Tumor Bioelectric Potential and its Possible Exploitation for Tumor Growth Retardation

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Abstract
The objective was to observe the effect of externally applied direct current on a murine tumor model (fibrosarcoma Sa-1 syngeneic to A/J mice) and to test a hypothesis involving changing the tumor's inherent negative bioelectric potential by that means. Direct current of 0.6 mA, 15 min/day, 9 consecutive days, was started after the tumors reached 50 ± 30 mm4 and delivered through stainless-steel needle electrodes with the cathode inserted into the tumor and the anode subcutaneously placed in its vicinity, Electrotherapy produced significant retardation of tumor growth. Tumor bioelectrical potential with respect to surrounding tissue was measured prior to and immediately after the therapy. The short-term imposition of tumor bioelectric potential (voltage difference imposed by the therapy) depended on the bioelectric potential prior to the therapy in the electrotherapy group: Pearson's correlation coefficient was 0.035 in the control and 0.569 in the electrotherapy group. Long-term imposition of tumor bioelectric potential was investigated by comparing measurements prior to the daily treatment. There was no significant difference in the means, but the control group exhibited a higher variance. Microscopic examination of tumor tissue at the end of the experiment showed extensive necrosis in the electrotherapy group with focused necrosis in the center where the electrode was inserted; in the control group the necrosis was less extensive and unevenly distributed.