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Carriers of Mutated Gene at Risk for Colon Cancer

Study Adds to Evidence About Genetic Cancer Causes
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WebMD Health News

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Sept. 20, 2002 -- Researchers have discovered that carriers of a genetic mutation appear to have an increased risk for colon cancer.

The new study looks at Bloom syndrome, a rare disorder that frequently leads to cancer. Bloom syndrome is caused by mutations in a protective gene known as BLM. There are usually two copies of this gene, and researchers already know that if both are abnormal, the carriers are at increased risk for colon cancer. For this study, they looked at whether individuals who have just one abnormal copy of the gene are also at risk for colorectal cancer.

Researchers obtained genotypes of more than 3,000 people of Ashkenazi-Jewish ancestry - 1,244 of whom had been diagnosed with colorectal cancer -- plus 1,839 controls. The mutated gene, identified as BLM-Ash, is most common in Ashkenazi Jews.

Those with colorectal cancer were more than twice as likely to be a carrier of the mutated gene. Researchers also found the BLM mutation in other cancers: 1 of 108 lymphoma cases, 5 of 375 breast cancers, 1 of 174 ovarian cancers, and 1 of 149 uterine cancer cases.

"Our data ... show that carriers of BLM mutation have an increased risk of [colorectal cancer]," writes Stephen B. Gruber, PhD, an epidemiologist at the University of Michigan in Ann Arbor. His study appears in this month's issue of Science.

While researchers don't understand how the mutation occurs, the data confirms that genetic mutation is a critical element in development of cancer, Gruber adds.

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