Determination of EGFR status in gliomas: usefulness of immunohistochemistry and fluorescent in situ hybridization.
ABSTRACT Epidermal growth factor receptor (EGFR) is produced during the molecular pathogenesis of glioma, and new anti-EGFR molecules are available for therapeutics. Consequently, analyses of the EGFR gene and protein are frequently used for glioma characterization. We compare the accuracy and the usefulness of 2 currently used techniques for histologic classification of gliomas. Fluorescent in situ hybridization (FISH) and immunohistochemistry (IHC) techniques were used to assess EGFR gene amplification and protein abundance in a series of 35 gliomas, including World Health Organization (WHO) grade I, II, and III astrocytomas (AI, AII, AIII), grade II and III tumors with oligodendroglial component (OII, OIII) and grade IV glioblastomas (GBs). EGFR gene amplification was found in one-third of the tumors studied. It was frequent in GB and OIII but was never found in AI, AII, AIII, and OII tumors. IHC and FISH provided similar findings for grade of tumor, despite the fact that, in contrast to the FISH gene amplification, EGFR protein was overexpressed in AIII and in GB. EGFR gene amplification was never observed in tumors not containing EGFR protein: therefore FISH is unnecessary when IHC shows no EGFR protein expression. EGFR gene amplification seems to be restricted to high-grade tumors, WHO grade IV astrocytomas, and grade III oligodendroglial tumors.
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ABSTRACT: The fourth edition of the World Health Organization (WHO) classification of tumours of the central nervous system, published in 2007, lists several new entities, including angiocentric glioma, papillary glioneuronal tumour, rosette-forming glioneuronal tumour of the fourth ventricle, papillary tumour of the pineal region, pituicytoma and spindle cell oncocytoma of the adenohypophysis. Histological variants were added if there was evidence of a different age distribution, location, genetic profile or clinical behaviour; these included pilomyxoid astrocytoma, anaplastic medulloblastoma and medulloblastoma with extensive nodularity. The WHO grading scheme and the sections on genetic profiles were updated and the rhabdoid tumour predisposition syndrome was added to the list of familial tumour syndromes typically involving the nervous system. As in the previous, 2000 edition of the WHO 'Blue Book', the classification is accompanied by a concise commentary on clinico-pathological characteristics of each tumour type. The 2007 WHO classification is based on the consensus of an international Working Group of 25 pathologists and geneticists, as well as contributions from more than 70 international experts overall, and is presented as the standard for the definition of brain tumours to the clinical oncology and cancer research communities world-wide.Acta Neuropathologica 09/2007; 114(2):97-109. · 9.73 Impact Factor
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ABSTRACT: We investigated the molecular effect of the epidermal growth factor receptor (EGFR) inhibitors erlotinib and gefitinib in vivo on all available tumors from patients treated on North American Brain Tumor Consortium trials 01-03 and 00-01 for recurrent or progressive malignant glioma. EGFR expression and signaling during treatment with erlotinib or gefitinib were analyzed by Western blot and compared with pre-erlotinib/gefitinib-exposed tissue or unexposed controls. Tumors were also analyzed for EGFR mutations and for other genomic abnormalities by array-based comparative genomic hybridization. Clinical data were used to associate molecular features with tumor sensitivity to erlotinib or gefitinib. Erlotinib and gefitinib did not markedly affect EGFR activity in vivo. No lung signature mutations of EGFR exons 18 to 21 were observed. There was no clear association between erlotinib/gefitinib sensitivity and deletion or amplification events on array-based comparative genomic hybridization analysis, although novel genomic changes were identified. As erlotinib and gefitinib were generally ineffective at markedly inhibiting EGFR phosphorylation in these tumors, other assays may be needed to detect molecular effects. Additionally, the mechanism of erlotinib/gefitinib sensitivity likely differs between brain and lung tumors. Finally, novel genomic changes, including deletions of chromosomes 6, 21, and 22, represent new targets for further research.Clinical Cancer Research 12/2005; 11(21):7841-50. · 7.84 Impact Factor
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ABSTRACT: Glioblastoma multiforme (GBM) is the most aggressive brain tumor in adults and remains incurable despite multimodal intensive treatment regimens. EGFRvIII is a truncated extracellular mutant of the EGF receptor (EGFR) commonly found in GBMs that confers enhanced tumorigenic behavior. To gain a molecular understanding of the mechanisms by which EGFRvIII acts, we have performed a large-scale analysis of EGFRvIII-activated phosphotyrosine-mediated signaling pathways and thereby have identified and quantified 99 phosphorylation sites on 69 proteins. Distinct signaling responses were observed as a function of titrated EGFRvIII receptor levels with the phosphatidylinositol 3-kinase pathway being dominant over the MAPK and STAT3 pathways at a high level of EGFRvIII expression. Within this data set, the activating phosphorylation site on the c-Met receptor was found to be highly responsive to EGFRvIII levels, indicating cross-activation of the c-Met receptor tyrosine kinase by EGFRvIII. To determine the significance of this finding, we devised a combined treatment regimen that used a c-Met kinase inhibitor and either an EGFR kinase inhibitor or cisplatin. This regimen resulted in enhanced cytotoxicity of EGFRvIII-expressing cells compared with treatment with either compound alone. These results suggest that the clinical use of c-Met kinase inhibitors in combination with either EGFR inhibitors or standard chemotherapeutics might represent a previously undescribed therapeutic approach to overcome the observed chemoresistance in patients with GBMs expressing EGFRvIII.Proceedings of the National Academy of Sciences 08/2007; 104(31):12867-72. · 9.74 Impact Factor