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Small changes in just four genes may triple a person's lifetime bowel cancer risk, according to new findings published in the journal Nature Genetics. The researchers, based at Cancer Research UK's London Research Institute, hope that the discoveries will one day lead to new tests which might flag up those at highest risk from bowel cancer - the second most common cause of cancer death in the UK.

Although the risk of bowel cancer associated with each of the two genetic variations is small, this risk is amplified if either are combined with two other genes which have previously been linked to cancer. People who have all four genes in combination are two or three times more likely than normal to develop bowel cancer, say the scientists.

'The lifetime risk is about 5 per cent in the UK so it's going up to 7 per cent or so if you've got both bad copies of a variant,' said Ian Tomlinson, who led the study.

In the hunt for genes associated with a specific form of bowel cancer called hereditary mixed polyposis syndrome (HMPS), which mostly affects people of Ashkenazi Jewish descent, the researchers scanned the entire genetic make-up of 15,000 volunteers - 8,000 of which had bowel cancer. However, instead of finding the gene they were looking for, they found other gene changes near the region they were studying, which were linked to cancer in the general population.

'Increasing our understanding of genes like this may make it possible for scientists to eventually develop ways of stopping many people at increased risk of bowel cancer from developing the disease altogether', said Professor Tomlinson.