Effective treatment of bladder tumor-bearing mice by direct delivery of bleomycin using electrochemotherapy.

We investigated the cytotoxicity on the combination of bleomycin (BLM) with electric pulses against transplanted bladder tumors in nude mice. Loading with high-voltage electric pulse after injection of BLM was associated with a decrease in tumor size; tumor size became smaller and disappeared 8 days after the treatment. Such complete regression was achieved with one treatment using BLM of one-tenth the lethal dose (LD(50)) combined with electric pulses. On day 20, regrowth was observed at a much slower rate than at lower concentrations of BLM. Pathological examinations of the tumor tissues after treatment revealed disruption of the nucleus in the exposed tissues on day 2. Furthermore, a decrease in number of the stained nuclei and cytoplasmic lysis were observed on day 4. These results showed that electric pulses was an effective tool to deliver drugs into bladder tumor cells and an effective treatment method for bladder tumors.