The incidence of the most aggressive form of skin cancer, melanoma, has doubled over the last 20 years in the U.S. The increase is thought to be due in part to increased exposure to UV light, although the disease can develop in skin that is typically hidden from the sun. Because malignant melanoma is generally unresponsive to chemotherapy, scientists are particularly interested in figuring out how it progresses and developing new means of treatment. Findings published online today by the journal Nature Genetics could help. Researchers report that they have identified a gene that causes melanoma in mice. In humans, the same gene is involved in a third of melanoma cases.

The discovery, made by Suzie Chen of Rutgers University and her colleagues, started with an investigation into how fat cells develop. Chen noted that some of the study mice were developing pigmented skin tumors, which turned out to be melanoma. When the scientists mapped the animals' genomes, they discovered aberrant expression of a gene known as Grm1. The gene was not previously known to be an oncogene. "It is only in a melanocyte skin cell when the expression of this particular gene is turned on that it leads to the development of melanoma," Chen notes. "While in the brain, where it is expressed normally, its functions are associated with learning and memory."

The researchers next examined biopsy tissue taken from patients suffering from melanoma. Signs of similarly abnormal expression of Grm1 existed in more than one third of the cases, they report. The authors hope that their findings will point toward future treatments for the disease. "With our understanding of at least one genetic factor in melanoma," Chen says, "we may now have the ability to design a new, more specific drug to target that gene or the protein it expresses."