The microbiome – the collection of bacteria that live in our stomachs – has previously been linked to other health problems such as obesity and heart disease. But scientists have now found that the micro-organisms produce chemicals that can influence how well chemotherapy works.
They discovered that patients who responded to chemo and beat the disease had smaller amounts of some substances – called short chain fatty acids (SCFAs) – which encourage the body to produce cancer fighting T-cells.
While the experiment was small – including only 42 women – the team behind it believes the results are promising and is planning more research. Dr Kirsty Ross, from the Beatson West of Scotland Cancer Centre in Glasgow, and her colleagues measured the amount of SCFAs in patients’ faeces samples.
These chemicals are produced when bacteria in the bowel break down the fibre in food. The team found smaller amounts of two specific SCFAs – propionate and butyrate – in women who responded to chemotherapy, compared with the patients who did not.
Previous research has shown that these SCFAs encourage the development of cells called regulatory T-cells – which are known to “dampen down” the immune system’s ability to target cancer cells.
Dr Ross said: “We already know that these chemicals play a role in the immune system.
“It could be that patients who have lower levels of particular SCFAs are more able to mount an immune response to target the cancer alongside the chemotherapy and we will test this in future studies.”
In some women, where the chemotherapy seemed to eliminate all the cancer cells, researchers saw particular patterns in the women’s gut bacteria before and during their treatment.
Dr Ross added: “Patients with breast cancer often receive treatment with chemotherapy before surgery.
“Tests on the tissue removed during surgery can then show how sensitive a patient’s cancer is to the chemotherapy. If all the cancer cells are eliminated, this predicts a very high chance of cure for the patient.
“However, in many patients we do find cancer cells in the tissue that’s removed and these people have a higher risk of their cancer returning.”
Dr Ross and her colleagues are planning a larger study to look at how anti-cancer immune responses are affected by gut bacteria and why it affects chemotherapy.