February 27, 2020

expert reaction to study looking at toxins produced by gut bacteria and colorectal cancer

Research, published in Nature, reports a possible link between bacterial infection and correctional cancer. 

Prof David Dearnaley, Professor of Uro-Oncology at The Institute of Cancer Research, London, and Consultant Clinical Oncologist at The Royal Marsden, said:

“In recent years, the number of studies looking at the impact of the gut microbiome on diseases like cancer has increased.  This exciting study is the first to find a clear relationship between a specific type of gut bacteria and the development of colorectal cancer in a small group of patients.

“The findings provide a good basis for researchers to further investigate other gut bacteria in relation to colorectal cancer.  As it stands, dietary advice and appropriate bowel screening to detect disease at an early stage disease should continue.”

Dr Nicola Valeri, Team Leader in Gastrointestinal Cancer Biology and Genomics at The Institute of Cancer Research, London, and Consultant Medical Oncologist at The Royal Marsden NHS Foundation Trust, said:

“This new study is a great step towards understanding the connection between the presence of bacteria producing DNA damaging toxins and specific types of errors in the genome – known as mutational signatures – of bowel and other cancers.

“The study combines experimental pre-clinical data, as well as samples from actual patients in the UK and the Netherlands.

“Interestingly, these findings echo and complement observations from recent studies in the field and provide important insights into the role bacteria may have in promoting cancer progression.

“Taken together, these observations could help us design better studies that aim at early detection and prevention of bowel and other cancers.”

Dr Vivian Li, Group Leader, Stem Cell and Cancer Biology Laboratory, the Francis Crick Institute, said:

“I think this is a very exciting finding. Previous work on bowel cancer focused mainly on the genetic cause, while evidence of environmental contribution is very limited. This paper shows that the gut bacteria can directly induce DNA damage and possibly cause bowel cancer development. The unique bacterial toxin produced by the bacteria may also be used as biomarker for early diagnosis. Although this is linked to only 5% of patients, it will be interesting to further explore if additional microbiome might be involved in other bowel cancer patients. This paper also highlights the important use of “mini-guts” for biomedical research in addition to personalised medicine.”

Dr Ian Johnson, Nutrition researcher and Emeritus Fellow, Quadram Institute Bioscience, said:

“This is a very interesting piece of research using molecular biology to implicate a toxin produced by a particular type of gut bacterium as having a direct role in at least some cases of colorectal cancer. It is important however to realise that this is a complex disease that is likely to have many contributory causes.  The risk of colorectal cancer varies by about five-fold between countries, and the risk is consistently higher in populations consuming typically western diets and having a high prevalence of obesity.  It would be valuable in the future to discover whether gut bacteria implicated in the development of colorectal cancer are also more common in populations at higher risk, and if so, how they can be reduced. For now, the best advice is to maintain a healthy body weight, exercise regularly and consume a diet rich in dietary fibre from whole-grain cereals.”

Genevieve Edwards, Chief Executive at Bowel Cancer UK, says:

“Although this research is at an early stage, it adds to the growing body of evidence about the role that bacteria and other microorganisms that live in our gut may play in bowel cancer development.

“Bowel cancer is the fourth most common cancer in the UK, with over 42,000 people diagnosed every year. Making simple changes to your lifestyle can help stack the odds against bowel cancer. Including wholegrains, fibre and fish in your diet, being of a healthy body weight, having regular physical activity, avoiding processed meats and limiting red meat, can all make a real difference.”

‘Mutational signature in colorectal cancer caused by genotoxic pks+ E. coli’ by Cayetano Pleguezuelos-Manzano et al. was published in Nature at 16:00 UK time on Thursday 26th February.

DOI: https://doi.org/10.1038/s41586-020-2080-8 (2020).

Declared interests

Dr Nicola Valeri: “No conflicts of interest to declare.”

Dr Vivian Li: I have no conflict of interest in this paper. I do have a link with the last author Hans Clevers. We are both part of a EU consortium grant about the work on intestinal tissue engineering (INTENS), which will end by the end of this year. The grant has nothing to do with the paper though.

Dr Ian Johnson: No conflicts of interest.

None others received.