EGFR and EGFRvIII coopt host defense pathways, promoting progression in glioblastoma.

Background: Co-amplification of EGFR and EGFRvIII, a tumor-specific truncation mutant of EGFR, represent hallmark genetic lesions in glioblastoma.

Methods: We used phospho-proteomics, RNA-sequencing, TCGA data and glioblastoma cell culture and mouse models to study the signal transduction mediated by EGFR and EGFRvIII.

Results: We report that EGFR and EGFRvIII stimulate the innate immune defense receptor Toll-like Receptor 2 (TLR2); and that knockout of TLR2 dramatically improved survival in orthotopic glioblastoma xenografts. EGFR and EGFRvIII activated TLR2 in a ligand-independent manner, promoting tumor growth and immune evasion. We show that EGFR and EGFRvIII cooperate to activate the Rho-associated protein kinase ROCK2, which modulated malignant progression both by activating TLR2 and WNT signaling, and through remodeling the tumor microenvironment.

Conclusion: Together, our findings show that EGFR and EGFRvIII cooperate to drive tumor progression through ROCK2 and downstream WNT-β-catenin/TLR2 signaling pathways.