Engineered extracellular vesicles enriched with the <scp>miR</scp> ‐214/199a cluster enhance the efficacy of chemotherapy in ovarian cancer

Recurrent ovarian cancer (OC) remains a major cause of mortality due to chemoresistance and metastasis. Epigenetic aberrations, particularly dysregulated microRNA (miRNA) expression, contribute to disease progression and represent a promising therapeutic target. Here, we identify the miR-214-3p/miR-199a-5p cluster as a stage-associated, tumor-suppressive network that is lost in recurrent and chemoresistant OC but can be elevated using engineered small extracellular vesicles enriched with this miRNA cluster (m214-sEVs). Using a clinically relevant mouse model that recapitulates spontaneous OC relapse following platinum-based chemotherapy, we show that m214-sEVs are internalized by OC cells and niche fibroblasts, leading to increased intracellular levels of this cluster and suppression of key chemoresistance-associated pathways, including through downregulation of Toll-like receptor 4 (TLR4), β-catenin, and the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein YKT6. m214-sEV treatment reprograms secondary tumor-derived sEVs toward a less prometastatic cargo profile and decreases carboplatin resistance and cell migration. Enforced YKT6 overexpression abrogates these effects, establishing YKT6 as a key downstream effector. Collectively, these findings support engineered sEVs as a translatable strategy to overcome chemoresistance and disrupt pro-tumorigenic EV signaling in recurrent OC.