New tan drug gives sun-kissed glow sans cancer risk

The days of lounging on a beach or in a tanning booth may soon become a history as a team of researchers has come up with a drug that can give you the golden-coloured skin sans exposure to harmful UV rays.

Researchers in Boston developed a class of small molecules that successfully penetrates and darkens human skin samples in the laboratory.

The drug also generates protective tans in red-haired mice, which like their human counterparts are more susceptible to skin cancer via ultraviolet (UV) radiation. The molecule works by stimulating cells to produce more UV-absorbing pigments, but more preclinical tests need to be done before it is proven safe in humans.

The work follows up on a 2006 study in Nature that showed how another topical compound, forskolin, could induce a cancer-protecting tan in red-haired mice without the need of UV radiation. However, the researchers soon found that forskolin could not get into human skin. Because humans are relatively hairless compared to other mammals, our skin has had to toughen up, evolving to withstand a range of environment threats, such as ultraviolet radiation, muddy water, and cold temperatures.

"Human skin is a very good barrier and is a formidable penetration challenge, therefore other topical approaches just did not work," said senior author David E. Fisher. "But ten years later, we have come up with a solution. It's a different class of compounds, that work by targeting a different enzyme that converges on the same pathway that leads to pigmentation."

The researchers tested the small molecules on discarded extra skin that they maintained in the laboratory on a Petri dish, and found that darkening took place proportional to the dose and the schedule at which the drug was applied. These artificial tans lasted for days. When applied to the red-haired mice, they could become almost jet black in a day or two with a strong enough dose. The colour fades away over time as normal skin cells slough off the surface, and skin tone gets back to normal within a week or so.

"We believe the potential importance of this work is towards a novel strategy for skin cancer prevention," Fisher noted. "Skin is the most common organ in our bodies to be afflicted with cancer, and the majority of cases are thought to be associated with UV radiation. But we've found that the picture is more complicated, that red-blonde pigments are also more intrinsically carcinogenic, whereas dark melanin is intrinsically beneficial if not produced through use of dangerous UV injury to skin. Our approach could help switch pigments to those found in darker skin, without a need for UV exposure."

The long-term goal of this research is to create something that could be used in combination with traditional UV-absorbing sunscreens. The team's next step is to continue testing the safety of the small molecule in animals before doing toxicity studies in humans.

The study appears in the journal Cell Reports.

-ANI