[Anti-tumor effect of hyperthermia plus hematoporphyrin derivative on malignant brain tumor]

Photoradiation therapy using the photosensitizing agent, hematoporphyrin derivative (HpD), and laser light has been currently employed as a new modality for the treatment of cancer. At present, however, the application of this therapy is limited to superficial tumors because of difficulties in achieving light penetration, whereas 13.56 MHz radiofrequency (RF) used in hyperthermia is capable to penetrate into deeper regions and elevate the temperature of brain tumors. In the present studies, the author evaluated an anti-tumor effect of hyperthermic treatment with HpD administration on experimental malignant brain tumors both in vitro and in vivo and, moreover, investigated the histological changes of subcutaneous tumors following water bath heating and the uptake of HpD into the brain and subcutaneous tumors. In vitro, C-6 and Rous sarcoma virus-induced mouse glioma cells (RSV glioma cells) were incubated in the medium containing HpD (0-125 micrograms/ml) for 24 hours. Hyperthermia was performed either in a water bath or by 13.56 MHz RF heating in the range of 37-43 degrees C. All procedures were carried out in the dark. The anti-tumor effect was evaluated by counting the viable glioma cells. HpD itself showed a growth inhibitory effect on C-6 and RSV glioma cells dose-dependently, while synergistic effect was observed in combination with hyperthermia. C-6 cells were more sensitive to this treatment than RSV glioma cells. The degree of response depended on the heating time and the temperature. In both cells, the effect of heating by water bath and 13.56 MHz RF was similar at each temperature.(ABSTRACT TRUNCATED AT 250 WORDS)