Healthy living

E.coli infection linked to colon cancer

A scanning electron micrograph of Escherichia coli bacteria magnified 3418 times. EPEC bacteria interfere with colon cells repair mechanisms

People carrying a virulent strain of E.coli bacteria may be more susceptible to developing colon cancer, according to new research.

E.coli is frequently found in the colon of patients with colon cancer, and it's already known that some strains of E.coli, such as enteropathogenic E.coli (EPEC), can attach to epithelial cells which line the colon. Scientists at the University of Edinburgh decided to investigate whether strains of E.coli such as EPEC were able to change or predispose colon cells to become cancerous.

They discovered that not only did EPEC attach to colon cells, but also injected several proteins into them. Two of the proteins were shown to interfere with the colon cells DNA repair mechanisms, causing the cellular DNA to be more susceptible to genetic mutation. This process could put the colon cells at greater risk of becoming cancerous.

When tissue samples fromcolon cancer patients were analysed, they found that 50% per cent of the tumour samples were infected with E.coli, half of which were positive for the virulent EPEC strain. No EPEC bacteria were found in tissue samples from healthy volunteers.

Lead researcher, Dr. Oliver Maddocks from the University of Edinburgh said:

"We can't say for certain that this type of E.coli bacteria definately cause colon cancer, as it is possible these patients acquired the bug after the tumours developed.

"But our laboratory work does stongly suggest that bacteria are able to influence colon cells in a way that might predispose them to cancer, and so there is a real chance that infection could aid the development of colon tumours. We hope our findings stimulate further research to clarify the causes of this common cancer."

Colon cancer is the second most common cancer in the UK. Each year, more than 35,000 people are diagnosed with colon cancer, and 10,000 die of the disease.

Poor food hygiene can result in an EPEC infection. Children infected with EPEC may have diarrhoea, but the bacterium can be carried in adults and children without causing any symptoms. Current estimates suggests tht between two and ten per cent of the healthy population carry EPEC.

The scientists went on to suggest that a further larger study investigating the occurrence of EPEC bacteria in colon cancer patients and healthy people should be carried out.

This article was published on Thu 14 May 2009



Image © Janice Haney Carr (CDC)


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