A tan to fight skin cancer?

In the not-too-distant future, you may be able to slather on a lotion that protects your skin from cancer and gives you a tanned look at the same time.

Researchers are reporting that they've discovered a way to repair the pathway that keeps fair-skinned people from tanning. And, it looks like repairing that pathway can help prevent the development of skin cancer too, according to the study authors.

"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 the study's lead author, Dr David E. Fisher, director of the Melanoma Program at the Dana-Farber Cancer Institute in Boston. "What we're learning will hopefully be leading us to new strategies for skin-cancer prevention."

The findings were published in the Sept. 21 issue of Nature.

Not everybody is convinced
But, not everyone is convinced the approach will work - at least any time soon.

"I think it will be a while before we have a cream that can safely increase melanin in the skin," said Dr Seth J. Orlow, chairman of the department of dermatology at New York University Medical Centre in New York City. "I think this study was carefully done, but we would be well advised to temper any enthusiasm."

Orlow said the skin on mice is much thinner than it is on humans, so it would be harder for any potential medications to penetrate deep enough to be effective. He also said he'd be concerned about potential side effects from such a medication.

Over 90 percent of skin cancers can be attributed to sun exposure.

Why fair skin means higher risk
People with fair skin, light hair and/or light eyes tend to develop skin cancer at higher rates than people with darker skin. That's because people with darker skin produce more melanin, a pigment that protects against the development of deadly skin cancer, according to Fisher.

To figure out what's going on under the skin, Fisher and his team studied red-haired, fair-skinned mice. Like people with red hair and light skin, these mice didn't tan, but instead burned when exposed to the sun and its ultraviolet rays.

Melanin is manufactured when a chemical known as cyclic AMP (cAMP) stimulates melanocytes, the melanin-producing cells in the skin. Different people produce different levels of cAMP. People with red hair and fair skin tend to have low levels of cAMP.

Levels of cAMP are controlled by a hormone called melanocyte stimulating hormone (MSH). The reason that fair-skinned, red-haired mice have low levels of cAMP is that the receptor for MSH, which is called MC1R, is shaped differently and can't be effectively stimulated by MSH. The result is fair skin, because less pigment is produced.

Helping mice tan
Fisher and his colleagues believed that this pathway to melanin production could be repaired in the fair mice. To test this theory, the researchers used a compound known as forskolin on the mice because it's believed to raise cAMP levels.

Indeed, after forskolin was rubbed on the skin of the mice, their skin darkened. According to Fisher, the tanning process appeared to be indistinguishable from the normal tanning process that skin goes through when exposed to sunlight. And, he said, the mice didn't have the same inflammatory response in their skin after being exposed to the sun. Additionally, the researchers didn't notice any ill effects from the treatment, he added.

But, Fisher said, "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 forskolin is only one potential drug, and that there are many others that can be tested.

"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," Fisher said. And, he added, if a lotion can tan the skin, such "darkening may diminish sun-seeking behaviour," which would also help prevent skin cancer.

Fisher's group isn't the only team of researchers hoping to develop a product that can tan the skin and protect against skin cancer. A group of Australian researchers has already conducted Phase I and II clinical trials on an injectable medication called melanotan. Melanotan is a synthetic version of MSH. In a small trial involving 12 people, those who took the manufactured hormone had about a 20 percent increase in MSH levels. – (HealthDayNews)

Read more:
Skin Centre

September 2006

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