BOSTON - Scientists say they have discovered a
cream that may ward off skin cancer by tanning skin a golden bronze without
exposure to the sun.
Tests so far have been confined to mice, but researchers at the Dana-Farber
Cancer Institute and Children's Hospital in Boston say the findings would mark a
seismic shift in the biology of tanning if the cream was determined to be safe
for humans.
Unlike sunless tanning lotions that color the skin, the cream alters skin
pigmentation much like a suntan. The more days it was applied, the darker the
skin became. A heavy application over more than a week left some mice nearly
black.
The mice experienced no dangerous side effects, scientists said.
And researchers said the findings suggest people may be able to change their
skin pigmentation to ward off skin cancers like melanoma, the world's
fastest-growing cancer.
"We just kind of smeared it on once a day, five days a week. Within a couple
of days you could clearly see they were becoming darker," said David Fisher,
director of the Melanoma Program at Dana-Farber and senior author of the study
published in the journal Nature on Thursday.
The cream "switched on the tanning machinery" in mice skin cells that were
genetically designed to resemble those in blond and redheaded people, the study
said.
People who tan easily, or have naturally dark skin, are far less likely to
develop skin cancer than those with fair skin, the study said, a point which
Fisher said underlined its potential significance in reducing cancer rates at a
time when more fair-skinned people are living in sun-belts like the southern
United States, Australia and the Middle East.
TESTING ON HUMANS
In the United States, melanoma accounts for 62,000 new cases of cancer a year
and nearly 8,000 deaths, according to the American Cancer Society.
The molecule at the heart of the cream recreates a process that occurs
naturally when ultraviolet sunlight strikes skin cells. The cells respond
differently depending on a person's skin type. For people who tan well, the
sun's ultraviolet rays initially harm DNA in the skin, but this is followed by a
robust tanning that curbs the DNA damage.
For lousy tanners, even a light tan can inflict significant DNA damage that
can lead to cancers like melanoma by causing pigment-making skin cells known as
melanocytes to begin dividing rampantly. The researchers say a darkening in
pigmentation can help these people reduce that risk.
"Our strategy turns on pigment but doesn't touch the DNA," said Fisher. "This
actually may represent a broader strategy to prevent the damage that UV causes
in the skin, shielding the skin in ways that traditional sunscreens cannot."
The next step, he said, is to test it on humans to see whether ultraviolet
light follows the same path to stimulating pigment change as in the mice, which
have thinner skin.
"Preliminarily it looks like it is exactly the same as human skin," Fisher,
who is also a professor of pediatrics at Harvard Medical School, told Reuters.
"You could give this drug as much as you wanted," he added. "It could get to
a point where it would literally turn the skin a very dark brown/black."
But he said a number of hurdles remain before determining whether it was safe
for humans, including whether it would cause side effects. "The initial glimpses
look promising but it's early still," he said.