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Glioblastoma-derived extracellular vesicles facilitate transformation of astrocytes via reprogramming oncogenic metabolism

ABSTRACT: Background: Glioblastoma (GBM) may arise from brain astrocytes through a multistep process that occurs by the temporal accumulation of genetic mutations. Here, we explore whether GBM-derived extracellular vesicles (EVs) may facilitate neoplastic transformation and malignant growth of astrocytes. Methods: We utilized conditioned medium (CM) of glioma cell and stem cell, its sequential filtration, diverse cell-based assays, RNA sequencing, and metabolic assays to compare the effects of EV-containing and EV-depleted CM on the transformation of human and mouse astrocytes in vitro and tumor growth in vivo. Results: GBM EVs facilitated the neoplastic growth of astrocytes pre-transformed by oncogenic mutations or viruses but were unable to transform normal human and mouse astrocytes. GBM EVs induced proliferation, self-renewal, and colony formation of pre-transformed astrocytes, and enhanced astrocytoma growth in a mouse allograft model. Analysis of extracellular RNAs (exRNAs) in GBM identified multiple full-length mRNAs encoding ribosomal proteins, oxidative phosphorylation, and glycolytic factors. GBM EVs appear to reprogram astrocyte metabolism by inducing a shift in gene expression that may be partly associated with EV-mediated mRNA transfer from glioma cells. Conclusions: Our study suggests a novel EV/exRNA-mediated mechanism contributing to astrocyte transformation via metabolic reprograming and implicates horizontal mRNA transfer in this process.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE143189 | GEO | 2020/07/12

REPOSITORIES: GEO

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Project description:Glioblastoma multiforme (GBM) is a highly aggressive and heterogeneous form of primary brain tumors, driven by a complex repertoire of oncogenic alterations, including the constitutively active epidermal growth factor receptor (EGFRvIII). EGFRvIII impacts both cell-intrinsic and non-cell autonomous aspects of GBM progression, including cell invasion, angiogenesis and modulation of the tumor microenvoiront, this is, at least in part, attributable to the release and intercellular trafficking of extracellular vesicles (EVs), heterogeneous membrane structures containing multiple bioactive macromolecules. Here we analyzed the impact of EGFRvIII on the profile of glioma EVs using a series of isogenic tumor cell lines, in which this oncogene exhibits a strong transforming activity. Thus, we observed that EGFRvIII expression alters several properties of glioma EVs, including their output and global protein composition. Using mass spectrometry, quantitative proteomic analysis and Gene Ontology terms filters, we observed that EVs released by EGFRVIII-transformed cells were enriched for extracellular exosome and focal adhesion related proteins. Among them, we validated the association of pro-invasive proteins (CD44, BSG, CD151) with EVs of EGFRvIII expressing cells, and down-regulation of exosomal markers (CD81 and CD82) in EVs of their indolent counterparts. Nano-flow cytometry revealed that the EV output from individual glioma cell lines was highly heterogeneous, such that only a fraction of EVs contained specific proteins such as EGFR, CD9, or others. Notably, cells expressing EGFRvIII released ample EVs double positive for CD44/BSG, and these proteins also co-localized in cellular filopodia. We also detected the expression of homophilic adhesion molecules and increased homologous EV uptake by EGFRvIII-positive glioma cells. These results suggest that oncogenic EGFRvIII reprograms the proteome of GBM-related EVs, a notion with considerable implications for their biological activity and properties relevant for development of EV-based cancer biomarkers.

Project description:Background: Glioma-associated macrophages (GAMs) are one of the most important cellular components in the tumor immune microenvironment (TIME). GAMs display a mostly M2-like phenotype with anti-inflammatory features, which is closely related to the malignancy and progression of cancers. Extracellular vesicles derived from GAMs (GAM-EVs), which are important components of the TIME, contain a variety of microRNAs (miRNAs). These miRNAs play a crucial role in communication between tumor cells and GAMs. In this study, we aimed to explore the effect of GAM-EVs on the malignancy and progression of glioblastoma multiforme (GBM) through miRNA-mediated communication and its possible signaling pathway. Methods: The GBM and LGG data from The Cancer Genome Atlas (TCGA) were analyzed, and the immunological features of 12 clinical glioma samples, including GBM and low-grade glioma (LGG) samples, were estimated by immunohistochemistry. To evaluate the changes induced by M2-EVs compared to M1-EVs, the human GBM cell lines U87MG and A172 were cocultured with M2-EVs and M1-EVs, and their epithelial-mesenchymal transition (EMT) behaviors were investigated. The contents of M2-EVs and M1-EVs were determined by miRNA sequencing, and the differences were analyzed. Then, the EMT signatures were evaluated after a miRNA mimic was transfected into GBM cells. Six databases were used to predict the targets of the miRNA. Human GBM cell lines with interference and overexpression of the most valuable candidate miRNA targets were established. The related signaling pathways were further explored. Finally, an orthotopic homograft mouse model was employed to verify the results of the in vitro experiments. Results: The immunosuppressive GAM genes were upregulated in GBM compared with LGG, showing that the TIME of GBM is more immunosuppressive. To explore the effect of the immunosuppressive GAMs and TIME on the progression of GBM, we established immunostimulatory (M1-like) and immunosuppressive (M2-like) GAMs and compared the differences in their EVs. The migration and invasion of U87MG and A172 cells were enhanced under coculture with M2-EVs. MiR-146a-5p was deficient in M2-EVs compared with M1-EVs. Upon treatment with the miR-146a-5p mimic, the migration and invasion abilities of GBM cells were weakened, and the EMT signature was correspondingly decreased. According to the database prediction, tumor necrosis factor receptor-associated factor 6 (TRAF6) and interleukin 1 receptor-associated kinase 1 (IRAK1) are the targets of miR-146a-5p. TRAF6 is an E3 ubiquitin ligase, and IRAK1 is the substrate. Bimolecular fluorescence complementation (BiFC) and coimmunoprecipitation assays confirmed interactions between TRAF6 and IRAK1. Interference with both TRAF6 and IRAK1 expression weakened but overexpression of both TRAF6 and IRAK1 promoted the EMT behaviors of GBM cells. The TRAF6-Glioma-associated macrophages (GAMs) are pivotal chains in the tumor immune microenvironment (TIME). GAMs mostly display M2-like phenotypes with anti-inflammatory features related to the malignancy and progression of cancers. Extracellular vesicles derived from immunosuppressive GAMs (M2-EVs), the essential components of the TIME, greatly impact the malignant behavior of GBM cells. M1- or M2-EVs were isolated in vitro, and human GBM cell invasion and migration were reinforced under M2-EV treatment. Signatures of the epithelial-mesenchymal transition (EMT) were also enhanced by M2-EVs. Compared with M1-EVs, miR-146a-5p, considered the key factor in TIME regulation, was deficient in M2-EVs according to miRNA-sequencing. When the miR-146a-5p mimic was added, EMT signatures and the invasive and migratory abilities of GBM cells were correspondingly weakened. Public databases predicted the miRNA binding targets and interleukin 1 receptor-associated kinase 1 (IRAK1) and tumor necrosis factor receptor-associated factor 6 (TRAF6) were screened as miR-146a-5p binding genes. Bimolecular fluorescent complementation and coimmunoprecipitation confirmed interactions between TRAF6 and IRAK1. The correlation between TRAF6 and IRAK1 was evaluated with immunofluorescence (IF)-stained clinical glioma samples. The TRAF6-IRAK1 complex is the switch and the brake that modulates IKK complex phosphorylation and NF-κB pathway activation, as well as the EMT behaviors of GBM cells. Furthermore, a homograft nude mouse model was explored and mice transplanted with TRAF6/IRAK1-overexpressing glioma cells had shorter survival times while mice transplanted with glioma cells with miR-146a-5p overexpression or TRAF6/IRAK1 knockdown lived longer. This work indicated that in the TIME of GBM, the deficiency of miR-146a-5p in M2-EVs enhances tumor EMT through disinhibition of the TRAF6-IRAK1 complex and IKK-dependent NF-κB signaling pathway providing a novel therapeutic strategy targeting the TIME of GBM.

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Glioblastoma-derived extracellular vesicles facilitate transformation of astrocytes via reprogramming oncogenic metabolism

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