For a number of years, the association between red hair and increased risk of skin cancer has been alluded to, yet the molecular mechanisms have been poorly understood. However now, researchers at the Wellcome Trust Sanger Institute and the University of Leeds have proved, for the first time, that gene variants associated with red hair, pale skin, and freckles are linked to a higher number of genetic mutations in skin cancers. The burden of mutations associated with these variants is comparable to an extra 21 years of sun exposure in people without this variant.
“It has been known for a while that a person with red hair has an increased likelihood of developing skin cancer, but this is the first time that the gene has been proven to be associated with skin cancers with more mutations,” explained co-senior study author David Adams, Ph.D., group leader at Sanger. “Unexpectedly, we also showed that people with only a single copy of the gene variant still have a much higher number of tumor mutations than the rest of the population. This is one of the first examples of a common genetic profile having a substantial impact on a cancer genome and could help better identify people at higher risk of developing skin cancer.”
Redheads constitute close to 2% of the world's population, and many carry variant copies of the MC1R gene, which affects the type of melanin pigment they produce—leading to red hair, freckles, pale skin, and a strong tendency to burn in the sun. While many individuals with red hair contain two copies of the variant MRC1 gene, investigators in this new study found that even a single copy of a red hair–associated MC1R gene variant increased the number of mutations in melanoma skin cancer—the most severe form of skin cancer. Moreover, many non-red-haired people carry these common variants, and the study shows that everyone needs to be careful about sun exposure.
The findings from this study were published recently in Nature Communications in an article entitled “Germline MC1R Status Influences Somatic Mutation Burden in Melanoma.”
The U.K. researchers analyzed publicly available datasets of tumor DNA sequences collected from more than 400 people. They found an average of 42% more sun-associated mutations in tumors from people carrying the gene variant.
“This is the first study to look at how the inherited MC1R gene affects the number of spontaneous mutations in skin cancers and has significant implications for understanding how skin cancers form,” noted co-senior study author Timothy Bishop, Ph.D., professor, and director at the Leeds Institute of Cancer and Pathology. “It has only been possible due to the large-scale data available. The tumors were sequenced in the USA, from patients all over the world and the data was made freely accessible to all researchers. This study illustrates how important international collaboration and free public access to datasets is to research.”
Previously, researchers have hypothesized that the type of skin pigment associated with redheads could allow more ultraviolet (UV) light to reach the DNA. Although this is still a potential mechanism of damage, the current study showed that the MC1R gene variation not only increased the number of spontaneous mutations caused by UV light but also raised the level of other mutations in the tumors. This suggests that biological processes exist for cancer development in people with MC1R variation that are not solely related to ultraviolet light.
“This important research explains why red-haired people have to be so careful about covering up in strong sun,” remarked Julie Sharp, Ph.D., head of health and patient information at Cancer Research UK, who was not directly involved in the study. “It also underlines that it isn't just people with red hair who need to protect themselves from too much sun. People who tend to burn rather than tan, or who have fair skin, hair, or eyes, or who have freckles or moles are also at higher risk. For all of us, the best way to protect skin when the sun is strong is to spend time in the shade between 11 am and 3 pm, and to cover up with a t-shirt, hat, and sunglasses. And sunscreen helps protect the parts you can't cover—use one with at least SPF15 and 4 or more stars, put on plenty and reapply regularly.”