Bowel cancer potentially linked to E coli
Exposure to the bacteria in childhood may be part of the puzzle over why there has been a jump in cancer rates among the young.
Exposure to E. coli bacteria in childhood could be driving an alarming increase in rates of bowel cancer in young adults, scientists have discovered.
A toxin called colibactin, which can cause changes in DNA, is produced by a strain of E. coli, though not the strain linked to symptoms such as diarrhoea.
Researchers backed by Cancer Research UK found exposure to colibactin before the age of 10 leads to mutations in the DNA of bowel cells, which may then increase the risk of developing cancer before the age of 50.
Experts believe the finding could help to solve the puzzle of why rates of bowel cancer are rising among young adults around the world.
Data from the charity showed that there has been a 52 per cent increase in bowel cancer incidence among adults aged between 25 and 49 since the 1990s. Cases of such “early-onset” cancers are rising more rapidly in England than anywhere else in Europe.
Scientists have speculated that factors including obesity, lack of exercise and consumption of alcohol and ultra-processed foods are partly to blame for this increase. The latest study, published in the journal Nature, points to E. coli as another possible culprit.
Researchers examined the genetic information of 981 bowel cancers. They found that colibactin can leave behind specific patterns of DNA mutation that were 3.3 times more common in those diagnosed with bowel cancer before they turn 40 than in those diagnosed after the age of 70. These mutation patterns were also particularly common in countries with a higher rate of early-onset bowel cancer.
Ludmil Alexandrov, a professor at the University of California San Diego and the study’s senior author, said: “These mutation patterns are a kind of historical record in the genome, and they point to early-life exposure to colibactin as a driving force behind early-onset disease.”
The study also found that colibactin-related mutations accounted for about 15 per cent of APC driver mutations – some of the earliest genetic alterations that directly promote cancer development in bowel cancer.
“If someone acquires one of these driver mutations by the time they’re 10 years old, they could be decades ahead of schedule for developing colorectal cancer, getting it at age 40 instead of 60,” Alexandrov said.
The work is led by Mutographs, a project that is part of a $40 million cancer “grand challenge” tasked with solving the mystery of rising bowel cancer cases in the young.
Dr David Scott, the director of Cancer Grand Challenges, said: “Globally and in the UK, we’re witnessing an alarming increase in some types of cancer in people under the age of 50.
“Many early-onset colorectal cancer patients appear to have been exposed to colibactin, produced by some strains of the bacteria E. coli, in early life.
“It’s unclear how the exposure originates, but we suspect that a combination of factors – including diet – may intersect during a crucial phase in the development of the gut microbiome.
“This study adds an important piece to the puzzle of early-onset cancers, but it isn’t conclusive, and more research will be needed to establish a definitive link between colibactin and an increased risk of early-onset colorectal cancer.”
Professor Sir Mike Stratton, the Mutographs team leader and senior group leader at the Wellcome Sanger Institute, said: “If [the finding] turns out to be correct, we can explore preventive measures such as tests that tell us if the toxin, or the bacterium that makes it, is present, and finding ways to eliminate them from our bodies at a young age.”
The Times
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