TWEAK-stimulated macrophages inhibit metastasis of epithelial ovarian cancer via exosomal shuttling of microRNA.

Exosomal-miRNAs are emerging as mediators of crosstalk between tumor cells and macrophages. In this study, we observed that exosomes derived from TWEAK-stimulated macrophages (TMs) could be internalized by epithelial ovarian cancer (EOC) cells and inhibit cell metastasis. Through a miRNA microarray analysis, we identified 19 miRNAs that are differentially expressed in exosomes derived from macrophages treated with or without TWEAK. The study validated that TWEAK not only increased the levels of microRNA-7 (miR-7) in macrophages and its secreted exosomes but also resulted in an elevated level of miR-7 in recipient EOC cells, which eventually reduced the activity of the EGFR/AKT/ERK1/2 pathway. Pre-transfection of antagomiR-7 in TMs substantially decreased the levels of miR-7 in macrophages, its secreted exosomes and the recipient EOC cells with a concomitant enhancement of EOC metastasis, suggesting an involvement of exosomal miR-7 from TMs in modulating the metastasis of EOC cells. Finally, the exosomes from TMs significantly blocked EOC metastasis in a xenograft mouse model. These findings provide a novel model in which TMs inhibit the metastasis of EOC cells via shuttling of exosomal miR-7 to EOC cells, thereby inhibiting the EGFR/AKT/ERK1/2 pathway.