EGFRvIII Deletion Mutations in Pediatric High-Grade Glioma and Response to Targeted Therapy in Pediatric Glioma Cell Lines

Abstract

Purpose: The epidermal growth factor receptor (EGFR) is amplified and overexpressed in adult glioblastoma, with response to targeted inhibition dependent on the underlying biology of the disease. EGFR has thus far been considered to play a less important role in pediatric glioma, although extensive data are lacking. We have sought to clarify the role of EGFR in pediatric high-grade glioma (HGG). Experimental Design: We retrospectively studied a total of 90 archival pediatric HGG specimens for EGFR protein overexpression, gene amplification, and mutation and assessed the in vitro sensitivity of pediatric glioma cell line models to the small-molecule EGFR inhibitor erlotinib. Results: Amplification was detected in 11% of cases, with corresponding overexpression of the receptor. No kinase or extracellular domain mutations were observed; however, 6 of 35 (17%) cases harbored the EGFRvIII deletion, including two anaplastic oligodendrogliomas and a gliosarcoma overexpressing EGFRvIII in the absence of gene amplification and coexpressing platelet-derived growth factor receptor α. Pediatric glioblastoma cells transduced with wild-type or deletion mutant EGFRvIII were not rendered more sensitive to erlotinib despite expressing wild-type PTEN. Phosphorylated receptor tyrosine kinase profiling showed a specific activation of platelet-derived growth factor receptor α/β in EGFRvIII-transduced pediatric glioblastoma cells, and targeted coinhibition with erlotinib and imatinib leads to enhanced efficacy in this model. Conclusions: These data identify an elevated frequency of EGFR gene amplification and EGFRvIII mutation in pediatric HGG than previously recognized and show the likely necessity of targeting multiple genetic alterations in the tumors of these children. (Clin Cancer Res 2009;15(18):5753-61) Amplification, overexpression, and/or mutation of the epidermal growth factor receptor (EGFR) represent a compelling set of molecular genetic indicators for targeted therapy in adult glioblastoma. About 40% of glioblastomas show amplification of the EGFR gene locus, and about half of these tumors express a mutant receptor (EGFRvIII) that is constitutively active due to an in-frame truncation within the extracellular ligand-binding domain (1). In addition, novel missense mutations have been reported in the extracellular domain of tumors and cell lines (2), and recently, additional mutations have been described outside of these regions (e.g., in the transmembrane domains), although the significance of these is not yet clear (3).EGFRvIII is caused by deletion of exons 2 to 7, resulting in a protein that lacks a ligand-binding domain and is constitutively activated and is further resistant to down-regulation due to a low rate of receptor endocytosis (4). EGFRvIII has been shown

Receptor Tyrosine Kinase Genes Amplified in Glioblastoma Exhibit a Mutual Exclusivity in Variable Proportions Reflective of Individual Tumor Heterogeneity

“…Although tumor clonality would imply that these events would be present in all neoplastic cells, we and others have previously noted through detailed fluorescent and chromogenic in situ hybridization (FISH/CISH) experiments on pathologic specimens that not all cells harbor individual amplification events (15,16).…”

Treatment of children with high grade glioma with nimotuzumab: A 5-y institutional experience

“…14 Other authors have reported a high degree of immunopositivity for wild type EGFR in pediatric glioma, together with low expression of EGFRvIII. 15,16 Nimotuzumab is a humanized IgG1 monoclonal antibody that targets EGFR. Its preclinical activity has been summarized previously 17 and more than 30,000 patients bearing epithelial-derived tumors have been treated worldwide with nimotuzumab.…”

Distinct genetic alterations in pediatric glioblastomas

“…The mean age of the patients was 8.8 (range, [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] years, and the male to female ratio was nearly 2.3:1. Diagnoses were based on histological and immunohistochemical features according to the 2007 WHO classification system and were reviewed by three pathologists (PSH, BSJ, and KSH).…”

“…Some chromosomal gains, losses, and amplifications observed frequently in aGBs have not been well characterized in pGBs [11]. In pediatric HGGs, the reported frequencies of EGFR gene amplification and EGFR vIII mutations and deletions are low (11, 0, and 17 %, respectively) [12]. PDGFR α polypeptide (PDGFRA) gene amplification was detected in only a small subset of aGBs and 12 % of pGBs [13][14][15].…”