Gene discovery could explain a third of bowel cancers

Two genetic variants that may triple a person's lifetime bowel cancer risk have been identified in a study published in the journal Nature Genetics last week. 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 gene variants is small, this risk is amplified significantly 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 researchers.

'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,' Ian Tomlinson, who led the study, told the Guardian.

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 genomes 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 variants 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', Professor Tomlinson told the Daily Telegraph.

These discoveries are part of a higher goal to map all the genetic variation responsible for bowel cancer leading to a test which could identify those at risk, say the researchers. 'We hope that step by step we are coming closer to some form of screening', added Dr Lesley Walker, a Cancer Research UK spokesperson. 'By identifying the genes responsible for the disease we would also be able to develop treatment specific to people with that genetic make-up'.