Sonodynamic action of pyropheophorbide-a methyl ester in liver cancer cells

Abstract

Objective: This study aimed to investigate the sonodynamic action of pyropheophorbide-a methyl ester (MPPa) in liver cancer cells to explore a novel therapeutic modality. Methods: H22 cells were chosen as model cells to investigate the sonodynamic action of MPPa on liver cancer. The MPPa concentration was kept constant at 2 μmol/L, and the cells were subjected to ultrasound exposure at an intensity of 0.97 W/cm2. Cytotoxicity was investigated 24 hours after ultrasound exposure. Apoptosis was evaluated using flow cytometry with annexin V-fluorescein isothiocyanate and propidium iodine staining and nuclear staining with Hoechst 33258. Reactive oxygen species (ROS) were analyzed using flow cytometry with 2,7-dichlorodihydrofluorescein diacetate staining. Results. No significant dark cytotoxicity of MPPa was shown in the H22 cells at the concentration of 2 μmol/L. The cell death rate induced by ultrasound treatment was significantly higher in the presence of MPPa than in the absence of it (P < .05). Flow cytometry showed that the sonodynamic action of MPPa significantly increased the early and late apoptotic rates of the H22 cells. Nuclear condensation and an ROS increase were found after sonodynamic treatment. Conclusions: Our findings showed that MPPa-mediated sonodynamic action significantly enhanced death of H22 cells and the ROS level, suggesting that MPPa is a novel sonosensitizer and the sonodynamic action of MPPa might be a potential therapeutic modality in the management of liver cancer. © 2010 by the American Institute of Ultrasound in Medicine.