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 (miR326@SPION) and transfected them into HuECSCs. Results: In the present study, we found that the expression levels of members of the Gprotein 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 miR326 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.