This common gut bacteria could be a cause of bowel cancer

A common type of gut bacterium may play a role in the development of bowel cancer, according to a new study published in the journal Nature. The bacterium is a type of E. coli infection, present in up to one in five people, scientists believe. Researchers found that it releases a toxin which may damage the cells in the lining of the bowel, potentially turning some cells cancerous over time. Bowel cancer is the fourth most common cancer in the UK and there are around 42,000 new cases diagnosed each year. The breakthrough suggests that thousands of cases of the disease might be prevented, or at least delayed, by screening for the strain and eradicating the bug in those who test positive. What did the study find? Hans Clevers and others at Hubrecht University in the Netherlands investigated the effects of a toxin called colibactin, which is produced by certain strains of E coli and another gut microbe called Klebsiella pneumoniae. Previous studies have shown that colibactin can damage the DNA in living cells. The team, from The Netherlands, the UK and the US, used miniature replicas of the human gut, grown in the lab, to test the effects of the toxin on cells. They then compared the damage seen with more than 5,000 bowel cancer samples taken from patients and found identical patterns or "fingerprints" of DNA damage in around five per cent of the samples They said that other bacterial toxins from gut bacteria might have similar effects and now researchers seek to determine whether this mechanism of DNA damage is widespread. How do these findings help us? Experts say it may be possible to develop a more sensitive test to detect early bowel tumours using this knowledge about the toxin. One of the researchers, Prof Hans Clevers, from the Hubrecht Institute in The Netherlands, said, "Common antibiotics will kill these bacteria. "This is the first time we've seen such a distinctive pattern of DNA damage in bowel cancer, which has been caused by a bacterium that lives in our gut." "Although it might sound scary, there's still lots left to understand about how our gut bacteria affects our health, what we could do about it, and how much impact it has on bowel cancer risk," says Nicola Smith, senior health information Manager at Cancer Research UK, who funded the work. "In the future, knowing what role bacteria in our gut plays could change the way we detect and prevent bowel cancer.”