Gut bacteria 'control response to cancer treatments'

In collaboration with the Press Association

Bacteria in our intestines may help some cancer drugs work more effectively, according to studies from the US and France.

“These two new studies in mice explore the intriguing idea that the bacteria in the gut may influence the response to cancer treatment” - Dr Kat Arney, Cancer Research UK

Researchers found that gut bacteria in mice controlled parts of the immune system response triggered by certain treatments.

Scientists from the US National Cancer Institute (NCI) showed how some immune-boosting treatments and certain chemotherapy drugs were less effective in mice with bacteria-free guts and mice that had been treated with germ-killing antibiotics.

Their study, published in the journal Science, found that the bacteria are needed to activate parts of the immune response against tumours. Without them, the mice responded poorly to drug therapy for their tumours.

In a second study, also published in Science, researchers at Inserm and the Gustave Roussy Institute in France found that the cancer drug cyclophosphamide causes gut bacteria to trigger the production of immune cells that attack tumours. In mice without gut bacteria this process was again reduced.

Dr Giorgio Trinchieri, who was involved in the NCI study, said: "These findings raise the possibility that the frequent use of antibiotics during a patient's lifetime or to treat infections related to cancer and its side-effects may affect the success of anti-cancer therapy."

Dr Kat Arney, Science Communications Manager at Cancer Research UK, said: "There are more bacterial cells in our bodies than human cells, but very little is known about how each person's personal collection of bugs affect their health."

"These two new studies in mice explore the intriguing idea that the bacteria in the gut may influence the response to cancer treatment, but it still remains to be seen whether the effects hold up in humans too."

She highlighted that previous research has shown that certain mouth bacteria could actually fuel the development of bowel cancer.

"This whole area is relatively unexplored at the moment, and we look forward to seeing more research in the future that helps us to understand the role bacteria play in cancer and its treatment," she added.

Copyright Press Association 2013


  • Iida N, et al. (2013). Commensal Bacteria Control Cancer Response to Therapy by Modulating the Tumor Microenvironment, Science, 342 (6161) 967-970. DOI:
  • Viaud S, et al. (2013). The Intestinal Microbiota Modulates the Anticancer Immune Effects of Cyclophosphamide, Science, 342 (6161) 971-976. DOI: