Epidermal Growth Factor Receptor Activation in Glioblastoma through Novel Missense Mutations in the Extracellular Domain (original) (raw)
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2012
MAY 2012 CANCER DISCOVERY | 459 Glioma EGFR Mutants Selectively Respond to Type II EGFR TKIs The BATTLE Trial: Personalizing Therapy for Lung Cancer research article includes HER2 (ErbB2), HER3 (ErbB3), and HER4 [ErbB4 (6)]. EGFR has generated particular interest as a drug target in GBM because of the high frequency of EGFR alterations in this disease (7) and because ATP-site competitive EGFR kinase inhibitors are active agents in patients with EGFRmutant lung cancer (8). EGFR kinase inhibitors that received regulatory approval for the treatment of lung cancer (erlotinib, gefitinib), however, have shown disappointing results in patients with GBM (9). Reasons for this lack of response in GBM remain poorly understood and include redundancy in signaling pathways (10) and intratumoral heterogeneity (11). One key difference between EGFR in GBM and lung cancer is the distribution of mutations within the EGFR coding sequence. EGFR mutations in lung cancer reside in the intracellular kinase domain [KD (12)]. EGFR mutations in GBM cluster in the extracellular (EC) domain and include in-frame deletions [such as the common "variant III" (7)] and missense mutations [Fig. 1A (13)]. Both EGFR ectodomain and KD mutations encode oncoproteins with the ability to transform NIH-3T3 cells in the absence of ligand (13-15). In this study, we examined the role of EGFR for the survival of GBM cells harboring EGFR ectodomain mutations. We demonstrate that EGFR signals are essential for the survival of these cells and that EGFR EC mutants differ markedly from EGFR KD mutants in their sensitivity to ATP-site competitive EGFR kinase inhibitors. Results EGFR-Mutant GBM cells are addicted to eGFr Missense mutations in the EGFR EC domain are found in 10% to 15% of GBMs (4, 5, 13). To determine whether EGFR signals are essential for the survival of GBM cells endogenously expressing such mutations, we first sequenced the coding region of EGFR in a panel of GBM cell lines. We found 2 lines with EGFR EC mutations. Both mutations Activation of the epidermal growth factor receptor (EGFR) in glioblastoma (GBM) occurs through mutations or deletions in the extracellular (EC) domain. Unlike lung cancers with EGFR kinase domain (KD) mutations, GBMs respond poorly to the EGFR inhibitor erlotinib. Using RNAi, we show that GBM cells carrying EGFR EC mutations display EGFR addiction. In contrast to KD mutants found in lung cancer, glioma-specific EGFR EC mutants are poorly inhibited by EGFR inhibitors that target the active kinase conformation (e.g., erlotinib). Inhibitors that bind to the inactive EGFR conformation, however, potently inhibit EGFR EC mutants and induce cell death in EGFR-mutant GBM cells. Our results provide first evidence for single kinase addiction in GBM and suggest that the disappointing clinical activity of first-generation EGFR inhibitors in GBM versus lung cancer may be attributed to the different conformational requirements of mutant EGFR in these 2 cancer types. siGniFicance: Approximately 40% of human glioblastomas harbor oncogenic EGFR alterations, but attempts to therapeutically target EGFR with first-generation EGFR kinase inhibitors have failed. Here, we demonstrate selective sensitivity of glioma-specific EGFR mutants to ATP-site competitive EGFR kinase inhibitors that target the inactive conformation of the catalytic domain. Cancer Discov; 2(5); 458-71. ©2012 AACR. IntRoductIon Glioblastoma (GBM) is the most common malignant brain tumor in adults. Most patients with GBM succumb to their disease within 2 years, and there is a dire need for the development of novel therapeutics (1). Inhibitors of deregulated signaling pathways are active agents in a variety of human cancers (2, 3) and represent a compelling area of drug development for GBM because many of these tumors harbor genetic alterations in growth factor-signaling pathways (4, 5). The epidermal growth factor receptor (EGFR) is a member of the EGFR family of receptor tyrosine kinases, which also
International journal of oncology, 2004
The accumulated results of recent clinical studies have indicated that aberrant epidermal growth factor receptor (EGFR) activation due to gene amplification and/or rearrangement contributes to increased malignancy and poor prognosis in many human cancers, especially in human glioblastoma multiforme (GBM). The elevated EGFR signaling in GBM has been correlated with shorter interval to relapse and lower survival rates, even in patients treated with surgery, radiation therapy, and/or chemotherapy. Therefore, the blockade of EGFR signaling in GBM may provide an ideal alternative therapeutic strategy. In this study, two EGFR-overexpressing human GBM cell lines (i.e., DBTRG and GBM 8901) were used as a model system. We demonstrated that expression of a human EGFR (EGFRt-EGFP) chimera protein in which the cytoplasmic domain is substituted by EGFP significantly reduced the EGF-induced endogenous EGFR autophosphorylation, EGF-induced downstream extra-cellular signal-regulated kinase (ERK) an...
Clinical Cancer Research, 2004
Purpose: We have reported previously that tumors expressing wild-type epidermal growth factor receptor (EGFR) in a murine model are sensitive to the EGFR tyrosine kinase inhibitor gefitinib, whereas tumors expressing mutant EGFR variant III (EGFRvIII) are resistant. Determination of how this differential inhibition occurs may be important to patient selection and treatment criteria, as well as the design of future therapeutics for glioblastoma multiforme. Experimental Design: We have determined and quantified how treatment with gefitinib at commonly used, noncytotoxic doses affects neoplastic functions ascribed to EGFRvIII, including downstream signaling by Akt, DNA synthesis, and cellular invasion. In doing so, we have tested and compared a series of wild-type and mutant EGFRvIII-expressing fibroblast and glioblastoma cell lines in vitro after treatment with gefitinib. Results: The results of these experiments demonstrate that short-term treatment with gefitinib (∼24 h) does not re...
Pathology oncology research : POR, 2009
Gefitinib and erlotinib are both selective EGFR tyrosine kinase inhibitors (EGFR-TKIs) that have produced responses in a small subgroup of lung cancer patients. The strongest evidence for a role of EGFR in the biology of glioblastoma stems from clinical trials in which 15-20% of recurrent glioblastoma patients experienced significant tumour regression in response to these small-molecule EGFR kinase inhibitors. We examined the protein-kinase domain of the EGFR gene, EGFR protein expression and EGFR gene amplification in 20 cases of recurrent GBMs. EGFR protein over-expression was found in 65% of cases. EGFR protein over-expression was associated with EGFR gene amplification in 35% of cases, and with high polysomy in 15% of cases. No mutations were found in the TK domain of the EGFR gene. Our results confirm that mutations in the kinase domain are absent in recurrent GBM, and this might be a preponderant factor in the lack of major clinical responses of TKIs in GBM, recent studies hav...
Cancer Research, 2011
Genomic alterations of the epidermal growth factor receptor (EGFR) gene play a crucial role in pathogenesis of glioblastoma multiforme (GBM). By systematic analysis of GBM genomic data, we have identified and characterized a novel exon 27 deletion mutation occurring within the EGFR carboxyl-terminus domain (CTD) in addition to identifying additional examples of previously reported deletion mutations in this region. We show that the GBM-derived EGFR CTD deletion mutants are able to induce cellular transformation in vitro and in vivo in the absence of ligand and receptor autophosphorylation. Treatment with the EGFR-targeted monoclonal antibody, cetuximab, or the small molecule EGFR inhibitor, erlotinib, effectively impaired tumorigenicity of oncogenic EGFR CTD deletion mutants. Cetuximab in particular prolonged the survival of intracranially xenografted mice with oncogenic EGFR CTD deletion mutants, compared to untreated control mice. Therefore, we propose that erlotinib and especially cetuximab treatment may be a promising therapeutic strategy in GBM patients harboring EGFR CTD deletion mutants.
Cancer research, 2015
Epidermal growth factor receptor (EGFR) is highly amplified, mutated and overexpressed in human malignant gliomas. Despite its prevalence and growth-promoting functions, therapeutic strategies to inhibit EGFR kinase activity have not been translated into profound beneficial effects in glioma clinical trials. To determine the roles of oncogenic EGFR signaling in gliomagenesis and tumor maintenance, we generated a novel glioma mouse model driven by inducible expression of a mutant EGFR (EGFR*). Using combined genetic and pharmacological interventions, we revealed that EGFR*-driven gliomas were insensitive to EGFR tyrosine kinase inhibitors although they could efficiently inhibit EGFR* auto-phosphorylation in vitro and in vivo. This is in contrast to genetic suppression of EGFR* induction which led to significant tumor regression and prolonged animal survival. But in spite of their initial response to genetic EGFR* extinction, all tumors would relapse and propagate independent of EGFR*...
Nuclear Signaling of EGFR and EGFRvIII in Glioblastoma
The pivotal role of kinases in signal transduction and cellular regulation has lent them considerable appeal as therapeutic targets across a broad spectrum of cancers. The epidermal growth factor receptor (EGFR) was the first receptor tyrosine kinase to be discovered and remains the most investigated. Most of the mechanistic principles of receptor tyrosine kinases were first established with the EGFR family as a model.