Up to 70 per cent of cases of malignant melanoma, the most deadly form of skin cancer, may be triggered by a mutation in the BRAF gene caused by ageing and over-exposure to the sun. Details of the new findings were published in the journal Cancer Cell by a team from the UK's Institute of Cancer Research (ICR).
At least two-thirds of all malignant melanomas, and up to 90 per cent of other skin cancers, are caused by over-exposure to sunlight, and the DNA damage it causes in sunburnt skin cells. ICR scientists had previously linked mutations in damaged BRAF genes to skin cancer but did not know if it was the cause. The same researchers have now established that the BRAF gene mutation can be the first event in a cascade of genetic changes that eventually lead to melanoma. Although the findings come from experiments involving mice, the researchers are confident that the melanomas which develop in the animals closely resemble those that develop in humans.
Skin cancer is seventh most common cancer in the UK with about 100,000 cases being diagnosed each year. Whilst malignant melanoma accounts for only a small percentage of these skin cancers (around 9,500 cases a year) it is responsible for the most skin-cancer deaths, killing about 2,300 people annually in the UK. Like most cancers, skin cancer is more common with increasing age, but malignant melanoma is disproportionately high in young people. Almost one third of all cases of malignant melanoma occur in people under 50 and it is the second most common cancer in young adults aged 15-34. Over the last 25 years, rates of malignant melanoma in Britain have risen faster than any other common cancer, and incidence rates have risen 40 per cent in just six years, and quadrupled since the 1970s.
'We know that excessive sun exposure is the main cause of cancer, but not much is known about the genetics behind it' said Professor Richard Marais, lead researcher on the project. 'Our study shows that genetic damage of BRAF is the first step in skin cancer development. Understanding this process will help us develop more effective treatments for the disease'.
'There is lots of exciting research focused on developing new therapies that will block the function for the mutant BRAF' said Dr Lesley Walker, the director of information at Cancer Research UK who funded the new ICR study. 'A better understanding of the genetics of skin cancer can help scientists develop more targeted drugs with fewer side effects to treat the disease'. She continued: 'This week, Cancer Research UK launches our SunSmart campaign to help raise awareness of the risks and causes of skin cancer'. It is recommended that holiday-makers only sunbathe before 11am and after 4pm, when the sun is less intense. Broad spectrum sunscreen should be applied liberally and regularly, and skin should be covered up wherever possible.
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Genetic defect 'skin cancer link'