The role of active oxygen species and lipid peroxidation in the antitumor effect of hyperthermia.

The role of active oxygen species and lipid peroxidation in the antitumor effect of hyperthermia was studied in an experimental rabbit model. VX2 tumors were transplanted into rabbit hind legs, and the effect of hyperthermia on tumor growth was measured at 7 and 14 days after heating. As an index of lipid peroxidation, thiobarbituric acid-reactive substances in the tumor tissue were measured prior to hyperthermia and 3, 6, 12, and 24 h after hyperthermia. Tumor growth in rabbits treated with hyperthermia was significantly reduced, and thiobarbituric acid-reactive substances in the tumor tissue treated with hyperthermia were significantly increased until 6 h after hyperthermia. In addition, alpha-tocopherol in the tumor tissue was significantly decreased after hyperthermia. The antitumor effect of hyperthermia and the increase of thiobarbituric acid-reactive substances in the tumor tissue treated with hyperthermia were significantly inhibited by the administration of superoxide dismutase and catalase or dimethyl sulfoxide. These results suggest that lipid peroxidation mediated by active oxygen species plays an important role in the antitumor effect of hyperthermia.