Effect Of Methylene Blue-Mediated Sonodynamic Action On Apoptosis And Metastasis Of Ovarian Cancer Cells

Background and objective: Ovarian cancer is the leading cause of death in gynecological cancer. Chemotherapy plays an important role in treatment of ovarian cancer, however, the long-term efficacy is still unsatisfactory. With the development of ultrasonics, sonodynamic therapy has become a new modality for treating tumor because of its advantages in tissue penetration in comparison with photodynamic therapy. Sonosensitizer is a key component affecting SDT's efficacy. Methylene blue(MB) is a second-generation photosensitizer from phenothiazine dye. Recen study showed that MB might be a sensitizer to enhance ultrasound therapy on tumor. Our aims are to explore the mechanism of MB-induced sonodynamic therapy on ovarian cancer cells.Materials/Methods: Cytotoxicity was detected using trypan blue exclusion test after treatment with MB-mediated SDT. Light microscope was used to observe the morphological changes of the HO-8910 cells. Apoptosis was evaluated using FCM with Annexin V-FITC/PI staining, and the nuclear staining with Hoechst 33258. Ultrastructure was observed by TEM. Mitochondrial membrane potential was evaluated using CLSM with rhodamine123 staining. Intracellular reaction oxygen species were detected by DCFH-DA staining. Finally, clone assay, invasion assay, migration assay, and adhesion assay were investigated in this study.Results: The cytotoxicity of MB-mediated SDT on HO-8910 cells after MB-mediated SDT was significantly higher than those of other treatments including ultrasound alone, MB alone and sham treatment. And the above finding was also confirmed by inverted light microscopy. Nuclear staining showed DNA condensation and fragmentation after MB-mediated SDT. FCM showed the MB-mediated SDT significantly increased the early or late apoptotic rate up to 7.91% and 18.17% compared to the controls. The apoptotic bodies of the HO-8910 cells can be found by TEM after MB-mediated SDT. The collapse of mitochondrial membrane potential and ROS increase were found in HO-8910 cells after MB-mediated SDT. And adhesive, migrative and invasive ability of HO-8910 cells were significant inhibited after MB-mediated SDT.Conclusion: MB-mediated SDT could significantly kill ovarian cancer cells and inhibit the spread of the cells. Our results indicated that MB was a novel sonosensitizer and MB-mediated SDT might be a new therapeutic modality in the treatment of ovarian cancer.