Expression of activated epidermal growth factor receptors, Ras-guanosine triphosphate, and mitogen-activated protein kinase in human glioblastoma multiforme specimens

OBJECTIVE: Amplification of the epidermal growth factor receptor (EGFR) is a common event in the molecular pathogenesis of high-grade astrocytic tumor s, occurring in 50% of glioblastoma multiforme (GBM) cases. A subset of GBM s also express a constitutively phosphorylated truncated receptor (EGFRvIII ). Expression of transfected EGFRvIII in cells has been reported to activat e the Ras-mitogen-activated protein kinase pathway and to provide a growth advantage. Novel therapeutic agents targeting signal transduction pathways are entering early clinical trials; determination of which GBMs express EGF RvIII might help identify patients who might benefit from these biological agents. METHODS: A cohort of 15 flash-frozen surgical specimens (12 GBMs, 2 gliosar comas, and 1 adult low-grade glioma) were evaluated for EGFR and EGFRvIII e xpression and for EGFR activation status using immunohistochemical (IHC) an alysis, Western blotting, and reverse transcription-polymerase chain reacti on assays. Levels of activated Ras-guanosine triphosphate were measured usi ng a nonradioactive luciferase-based technique. Mitogen-activated protein k inase activation was determined using a myelin basic protein assay. IHC ana lysis was performed on paraffin-embedded, formalin-fixed, pathological spec imens. Normal control samples included white matter specimens distal to tum ors (n = 5), a sample obtained during a lobectomy for treatment of epilepsy (n = 1), and cultured fetal human astrocytes (n = 1). RESULTS: We demonstrated higher levels of activated Ras and mitogen-activat ed protein kinase in GEM specimens, compared with normal brain tissue or th e low-grade glioma. There was a very good correlation between results obtai ned using specialized molecular techniques and those obtained using routine IHC techniques. Screening for EGFRvIII expression may be of prognostic imp ortance, because patients with EGFRvIII-positive tumors exhibited shorter l ife expectancies (mean survival time for patients with EGFRvIII-positive tu mors, 4.5 +/- 0.6 mo; mean survival time for patients with EGFRvIII-negativ e tumors, 11.2 +/- 0.9 mo). CONCLUSION: We demonstrated that routine IHC techniques using commercially available antibodies are capable of identifying which GBM specimens express EGFRvIII and whether the EGFRs are activated. Such a molecular classificat ion of GBMs might allow us to determine which patients might benefit from b iologically targeted therapies. In addition, characterization of specimens with respect to their EGFRvIII status seems to be of prognostic value.