Nanog+F10-Derived Extracellular Vesicles Suppress Melanoma Metastasis, Implicating miR-19a-3p in Macrophage-Dependent Innate Immune Regulation

Background/Objectives: Extracellular vesicles (EVs) participate in tumor progression and immune regulation through the transfer of bioactive molecules. Although tumor-derived EVs are generally considered to promote metastasis, accumulating evidence suggests that their functions vary according to the biological characteristics of their cells of origin. This study investigated the mechanisms underlying the anti-metastatic effects of EVs derived from Nanog-overexpressing melanoma cells (Nanog+F10-EVs). Methods: Nanog+F10-EVs were isolated and characterized by EV marker expression. Their anti-metastatic activity was evaluated using melanoma liver metastasis models in Rag2-deficient and macrophage-depleted mice. Differential miRNA expression analysis was performed to identify candidate functional mediators. Functional studies were conducted using miR-19a-3p-overexpressing cells and EVs. Results: Nanog+F10-EVs significantly suppressed melanoma metastasis. Rag2 deficiency only modestly affected this activity, whereas macrophage depletion abolished the anti-metastatic effect, suggesting a predominant role of innate immunity. miRNA profiling identified miR-19a-3p as a candidate mediator enriched in Nanog+F10-EVs. Despite promoting tumor cell proliferation and migration, miR-19a-3p-enriched EVs partially reproduced anti-metastatic activity. Macrophage marker analysis suggested that these effects were not fully explained by classical M1/M2 polarization. Conclusions: Nanog+F10-EVs may suppress metastasis through macrophage-dependent innate immune regulation potentially mediated by miR-19a-3p and are consistent with a model of preemptive immune education.