- Of Monkeys And Men
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- An ebullient Italian researcher and a button-down American
believe a virus in polio vaccines of the 1950s and early 1960s may make
millions susceptible to cancer caused by asbestos
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- Months after the dust settled around the collapsed World
Trade Center buildings, doctors now fear the Sept. 11 attacks may pose
a further danger to New York's residents. Amid the white clouds that coated
the city were hundreds of tonnes of asbestos fibres. Exposure to the building
material -- sometimes even briefly -- can cause a fatal lung cancer called
mesothelioma.
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- "While the exact quantity of asbestos fibres emitted
into the air ... remains unclear, it is likely that those individuals who
live and work in close vicinity to the site are at some increased risk
for the development of asbestos-related cancers, including malignant mesothelioma,"
says Stephen Levin, a professor of occupational and environmental medicine
at Mount Sinai School of Medicine in New York.
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- Last week, an expert panel convened by the American College
of Preventive Medicine began asking some key questions. Why do some people
exposed only briefly to asbestos get the cancer? Who is at increased risk?
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- The answer may be unsettling, even to non-New Yorkers.
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- According to a group of influential U.S. scientists,
anyone vaccinated against polio before 1963 may be particularly vulnerable.
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- The links between polio vaccine, asbestos and mesothelioma
began during the early 1950s, when Jonas Salk used monkey kidneys to culture
the great quantities of polio virus needed for his famous vaccine. In 1960,
scientists found a virus in the monkey kidneys, known as simian virus 40
(SV40), had contaminated the vaccine. When the virus was injected into
hamsters, they grew tumours.
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- By then, almost 100 million Americans and millions of
Canadians had been given the vaccine.
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- U.S. officials ordered manufacturers to eliminate SV40
from the vaccines in 1961. However, to avoid widespread panic, they kept
news of the virus secret and did not recall existing stocks of polio vaccine,
which lasted until 1963. Scientists who did a flurry of tests said the
virus did not appear to cause human cancer, and the matter seemed dead.
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- Then, in 1993, as part of a larger experiment at the
U.S. National Cancer Institute, an Italian pathologist named Michele Carbone
happened to inject some mice with a solution containing SV40. The results
startled him. More than 60% of the mice developed a strange lung cancer.
When he examined the tumours under a microscope, he realized they were
mesothelioma, an exceedingly rare disease.
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- Carbone recalled from textbooks that it was caused by
asbestos. But why did these mice have it? They had no asbestos in their
cages. Intrigued, he sat down with a stack of medical journals.
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- "The more I read, the more curious I became, because
the number of coincidences was amazing," says Carbone, now a professor
of pathology at Loyola University Medical Center in Maywood, Ill.
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- "I mean, here you have a tumour that basically did
not exist until 1950, that suddenly is climbing up, climbing up, and we
say that the reason is asbestos. But that cannot explain what happened,
because asbestos has been out there for years. The Romans used asbestos
to make their armours."
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- About 3,000 North Americans die each year of mesothelioma,
which can linger for decades before symptoms appear. The average survival
time after diagnosis is only one year. Its incidence has risen 10-fold
in the past 30 years.
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- The cause is difficult to isolate. Up to 96% of miners,
who breathe in vast amounts of asbestos, do not get tumours.
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- "So what is it?" says Carbone. "Is it
bad luck? Or are there other things that make some people more susceptible
to asbestos?"
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- Carbone suspected SV40 was the missing piece of the puzzle.
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- To test his theory, in 1993, he approached Dr. Harvey
Pass, chief of thoracic surgery at the National Cancer Institute in Bethesda,
Md. One of the world's leading mesothelioma surgeons, Pass had saved portions
of dozens of tumours he had removed.
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- It is hard to imagine two more different people than
Michele Carbone and Harvey Pass. Carbone, with his shoulder-length hair
and fashion-model looks, is buoyant and spirited. Pass is stern, button-down
and skeptical.
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- "I was a little worried, because people told me
Harvey Pass has a, uh, strong character," Carbone recalls. "I
didn't know if he would agree."
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- Pass had never heard of SV40. But he was impressed by
what Carbone told him about the mice and agreed to allow tests of his tumour
samples for evidence of the virus.
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- He was not disappointed. More than 60% of the tumours
contained SV40. Pass was fascinated. The virus gave him a target for new
drugs that might kill the cancer.
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- Instead of his usual jubilant self, however, Carbone
was solemn.
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- "Then he says to me, 'Thees ees really a problem'
in his thick Italian accent," recalls Pass, who now considers Carbone
a close friend.
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- "That's when he told me about the polio vaccine
and SV40."
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- Not surprisingly, the scientific world greeted their
discovery with fangs bared.
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- No one was prepared to believe a virus, much less a monkey
virus that entered the human population by the revered polio vaccine, could
cause cancer. Some scientists said Pass and Carbone had accidently contaminated
the tumour samples with SV40 in the lab. But in the years that followed
the Carbone and Pass discovery, more than 40 scientific papers have confirmed
their initial findings.
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- It is unclear how much of the original vaccine was contaminated.
Almost none of the original, contaminated vaccine exists. Carbone has two
samples from the 1955-63 period. "Both contain SV40," he says.
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- One of the biggest critics of the SV40 theory was Adi
Gazdar, a cancer researcher at the University of Texas Southwestern Medical
Center in Dallas, Tex., who set out to prove the findings wrong.
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- Instead, he found something even more more disturbing.
Earlier this year, he published results from a study that found traces
of SV40 in 43% of patients with non-Hodgkin's lymphoma. Among healthy people
and patients with other types of cancer, no more than 6% carried the virus
in their cells.
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- Non-Hodgkin's disease is far more common than mesothelioma;
last year it killed close to 30,000 people across North America. And like
mesothelioma, its incidence has soared in recent decades.
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- Janet Butel, a researcher at Baylor College of Medicine
in Houston, Tex., who duplicated Gazdar's results, says the polio vaccine
connection may now be irrelevant. She says 10% of patients who were too
young to be exposed to the contaminated vaccine test positive for SV40.
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- "It is being spread among individuals by an unknown
route," Butel said. "It may be spread via mother to fetus, through
breast milk, sexual activity or possibly by airborne transmission. We don't
know."
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- Notably, the molecular fingerprint of the SV40 strains
Butel found in lymphoma tumours are identical to the ones Carbone found
in his polio vaccine samples. That makes the odds of accidental contamination
quite low.
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- "How did it pop up in her lab?" Carbone says.
"I assure you, I didn't mail it to her. There's only one way."
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- The SV40 virus consists of six proteins, one of which
is called "large T antigen" -- for tumour antigen -- which scientists
say is one of the most potent cancer-causing proteins ever discovered.
The protein can deactivate a series of proteins called Rbs which control
the normal cellular life cycle, creating immortal malignant cells.
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- When combined with such carcinogens as asbestos, or possibly
chemical pesticides, these transformed cells become tumours.
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- This is why doctors are so concerned about the cloud
of asbestos fibres that hovered in the autumn skies over New York City
in the weeks after the terrorist attacks.
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- "It's a very, very worrisome situation," Pass
says.
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- Pass, Carbone and others believe a potential treatment
is on the horizon. In mouse studies, several experimental materials have
proved effective in targeting the large T antigen and blocking tumour growth.
However, the form this treatment will take may strike many as ironic: It
is a vaccine.
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- bevenson@nationalpost.com Copyright © 2001 National
Post Online
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