Specific Isoform of Vascular Endothelial Growth Factor in Glioblastoma-Derived Exosomes Is Involved in Tumour Angiogenesis by Inhibiting Hippo Signalling Pathway

Background: Recently, several pieces of research verified that YAP/TAZ acted as downstream signalling molecules of VEGF involving in sprouting angiogenesis during embryonic development. We also found TAZ in endothelial cells is positively correlated with tumour vascular density in glioma. We speculate the role of glioblastoma-derived exosomes in promoting the expression of TAZ in endothelial cells. Methods: Exosomes were isolated from glioblastoma cell culture medium. VEGF subtypes in exosomes were identified by western blot and liquid chromatography-tandem mass spectrometry. Confocal immunofluorescent staining showed the co-localisation of PKH67-labelled exosomes and VEGFR 2 . Western blot and immunohistochemistry were used to detected protein expression. Bevacizumab or exosome inhibitor GW4869 was used for their blocking effects on glioblastoma angiogenesis. Findings: We found that glioblastoma-derived exosomes had a stimulatory effect on TAZ expression in endothelial cells. A special isformVEGF, 120 kDa, was found in glioblastoma-derived exosomes and confirmed as VEGF-C. The PKH67-labelled exosome co-localised with VEGFR 2 in endothelial cells. VEGF-C in glioblastoma-derived exosomes elevated the expression of TAZ by inhibiting the Hippo signalling pathway, which promoted the endothelial cell viability, migration, and tubulation. GW4869, an exosome release inhibitor, had a cooperative inhibitory effect with bevacizumab on LN229 cell xenograft subcutaneous tumour growth, microvessel density, and the expression of TAZ in endothelial cells. Interpretation: Our study highlights the unique properties of glioblastoma-derived exosomes in angiogenesis, which might help to explore new strategies for glioblastoma treatment. Funding Statement: Research reported in this paper was supported by funding from Chinese National Nature Science Foundation (Grant No. 81972356). Declaration of Interests: No potential conflict of interest was reported by the authors. Ethics Approval Statement: Animal experiments were carried out after receiving approval from the Institutional Animal Care and Use Committee (IACUC) of Fudan University (20180302-051).