Scientists have discovered a skin treatment that causes sunless tanning and decreases the risk of skin cancer in mice.

Credit: Polarqueen

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SYDNEY: A skin treatment that causes sunless tanning and decreases the risk of skin cancer in mice might one day lead to a similar treatment for fair-skinned people, according to a new U.S. study.

Just like humans, mice can work on their tan by catching some rays. But like humans, some mice just can't tan and are at greater risk of skin cancer.

Now a team of scientists from the Dana-Farber Cancer Institute and Children's Hospital in Boston, Massachusetts, have found a way to help these mice tan in the absence of sunlight. Their treatment also decreases the risk of skin cancer in the mice.

The researchers, who published their findings in the British journal Nature, hope that one day a similar treatment could be available to humans.

The ultra-violet (UV) component of sunlight is a known carcinogen that causes direct damage to DNA. In individuals with a healthy tanning response, UV light striking the skin triggers a complex molecular cascade that leads to the production of pigment - various forms of melanin - in specialised skin cells called melanocytes. This pigment provides the skin with protection against subsequent UV exposure.

To shed light on the tanning process, David Fisher of the Dana-Farber Cancer Institute and colleagues used mice with a defective pigmentation pathway. The mice were unable to respond to the UV-induced hormone, melanocyte stimulating hormone (MSH), so could not produce melanin, making them highly susceptible to skin cancer.

Fisher and his co-workers found that by applying the plant-derived compound forskolin to the skin of these mice, they could bypass MSH in the faulty signalling pathway, causing the mice to produce melanin. According to Fisher, this suggests that people who have difficulty tanning may still have a residual capacity to make pigment.

The treatment was found to promote pigmentation independent of exposure to sunlight – in effect producing a sunless tan. Most significantly, mice treated with forskolin had a reduced risk of various measures of skin damage, such as cell death, DNA lesions and various skin cancers.

The researchers hope that one day, the treatment might be available to people, but are cautious about the prospect: "It remains to be seen whether [this] will be achievable in man, and whether it would afford measurable protection against UV skin damage and cancer," they write.

One obstacle that must be overcome before clinical trials begin is the issue of skin thickness: mice have thinner skin than humans, and a similar treatment applied to pigs (which have thicker skin) was less successful. Fisher and colleagues are currently exploring a number of alternative compounds for use on human skin.

Australia suffers from one of the highest rates of skin cancer in the world, due a combination of genetic factors and high levels of exposure to sunlight.