Apoptosis induced by sonodynamic therapy in human osteosarcoma cells in vitro

The aim of the present study was to investigate the potential effect of hematoporphyrin monomethyl ether-sonodynamic therapy (HMME-SDT) on MG-63 osteosarcoma cells. The HMME concentration was kept constant at 20 µg/ml and the MG-63 osteosarcoma cell line was exposed to ultrasound with an intensity of 1.0 W/cm2 for 30 sec. Cell cytotoxicity was quantified using an MTT assay 6 h after HMME-SDT. The intracellular localization of HMME was imaged using inverted confocal laser scanning microscopy. Apoptosis was investigated using flow cytometry with Annexin V-fluorescein isothiocyanate and propidium iodine staining. The cytotoxicity of HMME-mediated sonodynamic action on MG-63 cells was significantly higher than that of other treatments, including ultrasound alone, HMME alone and sham treatment. Flow cytometry demonstrated that HMME‑SDT action markedly enhanced the apoptotic rate of MG-63 cells. The mechanisms of apoptosis were analyzed by measuring the protein expression of poly ADP-ribose polymerase (PARP), cleaved PARP, procaspase-3, cleaved caspase-3 and cleaved caspase-9. The data demonstrated that HMME-SDT action markedly induced the apoptosis of MG-63 cells.