The Skin Cancer Foundation Journal

MAY 2014

The 2012 edition of The Skin Cancer Foundation Journal features medically reviewed, reader-friendly articles such as tanning, the increasing incidence of skin cancer diagnoses among young women, & the prevalence of melanoma among white males over 50.

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work to ensure that the skin cells repair the damage before the cells can divide and start multiplying out of control, leading to skin cancer. But ironically, as these experiments have shown, the p53 gene itself is often mutated by expo- sure to the sun's UVR, and its important protective func- tion is lost. The fnding that broad spectrum sunscreen completely prevented p53 damage in the keratinocytes reinforces previous studies showing that sunscreens help prevent skin cancer. 2,3 Potentially of even greater importance were the obser- vations regarding the response of pigment cells to UVR. These cells are of particular interest because they are the launch pad for melanomas. At the site of the sun-exposed, unprotected skin, pigment cells rapidly increased in num- ber; by the 14-day mark, there were twice as many in the skin as there were before UVR exposure. At the site pro- tected by sunscreen, however, the number of pigment cells two weeks after sun exposure was the same as before sun exposure. Scientists believe that many melanomas arise be- cause of mutations that occur in the DNA of pigment cells following rapid proliferation; but the sunscreen completely prevented this proliferative response. These experiments suggest that sunscreen may provide protection against mel- anoma by blocking the pigment cells' proliferative response. Redheaded Twists and Turns U nexpectedly, the investigators found that the pigment cells of redheads – specifcally people who carried 'red hair' variants of the melanocortin 1 receptor gene (MC1R) – underwent signifcantly less proliferation after sun exposure Protecting the Skin Cells W hat happens to skin cells after exposure to sun- light? Researchers recently explored this ques- tion at the QIMR Berghofer Medical Research In- stitute and the Queensland University of Technology in Brisbane, Australia. 1 We have long known that the sun's ultraviolet radiation (UVR) can cause DNA mutations in keratinocytes, the most common skin cells, and that these mutations can lead to the non- melanoma skin cancers basal cell carcino- ma (BCC) and squamous cell carcinoma (SCC). However, comparatively little has been known about the efects of sunlight on melanocytes, the melanin-producing (pigment-producing) skin cells, from which melanomas arise. In a series of experiments, the re- searchers recruited 57 volunteers be- tween 18 and 34 years of age and exposed two small areas of their skin to modest doses of UVR, equivalent to about 20 minutes in the summer sun. For each subject, one skin site was pro- tected with broad spectrum SPF 30+ sunscreen ap- plied before UVR exposure, while the other site was left unprotected. The researchers asked the volunteers to return 24 hours after exposure, then again 14 days later, so that their skin could be examined and biop- sied for molecular analysis. As expected, biopsies of the unprotected UVR- exposed skin at the 24-hour mark showed consid- erable evidence of DNA damage in keratinocytes, par- ticularly in a key regulatory gene called p53. (Regulatory genes help control the expression of one or more other genes, either repressing or activating these genes to keep the body functioning in balance.) In contrast, the skin that had been protected by sunscreen showed no evidence of DNA damage in the keratinocytes. These important fndings demonstrate that sunscreen can help prevent the types of molecular damage induced by sunlight that are known to cause BCC and SCC. Normally, when sunlight damages the DNA in our skin cells, the p53 gene goes to No matter how careful someone is about sun- screen use, some UVR gets through to the skin. It must be seen as just one vital strat- egy in the arsenal of sun protection, along with shade, sun-protective clothing, wide- brimmed hats, and UV-blocking sunglasses. This is especially true for redheads. edheads face double trouble in the sun: their fair Type 1 skin is generally incapable of tanning, and after almost no time at all outdoors, they start to burn. The upshot? A heightened risk of all three major skin cancers, especially melanomas, which can be deadly. But according to new research, this doesn't mean they have to spend their daylight hours huddling indoors. 75

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