Scientists have discovered a common element in 70% of malignant skin cancers which could become a revolutionary new treatment.

Experts have high hopes for the discovery because the previously unknown mutation is very similar to another that helps cause a type of leukaemia.

In trials, a drug which blocks that gene has already been outstandingly successful in treating leukaemia patients.

The defect is not inherited and no-one yet knows what causes it, but it is believed to be a very powerful mutation.

It could be a direct lead to new treatments for malignant melanoma

Professor Mike Stratton, Cancer Genome Project

If it can be isolated, it is hoped it can be turned into a treatment for malignant melanoma.

The breakthrough, announced in an online report from the journal Nature, is the first to emerge from the Cancer Genome Project, based at Hinxton, Cambridgeshire.

Two years ago scientists at the Wellcome Trust Sanger Institute in Hinxton launched a search for cancer genes buried among the 3.2 billion letters of DNA code and estimated 30,000 genes that make up the human gene atlas.

The team is targeting 48 common cancers by looking for differences between their DNA and that of normal cells.

Trials

Professor Mike Stratton, head of the Cancer Genome Project, said: "The most exciting thing about this discovery is that it could be a direct lead to new treatments for malignant melanoma."

Skin cancer facts

1,600 people in the UK die each year from skin cancer 1,400 of those cases are caused by exposure to too much sun 300 more cases are reported each year in the UK

Prof Stratton said it could take about five years to identify a safe compound that could work.

This would have to be followed by several years of clinical trials.

It would probably be about 15 years before a drug became available, he said.

In the UK, 6,000 new cases of malignant melanoma are diagnosed each year and 1,700 people die from the disease.

Ultra-violet

The number of new cases in the US is 54,000, and the number of deaths each year 7,400.

Dr Mike Dexter, director of the Wellcome Trust, said he expected information from the human genome to lead to a revolution in cancer treatment.

"I hope that over the next five years the Cancer Genome Project will identify the vast majority of the genes involved in the most common cancers," he said.

Peter Lapsley, chief executive of the Skin Care Campaign, said: "This is an intriguing discovery which highlights the close association between genetics and cancer.

"The cause of this genetic mutation is unclear, but we do know that ultra-violet radiation damages DNA and triggers cancer.

"There is a direct link between sun exposure and melanoma, and people must remain alert to this danger."