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Skin Cancer May Be Helped by Inflammation

Posted: October 24, 2008

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The significance of the new study is that the researchers have shown that IDO, or indoleomine 2,3-dioxygenase, may be produced as a part of the inflammatory mix, which could then protect the malignant skin cells. "'Chronic' is the key word," Dr. Mellor says, noting high melanoma rates in Australians, for example, who live deep in the southern hemisphere. "We have long suspected that IDO is a component of certain kinds of inflammation that create suppression," says Dr. Mellor.

IDO's "firefighter" role probably resulted from the body's need to control inflammation in areas such as the gastrointestinal tract. The GI tract is constantly bombarded by food and microbes which could lead to debilitating and deadly inflammation. "You really set a fire," Dr. Mellor says of inflammation.

In fact, the English word inflammation comes from the Latin word inflamatio, which means to set a fire. But instead of helping protect healthy tissue as it does in the GI tract, IDO becomes problematic in cancer.

The latest finding shows IDO has a more important and earlier role than we thought in tumor formation, says Dr. Mellor. He and colleague Dr. David Munn led a research team that 10 years ago showed fetuses use IDO to avoid rejection by the mother's immune system. They and others have subsequently shown that tumors, including melanoma, as well as infectious agents such as HIV also use IDO to escape an immune attack. "IDO favors the tumor: The immune system basically sits back and watches the tumor grow," says Dr. Mellor.

Transplant patients, who require generalized immune inhibitors to keep their transplanted organs, also can be victims of this suppressive inflammation, says Dr. Mellor, noting their high risk of lymphoma after a few years of therapy.