ObjectiveTo explore the effect of miR-374a encapsulated by M2 macrophage exosomes on the malignant progression of prostate cancer(PCa) and explore its molecular mechanism.

MethodsBased on the successful establishment of M2 macrophages, the exosomes were extracted and identified, and the differentially expressed miRNAs in exosomes were detected. MiR-374a was verified in different PCa cells; M2 cells transfected with cy3 fluorescently labeled miR-374a were cocultured with PC3 cells, and the expression of cy3 fluorescence in PC3 cells was observed by fluorescence microscope; DU145 and PC3 cells were transfected with miR-374a inhibitor for cell function experiments. Forkhead box O1(FOXO1) was selected as the target gene through the database, which was verified by Western blotting, luciferase reporter gene assay and immunofluorescence experiment; after interfering with FOXO1, cell function experiments were carried out to observe whether miR-374a inhibitor could reverse the effects on DU145 and PC3 cells.

ResultsM2 cells were successfully established and their exosomes were extracted, and miR-374a was highly expressed in the exosomes of M2 cells; the results of fluorescence quantitative PCR showed that the expression of miR-374a in PC3 and DU145 cells was significantly higher than that in LNCaP cells, and the expression in M2 cells was higher than that in THP-1 cells. After co culture of PC3 cells and M2 cells, M2 cells could transmit miR-374a to PC3 cells through exosomes; knockdown of miR-374a expression in PC3 and DU145 cells significantly reduced their proliferation, migration ability and promoted their apoptosis. Knockdown of miR-374a expression in PC3 significantly reduced the subcutaneous tumor formation volume of nude mice; the results of Western blotting, luciferase reporter gene assay and immunofluorescence assay demonstrated that miR-374a could directly bind to FOXO1 and inhibit β-catenin enters nucleus and inhibits EMT in PCa cells; the results of rescue experiment showed that transfection of si-FOXO1 could reverse the inhibitory effect of miR-374a on the migration of PC3 and DU145 cells.

ConclusionsM2 cells can deliver miR-374a into PCa cells through exosomes to target FOXO1 and inhibit its malignant progression.