05-05-2025
An E. coli link to bowel cancer in younger patients
Scientists have found a possible link between a common bacteria and early-onset colorectal cases. — Positive Parenting
A toxin produced by Escherichia coli may be driving rates of bowel cancer in young people, scientists have discovered.
Experts believe the finding could help explain why rates of bowel cancer are rising among young people across the globe.
The bacterial toxin – called colibactin – is capable of altering DNA (deoxyribonucleic acid) and is produced by a strain of E. coli , though not the strain linked to infections that cause diarrhoea in some people.
Researchers found that exposure to colibactin in early childhood imprints a genetic signature on the DNA of bowel cells, which may then increase the risk of developing bowel cancer before the age of 50.
Work has been ongoing to discover why more younger people are developing bowel cancer, with experts believing that poor diet, more ultra-processed foods, obesity and a lack of exercise play a role.
This latest study was led by scientists from the University of California, San Diego, (UCSD) in the United States, funded by Cancer Research UK's Grand Challenge and published in the journal Nature .
The researchers examined 981 colorectal (bowel) cancer genomes from patients with both early and late-onset disease in 11 different countries.
They found that colibactin can leave behind specific patterns of DNA mutations that are 3.3 times more common in early-onset bowel cancer cases (for the study, this was in adults aged under 40 years) 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.
Study senior author and Grand Challenge Mutographs team member Professor Dr Ludmil Alexandrov 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.'
Study first author and former UCSD postdoctoral researcher Dr Marcos Diaz-Gay shared: 'When we started this project, we weren't planning to focus on early-onset colorectal cancer.
'Our original goal was to examine global patterns of colorectal cancer to understand why some countries have much higher rates than others.
'But as we dug into the data, one of the most interesting and striking findings was how frequently colibactin-related mutations appeared in the early-onset cases.'
The study also found that colibactin-related mutations account for around 15% of what are known as 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,' Prof Alexandrov said.
'Our research has allowed us to generate the hypothesis that the presence of colibactin leads to an increased number of mutations in colon cells, which then causes a greater risk of colorectal cancer at an early age,' said Mutographs team lead and Britain's Wellcome Sanger Institute senior group leader Prof Sir Dr Mike Stratton.
'If this 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.
'We know that diet and lifestyle choices drive the risk of developing colorectal cancer, but this study has opened up a new and exciting route we can take when researching how to lower the rate of early-onset colorectal cancer.' – By Jane Kirby/PA Media/dpa
