Monday May 13 2013
Redheads' fair skin is what increases their risk of skin cancer
'Redheads are at increased risk of skin cancer even if they don't spend time in the sun,' is the headline on the Mail Online website.
The story refers to a discussion piece in a journal that outlines theories about the results of some animal experiments. This research involved mice genetically engineered to have red fur and predisposed to develop melanoma.
Although exposure to ultraviolet (UV) light is known to be a major risk factor for melanomas, the researchers found that genetically engineered mice with red fur still had a high risk of developing melanomas even without UV exposure.
The article discusses potential explanations for why this could be the case, and these theories now need to be tested to see if they are correct.
It is not yet clear how well these animal studies represent what happens in people with red hair. It would be very difficult to test this directly, as keeping people completely away from sunlight would be impractical and potentially unethical.
UV light exposure is known to increase the risk of melanoma in redheads and non-redheads alike. It is important that people with red hair should continue to use sensible precautions to avoid excessive UV exposure and sunburn, despite this news.
Where did the story come from?
The article was written by researchers from the Cutaneous Biology Research Center at Massachusetts General Hospital in the US.
No sources of funding for the article were reported. It was published as an "Ideas and Speculations" article in the journal BioEssays. These pieces are described as "creative thinking and predictions on open questions and recent developments in biology".
The article has been peer-reviewed.
The news is based on an article by researchers that presents possible explanations for their previous finding that genetically engineered mice with red fur and a predisposition to melanoma develop this cancer even without UV exposure.
Some of the Mail Online reporting suggests that the findings of this research are more conclusive than is possible to say at this stage: "Scientists have discovered that the production of red hair pigment causes an increased risk of melanoma".
However, the BioEssays article was only presenting possible explanations for observations from animal experiments. It was not claiming to have definitive proof that these findings apply to humans.
What kind of article was this?
This was an article discussing the potential link between the red pigment in red hair and skin cancer.
People with red hair and fair skin are known to be at greater risk of getting melanoma, the least common but most serious form of skin cancer, which is responsible for around two thousand deaths a year in the UK.
In general, it is thought that redheads' pale skin makes them more susceptible to UV damage from the sun's rays.
However, the authors of the article say that a recent study from their lab suggests that the pigment that causes hair to turn red (pheomelanin) could itself be linked to the increased risk of cancer, even without UV exposure.
In their article, the authors discuss two possible ways in which the red pigment in red hair might increase the risk of cancer. These preliminary ideas – or hypotheses – are based on previous research and a general understanding of human and cancer biology.
A hypothesis is a possible explanation of why something that researchers have observed might happen. Researchers design experiments to test whether their hypothesis is correct. This process is fundamental to the scientific method.
What did the article say?
The researchers first describe how the red colour in red hair is made, and discuss the results of their recent study before going on to present their hypotheses.
Specific cells in the skin called melanocytes make two kinds of pigment – a brown pigment called eumelanin and a red-orange pigment called pheomelanin. A biochemical process within cells determines how much of each pigment is made.
This process involves a protein called MC1R, which influences the switch between the production of these pigments based on the strength of the signal it sends to the cell and whether the cell has enough of the amino acid cysteine.
In redheads, variations in the gene for the MC1R protein means that it sends weak signals. This means that the cells' stores of cysteine are usually enough for it to favour producing the red/orange pigment pheomelanin.
The researchers recently carried out a study where they introduced a genetic mutation commonly found in melanoma cells into the melanocytes of mice. When they also introduced a genetic mutation into these mice that inactivated the MC1R protein, the mice had red fur and developed melanoma, even without UV exposure. If they introduced another genetic mutation that stopped pigment being made altogether, the mice were albino but they did not develop melanoma.
This led the researchers to suspect that the red pigment pheomelanin could be itself increasing the risk of melanoma. Their research also found that the mice with red fur had more damage to their skin cell DNA caused by very reactive chemicals called free radicals. Free radicals can cause damage to cells at a molecular level.
The researchers do not yet know how the red pigment might be linked with the free radical DNA damage that can increase the risk of melanoma. However, they have presented two hypotheses:
The first hypothesis
The researchers' first hypothesis was that the red pigment itself might generate more free radicals, and that these cause DNA damage that could lead to melanoma. They say that the red pigment is already known to make free radicals when it is exposed to UVA light, but it may be able to do this without UVA light. These free radicals could potentially:
- damage DNA directly
- damage its building blocks, or
- use up the cell's stores of antioxidants, making it more vulnerable to damage by other free radicals
The researchers also discuss in detail the biochemical ways in which the red pigment might generate free radicals.
The second hypothesis
The second hypothesis was that the process of making the red pigment might use up the cell's stores of antioxidants, rather than the red pigment itself. This might make the cells more vulnerable to damage by other free radicals.
They say that the amino acid cysteine used in making the red pigment is also found in the most important antioxidant in the cell, glutathione. If cysteine is used to make the red pigment, this might reduce the cell's ability to make this antioxidant.
The researchers report that red-haired wild boars have been found to have less glutathione in their muscles. However, they acknowledge that it is not possible to say from this whether there is less glutathione due to free radicals from the red pigment itself or the making of the red pigment.
What were the researchers' conclusions?
The researchers presented two hypotheses that could explain how the red skin and hair pigment pheomelanin could increase the risk of the skin cancer melanoma.
They say that their two proposed methods could both be occurring, and that more research could help identify how redheads can reduce their risk of melanoma.
The researchers' article discusses potential ways in which the red pigment found in the cells of people with red hair might increase the risk of melanoma, the most serious form of skin cancer. It is not a standard report of a research study, but the authors put forward potential explanations for their previous research findings. These now need to be tested to see if they are correct.
The researchers' previous research found that mice genetically engineered to be predisposed to melanoma and red fur developed melanomas even without UV exposure. It is not clear to what extent these genetically engineered mice represent what happens in humans.
It would be very challenging to test this – keeping people completely away from UV light would not be feasible or ethical, as we need some sun exposure to make vitamin D, which is needed to make and maintain strong bones. For this reason, research in mice can be very helpful.
It is important that redheads do not take this news as a reason not to protect themselves from the effects of the sun. We already know that UV light exposure increases the risk of melanoma in people regardless of hair colour. People with red hair should continue to use sensible precautions to avoid excessive UV exposure and sunburn.
Read more about reducing your melanoma risk.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.