Racial differences in response to bowel cancer genetic risk factor

Scientists have for the first time discovered that people with the same cancer susceptibility genes respond differently depending on their race.

Their results are published in Nature Genetics*.

The team from the University of Edinburgh has shown that a genetic marker is associated with an increased the risk of colon cancer in Europeans, but not in the Japanese population. But this genetic variant was associated with a similar risk of rectal cancer in both populations.

While dietary differences are already well known to be important, this discovery shows for the first time that genetic factors might explain some of the differences in bowel cancer risk between populations**.

This is one in a series of Cancer Research UK funded studies searching for bowel cancer susceptibility genes. The international collaborative project has the long term aim to find a set of genetic markers that could be used to identify subgroups of the population with an increased risk of bowel cancer.

Lead author, Cancer Research UK's Professor Malcolm Dunlop based at the Institute of Genetics and Molecular Medicine at the University of Edinburgh, said: "This is the first time that a race-specific effect has been found for a genetic marker. I's an important step forward in our knowledge of the causes of bowel cancer, bringing us ever closer to a genetic test for those at high risk of the disease.

"It's important to catch bowel cancer at an early stage when it's more likely to be treated successfully."

Prof Dunlop and his team looked at the complete genetic make up of over 33,000 people in seven different countries.

In a parallel study, also published today in Nature Genetics***, a team of researchers led by Professor Richard Houlston based at the Institute of Cancer Research and Professor Ian Tomlinson at Cancer Research UK's London Research Institute, along with Professor Dunlop and Professor Campbell in Edinburgh, found two new gene variants that increase the risk of bowel cancer.

Cancer Research UK's director of cancer information, Dr Lesley Walker, said: "Our understanding of the causes of bowel cancer is quickly increasing. We can now begin to explain the some of the difference in rates of the disease between populations through specific genes.

"This international collaboration has helped us appreciate the complexity of the genetics behind bowel cancer. This collaboration will continue to bring knowledge that will eventually allow us to test people with a family history of the disease, catching cancer earlier in those who are at the highest risk or preventing it all together."

* A genome-wide association scan identifies a new colorectal cancer susceptibility locus on 11q23 and replicates risk loci at 8q24 and 18q21. Dunlop et al. 2008. Nature Genetics.

** Statistics on colon and rectal cancer from the International Agency for Research on Cancer.

*** A genome-wide association study identifies novel colorectal cancer susceptibility loci on chromosomes 10p14 and 8q23.3. Houlston et al. 2008. Nature Genetics.

Bowel cancer

Every year in the UK, around 36,000 people are diagnosed with bowel cancer. It is the third most common cancer after breast and lung and the disease causes almost 16,100 deaths in the UK every year. Around two-thirds of cases are in the large bowel (colon) and the remaining third are in the back passage (rectum). The occurrence of bowel cancer is strongly related to age, with over 80 per cent of cases arising in people who are 60 years of older.

About the Institute of Cancer Research

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