Toxin may put sting on brain tumors

ST. LOUIS — The search for cancer cures can at times produce some curious treatments, but the latest study just might stun you.

Neurosurgeons at St. Louis University are among the doctors injecting radioactive scorpion toxin directly into the brains of patients with a deadly brain cancer.

"It's not like people said, 'Scorpion venom — this must be a good way to treat cancer,"' said Dr. Alison M. O'Neill, vice president for medical affairs for TransMolecular Inc. The company, based in Cambridge, Mass., is developing the toxin as a chemotherapy drug.

Results from an initial study show that the toxin delivers radioactive iodine to brain tumors but leaves healthy brain cells unharmed. The study involved 18 people with recurrent brain cancer at three sites, including two people treated at SLU. The report will appear in the August issue of the Journal of Clinical Oncology.

The toxin used in the study is not raw scorpion venom. It is a part of a toxin protein from the giant yellow Israeli scorpion.

Using the toxin to put the sting on brain tumors wasn't an immediately obvious application.

Scientists at the University of Alabama in Birmingham were exploring how the toxin targeted nerve cells in the scorpion's prey, O'Neill said. The researchers noticed that the toxin also had an affinity for tumor cells.

The toxin attaches to proteins found on primitive nerve cells, said Dr. Richard D. Bucholz, director of the division of neurosurgery at St. Louis University. Brain cancer cells, called glioblastoma cells, are also primitive nerve cells, unlike normal brain tissue.

About 18,000 new cases of brain cancer are diagnosed yearly in the United States. About half are glioblastomas, said Dr. Gerry Linette, a neural oncologist at Siteman Cancer Center and Washington University. Only 3 percent of people diagnosed with the cancer are alive five years later.

Glioblastoma is a fast-growing type of tumor that destroys surrounding brain tissue, Bucholz said.

"Glioblastoma is the neurosurgeon's nightmare," he said. "We really haven't made progress on it in over 34 years."

Even with the very best therapy, glioblastoma is "a disease that, at this point, is nearly uniformly fatal," O'Neill said.