Multi-institutional study identifies new form of inherited risk...( NEW YORK (March 25 2008) -- Like th...)

NEW YORK (March 25, 2008) -- Like the subtext of a novel, the human genome sequence harbors more information than appears just in its "letters" of A, C, T and G. Since DNA is a data-packed molecule passed from generation to generation, comparing genome sequences among individuals also holds clues to ancestry.

So-called association studies that match unusual DNA sequence variations to diseases are very common nowadays. But a multi-institution group led by Dr. Francis Barany, professor of microbiology and immunology at Weill Cornell Medical College, has instead zeroed in on parts of the genome that are strikingly similar among people from a particular population group who have the same type of cancer. This "autozygosity" (identical copies of DNA inherited from both parents) might serve not only as a way to predict susceptibility to cancer in some people, but may lead researchers to novel cancer-causing genes. More broadly, the work suggests a new type of genetic signpost that clinicians might follow for a range of cancers, in many population groups.

In a paper "The Signatures of Autozygosity Among Patients with Colorectal Cancer," to be published online on March 28, and in print on April 15, in the journal Cancer Research, Dr. Barany and his colleagues report Identity by Descent (IBD) segments that are the same in sequence (autozygous) among individuals who have colorectal cancer. About half the cases are of Jewish heritage. The simplest explanation for their IBD segments is that they were inherited from a long-ago, shared ancestor. The investigators compared IBD regions among 74 colorectal cancer patients to two control groups, and found the segments to be twice as numerous and longer among the cancer patients.

Tellingly, the identical DNA stretches were more common among Jewish cancer patients. Scientifically, the power of this new approach derives from the common practice wherein individuals marry within the same ethnic or socia
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