Bowel Cancer
A man holds out a hot dog he bought from a street vendor in Washington October 26, 2015. Eating processed meat can lead to bowel cancer in humans while red meat is a likely cause of the disease, World Health Organization (WHO) experts said on Monday in findings that could sharpen debate over the merits of a meat-based diet. Reuters/Kevin Lamarque

A recent study, led by scientists at The Institute of Cancer Research (ICR), London, has provided the most detailed picture yet of the genetics of bowel cancer. The researchers involved in the study analysed all genes from more than 1,000 bowel cancer sufferers. The research is the largest ever conducted. The scientists uncovered five new potential genes that when mutated cause bowel cancer in a small proportion of cases.

Cancer Research UK largely funded the study published in Nature Communications. The researchers have The study revealed that all discovered variants when added together in known bowel cancer genes accounted for less than a third of familial cases of bowel cancer.

Therefore, the rest of the familial cases must have been caused largely minor DNA variations. These variations add up to increase risk in combination. Environmental factors also contributed. About 12 percent of cases occur in people who have a family history of bowel cancer. There are inherited mutations in known cancer-causing genes like MLH1 and APC that often play a major role.

The risk of developing bowel cancer in an individual comes from environmental risk as well as a mix of inherited risk through his/her genes. Environmental risk is the outcome of non-genetic factors such as lifestyle. The 1,000 people studied developed bowel cancer at a relatively young age and also had a strong family history.

By sequencing all DNA used to produce protein, the exome, from the 1,000 patients, the researchers further explored the genetics of bowel cancer. The ICR researchers said that it is unlikely that there will be more major bowel cancer genes beyond the five identified. They put the total number of genes to 12, excluding the new ones.

Out of the 1,000 familial cases, mutations in the genes accounted for 15-31 percent. This meant that much of the remaining risk came from DNA’s common variations, each with a little individual impact on risk. Discovery of the variants may help in developing new way of preventing bowel cancer.

“This study represents an important contribution to our understanding of the genetics of bowel cancer. It provides a marker of the dramatic progress we have made so far in decoding the inherited risk of the disease, and gives us confidence that the most important risk genes have now been found,” Chief Executive of the ICR, professor Paul Workman, said in a statement.