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Gene Mutation, Disease Linked

September 23, 1999

WASHINGTON (AP) _ A gene mutation already linked to cancer has been shown in laboratory studies to also cause the immune system to attack the kidneys and other organs.

In mouse studies, researchers at Memorial Sloan-Kettering Cancer Center found that a single mutation in a gene called PTEN is enough to trigger cancer and autoimmune diseases.

Dr. Pier Paolo Pandolfi of Memorial Sloan-Kettering, senior author of a study appearing Friday in the journal Science, said PTEN is normally present in pairs in each cell and its function is to kill abnormal cells that could develop into cancer.

But Pandolfi said his team found in the mouse studies that a mutation of a single PTEN gene is enough to start a disease process. PTEN mutation has been linked to cancers of the breast, prostate, ovary, colon, skin and lymph system.

``Our study shows that the loss of just one PTEN gene is enough to ... begin the process of uncontrolled cell growth (cancer),″ Pandolfi.

PTEN is one of a number of gene pairs that help to eliminate cells that are at risk of converting to cancerous growths. The genes work by causing flawed cells to kill themselves, a process called apoptosis. For most gene pairs, both copies must be lost or mutated for the apoptosis process to be eliminated.

Pandolfi said, however, that apoptosis is lost or restricted in a cell when only one PTEN gene is mutated.

The study in mice showed that a single PTEN mutation also allows white blood cells, or lymphocytes, to accumulate in tissue and to eventually start attacking organs in the body, a process called autoimmune disease.

In mice bred with the PTEN mutation, the lungs, kidneys, spleen and other organs became enlarged and inflamed from attack by the lymphocytes. Eventually, the mice died from a disease process similar to lupus, an autoimmune disease often fatal in humans, said Pandolfi.

Although PTEN mutation has been linked to a number of human cancers, it has not been determined if the mutation is also present in patients with lupus. Pandolfi said he and his team are now looking for the PTEN mutation in DNA samples from lupus patients.

If it is shown the mutation is present in lupus, he said, it might then be possible to develop a drug that blocks the effects of the gene mutation.

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