EGFR and EGFRvIII analysis in glioblastoma as therapeutic biomarkers

Abstract

Introduction. EGFR and EGFRvIII analysis is of current interest because of new EGFRvIII vaccine trials opened in the UK. EGFR activation promotes cellular proliferation via activation of MAPK and PI3K-Akt pathways. EGFRvIII is the most common variant resulting from an in-frame deletion of 801bp, leading to constitutively active EGFR. Method. 51 glioblastoma samples from a cohort of 50 patients were tested for EGFR amplification by FISH and immunohistochemistry and EGFRvIII expression by reverse-transcriptase PCR (RT-PCR), and immunohistochemistry. EGFR and EGFRvIII expression was compared with Overall Survival in the cohort. Results. Overall 22/51 samples (43%) were positive for EGFR, 16/51 (31%) were positive for EGFRvIII and 13/51 (25%) were positive for both. 9/51 cases (18%) were positive for EGFR alone, and 3/51 (6%) were positive for EGFRvIII alone. Of the EGFR positive cases, 22/51 (43%) were positive by FISH, 24/51 (47%) were positive by IHC and 2/51 (4%) were discrepant between methods (positive by IHC but non-amplified by FISH). Of the EGFRvIII positive cases, 16/51 (31%) were positive by RT-PCR, 17/51 (33%) were positive by IHC and 1/51 (2%) sample was discrepant (positive by IHC but not by RT-PCR). Neither EGFRvIII or EGFR are predictive of overall survival in this cohort. Conclusion. In our cohort, 25/51 (49%) of GBM showed EGFR alterations, including 16/51 (31%) with EGFRvIII. There was high concordance between IHC and FISH (96%) and IHC and RT-PCR (98%) as diagnostic methods. Neither EGFR or EGFRvIII is predictive of overall survival in this cohort. These results are key for selecting patients for novel individualised anti-EGFR therapies.

EGFRvIII upregulates DNA mismatch repair resulting in increased temozolomide sensitivity of MGMT promoter methylated glioblastoma

“…To test if EGFRvIII has an influence on TMZ sensitivity we retrospectively analyzed the overall survival of 336 patients with IDH1 wild type (wt) GBM and known MGMT promoter, EGFR amplification and EGFRvIIII status who had been treated with standard of care. Patients from three different cohorts were included, namely the UPenn cohort [28], the Bristol cohort [18] and the TCGA cohort [29] (Table S2). We initially fitted a univariate cox proportional hazards model to include the variables of EGFRvIII status, EGFR amplification status, MGMT promoter methylation status, gender and age.…”

“…The significance of the separation of Kaplan-Meier survival curves, based on EGFRvIII status, was calculated using a log-rank test. The data originated from three independent cohorts, herein referred to as the University of Pennsylvania (UPenn [28]) cohort (230 cases), the North Bristol NHS Trust (Bristol [18]) cohort (29 cases) and the TCGA cohort (79 cases, extracted from the Brennan et al publication [29]).…”

“…The EGFRvIII is accepted to be an oncogene and its expression is therefore assumed to have a negative impact on treatment outcome of GBM patients [11][12][13]. However, clinical studies have so far failed to prove that EGFRvIII is a reliable prognostic marker: while in smaller studies EGFRvIII expression was found to be associated with either better or worse survival, larger studies did not observe any predictive or prognostic impact of EGFRvIII expression [12,[14][15][16][17][18][19]. A summary of the relevant literature is given in supplementary Table S1 (Table S1).…”

Sensitivity of glioma initiating cells to a monoclonal anti-EGFR antibody therapy under hypoxia

“…Our two GIC models did not express EGFR variant III, which is a mutated form of EGFR activated constitutively, and can be involved in the resistance mechanism to cetuximab [31]. 30% of glioma expresses the active mutant EGFRvIII protein [12] and the mutation promotes glioma growth and vascularization through NF-Kappa B signaling [6]. It would be interesting to evaluate the self-renewal of GICs expressing EGFRvIII to cetuximab due to the ability of cetuximab to decrease strongly the in vitro activity of EGFRvIII [17].…”

Biomarkers for glioma immunotherapy: the next generation

“…CAR targeting the EGFRvIII mutated protein was first demonstrated in glioma cell culture [26], then by in vivo localization in pre-clinical murine studies, leading to tumor cell infiltration and increased survival [27, 28]. Currently, a single-group pilot clinical study of an optimized EGFRvIII-CAR [29] in GBM (NCT02209376) includes pre-screening for expression of EGFRvIII (31 % of GBM [30]) as an enrollment criterion, utilizing the artificially-targeted nature of these constructs as a biomarker to ensure targeting potential in light of the severity of off-target, adverse events. The more general tumor antigens HER2 and EphA2 have been successfully targeted by CARs in glioma cell culture and preclinical models [31, 32], leading to a phase I clinical trial of autologous generated HERT-CD28 fusion receptor cells (NCT01109095).…”