MedicalResearch: What is the background for this study? What are the main findings?
Dr. Brash: We wanted to know whether the origin of melanoma differed from other cancers because of the melanin. It has long been known that blondes and redheads are sensitive to sunlight, but the prevailing view was that this was because their skin is light. But there are light-skinned, dark-haired people in countries near the equator and they don’t have the high skin cancer incidence seen in Australia. Several labs, including ours, had irradiated cells or mice with UV and found more cell death in cells containing melanin than cells lacking melanin. In the last couple of years, two papers have focused attention on the issue; one study found that irradiating mice with UVA only gave melanomas if the skin contained melanin and the other study found that mice genetically predisposed to UV-induced melanoma developed melanomas even without UV if they also had red melanin.
The most important findings are:
First, our skin continues to be damaged by sunlight even when we’re out of the sun.
Second, the melanin pigment in your skin is bad for you as well as good: it may be carcinogenic as well as protective.
Third, the chemistry underlying these events, chemical excitation of electrons, has not been seen in mammals before.
MedicalResearch: What should clinicians and patients take away from your report?
Dr. Brash: These findings don’t change how we should regulate our sun exposure. I tell people to enjoy the sun but just don’t lie on the beach between 10 and 2, and wear a hat. Sunscreens are useful, too, so long as they block both UVB and UVA. The same rules apply to skiing. After some further research, we should be able to add a new habit: putting on an after-sun cream as soon as we leave the beach.
MedicalResearch: What recommendations do you have for future research as a result of this study?
Dr. Brash: We’re designing studies to identify chemicals that might make a new “after-sun sunscreen”. We are also investigating whether the unusual chemistry of exciting electrons underlies other diseases.
Douglas E. Brash et al. Chemiexcitation of melanin derivatives induces DNA photoproducts long after UV exposure. Science, February 2015 DOI: 10.1126/science.1256022
MedicalResearch.com Interview with: Douglas E. Brash, PhD (2015). Skin Damaged by Sunlight Even When Out of the Sun