Canadian Scientists Use Deadly E. Coli Bacteria to Kill Cancer Cells

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					    Canadian Scientists Use Deadly E. Coli
        Bacteria to Kill Cancer Cells
(Toronto, October 12, 1999) – A toxin produced by the deadly E. coli bacteria
most commonly linked to illness caused by undercooked meat has been used to rid
bone marrow of cancer cells for the first time by a research team led by scientists at
Princess Margaret Hospital’s Ontario Cancer Institute, the Cross Cancer Institute
and the University of Alberta.

The dangerous toxin could be effective in completely purging all traces of cancer in
a patient’s stem cell graft, greatly improving the success of autologous stem cell
transplants in patients with some cancers.

The finding paves the way for future research into improved treatments for some
particularly deadly forms of cancer such as non-Hodgkin’s lymphoma, multiple
myeloma, and breast cancer.

A group in Toronto led by Dr. Jean Gariépy originally pioneered the new technique.
It is expected to reduce the likelihood of re-infusing diseased cells back into patients
suffering from breast cancer, lymphoma and multiple myeloma.

Researchers have been grappling with a major problem—mainly, that the failure of
high-dose chemotherapy with stem cell transplantation may be caused, at least
partly, by the re-infusion of contaminated tumor cells in the stem cell graft.

The researchers are using a toxin called SLT-1 to clean blood cells of cancer cells
by using a receptor on the surface of the cancer cells recognized by the toxin. The
toxin is then removed from blood cells prior to re-infusing the stem cells back into
cancer patients. The researchers found that while the toxin kills a broad range of
cancer cells, particularly breast, lymphoma and multiple myeloma cells, it does not
kill healthy blood stem cells.

University of Alberta Oncology Professor Linda Pilarski and colleagues in Edmonton
and Toronto have studied the use of this "purging agent" to kill the malignant cells in
multiple myeloma patients and leaving the normal stem cells intact. "We’ve shown
that myeloma cells are effectively purged by SLT-1—a ribosome inactivating toxin—
and that the normal stem cells survive. This means it is potentially safe to use as a
purging agent for the graft before re-infusing it into the patient," Dr. Pilarski says.

"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
other patients treated with autologous transplants such as lymphoma and breast
cancer patients."

Multiple myeloma, a cancer of the immune system located in the bone marrow, is
incurable with an average survival of only three to four years. Even though patients
usually respond to chemotherapy, they nearly always relapse. They are treated with
high-dose chemotherapy to kill off malignant cells. Then, they are transplanted with
white blood cells, taken from the patient usually when the disease is in
remissionCancer researchers know, however, that some of the malignant cells are
being transplanted back into patients. Moreover, graft cells have been shown to
cause myeloma.

Principle investigator Dr. Jean Gariépy, a professor in the Department of Biophysics,
University of Toronto, and a Senior Scientist at Princess Margaret Hospital’s Ontario
Cancer Institute, says, "In particular, the use of the toxin as an agent to clean a
patient's stem cells contaminated with cancerous cells, seems well suited to patients
with multiple myeloma. Our group has seized an opportunity to use a deadly
bacterial toxin responsible for hamburger disease to treat a variety of cancer

Dr. Andrew Belch, a professor in the Department of Oncology, University of Alberta,
points out that having a "clean" graft may 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. We hope that toxin-based purging will provide a
disease-free graft for the majority of patients who have no twin."

Dr. Pilarski, Dr. Gariépy and Dr. Belch were recently awarded a Terry Fox New
Frontiers Grant to improve the new technique and pioneer it in the clinic.

Dr. Gariepy’s work was supported by a translational research grant from the
Leukemia Society of America. The work of Drs. Pilarski and Belch, both of whom
work at the Cross Cancer Institute, was supported by the Medical Research Council
of Canada and the Cancer Research Society. The results of the study will be
published in the October 15 issue of the journal, Blood.

The Princess Margaret Hospital, a teaching hospital of the University of Toronto,
has achieved an international reputation as a global leader in the fight against
cancer and is considered one of the top comprehensive cancer treatment and
research centres in the world. Located in Toronto, Canada, Princes Margaret
Hospital and its research institute the Ontario Cancer Institute is a member of the
University Health Network, which also includes the Toronto General Hospital and
the Toronto Western Hospital.


For more information, please contact:

Keri Downs Schoonderwoerd
Communications Specialist
Public Affairs and Communications
Princess Margaret Hospital
416-946-4501 ext. 5771

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