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Silenced gene may foretell colon cancer.

A genetic defect present in many colorectal tumors can also occur in healthy colon or rectal tissues, a new study finds. This suggests that the defect could play a role in the cancer's origins and thus could become part of a screening test for identifying people at risk of developing colorectal cancer colorectal cancer

Malignant tumour of the large intestine (colon) or rectum. Risk factors include age (after age 50), family history of colorectal cancer, chronic inflammatory bowel diseases, benign polyps, physical inactivity, and a diet high in fat.

Past research has shown that the gene for 06-methylguanine-DNA methyltransferase (MGMT MGMT Management
MGMT Methyl Guanine Methyl Transferase
MGMT Make Good a Magnetic Track of ___ Degrees
), a protein with tumor-suppressing properties, is silenced in many colorectal tumors. MGMT normally plays a role in DNA repair DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light can cause DNA damage, resulting in as many as 1 , but when the promoter region near the MGMT gene acquires a group of methyl molecules, the gene switches off and MGMT production stops.

In the new study, researchers in Texas and Arizona examined colorectal tumors removed from 36 cancer patients. The team also examined samples of healthy tissue taken from 1 centimeter centimeter (sĕn`tĭmē'tər), abbr. cm, unit of length equal to 0.01 meter, the basic unit of length in the metric system. The centimeter is the unit of length in the cgs system. It is approximately equal to 0.  and 10 cm away from each tumor. Lab results indicated that 18 of the tumors had a methylated meth·yl·ate  
An organic compound in which the hydrogen of the hydroxyl group of methyl alcohol is replaced by a metal.

tr.v. meth·yl·at·ed, meth·yl·at·ing, meth·yl·ates
 MGMT promoter. Among the patients who had these tumors, 13 also had methylated MGMT promoters in adjacent healthy tissue and 10 had methylated MGMT promoters in the healthy tissue collected 10 cm away from the tumor, researchers report in the Sept. 21 Journal of the National Cancer Institute.

Many physicians recommend that any person over 50 get colonoscopy Colonoscopy Definition

Colonoscopy is a medical procedure where a long, flexible, tubular instrument called the colonoscope is used to view the entire inner lining of the colon (large intestine) and the rectum.
 screening for cancer at least every 10 years, or more often if there's a family history of the disease. A test for MGMT genes silenced by a methylated promoter could identify people at high risk of cancer but who show no obvious signs during colonoscopies. These people would benefit from more-frequent colonoscopy screening, says study coauthor Jean-Pierre J. Issa, an oncologist at the M.D. Anderson Cancer Center in Houston.--N.S.
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Title Annotation:BIOMEDICINE
Publication:Science News
Geographic Code:1USA
Date:Oct 1, 2005
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