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Scientists have identified a gene mutation found exclusively in deadly skin cancers caused by exposure to ultraviolet radiation.

The discovery by Yale University researchers in the US, in collaboration with the Queensland Institute of Medical Research, could eventually lead to new drugs to target the mutation found in about 9 per cent of melanoma patients.

The finding emerged from the biggest melanoma gene study to date, which involved the examination of every gene in 147 skin cancers.

Professor Nick Hayward from the QIMR's Oncogenomics Laboratory said scientists also showed the mutation promoted malignant cell growth, spreading the cancer beyond the skin to critical organs.

Most importantly, the mutation was caused by exposure to sunlight.

"This mutation was exclusively found in melanomas on parts of the body that were exposed to sunlight," Professor Hayward said.

"The actual mutation itself has a chemical or molecular signature that indicates it was likely caused by ultraviolet light.

"This particular defect seems to be one that occurs in melanomas that have had excessive sun exposure."

The abnormality in the RAC1 gene is the third most frequent cancer-driving mutation found in melanomas, but the two other most common mutations - BRAF and NRAS - do not have the characteristic of ultraviolet light exposure.

Professor Hayward predicted that pharmaceutical companies might already be thinking about how to target with drugs this particular type of defect, because of its biological similarities with other gene mutations.

If this was the case, the first wave of drugs to treat the new mutation could be in clinical trials within three to five years, he said.

Oncologist and researcher Dr Georgina Long from Melanoma Institute Australia said the discovery of the new mutation was particularly significant for Australia which had the highest incidence of melanoma in the world.

"Genetic mutations including the BRAF mutation present in about half of all melanomas in Australia has led to recent new drug treatments showing great promise for patients with metastatic melanoma," Dr Long said.

"Our aim is to be able to tailor each patient's treatment to the genetic nature of their tumour and this discovery is a great step in the potential for the development of improved treatment options for patients with melanoma."

Metastatic melanoma is when the cancer spreads from its original location to other parts of the body.

The research was published in the journal Nature Genetics.