Scorpion venom can kill some brain cancer cells

American Association: Trials planned on drug to fight tumours

A TOXIN from the venom of a scorpion has been found to attack human cancer cells yet leave healthy tissue unharmed, according to scientists who have applied to begin clinical trials with the drug later this year.

Laboratory tests on the tumour cells of a rare form of brain cancer have revealed that the toxin - a protein fragment known as a peptide - can distinguish between healthy and cancerous cells and so act as a "magic bullet" for killing diseased tissue while leaving the rest of the body unaffected.

Scientists believe the research could lead to a treatment for a form of brain cancer called glioma, which kills thousands people each year, and it might be further developed to treat other types of tumours.

Professor Harald Sontheimer, a neurobiologist at the University of Alabama in Birmingham, told the meeting of the American Association for the Advancement of Science in Los Angeles it was surprising to find that the venom of the giant Israeli scorpion, Leiurus quinquestratum, worked against cancerous glial cells, which act as the brain's packing material to support its nerve cells.

"Interestingly, during the course of evolution, a lot of animals have developed peptides in their venom which shut down the nervous system of their prey - what better way to catch their food. We know for instance that the same peptide paralyses cockroaches," Professor Sontheimer said.

The scorpion toxin also targets the "molecular batteries" of human glial cells, which allow the cells of a developing embryo to shrink and so migrate around the brain. These batteries normally stop functioning once a brain has developed but are reactivated in a glioma, causing the cancer to spread.

"One of the problems this disease has is that although surgeons routinely remove these tumours, by the time they are detected cells have migrated away and have essentially infested the entire brain... the chances of the tumour re-occurring is essentially 100 per cent," the professor said.

The scientists plan to make the toxin even more lethal to tumour cells by binding it with additional poisons or radioactive substances. Trials on patients will begin once the United States Food and Drug Administration gives the drug a licence later this year, Professor Sontheimer said.

"Glioma is the deadliest form of cancer known, without any treatment possibilities at the moment. This gives us an opportunity to use this peptide, and its high affinity to bind to these cells, to take deadly poisons to these cells, for example we can make these molecules radioactive giving us the opportunity to do targeted radiation treatment," he said.

"The binding of the peptide to the tumour also stops the cells' ability to move around the brain and so consolidate the tumour to where it is," he added.