Sonodynamically induced antitumor effect of pheophorbide a.

The sonodynamically induced antitumor effect of pheophorbide a (Ph-a) was investigated. Both in vitro and in vivo effects on sarcoma 180 were tested in combination with ultrasound at 2 MHz. The rate of ultrasonically induced cell damage in air-saturated suspension was enhanced by twice with 80 microM Ph-a. This enhancement was significantly inhibited by histidine, which may suggest it was mediated by ultrasonically induced oxidation. For mice, 5 mg/kg Ph-a was administered before the insonation, and ultrasound stopped the tumor growth at an intensity with which ultrasound alone showed only a slight antitumor effect.