Breast cancer-derived exosomal miR-92a-3p stimulates malignant progression by driving TLR4/NF-κB-mediated macrophage...

Breast cancer (BC) cell-derived exosomes significantly reshape the tumor microenvironment; however, the key mechanisms driving tumor progression remain unclear. This study employed transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blotting to analyze exosomes from MCF-10A normal breast epithelial cells and MDA-MB-231/MCF-7 breast cancer cells. Treatment of parental BC cells with tumor-derived exosomes markedly enhanced malignant characteristics, whereas exosomes from miR-92a-3p-knockdown cells reversed these malignant phenotypes. Bioinformatics analysis of the EVMiRNA database initially identified miR-92a-3p as the most prominently upregulated miRNA in blood exosomes from BC patients. This finding was validated by qRT-PCR, which demonstrated significant overexpression of miR-92a-3p in tumor-derived exosomes. Exosomal miR-92a-3p induced immunosuppressive M2 polarization of THP-1-derived macrophages, evidenced by upregulated mRNA levels of Arg-1, Ym1, and IL-10, an increased proportion of CD206⁺cells; and elevated IL-10 secretion accompanied by reduced TNF-α secretion. Mechanistically, the TLR4/NF-κB pathway in macrophages was activated by parental exosomes, resulting in increased expression of TLR4 and phosphorylated p65, whereas miR-92a-3p-knockdown exosomes inhibited this pathway activation. Importantly, we confirmed that miR-92a-3p directly targets the 3'untranslated region (3'UTR) of TLR4 using a luciferase reporter assay. In conclusion, tumor-derived exosomal miR-92a-3p exerts dual effects: it directly enhances the invasiveness of BC cells and promotes M2 polarization by activating the TLR4/NF-κB axis in macrophages, thereby accelerating tumor progression. These findings highlight the pivotal role of miR-92a-3p in tumor-exosome crosstalk and identify it as a promising therapeutic target for BC.