Dissecting the role of cellular subpopulation harboring activating EGFRΔ mutation in Glioblastoma tumor architecture

Introduction The dispersive nature and the heterogeneous phenotype of glioblastoma (GBM) brain tumors imposes a great challenge for therapy. Most surgeries result in incomplete removal of the tumor, leading in most cases to a recurrence of the disease. Primary GBM frequently harbor epidermal growth factor receptor amplifications (EGFR+). In addition, ~50% of GBM patients may harbor activating mutation, EGFRΔ. It was previously demonstrated that minor intra-tumor subpopulation, harboring EGFRΔ, may enhance tumorigenicity of the entire tumor. We examine the cross-talk between the intra-tumor subpopulations harboring EGFRΔ and EGFR+ respectively, aiming to test its potential role in GBM architectures. This study may add an important layer to our understanding of how infiltrative GBM architectures can be manipulated.

Materials and Methods: U87 human GBM cells, overexpressing EGFR (U87EGFR+) were either co-cultured with U87EGFRΔ or grown under U87EGFRΔ condition medium (CM) to examine how communication between the two different subpopulations, though, for example, secreted factors, may influence GBM architectures. Cell live imaging and Western blot analysis were utilized to characterize different parameters of cell movement in 2D and 3D structures and the molecular mechanism influencing the cellular architectures and cell movement.

Results U87EGFRΔ cells increased the velocity and the length of migration of U87EGFR+ cells when the cells were co-cultured with or grown under U87EGFRΔ CM. Moreover, U87EGFRΔ cells increased significantly the ability of U87EGFR+ to spread. These phenotypes corresponded to the activation of pSrc signaling in U87EGFR+ when were co-cultured with or grown under U87EGFRΔ CM. pSrc inhibitor, dasatanib, used at very low concentrations, reduced significantly the ability of the GBM population to spread out, whereas other inhibitors, such as erlotinib (EGFR inhibitor) didn’t.

Conclusions EGFRΔ-subpopulation can influence GBM infiltrative phenotypes through activation of pSrc signaling in the tumor population. Our findings suggest that treating GBM tumor with pSrc inhibitors at very low doses that do not necessarily influence the cellular proliferation, may be especially useful strategy to reduce the GBM infiltration within the brain, thereby enabling more effective surgical tumor removal.