NEW YORK — Scientists have identified a defective gene that appears to cause an inherited tendency to the deadly skin cancer melanoma and may also play a role in non-inherited melanoma.
In its normal state, the gene acts as a brake on cancer. But people who inherit a defective version apparently lose part of the protection, making them unusually vulnerable to melanoma, the researchers said.
About 32,000 melanoma cases and nearly 7,000 melanoma deaths are expected in the United States this year. Only about 10% of melanoma occurs in people with an inherited tendency and it is unclear what percentage of inherited cases are because of the gene.
Defective versions of the gene may also be involved in many, or maybe even most, cases of non-inherited melanoma, researchers said. In those cases, the gene would be inherited in normal form but later damaged by sunlight or other causes.
Studying the gene may eventually lead to better treatments for the non-inherited disease, researchers said.
More immediately, the discovery of a susceptibility gene could be used to screen for people at risk for melanoma. They could be counseled to take steps such as limiting exposure to the sun, keeping track of possibly precancerous moles and using sunscreen, researchers said.
The normal gene tells the body how to make a protein called p16, which helps regulate cell division. Prior studies suggested the p16 gene discourages tumors. Previous studies also indicated defective versions play a role in cancer.
The new work is reported in the September issue of the journal Nature Genetics by two independent teams of researchers.
One study was done by Nicholas Dracopoli of the National Center for Human Genome Research, part of the National Institutes of Health in Bethesda, Md., and colleagues at NIH and elsewhere.
They found nine of 18 melanoma-prone families they screened showed defects in the p16 gene that appeared related to the disease. In the nine families, the gene was defective in 33 out of 36 people with melanoma.
The second study was done by Alexander Kamb of Myriad Genetics Inc. in Salt Lake City with scientists at the University of Utah and elsewhere.
They studied 13 families who already appeared to have a predisposition to melanoma from some abnormality in the neighborhood of the p16 gene. The researchers found a defective p16 gene in two of the families. They found no evidence of a defective p16 gene in 38 other melanoma-prone families.
Nonetheless, the Utah and NIH studies "really support each other, fundamentally," Kamb said, noting that two types of p16 gene defects appeared in both studies.