High level EGFR amplification in a newly established glioblastoma cell line 170-MG-BA

Roderick MacLeod, Bjorn Schneider, Ivana Sivakova, Stefan Nagel, Wilhelm Dirks, Peter Mraz, Eliska Kubikova,  Anna Perzelova

Abstract:

Glioblastoma multiforme is a highly invasive and incurable primary brain tumor. The most frequent genetic alteration therein is amplification of the epidermal growth factor receptor (EGFR) gene, the target of current clinical trials. However, EGFR amplification is poorly represented in glioblastoma cell lines. From the 30 cultures attempted herein, we were able to establish two glioblastoma permanent cell lines. The remaining cultures showed limited life span and underwent senescence between passage numbers (PN) 8 to 15. Our newly established glioblastoma cell lines, designated 170-MG-BA and 538-MG-BA, both originated between PN 3 and 5 when areas of smaller, more rapidly proliferating cells appeared. Both cell lines showed similar rates of growth, moderate morphological differences, cytoskeletal heterogeneity and multiple chromosome rearrangements. Analysis by molecular cytogenetics and comparative genomic hybridization (aCGH) revealed two copies of a stable marker chromosome in 170-MG-BA cells effecting focal amplification at 7q11 of the EGFR locus. Comparative RqPCR analysis confirmed that EGFR was uniquely highly expressed in 170-MG-BA cells. Combined targeted expression analysis and aCGH data excluded the recurrent EGFRvIII activating mutation. In contrast, EGFR expression in 538-MG-BA cells which lacked genomic EGFR amplification was not raised. Immunofluorescent staining showed high EGFR protein expression only in the 170-MG-BA cells. Cytogenetic, genomic and transcriptional analyses then confirmed high-level genomic amplification and transcriptional upregulation of wild type EGFR in 170-MG-BA; the first conventional cell line model for investigating the biology and targeted therapy of this key alteration in glioblastoma. Both cell lines are freely available from the DSMZ cell repository.