Differential cytotoxicity and sonosensitization by sanazole: Effect of cell type and acoustic parameters

Purpose: Although sanazole has been used as a hypoxic radiosensitizer, we recently reported on its ability to sensitize U937 cells to hyperthermia and X-irradiation under aerobic conditions, enhancing apoptotic cell death following the combined treatment. The current study was undertaken to evaluate the effect of sanazole as a sonosensitizer under previously studied acoustic conditions of different pulse repetition frequencies, using two cell lines representative of solid tumours and haematopoietic cancers. Methods: Cells were treated with different doses of sanazole. Flow-cytometric analysis and DNA fragmentation assay were carried out at different times, and morphological features were also inspected. For ultrasound treatment, cells were pre-incubated with a non-cytotoxic dose of sanazole for 30 min before exposure. Evaluation of cell killing and a parallel examination of intracellular oxidative stress levels in both cell lines were performed using flow cytometry. Results: Sanazole alone displayed selective cytotoxic effects towards solid tumour-derived cancer cells, resulting in complete cell death after 24 h of treatment, and enhanced the ultrasound-induced cell killing 6 h post-treatment. The enhancement seemed to be mediated by an additive increase in intracellular oxidative stress levels. Conclusion: Sanazole seems to be an efficient cytotoxic agent for the treatment of solid tumours and a promising sonosensitizer under aerobic conditions. © 2010 The Japan Society of Ultrasonics in Medicine.