Study suggests targeted drugs can induce protective tans

Boston - Results of a recent study show promise for developing an effective means of protecting fair-skinned people from skin cancer caused by exposure to sunlight.

The study, led by researchers at Dana-Farber Cancer Institute and Children’s Hospital Boston, was published in the Sept. 21 issue of the journal Nature. The research involved “tanning” specially engineered red-haired, light-skinned mice by applying a cream that activated their skin cells’ tanning mechanism. Although the tan-inducing compound used on the mice has not yet been tested in humans, the study’s findings suggest that medicinally induced tanning likely can occur in people who do not normally tan well - and who thus are deprived of a tan’s protective qualities.

Many scientists have theorized that tanning occurs when UV radiation strikes the nuclei of melanocytes, causing DNA damage that prompts the melanocytes to produce pigment. The Dana-Farber researchers’ objective was to study melanoma in mice whose fair skin stemmed from the same genetic roots as the skin of fair-skinned humans. The team found that while tanning could not be induced in fair-skinned mice by exposure to UV rays - instead, sunburn occurred - tanning could be induced when the mice were treated with specific, targeted drugs.

It is known that the most common origin of red hair and pale skin in humans is found in MC1R, a tiny pouch-like receptor on the surface of melanocytes. When the melanocyte stimulating hormone (MSH) drops into the pouch, it causes a surge in the melanocyte’s production of the chemical cAMP, which in turn stimulates melanocytes to produce the melanin pigment. If cAMP levels are low, the melanocytes make red or blond melanin; if levels are high, they make brown or black melanin.

The Dana-Farber researchers treated the fair-skinned mice with a compound called forskolin, derived from the forskohlii plant found in India and known to increase cAMP levels. The treated mice turned dark, proving that melanocytes in fair-skinned mice - and, perhaps, fair-skinned humans - are not inherently unable to produce pigment if they are appropriately stimulated.

Further experiments showed that the red-haired mice treated with forskolin developed tans that were virtually indistinguishable from the natural tans in dark-haired mice.

The Dana-Farber researchers also showed that tans acquired through forskolin conferred significant protection against skin cancer caused by exposure to UV light. Finally, the study noted that while it is unknown whether forskolin can penetrate deeply enough in human skin to activate melanocytes, the research results suggest that other substances that do reach deep into the skin may well have the same pigmentation effects in humans as forskolin has in mice.