • ErbB Receptors
  • Proto-Oncogene Proteins c-akt
  • Mitogen-Activated Protein Kinase Kinases
  • Gefitinib