Electrochemical treatment of human KB cells in vitro

Electrochemical treatment (ECT) of cancer is a promising new method by whic h direct current is delivered into tumor tissue to induce tumor regression. The purpose of this study is to evaluate the effectiveness of ECT on human cancer cells and to investigate the factors that affect ECT. The biologica l mechanisms of ECT in cancer treatment were also explored. Using human KB cells, ECT was found to delay cell growth by using 0.3 coulombs (C)/ml(1.5 C in 5 mi of culture medium; 3 V, 400 mu A for 62.5 min). From the results of a colony-forming assay, it was clearly demonstrated that increasing the ECT dose decreases tumor cell survival. A cytotoxicity study, in which a me thylene blue assay was used, determined that, for 2.5 x 10(5) cells in cult ure, the ID50 was 0.68 C/ml. For a fixed dose of 0.6 C/ml (3 C in 5 mi), us ing higher current and shorter treatment time resulted in better cell survi val. Time, therefore, is an important factor. When cell concentration was a ltered, the survival was higher for increased cell concentrations. A thymid ine incorporation assay indicated that the amount of [H-3]thymidine incorpo rated into DNA decreased as the ECT dose increased. After treatment with 1 C/ml (5 C in 5 mi; 3 V, 400 mu A for 208.4 min), pH at the anode decreased to 4.53 and at the cathode increased to 10.46. These results indicate that ECT is effective for killing human KB cells in vitro and that the toxicity effect is related to charge, current, and treatment time. The effect of pH alteration on cells is one of the mechanisms of ECT. (C) 1999 Wiley-Liss, I nc.