A genetic link between red hair, freckles and skin cancer

Whether you call them redheads, devil’s offspring, or just plain sexy, be sure to call redheads out of the sun, because with their fiery tresses comes a powerful propensity to develop melanoma, a form particularly fatal from skin cancer.

And now scientists are starting to find out why redheads – and possibly non-gingers who carry a genetic variant common to redheads – can be so vulnerable: for those who carry an allele, or gene variant, associated with red hair and cancer-causing genetic mutations occur at a rate 42% higher than in people who do not carry this gene variant.

As a result, the average carrier of at least one problematic variant of the melanocortin 1 receptor gene, or MC1R, tends to develop cancer-promoting mutations at about the same rate as someone 21 years their senior.

And this despite the known tendency of these people to avoid spending days in the sun, a factor known to initiate cellular changes leading to skin cancer.

Redheads make up around 1% to 2% of the world’s population and up to 10% to 13% of the population in Scotland and Ireland, respectively. But they make up 16% of the world’s melanoma patient population.

At the same time, 26-40% of melanoma patients carry at least one R allele of the MC1R gene, which, because it is recessive, will not always result in redness and freckles. So, doctors treating people with red hair or a tendency to freckles, or whose parents had them, had known for a long time that something was wrong.

In a to study published Tuesday in the journal Nature Communications, an international team led by cancer geneticists from the Sanger Institute in the United Kingdom analyzed the “germinal” genes of 273 melanoma patients (more or less, the DNA carried by all their cells over a lifetime) for evidence of their MC1R carrier status. Then, they sequenced the genes of 343 tumors taken from these patients in search of “somatic” mutations. Somatic mutations are changes in the underlying germline genes that exist only in the tumor sample and are therefore believed to play a role in the initiation or growth of cancer.

Just over half of the patients whose genes were questioned were people who did not carry even a single copy of the problematic R allele of the MC1R gene. Most of the rest were carriers of a single allele, meaning that they were probably not classic redheads but had inherited a copy of the variant gene from a parent who was. Only 28 of the 273 individuals whose tumors were genetically sequenced carried two of the R alleles linked to redhead.

When they compared somatic mutations in tumors from these populations, the researchers observed a clear pattern: melanoma patients who were not carriers at all. In carriers of the MC1R variants, even non-cancerous cells seemed to accumulate mutations more easily, the researchers found.

These results suggest how it is that redheads and their colleagues carrying an R allele may be more likely than non-carriers to develop melanoma. Any of these mutations found in a patient’s tumor may play a role in allowing cancer to gain a foothold, stimulating its growth, or preventing DNA repair genes from intervening and correcting another. problematic mutation. In principle, the more mutations a tumor has, the more likely it is to become fatal.

This, according to Dr. Brian P. Pollack, a melanoma expert at Emory University, is a reasonable inference for researchers to make. But Pollack, who was not involved in the current study, warned that not all somatic mutations in a tumor are bad news: increasingly, as researchers pursue immunologic therapies for cancers such than melanoma, they discover that certain somatic mutations might be helpful, unmasking a tumor to the immune system as a foreign threat.

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Pollack added that more research is needed to establish whether carriers of a single R allele – people who likely have at least one parent with red hair and freckles but who do not exhibit this trait themselves – are in fact just as vulnerable to the development of melanoma as are redheads who carry both alleles.

“This is a very important question raised by this study,” Pollack said. If the risk of melanoma is also high for carriers of a single MC1R allele and for redheads with two of these variants, “should dermatologists and other healthcare professionals ask patients if they have a relative with the? Red hair ? ” He asked.

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