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Sunless Tanner May Block Rays

Tests show mice develop deep color that lessens the risk of cancer from excessive sun exposure.

September 23, 2006|Denise Gellene | Times Staff Writer

A sunless tanning lotion induced a deep tan in hairless mice that protected the animals from harmful ultraviolet rays, scientists have reported.

The experimental lotion might allow fair-skinned people who otherwise burn to sport protective tans. Sun damage is a leading cause of skin cancer.

In Thursday's issue of the journal Nature, the scientists said mice slathered daily with lotion became nicely tanned in a matter of days. With each application, the animals got darker.

The tans weren't permanent, scientists said. The mice lost their color two weeks after treatment stopped.

The lotion contained forskolin, a chemical derived from the root of the flowering plant Coleus forskohlii. Applied to the skin, forskolin activates the cellular machinery that produces the pigment melanin. A buildup of melanin results in a tan that resists burning.

Sunlight also triggers melanin production. But some light-skinned people have a genetic mutation that blocks the tanning response.

In the study, 18 mice -- nine untreated and nine with tans -- were exposed to ultraviolet light daily for 20 weeks. At the end of one year, the untreated mice had a total of 11 tumors, compared with six tumors among the tanned mice. Most of the tumors were squamous cell carcinomas, a common skin cancer.

The results suggested the lotion wouldn't eliminate the need for sunscreen or other protections.

Dr. David E. Fisher of Dana-Farber Cancer Institute & Children's Hospital in Boston, a study author, said the next step was to find out whether the lotion triggered protective tanning in human skin, which is thicker than mouse skin. In a previous experiment, the lotion didn't darken thick-skinned swine.

Magen Biosciences of Cambridge, Mass., a company co-founded by Fisher, has licensed rights to the lotion from Dana Farber.

denise.gellene@latimes.com

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