Circulating EV miRNA Cargo in Glioblastoma Patients Is Associated with Distinct Gene Expression Signatures in Peripheral Immune Cells, Suggesting an Early, Compartment-Specific Immune Priming State.

Background: Glioblastoma is the most lethal primary brain tumor, being characterized not only by marked intratumoral heterogeneity but also by strong systemic immunosuppression. Circulating extracellular vesicles (EVs) have gained growing recognition during the past decade as important mediators of intercellular communication, particularly through their microRNA (miRNA) cargo. However, the global EV miRNA landscape of circulating EV-associated miRNAs in glioblastoma patients and their relation with gene expression patterns in peripheral immune cells remain incompletely defined. Methods: To investigate these systemic associations, we profiled EV-associated miRNA expression in plasma samples from glioblastoma patients and matched healthy controls using the small RNA sequencing method, followed by differential expression and pathway analyses. Based on these findings and literature evidence, identified changes in selected EV miRNA levels were validated by qPCR in an extended cohort. In parallel, expression of their predicted immune-related mRNA targets was analyzed in peripheral blood mononuclear cells (PBMCs) obtained from the same individuals, allowing for the assessment of EV miRNA-PBMC mRNA correlation patterns. Results: Small RNA sequencing revealed a distinct circulating EV-associated miRNA profile in glioblastoma patients compared to controls. The validation analysis of relative expression of the identified DEmiRNAs has shown a statistically significant upregulation of hsa-miR-142-3p, hsa-miR-19b-3p, and hsa-miR-98-5p in circulating EVs of glioblastoma patients compared to controls. PBMCs from glioblastoma patients exhibited increased expression of the regulatory genes SOCS1, SOCS3, and PTEN, while CCND1 was downregulated. Correlation analyses suggested that certain EV miRNA changes parallel with alterations in PBMC gene expression in glioblastoma patients, suggesting early immune priming in the circulation. Conclusions: Our findings indicate that circulating EV miRNAs in glioblastoma patients are associated with specific gene expression patterns in peripheral immune cells, suggesting a complex regulatory balance between pro-inflammatory and anti-inflammatory cues, potentially preceding full tumor-associated macrophage polarization. These molecular interactions may offer opportunities for developing early biomarkers or new therapeutic approaches.