"Researchers at the Harvard- affiliated Dana-Farber Cancer Institute in Boston have conducted a series of experiments that put tanning in a different light. A suntan is the body's best effort to fend off the known cancerous effects of ultraviolet light, the invisible portion of the light spectrum that comes in short, energy- packed wavelengths that penetrate the skin and mutate DNA. "

"The Harvard researchers are emphatically on the side of sunscreen and avoidance of excessive sun or other UV exposure. But they're also looking for ways to harness the "tanning pathway" that might give fair-skinned people the protective benefits of having a tan without going through the hazards of getting one. "

"The conventional wisdom about how a suntan comes about has been that when UV light strikes cells in the skin called melanocytes, the cells produce the brownish-black pigment called melanin, which darkens the skin. So while a tan wouldn't cause cancer, it's a sign of the UV exposure that does. "

"But it's well documented that people with dark skin, as well as those who tan easily, are less likely to get skin cancer than fair-skinned people. If a tan signals skin damage, why is it also associated with a lower risk of skin cancer? Might a tan be protective? "

"Experiments have shown that tanning is circuitous process. It starts when UV light provokes keratinocytes, the main cells of the upper epidermis, to release hormones that stimulate melanocytes, which lie deeper in the skin than the keratinocytes. The melanocyte-stimulating hormones latch onto receptors located on the melanocytes, putting the key into the ignition of melanin production. But rather than hoarding the pigment, the melanocytes selflessly send much of it back to the keratinocytes, creating a tan. "

"When the melanin enters a keratinocyte, it concentrates over the nucleus - where the DNA, the cell's genetic material, is located. "

""It actually collects on the sun-facing side of the cell," says Dr. David Fisher, director of the Melanoma Program in Medical Oncology at Dana- "

"Farber. "Under a microscope, the pigment forms into these super-efficient little umbrellas protecting the nuclei." That protection may prevent mutations that could result in skin cancer. "

""The trigger for tanning - UV radiation - is absolutely damaging and absolutely carcinogenic," Fisher continues, noting that the protection afforded by melanin is not absolute. "But tanning itself appears to be an adaptive response to harmful stress." "

"That's the story of tanning, but what about people who don't tan? Fisher's lab and others have conducted experiments that suggest the melanocytes of redheads (who are nontanners) have a variant form of an important receptor. When melanocyte-stimulating hormones bind to those receptors, melanocytes
... read the whole article