Dissecting the role of cellular subpopulation harboring activating EGFRvIII mutation in glioblastoma tumor architecture

Introduction: Glioblastoma multiforme (GBM) is a highly infiltrative brain cancer, rendering the tumor difficult to operate. Most surgeries result in incomplete tumor removal, leading to recurrence of the disease. Primary GBM frequently harbors EGFR amplifications (EGFRwt). In addition, ~50% of those patients may harbor activating mutation (EGFRvIII). It was previously shown that minor subpopulation, harboring EGFRvIII, may enhance the entire tumor`s tumorigenicity. We took a step forward by examining the relationship between the diffusive architectures of GBM tumors and the paracrine interactions between GBM subpopulations aiming to manipulate GBM infiltration.

Materials and Methods: U87 human GBM cells overexpressing wtEGFR (U87EGFRwt) were either co-cultured or grown under U87 expressing EGFRvIII (U87EGFRvIII) cells conditioned medium to examine whether the communication between two different subpopulations through secreted factors may influence GBM architectures. Infiltration properties of the cells were characterized using live cell imaging, 2D/3D cultures, proteomic analysis, patient derived cells and in vivo mice model.

Results: EGFRvIII cells modulate the infiltrative properties of EGFRwt cells through soluble factors, HGF and IL6, which activate Src protein in EGFRwt cells. Src activation was associated with enhanced EGFRwt cellular velocity and their ability to spread in 2D/3D cultures. Non-killing concentrations of Src inhibitor, Dasatinib, affected significantly the migration and diffusive properties of GBM cellular populations.

Conclusions: U87EGFRvIII-subpopulation enhances diffusive phenotypes in less aggressive cells. The scattered distributions of tumors harboring EGFRvIII mutation can be controlled through Src inhibition. Stopping tumor infiltration can enhance the surgical brain tumor removal and provide an additional means for therapeutic intervention.