A consortium of European and Australian scientists doing a genome-wide association study found three gene variants were strongly linked to melanoma risk: two of them had previously been linked to pigmentation, freckling and sun sensitivity, and one was a new discovery. The findings may explain why people with the most moles on their skin have the highest risk of melanoma, the most dangerous form of skin cancer.

The study was led by Professors Julia Newton Bishop and Tim Bishop of the Melanoma Genetics Consortium (GenoMEL) at the University of Leeds and is published in the 5 July online issue of Nature Genetics.

For the study, they examined the genetic make up of more than 10,000 people, which meant looking at over 300,000 variants or "snips" (SNPs, single nuclotide polymorphisms) comparing those of people with melanoma to those who did not have the disease. They found a number of clear, genetic patterns.

Every year about 48,000 people worldwide die of melanoma, a disease responsible for most deaths from skin cancer. Many scientists suggest that the increase in melanomas in recent decades is partly due to the emergency of package holidays where people who don't get a lot of sun most of the year suddenly expose themselves to a lot of it for one or two weeks. They say intermittent, rather than daily exposure to the sun over longer periods puts people at higher risk of melanoma.

Also, it has already been shown that people who burn easily, have fair skin and red hair are most at risk of melanoma. The researchers found that the people in this study who had been diagnosed with melanoma were also more likely to be carrying genes that gave them red hair and freckles.

He and his colleagues found clear links between some genes on chromosomes 9 and 22 and increased risk of melanoma, but, as he explained:

"These genes were not associated with skin colour."

In fact, what they found, when they teamed up with colleagues at King's College London and in Brisbane, Australia, who had been counting moles on twins, was that:

"These genes actually influenced the number of moles a person has," said Bishop. However, we still don't know much about how sunshine and genetics come together to cause cancer in some people, he added, explaining that:

"If you take the people who have the greatest exposure to sunlight -- those who work outside for example -- and compare them to those with the least exposure, their risks of getting skin cancer are actually quite similar. Statistically, the differences are quite negligible."

"The research goes further and identifies the actual genes associated with this increased risk."