U.S. researchers said on Sunday they had identified an enzyme gene that suppresses tumor growth in melanoma, the deadliest form of skin cancer.

The researchers from the National Institutes of Health found that one of the most often mutated genes that code for matrix metalloproteinase (MMP) enzymes, MMP-8, actually serves as a tumor suppressor gene, but not an oncogene, as was previously thought.

MMP enzymes play a key role in the process of remodeling skin after sunburns, cuts or other injuries, and the MMP gene family has long been thought to increase the risk of cancers, including breast, colon and melanoma.

"The study suggests that a better approach may be to look for drugs that restore or increase MMP-8 function or for drugs that block only those MMPs that are truly oncogenes," the researchers said in a press release.

The findings were published in the British journal Nature Genetics.

In their study, the researchers studied a bank of tumor and blood samples collected from 79 patients with aggressive melanoma and found that at least six percent of melanoma patients had mutations in MMP-8.

In laboratory tests, mice injected with cells expressing normalMMP-8, said the researchers, did not develop skin ulcers, which are one of the most important measures of cancer aggression in melanoma.

In contrast, mice injected with cells expressing mutated MMP-8 went on to develop ulcerations and metastases in their lungs, they said.

Globally, melanoma is becoming more common every year. A major cause is thought to be overexposure to the sun. The ultraviolet radiation in sunlight can damage DNA and lead to cancer-causing genetic changes within skin cells.

(Xinhua News Agency March 30, 2009)