HYPERTHERMIC SENSITIZATION BY HEMATOPORPHYRIN ON GLIOMA-CELLS

This study investigated: (1) the effect of Hp as a hyperthermic sensit izer on glioma cells; and (2) the possible mechanism of hyperthermic s ensitization by Hp using an exogenous scavenger specific to a particul ar reactive oxygen species. Hp at nontoxic doses at 37 degrees C signi ficantly enhanced thermal cell damage at 41.5 degrees C and above in a dose-dependent manner. Thermal cell damage enhancement by HP was effe ctively suppressed by the addition of beta-carotene, a singlet oxygen scavenger, or SOD, a superoxide scavenger, but not by the addition of mannitol or catalase. These results support the following hypothesis: The generation of superoxide is increased in cells treated with Hp in combination with hyperthermia. Thermal cell damage enhancement by Hp i s probably mediated by singlet oxygen generated via superoxide in an a lternative pathway different from that of photosensitization. Hp has p otential as a hyperthermic sensitizer because of the following advanta ges: (1) its dose-dependent enhancement of thermal cell damage; and (2 ) the lack of toxicity at physiological temperature at doses of Hp req uired for hyperthermic sensitization of tumour cells.