(HealthDay News) – Metastatic melanomas from patients with chronic sun exposure have higher mutation rates, and a single gene is mutated in 14% of metastatic melanomas, according to a study published online May 9 in Nature.

Michael F. Berger, PhD, from the Broad Institute in Cambridge, MA, and colleagues performed whole-genome sequencing of 25 metastatic melanomas and matched peripheral blood.

The researchers found that, while the average mutation rate was 30 per megabase, the rate varied from three to 14 when the primary tumor originated from the nonultraviolet-exposed hairless skin of the extremities, and from five to 55 in tumors from the hair-bearing skin of the trunk. In a tumor from a patient with a history of chronic sun exposure, the mutation rate was 111 per megabase. The PREX2 gene was mutated at a rate of 14% in an independent set of 107 human melanomas, and a mutant PREX2 accelerated tumor formation in human melanocytes in vivo.

“Thus, whole-genome sequencing of human melanoma tumors revealed genomic evidence of ultraviolet pathogenesis and discovered a new recurrently mutated gene in melanoma,” Berger and colleagues conclude.

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