medicine forum Guru
Joined: 02 May 2005
|Posted: Wed Jul 19, 2006 1:34 am Post subject:
Seaweed extract may help halt cervical cancer virus
Peter Gorner, "Seaweed extract may help halt cervical cancer virus",
Chicago Tribune, July 14, 2006,
It's only a lab feat so far, but government researchers said Thursday
that they had discovered a potent inhibitor of human papilloma
viruses--particularly the types that cause cervical cancer and genital
warts--in a chemical commonly found in commercial products, including
food and sexual lubricants.
In a test tube, carrageenan inhibits the infectious ability of genital
HPV with nearly a thousand-fold greater potency than other inhibitors
tested, according to National Cancer Institute researchers, who
reported their findings in Pathogens, a peer-reviewed journal published
by the Public Library of Science.
How effective the compound would be in the human body remains to be
demonstrated, but the discovery raises the possibility that carrageenan
could be used with vaccines, condoms and lubricants as a protection
against HPV. The chemical is extracted from marine red algae, or
About 10,000 American women are diagnosed with cervical cancer each
year; about 250,000 women worldwide die from the disease annually.
The human papilloma virus normally attacks cells by attaching to the
proteins on the cell surface and then using chemicals to work its way
in. Carrageenan blocks this process by attaching to the virus and
preventing its access to cells.
The carrageenan discovery was made in the lab of Dr. John Schiller,
senior investigator at the National Cancer Institute, who also was a
key player in the initial development of the HPV vaccine.
Schiller was quick to put the new finding in perspective.
"Our results do not prove that carrageenan will work as a practical HPV
topical microbicide," he said in a prepared statement.
"The potent inhibition of infection of cells in dishes, coupled with
the fact that carrageenan-based products are already in use, are
promising. But we will need to do a well-controlled clinical trial
before use of any of these products as an HPV inhibitor could be
Still, Schiller said he and his colleagues were "floored" by how much
better the compound is than anything else they have tested.
"An effective HPV microbicide could reduce the burden of HPV-related
genital disease in women," Schiller said.
Christopher Buck, lead author of the study and a postdoctoral fellow at
the National Cancer Institute, methodically tracked down and tested
potential inhibitory compounds that were being considered as topical
treatments for other infectious agents.
Because carrageenan was already in clinical trials in South Africa as a
topical HIV inhibitor, Buck tested it against the HPV virus. It turned
out that HPV is much more sensitive to carrageenan than HIV is.
"When carrageenan came up to be the clear winner, Chris started to
search for products that might contain it," Schiller said.
"Although, carrageenan was identified in a systematic screen, the
serendipity that this seaweed-derived compound is already used in
over-the-counter products for genital application is really quite
The vaccine is virtually completely effective against some HPV strains,
particularly two that are the most aggressive and most highly
associated with cervical cancer. The vaccine also works on strains
associated with genital warts.
But there are still multiple strains of HPV that won't be covered by
This kind of cancer requires multiple weapons, said Dr. Connie Trimble,
an HPV researcher at Johns Hopkins University. Trimble was involved in
the early preventive vaccine trials and is currently working on a
maintenance vaccine for women who already have HPV.
She called the latest discovery "a great thing."
"With all the potential tools now, we could really start to think about
the end of cervical cancer. Between the vaccines and some of the
prophylactics--wouldn't that be a medical success story!"
The new vaccine doesn't prevent infection against every strain--more
than 100 have been discovered so far--and its cost--about $360 for the
three necessary doses--make it the world's most expensive vaccine.
That could be prohibitive, especially for women in developing
Another member of the research team whose work led to the vaccine, Dr.
Doug Lowy, chief of the Laboratory of Cellular Oncology at the National
Cancer Institute, said he believed the limits of the vaccine should not
"It's said to cover 70 percent of the viruses blamed for cervical
cancer, which means that you could be infected by one or more of the
remaining 30 percent and not be protected," Lowy said.
"So, I can imagine carrageenan could serve as an adjunct. We wouldn't
expect it to be as efficacious as the vaccine--you have to use it all
the time to prevent infection. But the vaccine's just too expensive for
some parts of the world."
Carrageenan's safety profile for long-term vaginal use may make it
useful as an inexpensive topical microbicide for blocking the sexual
transmission of HPV.
Recognized as safe
"If people wanted to, they could run a clinical trial tomorrow because
carrageenan falls under the FDA category of GRAS--Substance Generally
Recognized as Safe," Lowy said.
"We checked over-the-counter products and found several that already
are inhibitory. But the efficacy hasn't been shown to be effective in a
controlled clinical trial.
"It's entirely possible that it could be tried and found not very
effective. We hope that's not the case. We think the tissue culture
data are strongly suggestive that it would be well worthwhile to carry
out the clinical trial that addresses that question."
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