Electrochemotherapy (ECT) or electrical impulse chemotherapy, proposed by Okino and Mohri and Mir et al., is a new technique that enhances the antitumor effect of various anticancer agents by delivering high-voltage electrical impulses to tumors. Recently, several reports have described the effectiveness of ECT against tumor cell lines. However, few experimental studies have evaluated the optimum electrical conditions for ECT. We designed this study to determine the optimum electrical conditions for ECT against rat squamous cell carcinoma
in vitro and
in vivo.
SCC158 cells, a rat squamous cell carcinoma cell line, were cultured in Dulbecco's MEM with several concentrations of bleomycin (BLM) for 72 hours. The BLM concentration that inhibited cell growth by 50%(BLM-IC50) was determined by MTT Assay. Tumor cells in the media containing BLM-IC
50×10
-1, BLM-IC
50×10
-2, or BLM-IC
50×10
-3 recieved electrical pulses (200-1400V/cm, 0.1msec, 1-8 pulses) and were sequentially recultured for 72 hours. The surviving fraction of tumor cells was analyzed.
SCC158 cells were transplated into the tongue of Fischer rats. The rats recieved electrical pulses (125-1200V/cm, 0.1msec, 8 pulses) 30min after the administration of BLM. The antitumor effect of ECT on these tumors and damage to the surrounding normal tissue were then evaluated histologically.
The anticancer effect of ECT appeared when the voltage was more than 600V/cm. Futhermore, ECT of 1000-1200V/cm enabled the BLM concentration to be reduced to as low as 1/100 the BLM-IC50 to obtain a similar anticancer effect
in vitro. In addition, the anticancer effect of ECT was strongest when the voltage was 1000V/cm or more; however, the surrounding normal tissue within the electrical field was seriously damaged
in vivo.
In conclusion, ECT is expected to be useful in the treatment of human oral cancers, and the optimum voltage is considered to be 1000V/cm or more. It is hoped that problems related to damage to normal tissue will be resolved by future investigations.
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