Scientists Close to Finding Gene Linked to Skin Cancer

SAN DIEGO — Scientists are zeroing in on the gene that causes melanoma, the deadly form of skin cancer.

Several teams are working to find the gene, and one of the researchers said he expects it will be located within a year or two.

Unlike basal and squamous cell skin cancers, which are highly curable, melanoma is often quickly fatal unless caught early. This year, the American Cancer Society predicts that 6,800 Americans will die from melanoma.

“The rate of melanoma is increasing faster than any other cancer in the United States,” said Dr. Darrell Rigel of New York University. “At the current rate, approximately one in five Americans will develop melanoma during their lifetime.”

Melanoma runs in families; this suggests that an inherited genetic susceptibility plays some role in the cancer. In recent years, researchers have been looking for a melanoma gene in families afflicted with the disease.

Among them is Dr. Laurence Meyer of the University of Utah. At a recent cancer society conference, he said scientists believe they have narrowed the search to a small stretch of one human chromosome.

Animal studies hint that it might be a tumor-suppressor gene. These are genes that, when they work correctly, prevent cancer.

In some cancer families, people inherit one damaged copy of such a gene and one good copy. If the good copy somehow becomes scrambled, cancer occurs. Cancer is much less common among those born with two good copies of the gene, because they stay cancer free unless both copies are damaged.

Meyer said his group has narrowed the location of the gene to a stretch of DNA that contains 2 million bits of genetic information. He called this “a major step toward isolation of the melanoma risk gene.”

Finding the gene would have two major advantages: It would allow scientists to develop a blood test for the cancer gene, so people at high risk of melanoma could be identified and checked frequently for the cancer. And it would provide underlying clues about the cause of the disease, allowing researchers to search for new therapies to treat or prevent it.

Meyer’s group has been tracking the gene’s location among 82 melanoma victims who are members of 11 families.

He said several lines of evidence suggest the genetic spot they are looking at truly contains a melanoma gene:

* A 34-year-old woman whose genetic material was scrambled in this area had several melanomas.

* Sometimes parts of this genetic region are missing in people who have melanoma or moles that are also associated with the disease.

* Animal studies suggest a tumor-suppressor gene is located in this area.

Melanoma is most common in people who have light complexions, who tan poorly and who have large numbers of irregularly shaped moles known as dysplastic nevi. Doctors warn that such people should be especially careful to avoid overdoing sun exposure.