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Last Updated: Nov 19th, 2006 - 12:21:58 |
21 Sep, (foodconsumer.org) - A molecule that can repair the tanning pathway in fair-skinned people may be able to produce a sunless tan and prevent the development of skin cancer, a new study claims. Researchers at the Dana-Farber Cancer Institute in Boston say that the molecule is able to correct a distorted pathway in fair-skinned mice.
Fair-skinned people generally have a higher risk of skin cancer and are also unable to tan easily. The more time they spend in the sun, the higher is their risk of skin cancer. Researchers said that repairing the tanning pathway in fair-skinned people may also confer a protective effect against skin cancer.
Previous research has documented several reasons why fair-skinned people have a high risk of skin cancer.
A pigment called melanin, which produces darker skin is either absent or present in very low levels in fair-skinned people. Melanin also has a protective effect against skin cancer. Melanin is produced when a chemical known as cyclic AMP (cAMP) triggers the production of the pigment from cells called melanocytes.
These cells are typically present under the skin. The level of cAMP is not uniform in all people. People with red hair and fair skin tend to have low levels of cAMP. That is why when the rays of the sun containing ultraviolet rays hit the skin, instead of turning dark or tanning, the skin in fair-skinned people burns.
A hormone present in the body called melanocyte-stimulating hormone (MSH) is responsible for controlling the levels of cAMP. The receptor for this hormone is called MC1R. In fair-skinned people this receptor is out of shape and cannot provide attachment for MSH.
This is the reason for low cAMP levels in fair-skinned people.
In the present study Dr. David E. Fisher and colleagues at the Dana-Farber Cancer Institute in Boston set out to demonstrate that the melanin-producing pathway could be repaired in fair-skinned mice. The used a Forskolin extract from the Coleus plant to se whether an enzyme called adenylate cyclase is stimulated in these mice.
Stimulating the enzyme is believed to trigger production of dark pigments. Fisher's team worked on genetically engineered mice that had a rare skin disorder called xeroderma pigmentosum, in which cells are unable to repair DNA damage done by radiation.
These mice were exposed to blasts of ultraviolet rays, equivalent to a day spent on a Florida beach, for 20 days.
Researchers found that fair-skinned mice with the disorder as well as a dysfunctional MC1R receptor burned badly and showed signs of skin cancer in five weeks. At the end of 30 weeks, all these mice had died.
But genetically engineered mice that were lathered with forskolin lotion for a month before the treatment and before each ultraviolet exposure did not show any signs of cancer. Some of them became nearly black and they were as protected from sunburn as mice with natural tans.
Researchers report in the journal Nature, that half of these mice showed signs of skin cancer after nearly 50 weeks. Researchers said that the forskolin extract protects from both ultraviolet-A and ultraviolet-B rays in both fair-skinned and dark-skinned animals.
"A small molecule applied to the skin of red-haired, fair-skinned mice essentially rescued the pathway and allowed the mice to darken. The reactivation of that pathway was protective to the mice,” said Dr Fisher.
However he said there was still some way to go before these treatments could be recommended to people. "Long before this could be recommended for people, it has to be rigorously tested. We have to be sure what we're doing is safe. We don't want to cause problems in people who are otherwise healthy."
Fisher said that the forskolin extract may be only one drug that showed such protective effects. Many more need to be tested, he added. "Skin cancer appears to be one of the most preventable cancers in man, yet its incidence is rising. We need to develop more strategies to help people prevent it."
Australian researchers have already experimented with an injectable medication called melanotan, which is a synthetic version of MSH. In a small study of 12 people the drug produced a 20 percent increase in MSH.
Skin cancer is the most common type of cancer and will be diagnosed in more than a million people this year, according to the Skin Cancer Foundation. Almost 90 percent of all skin cancers result from exposure to the sun. The World Health Organization estimates that as many as 60,000 people a year worldwide die from skin cancer resulting from sun exposure.
"These studies suggest that a drug-induced 'rescue' of the tanning mechanism may correspondingly rescue at least some aspect of skin cancer protection," Fisher said. "Such sunless tanning may also dissuade sun-seeking behaviors, which undoubtedly contribute significantly to high skin cancer incidence."
But Dr. Seth J. Orlow, chairman of the department of dermatology at New York University Medical Center in New York City said that it might be a long time before any viable skin-cancer preventing products hit the market.
"I think it will be a while before we have a cream that can safely increase melanin in the skin. I think this study was carefully done, but we would be well advised to temper any enthusiasm," he added.
© 2004-2005 by foodconsumer.org unless otherwise specified
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