miRNome and Proteome Profiling of Small Extracellular Vesicles Secreted by Human Glioblastoma Cell Lines and Primary Cancer Stem Cells

Glioblastoma (GBM) is the most common and aggressive brain tumor in adults. Despiteavailable therapeutic interventions, it is very difficult to treat, and a cure is not yet available. Theintra-tumoral GBM heterogeneity is a crucial factor contributing to poor clinical outcomes. GBMderives from a small heterogeneous population of cancer stem cells (CSCs). In cancer tissue, CSCsare concentrated within the so-called niches, where they progress from a slowly proliferating phase.CSCs, as most tumor cells, release extracellular vesicles (EVs) into the surrounding microenvironment.To explore the role of EVs in CSCs and GBM tumor cells, we investigated the miRNA and proteincontent of the small EVs (sEVs) secreted by two GBM-established cell lines and by GBM primary CSCsusing omics analysis. Our data indicate that GBM-sEVs are selectively enriched for miRNAs that areknown to display tumor suppressor activity, while their protein cargo is enriched for oncoproteins andtumor-associated proteins. Conversely, among the most up-regulated miRNAs in CSC-sEVs, we alsofound pro-tumor miRNAs and proteins related to stemness, cell proliferation, and apoptosis. Collectively,our findings support the hypothesis that sEVs selectively incorporate different miRNAs and proteinsbelonging both to fundamental processes (e.g., cell proliferation, cell death, stemness) as well as to morespecialized ones (e.g., EMT, membrane docking, cell junction organization, ncRNA processing).