Magnesium isoglycyrrhizinate (MI), a magnesium salt of 18α-GA stereoisomer, has been reported to exert efficient hepatoprotective activity. However, its effect on bladder cancer remains unclear. The study explored the effects of MI on the growth, colony formation, apoptosis, invasion, and migration of bladder cancer cells (HTB9 and BIU87 cells). Typical apoptotic changes of bladder cancer cells such as nuclear concentration and fragmentation were observed using Hoechst staining. The effects of MI on the expression levels of microRNA-26b (miR-26b), NADPH oxidase 4 (Nox4), nuclear transcription factor-κB (NF-κB), and hHypoxia inducible factor-1α (HIF-1α) were detected using qRT-PCR and Western blot. The potential targets of miR-26b were predicted using Targetscan, and their interactions were determined by luciferase reporter assay. A xenograft mouse model was established to evaluate the anti-tumor effects of MI in vivo. MI significantly suppressed the proliferation, colony formation, invasion, and migration and induced apoptosis of human bladder cancer cells, and MI significantly increased miR-26b expression. Nox 4 was identified to be a direct target of miR-26b. MiR-26b mimics significantly decreased the relative luciferase activity of wild type (WT) Nox 4 but not mutant type (MUT) Nox4. Meanwhile, MI markedly downregulated the expression levels of Nox4, NF-κB, and HIF-1α both in vitro and in vivo. Moreover, MI inhibited xenograft tumor growth in vivo and decreased the expression of Nox4, NF-κB, and HIF-1α. Overall, MI showed a potent anti-tumor effect against bladder cancer partially via modulating the miR-26b/Nox4 axis.
Keywords: Magnesium isoglycyrrhizinate; Nox4/ NF-κB/HIF-1α; apoptosis; bladder cancer; miR-26b.