Inhibitory effect of DNA topoisomerase inhibitor isoliquiritigenin on the growth of glioma cells

Objective: To investigate the effect of isoliquiritigenin on the activity of DNA topoisomerase (TOP I) and its inhibitory effect on the growth of U87 glioma cells. Methods: This study investigated the inhibitory effect of isoliquiritigenin on the growth of U87 glioma cells and its cytotoxicity by MTT method and determined the effect of isoliquiritigenin on TOP I activity by agarose gel electrophoresis. On this basis, we studied the interaction between isoliquiritigenin and TOP I and DNA. Finally, we further discussed the effect of isoliquiritigenin on the activity of Caspase 3, the apoptosis protein of U87 glioma cells. Results: Isoliquiritigenin could inhibit the growth of U87 glioma cells (half inhibitory concentration IC50: 0.221 mM) and is of low cytotoxicity to normal cells. Agarose gel electrophoresis showed that isoliquiritigenin had significant inhibitory effect on TOP I activity. Molecular simulation results indicated that isoliquiritigenin took priority of binding to the active center of TOP I, and formed hydrogen bonds with the catalytic site Try723. Finally, Caspase 3 activity detection results suggested that isoliquiritigenin could significantly increase the activity of Caspase 3 (P < 0.05). Conclusion: Isoliquiritigenin had a reversible inhibitory effect on TOP I activity, reduced the rate of single strand DNA unwinding in tumor cells, and thus played an important role in inducing the apoptosis of U87 glioma cells.