Superparamagnetic iron oxide nanoparticle-mediated expression of miR-326 inhibits human endometrial carcinoma stem cell growth

Background: Previously, our group confirmed the presence of a subset of cancer stem cells in the tissues of endometrial carcinoma (ie, human endometrial carcinoma stem cells [HuECSCs]). However, the mechanisms by which microRNAs regulate the growth of HuECSCs remain elusive. Methods: We loaded miR-326 onto superparamagnetic iron oxide nanoparticles (miR-326@SPION) and transfected them into HuECSCs. Results: In the present study, we found that the expression levels of members of the G-protein coupled receptor 91 (GPR91)/signal transducer and activator of transcription 3 (STAT3)/vascular endothelial growth factor (VEGF) pathway were significantly elevated in CD44+/CD133+ HuECSCs. Luciferase reporter assays indicated that the succinate receptor 1 (SUCNR1) gene, also known as the G-protein coupled receptor 91 (GPR91) gene, was one of the potential targets of miR-326. Transmission electron microscopy revealed that the SPIONs could cross the cell membrane and accumulate in the cytoplasm. The overexpression of miR-326 significantly inhibited the proliferation and cell cycle progression of HuECSCs in vitro. MiR-326 overexpression also effectively inhibited the invasion and angiogenic capacities of HuECSCs in the extracellular matrix. Meanwhile, miR-326 overexpression significantly inhibited the tumorigenicity and tumour neovascularization capacity of HuECSCs in nude mice. Both quantitative real-time PCR and Western blotting confirmed that overexpression of miR-326 significantly reduced the expression of members of the GPR91/STAT3/VEGF pathway in HuECSCs, and the activity (level of phosphorylation) of key molecules in this pathway was also reduced. Conclusion: Collectively, we confirmed that SPIONs are highly efficient nanocarriers for nucleic acids, on which the loading of miR-326 inhibited the activation of the GPR91/STAT3/VEGF signaling pathway and significantly attenuated the activity of stem cells in endometrial carcinoma, both in vitro and in vivo.