Abstract
OBJECTIVE
High invasiveness of malignant gliomas frequently causes local tumor recurrence. To control such recurrence, novel therapies targeted toward infiltrating glioma cells are required. Here, we examined cytotoxic effects of sonodynamic therapy (SDT) combined with a sonosensitizer, 5-aminolevulinic acid (5-ALA), on malignant gliomas both in vitro and in vivo.
METHODS
In vitro cytotoxicity of 5-ALA-SDT was evaluated in U87 and U251 glioma cells and in U251Oct-3/4 glioma stemlike cells. Treatment-related apoptosis was analyzed using flow cytometry. Intracellular reactive oxygen species (ROS) were measured and the role of ROS in treatment-related cytotoxicity was examined. Effects of 5-ALA-SDT with high-intensity focused ultrasound (HIFU) on tumor growth, survival of glioma-transplanted mice, and histological features of the mouse brains were investigated.
RESULTS
The 5-ALA-SDT inhibited cell growth and changed cell morphology. Flow cytometric analysis indicated that 5-ALA-SDT induced apoptotic cell death. The 5-ALA-SDT generated higher ROS than in the control group, and inhibition of ROS generation completely eliminated the cytotoxic effects of 5-ALA-SDT. In the in vivo study, 5-ALA-SDT with HIFU greatly prolonged survival of the tumor-bearing mice compared with that of the control group (p < 0.05). Histologically, 5-ALA-SDT produced mainly necrosis of the tumor tissue in the focus area and induced apoptosis of the tumor cells in the perifocus area around the target of the HIFU-irradiated field. Normal brain tissues around the ultrasonic irradiation field of HIFU remained intact.
CONCLUSIONS
The 5-ALA-SDT was cytotoxic toward malignant gliomas. Generation of ROS by the SDT was thought to promote apoptosis of glioma cells. The 5-ALA-SDT with HIFU induced tumor necrosis in the focus area and apoptosis in the perifocus area of the HIFU-irradiated field. These results suggest that 5-ALA-SDT with HIFU may present a less invasive and tumor-specific therapy, not only for a tumor mass but also for infiltrating tumor cells in malignant gliomas.
EXTH-70. ENHANCEMENT OF ANTITUMOR ACTIVITY BY USING 5-ALA–MEDIATED SONODYNAMIC THERAPY TO INDUCE APOPTOSIS AND NECROSIS IN A MOUSE GLIOMA MODEL
