Gene Defect Could Cause Colon Cancer

Testing for the defect might pinpoint those at higher risk, researchers say

WEDNESDAY, Sept. 21, 2005 (HealthDay News) -- Inactivation of a specific gene may be the underlying molecular defect driving the development of some colorectal cancers, researchers report.

The gene, called 06-methylguanine-DNA methyltransferase (MGMT), is involved in the repair of DNA. Detection of changes in MGMT could prove useful in measuring a person's risk for colorectal cancer, said the team from the University of Texas M.D. Anderson Cancer Center in Houston.

The researchers report their findings in the Sept. 21 issue of the Journal of the National Cancer Institute.

Cancer can begin in region of cells with what's called a "field defect." These cells appear normal but have an underlying molecular defect. In colorectal cancer cells, MGMT is often methylated -- meaning the gene's promoter region has methyl chemical groups added to it, resulting in an unhealthy inactivation of the gene.

In this study, researchers analyzed samples from 95 colorectal cancer patients and 33 people without cancer. MGMT promoter methylation was found in 50 percent to 94 percent of colorectal tumors.

"Given the high lifetime risk of colorectal tumor development in the U.S. population, it is reasonable to propose testing, to determine whether healthy persons with MGMT promoter methylation in normal colorectal [lining] are at higher risk of developing a colon tumor than those without such methylation," the researchers wrote.

More information

The American Cancer Society has more about colorectal cancer.

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