gms | German Medical Science

63rd Annual Meeting of the German Society of Neurosurgery (DGNC)
Joint Meeting with the Japanese Neurosurgical Society (JNS)

German Society of Neurosurgery (DGNC)

13 - 16 June 2012, Leipzig

Erlotinib resistance in an EGFR-amplified cell culture system is associated with upregulation of EGFRvIII and can be overcome by inhibition of PI3K

Meeting Abstract

  • A. Schulte - Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Deutschland
  • S. Zapf - Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Deutschland
  • M. Stoupiec - Institut für Tumorbiologie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Deutschland
  • S. Riethdorf - Institut für Tumorbiologie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Deutschland
  • M. Westphal - Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Deutschland
  • K. Lamszus - Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Deutschland

Deutsche Gesellschaft für Neurochirurgie. Japanische Gesellschaft für Neurochirurgie. 63. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit der Japanischen Gesellschaft für Neurochirurgie (JNS). Leipzig, 13.-16.06.2012. Düsseldorf: German Medical Science GMS Publishing House; 2012. DocFR.07.07

DOI: 10.3205/12dgnc220, URN: urn:nbn:de:0183-12dgnc2207

Published: June 4, 2012

© 2012 Schulte et al.
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Outline

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Objective: The objective of the current study was to identify mechanisms responsible for the resistance of glioma towards tyrosine-kinase inhibitors (TKI) directed against the epidermal growth factor-receptor (EGFR) in an EGFR-amplified, EGFRvIII-positive in vitro-model.

Methods: BS153-cells (EGFR-amplified, EGFRvIII- positive, kindly provided by Dr. A. Merlo, Basel, Switzerland) were maintained chronically in the presence of the EGFR TKI Erlotinib (Tarceva®), giving rise to a resistant cell line BS153resE. The cell lines were compared for amplification of the egfr gene by FISH analysis and quantitative PCR, the expression of EGFR, EGFRvIII as well as the activity of downstream signaling molecules by PCR, FACS analysis and Westernblot. In vivo-tumorigenicity was compared by orthotopic injection into nude mice. In vitro growth of both cell lines in response to pharmacological EGFR and PI3K inhibition was assessed by proliferation assays.

Results: Erlotinib resistance in the cell model analyzed was associated with a strong upregulation of EGFRvIII at the protein level, while amplification of the egfr gene remained unchanged in both the parental BS153 cell line as well as in the resistant BS153resE cells. Resistance towards Erlotinib appeared to be transient, as withdrawal of the inhibitor from the resistant cell line led to a regain in sensitivity towards EGF, which was absent in the chronically treated cells. In vivo, BS-153 cells formed highly invasive tumors with an unusual growth pattern, notably forming numerous satellites distant from the initial injection site. The Erlotinib-resistant phenotype led to delayed onset of tumor growth as well as to prolonged overall survival of mice injected with these cells, while the unusual morphology of tumors derived from BS153resE cells remained unchanged. Targeting downstream mediators of EGFR signaling, especially the phosphoinositide-3-kinase (PI3K), led to a dose-dependent decrease in cell viability in both the Erlotinib-sensitive and the Erlotinib-resistant BS153 cells, thereby overcoming resistance to the TKI.

Conclusions: Resistance towards Erlotinib, a common feature observed in glioma, is associated with upregulation of the oncogenic EGFRvIII in the model of Erlotinib-resistant, EGFR-amplified cells presented in this study. This model can be used to further identify resistance mechanisms associated with EGFR amplification. One attempt could be to bypass EGFR inhibition and directly target downstream effectors of EGFR signaling such as PI3K.