Small Extracellular Vesicles Released from Glioma Cells Under Hypoxic Conditions Induce Pericyte-phenotype Transition of Glioma Stem Cells.

Abstract Background:The prognosis of malignant glioblastoma (GBM) is dismal despite advances in surgery, radiation and chemotherapy treatments. Thus, alternative therapy strategies are urgently needed. Antiangiogenic therapy for cancer offers the possibility of universal efficacy. However, preclinical and clinical studies suggest that this therapy using anti-VEGF drug Avastin (Bevacizumab) may lead to a pro-migratory phenotype in therapy resistant GBM and thus actively promote tumor invasion and recurrent tumor growth. Methods: An ultracentrifugation strategy was used to isolate glioma-derived sEVs under hypoxic or normoxic conditions. Transmission electron microscopy (TEM), Western blotting, and nanoparticle tracking analysis (NTA) were used to characterize these isolated particles. Cytochalasin D was added to disrupt cellular sEVs uptake. A tube formation assay was used to evaluate angiogenic activity, while ELISAs and Western blotting were used to assess the activated TGF-β signaling pathway. The effects of sEVs on glioma stem cells (GSCs) in vivo were evaluated using subcutaneous xenografts model system in nude mice. Immunofluorescence and immunohistochemical staining were set out to evaluate the pericyte-phenotype transition of GSCs.Results: In this present study, we showed that hypoxia could promote the release of sEVs by glioblastoma cells and hypoxia-induced glioma-derived sEVs could be taken up by GSCs. This internalization of sEVs promoted tumor growth in mouse Xenografts through the pericyte-phenotype transition of GSCs. We also demonstrated hypoxia-derived sEVs can efficiently deliver TGF-β1 to GSCs. The activated TGF-β signaling pathway mediated this kind of phenotype transition. In addition, combination of Ibrutinib and Bevacizumab showed more effective in targeting GBM. Conclusion: This present study provides a new interpretation to the failure of antiangiogenesis therapy in noncurative surgical resection of GBM, and discovers promising brain-specific therapeutic targets for this damaging tumor.