Many genes influence bowel cancer risk

Around a fifth of all cases of bowel cancer are triggered by the combined effect of rare variations in many different genes, UK researchers say. A new study shows that 20 per cent of bowel cancer patients develop the disease because they inherit several different gene mutations. The Cancer Research UK team hopes that its findings, published in the Proceedings of the National Academy of Sciences, will lead to a blood test to identify people at high risk of bowel cancer.

Scientists have known for several years that some inherited forms of bowel cancer, such as familial adenomatous polyposis (FAP), are caused by a mutation in a single gene. However, hereditary bowel cancer is rare, and only accounts for less than four per cent of all cases of the disease. For the latest study, the researchers wanted to investigate the role of genes in non-inherited forms of the disease, thought to be caused by the interaction of several genetic and non-genetic factors.

The scientists studied DNA from 124 patients diagnosed with 'polyps', small growths in the gut that raise the risk of developing bowel cancer. They looked at variations in several genes known to be involved in cancer, and compared them with DNA from 483 individuals who did not have polyps. The researchers found that certain gene variants were twice as likely to occur in people with multiple polyps in their gut than in people who did not. Importantly, the study looked at inherited genetic variations, rather than the genetic changes that occur in cancerous tissues.

Team leader Walter Bodmer said that further work should pinpoint other gene variations associated with an increased risk of bowel cancer, and added 'I believe that we could eventually exploit this knowledge to develop a blood test to identify those at high risk of this disease'. Bodmer thinks that susceptibility to cancer is triggered by the combined effect of many rare gene variants, rather than the influence of one or two more common variants. He said that this scenario could also help explain why researchers have had difficulty in identifying genes involved in other diseases, such as schizophrenia and Alzheimer's disease.