Loss-of-Imprinting Test Predicts Risk of Colon Cancer

A recent study describes a new blood test for determining the risk for colon cancer, based on detection of a type of gene silencing known as loss of imprinting (LOI). The study was published in the March 14, 2003, issue of Science.

Imprinting means that the copy of a gene inherited from one parent is active while the same gene from the other parent is inactive, or silent. For some genes the active gene is the maternal copy and for others it is the paternal. Prior work had shown that LOI in the growth-promoting gene IGF2 (insulin-like growth factor) is one of the first genetic defects that occurs in up to 40% of colon cancers. In the current study, investigators from Johns Hopkins University (Baltimore, MD, USA; www.jhu.edu) found IGF2-related LOI present in blood samples as well as in colon tissue.

DNA analysis of blood samples from 172 individuals after colonoscopy revealed that 25 with various family and personal histories of colon cancer and polyps expressed LOI in their blood. Those with a family history of colon cancer were more than five times more likely to have LOI markers than those with no such family history. Individuals with polyps were nearly three and a half times more likely to have LOI markers present in the blood, while individuals with a personal history of colon cancer were nearly 22 times more likely to have LOI markers.

"We hope these findings will have the ability to identify people at increased risk for colon cancer, follow them closely, and prevent disease or at least catch it early, similar to the approach doctors use in identifying patients at risk of heart disease,” said Dr. Andrew P. Feinberg, professor of medicine at the Kimmel Cancer Center at Johns Hopkins University.



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