Gut bacteria might hitch a ride with spreading bowel cancer cells

Bacteria found in certain bowel cancers can also be found inside a small number of tumours that have spread to another part of the body, says new research.

The bacteria helped bowel cancer cells grow in mice.

Researchers said this adds to the evidence of a relationship between growing bowel cancers and the types of microorganisms in the gut. 

The Dana-Farber Cancer Institute team analysed tumour samples from 101 patients who had bowel cancer that had spread. Samples were taken from where the tumour started in the gut and where it spread to in the liver. 

43 patients had large amounts of a type of bacteria called Fusobacteria inside their bowel cancer cells. 20 patients also had the same bacteria inside bowel cancer cells that had spread to the liver.

Professor Alastair Watson, a Cancer Research UK-funded microbiome expert, said: “This study shows that bacteria can not only invade cancers in the bowel but remain in the cancers when they spread to other parts of the body.”

He said the most exciting aspect of the study, published in Science, was the effect antibiotics had on mice with bowel cancers carrying the bacteria.

Bowel cancer cells carrying Fusobacteria grew in mice, whereas cancer cells lacking the bacteria did not. The researchers suggest that Fusobacteria might help tumour cells survive and develop.

Antibiotics which kill Fusobacteria reduced the amount of bacteria present in the tumours in the mice. The treatment also slowed the growth of the tumours.

Watson said that while “in general antibiotics are not an effective cancer treatment, further research may reveal particular circumstances when it might be helpful to use antibiotics alongside other cancer treatments”.

The researchers behind the study said that further work is needed to fully understand the effects of antibiotics on these bacteria and growing cancers.