Scientists working on killer cure

Scientists at the Ontario Cancer Institute and Alberta's Cross Cancer Institute have found a way to use a toxin produced by the deadly Escherichia coli bacteria to purge cancer cells from bone marrow before transplantation.

Researchers are using a toxin called SLT-1 to clean blood cells by taking advantage of a receptor on the surface of the cancer cells that is recognized by the toxin. The toxin is removed from the blood cells prior to the reinfusion of stem cells into the patient.

Researchers say that although the toxin kills a broad range of cancer cells, particularly breast, lymphoma and multiple myeloma cells, it does not kill healthy blood stem cells. "There is a lot more work to be done to refine the technique and to ensure safety, but this could prove to be an important advance for myeloma patients and perhaps others," said Dr. Linda Pilarski, professor of oncology at the Cross Cancer Institute at the University of Alberta.

A group of researchers in Toronto led by Dr. Jean Gariépy originally pioneered the new technique while grappling with the failure of high-dose chemotherapy during stem cell transplantation, possibly caused by the reinfusion of contaminated tumour cells in the stem cell graft.

Dr. Andrew Belch, also an oncology professor at the Cross Cancer Institute, said a "clean" graft provided by the use of the toxin may help improve survival. "In studies using identical twin grafts, patient survival appears to be better than that when the patient's own cells are used for the graft, probably because the graft from the healthy twin is disease-free," said Belch. "We hope the toxin-based purging will provide a disease-free graft for the majority of patients who have no twin."

Results of the studies conducted by Belch and Pilarski were published in the Oct. 15 issue of Blood.