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[escepticos] RV: JHU Sci 00-06 (shark cancer myth debunked)

Title: RV: JHU Sci 00-06 (shark cancer myth debunked)

        Otro mito seudomédico que se derrumba...



-----Mensaje original-----
De:     Dennis O'Shea [SMTP:dro en jhu.edu]
Enviado el:     Miércoles 5 de Abril de 2000 02:25 PM
Para:   JHU News
Asunto: JHU Sci 00-06 (shark cancer myth debunked)

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April 5, 2000

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Businesses that sell shark cartilage as a cancer cure or preventative have
claimed for years that sharks never get cancer, but this week scientists
from The Johns Hopkins University and George Washington University
presented a detailed history of benign and malignant tumors found in sharks
and related fishes.

At a news conference at the annual meeting of the American Association for
Cancer Research, scientists noted that sharks can even get
chondromas-cancers of the cartilage now being sold as a cancer cure. Their
results come from a survey of data in the National Cancer Institute's
Registry of Tumors in Lower Animals at George Washington University. Using
very strict diagnostic criteria, scientists were able to find 40 cases of
tumors in sharks and related fishes like skates and rays.

"People are out there slaughtering sharks and taking shark cartilage pills
based on very faulty data and no preventative studies to show that it
works," Gary Ostrander, Hopkins professor of biology and comparative
medicine, says. "That's not only giving desperate patients false hope based
on misinterpreted data, it's also taking a top-level predator out of an
ecosystem, which could cause major disruptions in the ecosystem."

Ostrander and lead author John Harshberger, a professor at George
Washington University who directs the Registry of Tumors in Lower Animals,
note that the new study can't rule out the possibility that scientists may
one day find a useful cancer treatment in cartilage from sharks or other
animals. They also acknowledge that folk and alternative medicine can
sometimes offer legitimate insights to the biomedical sciences.

For now, though, no proof exists that shark cartilage can have positive
effects on cancer, and the pills' cost to patients, potential for
interference with proven cancer treatments, and the potentially devastating
impacts on marine ecosystems have scientists like Ostrander and Harshberger
deeply concerned.

"Cancer exists throughout the phylogenetic tree, science's system for
classifying the many forms of life," Ostrander explains. "The idea that
there's some animal out there that never gets cancer and never expresses it
just really doesn't resonate well with people who work in the field."
Scientists have not yet conducted a comprehensive study of cancer rates
among sharks, and currently available evidence does not allow them to
assess the causes of the cancers they have found. The myth that sharks do
not get cancer sprang up in part because of their isolation from humans,
which reduces their exposure to carcinogenic pollutants and the likelihood
that sharks with tumors will be caught, Ostrander explains

Proponents of shark cartilage also selectively used scientific results to
bolster their case, he notes. For example, a single effort to give sharks
tumors in a laboratory failed. But Ostrander points out that several
different efforts to give tumors in the lab to English sole also failed,
even though that fish has high cancer rates in habitats such as Puget Sound.

Shark cartilage advocates also seized upon scientists' efforts to suppress
angiogenesis, a tumor's ability to encourage growth of new blood vessels.
When researchers realized that angiogenesis allows tumors to obtain much of
the raw material they need to fuel their own abnormal growth, they began to
look for factors in the body that could stop angiogenesis. One of the first
places they looked was cartilage, a tissue with relatively few blood vessels.

Sharks are animals with a great deal of cartilage. All of those factors
left sharks vulnerable to myth and misperception, Ostrander explains, but
none of them changes the fact that sharks can get cancer or suggests that
they must have a key to beating cancer.

"Part of the reason your own blood vessels are laid out as they are is
because your body contains factors that stop them from growing," he
explains. "And chicken cartilage, human cartilage, and all other kinds of
tissue have anti-angiogenic factors in them. Yes, there may be some others
in shark, but to suggest they will be a cure-all for cancer based on
available data is bogus."

Related Web site:
Gary Ostrander: http://www.bio.jhu.edu/faculty/ostrander/ostrander.html


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