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Gene Variation Reduces Colorectal Cancer Risk

single nucleotide polymorphism

single nucleotide polymorphism

People with a variation in the gene that controls how fat is metabolized by cells have a lowered chance of getting colorectal cancer, even in families with already increased risk.

Scientists studied differences in short regions of the ADIPOQ gene called single nucleotide polymorphisms (SNPs) among patients with colorectal cancer and a similar group of people who didn’t have cancer. In two different study groups, they found that one variation reduced risk of getting cancer by about 30 percent.

Obesity has been identified as a risk factor for colorectal cancer in a number of studies, but it isn’t clear how increased body fat contributes to development of the disease. Because there is more adiponectin, a hormone released by fat tissue, in the blood of obese individuals and also patients with colorectal cancer, scientists wanted to know if SNPs in the ADIPOQ gene, which controls the release of adiponectin, made a difference.

Initally they studied 441 colorectal cancer patients from New York City matched with a group of 658 people without cancer.  Both groups were of Ashkenazi Jewish heritage.  Ashkenzi Jews from Eastern Europe have a significantly increased risk of colorectal cancer.

Having identified several SNPs associated with colorectal cancer risk in the first group, they studied a second matched group of 400 people in Chicago, half of whom had colorectal cancer.   The Chicago group included people of varying races and ethnic backgrounds.

One SNP was found in both the New York and Chicago groups that reduced cancer risk by 27 percent in those people where it occurred.

Virginia Virginia G. Kaklamani, M.D., D.Sc., of the Feinberg School of Medicine, Northwestern University, Chicago, and her colleagues said,

In this clinic-based case-control analysis, we found an association between 1 single nucleotide polymorphism [SNP; a gene variation] of the ADIPOQ gene (rs266729) and colorectal cancer risk in 2 separate case-control studies, as well as in the combined analysis of both studies after adjustment for age, sex and other SNPs.

If these exciting results can be confirmed in other studies, the adiponectin axis may emerge as an important modifier of colorectal cancer risk. Future studies will need to address the potential impact of adiponectin and its SNPs in the prognosis of colorectal cancer and also may be incorporated in genetic risk models for the disease.

SOURCE: Kaklamani et al., Journal of the American Medical Association, Volume 300, Number 13, October 1, 2008.

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