EGFRvIII Reduces Neural Stem/Progenitor Marker Expression in GFAP-Negative iNSCs: Evidence for a Context-Dependent Cellular Response.

Epidermal growth factor receptor variant III (EGFRvIII) is a constitutively active EGFR deletion variant found in a subset of glioblastomas (GB). Its association with stem-like tumor populations is well documented, but the outcome of EGFRvIII expression may vary with the developmental and molecular state of the recipient cell. Here, we used human induced pluripotent stem cell (iPSC)-derived, glial fibrillary acidic protein (GFAP)-negative-induced neural stem cells (iNSCs) to explore how this receptor variant affects a defined neural stem/progenitor background. EGFRvIII was introduced either constitutively by lentiviral transduction or through a doxycycline-responsive Tet-On system. Both experimental approaches were associated with remodeling of the neural stem/progenitor marker profile, with reduced SRY-box transcription factor 2 (SOX2) expression in the inducible model and significant reductions in both SOX2 and nestin in the constitutive model. Constitutive expression was also associated with increased senescence-associated β-galactosidase (SA-β-Gal) activity, while doxycycline induction produced a distinct change in cell-number dynamics at low doxycycline concentration. Thus, in this experimental setting, EGFRvIII was linked to substantial remodeling of the SOX2+/nestin+ marker profile. These observations do not define a differentiation pathway, prove cellular senescence or malignant transformation, or identify the cell of origin of EGFRvIII-positive GB. Rather, they support the view that the cellular response to EGFRvIII should be considered in relation to the specific neural-glioblastoma precursor context.