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South Island melanoma gene mutations raise questions

September 13, 2016

Mike Eccles


First ever genetic analysis of NZ melanomas

Mutations in a melanoma gene, called NRAS, are far more common in South Islanders' melanomas, raising new questions about excess sun exposure.

The disparity could be linked to sunburn, say the study's University of Otago researchers, whose findings are published in the journal Oncotarget.

New Zealand has the highest rate of melanoma in the world. Each year around 2200 new cases are diagnosed and more than 300 people die from the disease.

The researchers studied 20 mutated genes in samples from 529 patients with advanced melanoma.

In line with overseas findings, the most common mutation was in a gene called BRAF, and one-third of the melanomas in the study showed changes in this gene. The BRAF mutation rates were similar in the North and South of New Zealand.

But the mutation rate for the NRAS gene was 38 per cent for South Islanders and 21 per cent for those from the North Island.

The North Island rate is about the same as that found in other countries, but the South Island rate is almost double the rate in the North Island.

The researchers say the most likely explanation for this is sunburn due to strong exposure to ultraviolet radiation in the South Island. The South Island UV exposure might be the cause of high rates of NRAS mutations in the South Island. However, it is known that the intensity of UV on average is higher in the North Island than in the South Island, and so this raises a paradox. To add to the paradox it has been published by other researchers that younger individuals (<45 years old) have a higher risk of developing melanoma in the South Island than similar aged individuals in the North Island, when adjusted for sex and socio-economic status. Does this then tell us something about the South Island's UV exposure?

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