BOSTONA protein known as the "master watchman of the genome" for its ability to guard against cancer-causing DNA damage has been found to provide an entirely different level of cancer protection: By prompting the skin to tan in response to ultraviolet light from the sun, it deters the development of melanoma skin cancer, the fastest-increasing form of cancer in the world.

In a study in the March 9 issue of the journal Cell, researchers at Dana-Farber Cancer Institute report that the protein, p53, is not only linked to skin tanning, but also may play a role in people's seemingly universal desire to be in the sun an activity that, by promoting tanning, can reduce one's risk of melanoma.

"The number one risk factor for melanoma is an inability to tan; people who tan easily or have dark pigmentation are far less likely to develop the disease," says the study's senior author, David E. Fisher, MD, PhD, director of the Melanoma Program at Dana-Farber and a professor in pediatrics at Children's Hospital Boston. "This study suggests that p53, one of the best-known tumor-suppressor proteins in our body, has a powerful role in protecting us against sun damage in the skin."

In a study published last year, Fisher and his colleagues found that ultraviolet (UV) radiation from the sun causes skin cells called keratinocytes to make and secrete a hormone called alpha-MSH, which attaches to nearby skin cells called melanocytes and spurs them to produce skin-darkening pigment called melanin. The chain of events within keratinocytes that leads to alpha-MSH production, however, was a mystery.

Investigators knew that alpha-MSH is created when another protein, known as pro-opiomelanocortin (or POMC), is split apart. They also knew that the amount of POMC within cells rises sharply when they're exposed to UV rays. But they didn't know what caused the POMC to increase.

One possibility was p53. When Fisher and his colleagues examined the s
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Contact: Teresa Herbert
617-632-4090
Dana-Farber Cancer Institute
8-Mar-2007