Biophysical Interrogation of Signals that Drive GBM Invasion

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One major issue confounding successful treatment of glioblastoma multiforme (GBM) is the presence of highly invasive cells disseminating into the brain parenchyma. These cells evade surgical resection and often spread distally in brain parenchyma. Multiple and spatially distinct heterotypic populations exist within a single GBM, giving rise to the disease’s genetic heterogeneity and leading to complex cell intrinsic and extrinsic mechanisms of invasion. Amplification of the epidermal growth factor receptor (EGFR), a hallmark mutation present in 60% of cases, most often occurs in a heterogeneous manner and is frequently associated with deletion of exons 2-7, creating a constitutively active mutant, EGFRvIII. While significant focus has been placed on its kinase activity, comparatively little is known about EGFRvIII’s ability to enhance migration via interaction with adhesion receptors. Our preliminary data supports a dual role for EGFRvIII where it interferes with intrinsic adhesion receptors and also recruits non-transformed counterparts via extrinsic signaling to reduce adhesion of a mixed population. Based on our findings, we hypothesize that this difference in adhesive activity is due to differential signaling associated with EGFRvIII, and that this receptor conveys this phenotype to non-transformed counterparts through cytokine production (Inda, Genes & Dev, 2010; Zanca, Genes & Dev, 2017) to cooperatively invade parenchyma. With this hypothesis, we will use adhesion measurement technologies to dissect cell intrinsic EGFR-mediated invasion mechanisms; given the heterogeneity within tumors, we will also combine newly developed adhesion sorting technologies with high throughput sequencing technologies to identify cell extrinsic mechanisms and targets for subsequent intervention. The following lines of experimentation will be carried out: 1) implementation of biophysical assays and signaling pathway analyses to interrogate how cell intrinsic activity of EGFRvIII leads to labile adhesion and an invasive phenotype; 2) biochemical and functional analysis of the EGFRvIII cell extrinsic, secretome-mediated education of wtEGFR cell adhesive phenotype; 3) expression and epigenetic analyses on adhesion-sorted populations will be used to define a migratome signature, its stability in wtEGFR cells after exposure to the EGFRvIII secretome, and the ability of “educated” wtEGFR to propagate that epigenetic signature to naïve wtEGFR cells.