Scorpion may have a role in treating brain cancer

Venom from a dangerous scorpion may have an unlikely role in the treatment of a particularly lethal form of brain cancer. Early tests suggest that it could be used to target cancerous cells with radiation or chemotherapy drugs.

Dr Craig Sontheimer of the University of Alabama, Birmingham, has been working for the past three years with the venom from the giant Israeli scorpion which, he said, could yield a new drug for the treatment of glioma.

"Glioma is the most deadly type of cancer known," he said. While surgery could be used to clear the initial tumour, it spreads quickly throughout the brain, forming new tumour sites, with a 100 per cent prospect of recurrence. Glioma is diagnosed in about 24,000 people in the United States each year, he said, and 18,000 die within a year.

He initially looked at the venom because of its ability to react directly with nerve tissue. The venom blocks communication between nerves and muscles in the scorpion's victims, causing paralysis. When glial cells in the brain become cancerous they have the ability to shed water and shrink, making them small enough to pass through the narrow gaps between healthy brain cells. They do this using the glial cell's "chlorideion channel".

Dr Sontheimer found, however, that the scorpion venom has a particular affinity for the ion channel in these cells, binding directly to the channel and blocking its action. More importantly, the venom ignores all other types of ion channels, leaving healthy tissues untouched. Such selectivity is rare and could provide a "magic bullet" to target glioma.

"This particular peptide binds to this particular ion channel," he said. "It will only bind to the cancer cell, it won't bind to healthy cells." The strategy would be to use the active protein in the venom as a carrier that could bring either chemotherapeutic drugs or a radioactive substance such as radioiodine, he explained.

Dr Craig Stevens of Oklahoma State University described his work, which involves using a common North American frog. "We believe that the potential for pain will be less in earlier evolved species," he said. He discovered, however, that the northern grass frog has a single receptor site, compared with three in mammals, which could bind pain-killing opiod drugs. The study is to understand why opiods are able to block pain.