Intervening in hnRNPA2B1-mediated exosomal transfer of tumor-suppressive miR-184-3p for tumor microenvironment regulation and cancer therapy.

Background: Despite being a common malignant tumor, the molecular mechanism underlying the initiation and progression of triple-negative breast cancers (TNBCs) remain unclear. Tumor-associated macrophages (TAMs) are often polarized into a pro-tumor phenotype and are associated with a poor prognosis of TNBCs. Exosomes, important mediators of cell-cell communication, can be actively secreted by donor cells to reprogram recipient cells. The functions and molecular mechanisms of tumor cell-derived exosomes in TNBCs progression and TAMs reprogramming urgently need to be further explored.

Results: We demonstrated that tumor cell-derived exosomes enriched with miR-184-3p were taken up by macrophages to inhibit JNK signaling pathway by targeting EGR1, thereby inducing M2 polarization of macrophages and synergistically promoting tumor progression. Nanoparticles loaded with oncogene c-Myc inhibitor JQ1 could suppress the polarization process by reducing Rac1-related exosome uptake by macrophage. More importantly, it was found for the first time that tumor-suppressive miR-184-3p was actively sorted into exosomes by binding to RNA-binding protein heterogeneous nuclear ribonucleoprotein A2B1 (hnRNPA2B1), thus facilitating tumor cell proliferation and metastasis by relieving the inhibitory effect of miR-184-3p on Mastermind-like 1 (MAML1). Overexpressing miR-184-3p in tumor cells and simultaneously knocking down hnRNPA2B1 to block its secretion through exosomes could effectively inhibit tumor growth and metastasis.

Conclusions: Our study revealed that hnRNPA2B1-mediated exosomal transfer of tumor-suppressive miR-184-3p from breast cancer cells to macrophages was an important mediator of TNBCs progression, providing new insights into TNBCs pathogenesis and therapeutic strategies.