|
By
Susan Heavey
WASHINGTON (Reuters) - A
hybrid of the virus that causes polio and the virus that causes the common
cold could eliminate the most common type of brain cancer, researchers said
on Monday in a finding that might offer new hope for the growing number of
patients with the fatal disease.
Injecting the hybrid virus
into mice with malignant glioma, the most common kind of brain tumor,
resulted in complete recovery after one dose, researchers said.
"We have generated a
virus that is unable to cause disease in the brain but that still has the
ability to infect and destroy brain tumor cells," Matthias Gromeier,
an assistant professor of microbiology at Duke University, who led the
research team, said in an interview.
Results from the ongoing
study, already in its seventh year, were presented at a meeting of the
American Society for Microbiology in Orlando, Florida.
Poliovirus, which can cause
brain infections in humans, naturally seeks out brain tumor cells because
they carry a specific binding molecule. This molecule, known as CD155, is
not found in healthy brain cells and isolates the virus in cancerous cells.
But because poliovirus also
causes polio, which can lead to permanent paralysis and sometimes death,
researchers needed to disable the virus's destructive capabilities.
"It is a somewhat unusual
proposal that we are making because the virus that we are basing our
treatment on is a potentially dangerous, infectious agent," Gromeier
said. "If you want to propose using any kind of virus for therapy
purposes, you have to make sure that this virus can no longer cause
disease."
To do that, Gromeier said, his
team inserted a genetic piece of rhinovirus, a relative of poliovirus and
the cause of the common cold. Unaltered poliovirus infects every cell in
the brain, but rhinovirus does not.
Researchers said the
genetically altered strain of poliovirus provides a more targeted and
successful approach to treating malignant brain tumors, which respond
poorly to conventional methods of surgery, radiation and chemotherapy.
Unlike surgery, which often
leads to some removal of healthy brain tissue, Gromeier said his method
targets only tumor cells. The virus also has the ability to seek out tumor
"microsatellites," smaller tumors located away from the main
tumor spread out elsewhere in the brain, he said.
Because of the brain's
sensitivity, only small doses of radiation and chemotherapy can be
administered at one time, which does little to stop the invasive growth of
brain cancer cells.
BRAIN CANCER ON THE RISE
Gromeier's findings point the
way to possible treatment for the rising number of malignant brain tumors
in humans that almost always result in death.
Between 1973 and 1997, the
year for which the most recent data is available, the number of brain
cancer diagnoses rose 18 percent while brain cancer deaths rose 11 percent,
according to the Atlanta-based American Cancer Society.
"There are rare
exceptions, but it is almost invariably fatal," said Dawn Willis,
scientific program director for the society and a former virologist at St.
Jude's Hospital in Memphis.
Each year 17,000 people are
diagnosed with the disease and another 13,000 die from it, according to the
American Cancer Society, which funded the study along with the National
Cancer Institute, part of the U.S. government's National Institutes of
Health, and the Burroughs Wellcome Fund.
"The patients that are
suffering from this disease have really very little hope because there is
no effective treatment available," Gromeier said.
Gromeier and his team are now
looking to future human clinical trials, having already tested the modified
poliovirus successfully on monkeys and mice. They are preparing a prototype
of the combined virus with support from the National Cancer Institute but
say it will be years before they expect human trials to begin.
|
Germany
United
Kingdom
