Gene Could Link Obesity, Colon Cancer

Variant is tied to a fat hormone, adiponectin, study finds

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HealthDay Reporter

TUESDAY, Sept. 30, 2008 (HealthDay News) -- Researchers have uncovered a genetic link between obesity and the risk for colon cancer. The discovery could lead to greater accuracy in predicting who is at risk for the disease, experts say.

Research has suggested that colon cancer risk rises with increasing weight, but this finding points to a genetic reason for the link.

"We have discovered that a genetic variant of the adiponectin gene, called ADIPOQ, is associated with colon cancer risk," said lead researcher Dr. Boris Pasche, director of the division of hematology and oncology at the Comprehensive Cancer Center of the University of Alabama at Birmingham. "This genetic variant may identify individuals who have a higher risk to develop colorectal cancer," he said.

The report was published in the Oct. 1 issue of the Journal of the American Medical Association.

For the study, Pasche's team focused on ADIPOQ. This gene promotes the formation of a fat hormone called adiponectin. People who inherit a common variant of the gene have up to a 30 percent lower risk of colon cancer compared with people without this gene variant, the study found.

On the other hand, the researchers believe that people who do not have this gene variant, or those who have high levels of adiponectin in their blood, may be at a slightly increased risk for colon cancer and could benefit from early screening for the disease.

"Adiponectin, a hormone exclusively secreted by the adipose [fat] tissue, is now genetically linked with colorectal cancer," Pasche said. "This is the first evidence that genetic variants of a 'fat hormone' affect risk of colorectal cancer," he said.

Whether people without this gene variant can reduce their risk of colon cancer through diet and exercise isn't clear, the researchers noted.

"This adds a little bit more to our understanding of one place where genetics plays a role in colon cancer development," said Dr. Durado Brooks, director of colon and prostate cancer prevention programs at the American Cancer Society. "It helps point us in some more specific directions; it adds another piece to the puzzle," he said.

Brooks does not believe that the finding is definitive, however. "It supports some of the other work that has already been done, identifying this particular gene region with colorectal cancer," he said.

The finding does help clarify one element linking obesity and colon cancer, but "there is no clinical application to this finding in the immediate future," Brooks said. "I don't think we would alter any recommendation, other than encouraging people to maintain a healthy weight."

Dr. Georgia Wiesner, a cancer geneticist at University Hospitals' Case Medical Center in Cleveland, agreed.

"I'd love to say that any time we find a new gene that identifies risk or alters risk we would be able to put that into a new drug treatment or at least identify people who are more at risk," Wiesner said. "But in this study, it might just tease out the pathogenesis of disease," she said.

It's already known that people who are obese have a higher risk for colon cancer, Wiesner said. "I don't know that telling somebody they might have a specific marker is really going to alter what they are going to do," she said. "It doesn't mean that these people don't need regular screening."

More information

For more on colon cancer, visit the American Cancer Society.

SOURCES: Boris Pasche, M.D., Ph.D., director, division of hematology and oncology, Comprehensive Cancer Center, University of Alabama at Birmingham; Durado Brooks, M.D., director, colon and prostate cancer prevention programs, American Cancer Society, Atlanta; Georgia Wiesner, M.D., cancer geneticist, University Hospitals' Case Medical Center, Cleveland; Oct. 1, 2008, Journal of the American Medical Association

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