Understanding the Role of EGFRvIII in Glioblastoma Treatment: EGFRvIII Improves Temozolomide Response in MGMT Promotor Methylated Glioblastoma Patients

Abstract

Background: The EGF-receptor variant III (EGFRvIII) is expressed in approximately 30% of all primary glioblastoma (GBM). Although several anti-EGFRvIII strategies have already been tested, the importance of EGFRvIII expression on treatment response is still under debate. Our aim was to clarify the relevance of EGFRvIII for GBM treatment using uni- and multivariate analysis of clinical data and preclinical studies. Methods: We performed retrospective analysis of 338 IDH1 wild type GBM patients treated either at the University of Pennsylvania or North Bristol NHS Trust and included data from the TCGA database. Survival was stratified according to MGMT promoter methylation status, EGFRvIII expression and EGFR gene amplification. The effect of EGFRvIII expression was also analyzed at the cellular and tumor level using isogenic pairs of EGFRvIII-negative and -positive GBM cells and xenograft tumors. Findings: EGFRvIII expression was associated with a significantly prolonged median overall survival but only for GBM patients with MGMT promoter methylated tumors. Importantly, this effect was independent of EGFR gene amplification. We also observed increased temozolomide (TMZ) sensitivity of EGFRvIII positive cells, which translated into improved survival in xenograft experiments. This increase in TMZ sensitivity was associated with an elevated DNA damage induction accompanied by an increased expression of DNA mismatch repair (MMR) proteins. In line with this finding, knock down of MMR proteins or EGFRvIII restored TMZ resistance. Interpretation: EGFRvIII expression is of high relevance for the prediction of GBM therapy outcome. Due to EGFRvIII-dependent upregulation of MMR standard of care treatment is most efficient for GBM displaying both MGMT promoter methylation and EGFRvIII expression. Funding Statement: This work was supported by the Brigitte and Dr. Konstanze Wegener-Stiftung (M.K.), Wilhelm-Sander-Stiftung (M.K.), Forschungsforderungsfonds des Fachbereichs Medizin des Universitatsklinikums Hamburg-Eppendorf (N.S.) and the Federal Ministry of Education and Research (BMBF grant 02NUK032; M.K. K.R.), Cancer Research UK (CRUK/21600; S.C.S, T.B.), The Brain Tumour Charity (TBTC13/192; S.C.S., T.B.), Medical Research Council (MR/K015214/1; S.C.S., T.B.), University of Leeds Academic Fellowship (L.F.S), The Templeton Family Research Fund (Z.A.B) and the National Institutes of Health (NIH 2R01-NS042645-11A1; D.O.R.). U.S. is supported by the Fordergemeinschaft Kinderkrebs-Zentrum Hamburg Declaration of Interests: The authors declare that they have no competing interests. Ethics Approval Statement: Animal Use: All work was performed in accordance with the United Kingdom Animals (Scientific Procedures) Act (1986), under the authority of project licence 70/7340.