GBM heterogeneity as a function of variable epidermal growth factor receptor variant III activity

// Olle R. Lindberg 1 , Andrew McKinney 1 , Jane R. Engler 1 , Gayane Koshkakaryan 2 , Henry Gong 1 , Aaron E. Robinson 1 , Andrew J. Ewald 3 , Emmanuelle Huillard 4 , C. David James 5 , Annette M. Molinaro 1, 6, 7 , Joseph T. Shieh 8 , Joanna J. Phillips 1, 6, 9 1 Department of Neurological Surgery, Brain Tumor Center, University of California, San Francisco, CA, USA 2 Touro University California, College of Osteopathic Medicine. Vallejo, CA, USA 3 Departments of Cell Biology, Oncology, and Biomedical Engineering, School of Medicine, Johns Hopkins University, Baltimore, MD, USA 4 Universite Pierre et Marie Curie (UPMC) UMR-S975, Inserm U1127, CNRS UMR7225, Institut du Cerveau et de la Moelle Epiniere, Paris, France 5 Department of Neurological Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA 6 Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA, USA 7 Epidemiology and Biostatistics, University of California, San Francisco, CA, USA 8 Institute for Human Genetics, Department of Pediatrics, University of California, San Francisco, CA, USA 9 Department of Pathology, Division of Neuropathology, University of California, San Francisco, CA, USA Correspondence to: Joanna J. Phillips, email: Joanna.phillips@ucsf.edu Keywords: RTK activity, extracellular matrix, tumor heterogeneity, vessel co-option, invasion Received: August 06, 2016     Accepted: September 29, 2016     Published: October 12, 2016 ABSTRACT Abnormal activation of the epidermal growth factor receptor (EGFR) due to a deletion of exons 2-7 of EGFR (EGFRvIII) is a common alteration in glioblastoma (GBM). While this alteration can drive gliomagenesis, tumors harboring EGFRvIII are heterogeneous. To investigate the role for EGFRvIII activation in tumor phenotype we used a neural progenitor cell-based murine model of GBM driven by EGFR signaling and generated tumor progenitor cells with high and low EGFRvIII activation, pEGFR Hi and pEGFR Lo . In vivo , ex vivo , and in vitro studies suggested a direct association between EGFRvIII activity and increased tumor cell proliferation, decreased tumor cell adhesion to the extracellular matrix, and altered progenitor cell phenotype. Time-lapse confocal imaging of tumor cells in brain slice cultures demonstrated blood vessel co-option by tumor cells and highlighted differences in invasive pattern. Inhibition of EGFR signaling in pEGFR Hi promoted cell differentiation and increased cell-matrix adhesion. Conversely, increased EGFRvIII activation in pEGFR Lo reduced cell-matrix adhesion. Our study using a murine model for GBM driven by a single genetic driver, suggests differences in EGFR activation contribute to tumor heterogeneity and aggressiveness.