Tumour exosomes from cells harbouring PTPRZ1-MET fusion contribute to a malignant phenotype and temozolomide chemoresistance in glioblastoma

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Exosomes are carriers of pro-tumorigenic factors that participate in glioblastoma (GBM) progression, and many fusion genes are strong driver mutations in neoplasia and are involved in tumorigenesis. However, the ability of fusion genes to be transduced by exosomes is unknown. We characterized exosomes from GBM cells harbouring and not harbouring PTPRZ1-MET fusion (ZM fusion). We also determined the effect of the exosomes from ZM fusion cells (ZM exosomes) on pro-oncogenic secretions and showed that ZM exosomes are internalized by the recipient cells. In addition, we studied the effect of ZM exosome-mediated intercellular communication in the GBM microenvironment. MET proto-oncogene expression was higher in ZM exosomes. Moreover, phosphorylated MET was detected only in ZM exosomes and not in exosomes released by non-ZM fusion GBM cells. ZM exosomes transferred to non-ZM fusion GBM cells and normal human astrocytes altered gene expression and induced epithelial-mesenchymal transition. The uptake of ZM exosomes also induced an exosome-dependent phenotype defined by GBM cell migration and invasion, neurosphere growth and angiogenesis. In addition, ZM exosomes conferred temozolomide resistance to the GBM cells, and exosomederived ZM fusion network proteins targeted multiple pro-oncogenic effectors in recipient cells within the GBM microenvironment. Our findings show that exosomes mediate the aggressive character of GBM and demonstrate the role of ZM fusion in the exacerbation of this effect. These findings have possible implications for the foundation of gene fusion-based therapy for managing GBM.

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