Red-hair
gene tied to melanoma
It's no secret that fair-skinned redheads have a higher risk of
melanoma. Now, an Australian group has identified the genetic link.
People with dangerous variants of a gene called the melanocortin-1
receptor (MC1R) have at least double the risk of contracting skin
cancer, even if they have medium or olive skin, researchers said
here today. "The [variants] associated with red hair are the
ones with greatly increased risk of melanoma," says Richard
Sturm of the University of Queensland in Brisbane, Australia, lead
author of the study. Redheads are known to have about a five times
higher risk of melanoma than people with dark hair.
Although exposure to ultraviolet light places people at risk for
melanoma, genetic factors also play a role. People face a high risk
of melanoma if they have fair skin, red hair, blue eyes, freckles,
or a tendency to react to sun by burning rather than tanning.
Sturm's group has spent the last few years trying to pinpoint the
specific genes that underlie these risk factors. They focused on
the MC1R gene because it varies greatly among Caucasians, he says,
and because variants of the gene specify whether a person has red
hair.
The type of MC1R gene a person carries also determines whether
he or she produces the kind of melanin typical of fair-skinned people,
called pheomelanin, or that typical of brown-skinned people, called
eumelanin. "It's the gene that determines your tanning potential,"
Sturm says.
Because of the protective effects of eumelanin, dark-skinned peoples
- such as African-Americans or Australian aborigines - generally
do not develop melanoma, although they can develop other forms of
skin cancer and other sun-induced skin damage such as premature
aging.
In a small preliminary study, the Australian team examined 111
people at high risk and 109 people at low risk for three types of
skin cancer. The researchers then checked to see which alleles of
the MC1R gene were present. The results showed that the presence
of any of the three alleles for red hair triple the risk of skin
cancer and melanoma.
To confirm these results in a larger study, the Australian team
tested for variants of the gene in 459 Australians with melanoma
and 399 research participants who did not have melanoma.
People with one of the three dangerous MC1R variants were twice
as common in the melanoma group as in the control group. People
who were homozygous for the red-hair alleles had four times the
incidence of having skin cancer as people with the wild-type MC1R
gene. But even carriers with darker hair and medium or olive complexions
had more than twice the risk of developing melanoma.
Sturm plans to develop a genetic test that could let people know
their risk more accurately than a self-assessment of skin and hair
color. Still, everyone, no matter what his or her genetic make-up,
needs to limit sun exposure, Sturm says. "Anyone who thinks
they're protected because they have a wild-type genotype is fooling
themselves.
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