Tumor-Derived miR-378a-3p-Containing Extracellular Vesicles Promote Osteolysis by Activating a Dyrk1a/Nfatc1/Angptl2 Axis for Bone Metastasis
Abstract Background The majority of the deaths of prostate cancer (PCa) are caused by progression to bone metastatic PCa. The importance of extracellular vesicles (EVs) in the formation of the pre-metastatic niche has been demonstrated in recent years. However, whether and how tumor-derived EVs interact with bone marrow macrophages (BMMs) to release EV-delivered microRNAs to promote osteolysis and to activate pre-metastatic niche formation for PCa bone metastasis remain unclear. Methods Bioinformatics and qRT-PCR analyses were used to screen microRNAs and to identify the elevated expression of miR-378a-3p in both serum-derived EVs from PCa patients and in culture medium-derived EVs from PCa cell lines. Functional assays in vitro and in vivo were performed to investigate the functions of miR-378a-3p during PCa progression. IF staining and Dual-luciferase reporter, co-IP, western blot, RIP and ChIP assays were conducted to reveal the underlying mechanism. Results We found that EV-mediated release of miR-378a-3p from tumor cells was upregulated in bone-metastatic PCa which keeps a low intracellular concentration of miR-378a-3p, to promote proliferation and the MAOA-mediated epithelial-to-mesenchymal transition (EMT) in PCa cells. In addition, we demonstrated that the enrichment of miR-378a-3p in tumor derived EVs was induced by overexpression of hnRNPA2B1 as a transfer chaperone. After miR-378a-3p-enriched EVs were taken in by BMMs, elevated intracellular concentration of miR-378a-3p promoted osteolytic progression by targeting the Dyrk1a/Nfatc1 pathway. Mechanistically, inhibition of Dyrk1a by miR-378a-3p improved the nuclear translocation of Nfatc1 to promote expression of the downstream target gene Angptl2. As a feedback, increased secretion of Angptl2 into the tumor environment promoted PCa progression. Conclusions Our findings indicate that tumor-derived miR-378a-3p-containing EVs play a significant role in promoting prostate cancer bone metastasis by activating a Dyrk1a/Nfatc1/Angptl2 axis in BMMs to induce osteolytic progression, which implicates that miR-378a-3p may be a potential predictor of metastatic PCa. Moreover, reducing the release of miR-378a-3p-containing EVs or inhibiting the recruitment of miR-378a-3p into tumor-derived EVs might be a potential therapeutic strategy for PCa metastasis.