Tiny Messengers, Actionable Targets: sEV-Driven Epigenetic Changes in Cancer

Small extracellular vesicles (sEVs) are pivotal mediators of intercellular epigenetic communication in cancer. Following MISEV2023, we use the size- and isolation-based term sEV throughout, because most primary studies cited here cannot resolve which biogenetic route generated the vesicles they analyzed. By selectively packaging and transferring noncoding RNAs (ncRNAs), DNA fragments, chromatin-modifying enzymes, and metabolic effectors, sEVs reprogram recipient-cell chromatin architecture without altering the underlying DNA sequence. Tumor-derived sEVs engage stromal, immune, and vascular compartments to drive malignant progression through mechanisms that include miRNA-directed suppression of DNA methyltransferases (DNMTs), lncRNA-scaffolded Polycomb Repressive Complex 2 (PRC2) recruitment, depositing H3K27me3, and oncometabolite-mediated inhibition of TET dioxygenases. This narrative review synthesizes mechanistic, preclinical, and translational evidence on sEV-driven epigenetic regulation in cancer, applies a four-level evidence hierarchy to calibrate mechanistic claims, and critically evaluates how distinct cargo classes–microRNAs (miRNAs), long noncoding RNAs (lncRNAs), circular RNAs (circRNAs), DNMTs, and histone-modifying enzymes–contribute to chromatin remodeling, aberrant DNA methylation, acquired therapy resistance, and immune evasion in recipient cells. We further examine sEV cargo signatures as minimally invasive liquid biopsy biomarkers and appraise engineered sEV platforms for the precision delivery of miRNA mimics, siRNAs, and small-molecule epigenetic inhibitors. Key methodological challenges, EV isolation standardization, MISEV2023 compliance, cargo stoichiometry at physiological concentrations, in vivo biodistribution, and the transition from post-transcriptional regulation to durable chromatin-state change are critically evaluated, and a translational roadmap is proposed to guide reproducible clinical implementation of sEV-mediated epigenetic cancer therapeutics.