The Role Of Extracellular Vesicles In The Malignant Phenotype Of Glioma And Temozolomide Resistance

Part One: Exosomal Transfer of mi R-151 a Enhances Chemosensitivity to Temozolomide in Drug-resistant GlioblastomaBackground.Chemoresistance blunts the effect of Temozolomide(TMZ)in the treatment of glioblastoma multiforme(GBM).Whether exosomal transfer of mi RNAs derived from TMZ-resistant GBM cells could confer TMZ resistance re-mains to be determined.Methods.q PCR was used to determine mi R-151 a expression in two TMZ-resistant GBM cell lines.The direct targets of mi R-151 a were identified by microarray assays,bioinformatics and further RNA chromatin immunoprecipitation(RNA-Ch IP)assay.We characterized exosomes from TMZ-resistant cell lines,serum and cerebrospinal fluid(CSF)and determined the effect of exosomes from TMZ-resistant cells on recipient GBM cells.Results.mi R-151 a loss drove the acquisition of TMZ resistance.Restored mi R-151 a expression sensitized TMZ-resistant GBM cells via inhibiting XRCC4-mediated DNA repair.TMZ-resistant GBM cells conferred TMZ chemoresistance to recipient TMZ-sensitive cells in an exosomal mi R-151 a loss-dependent manner.Restoration of exosomal mi R-151 a from donor TMZ-resistant cells abolished the chemoresistance dissemination that was directed by donor TMZ-resistant cells.CSF-derived exosomes contained mi RNA signatures reflective of the underlying chemore-sistant status of GBMs in terms of mi R-151 a expression levels.Conclusions.Exosomal miR-151 a is not only essentially a less-invasive ‘liquid biopsy' that might predict chemotherapy response,but also represents a promising therapeutic target for therapy-refractory GBMs.Part Two: Exosomes from Cells Harboring PTPRZ1-MET Fusion Contribute to a Malignant Phenotype and Temozolomide Chemoresistance in GlioblastomaBackground.It is validated that exosomes are carriers of pro-tumorigenic factors that participate in glioblastoma progression.Many gene fusions are strong driver mutations in neoplasia and are involved in tumorigenesis.However,whether gene fusions are transduced by exosomes is unknown.Methods.We characterized exosomes from the medium of glioblastoma cells harboring and not harboring PTPRZ1-MET fusion(ZM fusion).We also determined the effect of the ZM exosomes on pro-oncogenic secretions from the cells with ZM fusion and showed how exosomes are internalized into the recipient cells,and studied the effect of exosome-mediated intercellular communication in the glioblastoma microenvironment.Results.MET proto-oncogene expression was higher in exosomes from the cells with ZM fusion(ZM exosomes).Phosphorylated MET(p-MET)was detected only in ZM exosomes,and not in non-ZM exosomes.ZM exosomes transferred to non–ZM fusion glioblastoma cells and normal human astrocytes altered gene expression and induced mesenchymal–epithelial transition.The uptake of ZM exosomes induced an exosome-dependent phenotype defined by glioblastoma cell migration and invasion,neurosphere growth and angiogenesis.Additionally,ZM exosomes conferred temozolomide resistance to the glioblastoma cells.Exosomes-derived ZM fusion network proteins targeted multiple pro-oncogenic effectors in recipient cells within the glioblastoma microenvironment.Our findings show how exosomes mediate the aggressive character of glioblastoma and how ZM fusion can aggravate it,with possible implications for the foundation of gene fusion–based therapy for managing glioblastoma.