New genetic risk factor for colon cancer identified

06/09/04

Discovery of mutant gene improves possibility of early screening and treatment for the disease

Irvine, Calif., June 9, 2004 -- An international research team has identified a virulent, new genetic risk factor for colon cancer – a discovery that could lead to early screening and treatment for people who have this genetic disposition to contract the disease.

The team, led by Dr. Steven Lipkin of the Chao Family Comprehensive Cancer Center at UC Irvine and Dr. Stephen B. Gruber of the University of Michigan, discovered a novel mutant gene in Israeli colon cancer patients. The researchers also discovered that the presence of the gene significantly increased the risk of colon cancer among these patients.

The researchers found that people with this genetic variant form of MLH1, a gene already linked with colon cancer, have a 40-percent lifetime risk of getting colon cancer, as compared to a 6-percent risk for the general population. Study results were posted on June 6 as an advance online publication on the Web site of Nature Genetics (www.nature.com/ng/).

Colorectal – or colon – cancer is one of the most common forms of cancer in the United States. The National Cancer Institute estimates that some 150,000 new cases will be diagnosed in 2004, and more than 55,000 deaths from colorectal cancer will occur. Approximately one-quarter of all patients have a family history of colorectal cancer, which suggests a genetic contribution. It is preventable though early detection.

Colorectal cancer rates in Israel are among the highest in the world. Over the past three years, the research team has been conducting a genetic epidemiological survey of colon cancer patients in northern Israel and found that more than 1 percent carried this previously unidentified variant gene, called MLH1 D132H. Significantly, these patients were found to have no other risk factors, and they could not be identified with one particular ethnic, cultural or religious group.

"We found the gene in a wide patient population of Sephardic and Ashkenazi Jews, Muslim and Christian Arabs, Druze Christians and Bedouins," said Lipkin, who is the director of the cancer genetics clinic at the Chao Center. "This leads us to believe that the population carrying this genetically variant gene is not limited to Israel, and this variant may have arisen during early phases of human evolutionary population migration. Although their numbers may be small, the people who have this specific genetic risk factor can be living anywhere in the world, and the odds of them getting colon cancer someday are very high."

As part of the study, the researchers developed new genetic screening tools to identify variant genes. Using these methods, Lipkin will work with UCI's Genetic Epidemiology Research Institute to survey colon cancer patients in other ethnic groups for this mutant gene.

Participating in the study along with Lipkin and Gruber, Jessica Peng-Chic and Brian Shin of UCI were Laura S. Rozek, Joel K. Greenson and Eric Fearon of Michigan; Dr. Gadi Rennert of the Carmedical Center and Technion Faculty of Medicine in Haifa, Israel; Wei Yang of the National Institute of Diabetes and Digestive Kidney Diseases in Bethesda, Md.; Joseph Hacia and Nathan Hunt of the University of Southern California in Los Angeles; Mark Kokoris of BioCaptus in Bothell, Wash.; Henry Lynch of Creighton University in Omaha, Neb.; Francis Collins of the National Human Genome Research Institute in Bethesda; and Steve Fodor of Affymetrix Corp. in Santa Clara, Calif. The American Cancer Society and the National Institutes of Health provided funding.

Source: Eurekalert & others

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