Interferon-gamma, a protein used by the immune system for intercellular communication, has been found in mice to promote melanoma, the deadly black skin cancer.
A National Institutes of Health (NIH) study, led by National Cancer Institute (NCI) researchers, was published on line in Nature, January 19, 2011.  This research sought to understand how the solar ultraviolet (UV) radiation causes melanoma.
Melanoma is an aggressive, often drug-resistant cancer seen increasingly more frequently in young women and middle-aged men. UV exposure through tanning beds contributes to the disease found in young women, while natural UV exposure in outdoor sporting activities attends the men.
The major melanoma risk factor is exposure to UV radiation from the sun, and the most potent carcinogenic effect comes from intermittent sun burning doses of UV in childhood.
The current study examined over 10 years lines of genetically engineered mice to understand the connection between UV radiation exposure and malignant melanoma. The researchers discovered that inhibiting interferon-gamma immediately after sunburn might prevent malignant melanoma formation. [2,3]
The gamma interferon is released by tissue macrophages into skin damaged by UV radiation. Tissue macrophages are cells, which orchestrate immune responses to infection, poison ivy, and other inflammatory skin disorders. Macrophages containing interferon-gamma were found in 70% of melanomas studied.
Most interferons exhibit antineoplastic effects. In these studies, gamma interferon was found to promote melanoma development in mice. The key to the experiments, led by Glenn Merlino, Ph.D., was the development of a unique genetically engineered mouse in which the melanocytes were exclusively labeled with a green fluorescent protein. This tag allowed visual tracking of the melanocytes in the mouse skin.
Researchers observed that UV radiation in doses capable of causing sunburn in human skin caused increased numbers and movement of melanocytes in the mouse skin.
When interferon-gamma was inhibited in the skin, the melanocyte changes were blocked. “We anticipate that this discovery may change how interferons are used in the clinic as anticancer agents,” said Merlino. “Our findings raise the possibility that targeting the interferon-gamma pathway may represent a novel, less toxic therapeutic alternative for effective treatment of malignant melanoma patients, who currently have poor cure rates.”
 NIH study in mice uncovers pathway critical for UV-induced melanoma. A National Institutes of Health (NIH) study, led by National Cancer Institute (NCI) researchers, was published on line in Nature, January 19, 2011.
[2www.cancer.gov. The National Institutes of Health (NIH) — The Nation’s Medical Research Agency — includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services.
 For more information about cancer, please visit the NCI Web site at www.cancer.gov or call NCI’s Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).