There could be a possible link between antibiotic use and the speed of breast cancer growth, a study of mice suggests.
Antibiotics are often prescribed to breast cancer patients undergoing chemotherapy to control infections during treatment.
Researchers at the University of East Anglia (UEA) set out to research whether disruption of the healthy bacteria in the gut caused by antibiotic use would have an effect on tumour growth.
The role of the gut microbiome has been examined in relation of several cancers.
The study, funded by the charity Breast Cancer Now, found that the use of antibiotics led to the loss of a beneficial bacterial species in the gut, which in turn sped up tumour growth.
Mice used in the study which were treated with broad-spectrum antibiotics had an increased rate at which breast cancer tumours grew in them.
The research team also noticed an increase in the size of secondary tumours that grew in other organs when the cancer spread.
But scientists also said that they have found a type of immune cell which can be targeted to reverse the effects.
Further investigation found a larger number of immune cells, known as a mast cell, in tumours found in mice treated with antibiotics.
Publishing their findings in iScience, researchers said that when the function of these cells can be blocked then the aggressiveness of the tumour reduced.
Dr Stephen Robinson, group leader at the Quadram Institute at UEA, said: “With the rise in bacteria resistance to antibiotics we have known for many years that we need to be very careful about clinical antibiotic use.
“This research further demonstrates the important role a healthy gut microbiota plays in regulating the body’s response to disease and that antibiotics play a significant role in unbalancing a healthy gut microbiome.
“Our research has shown that losing ‘good’ bacteria in the gut, as the result of antibiotic use, can lead to an increased rate of breast cancer growth.
“We believe there is a complex immune element to this mechanism involving mast cells, a type of cell whose role in many cancers is not yet fully understood.
“Therefore, future studies will focus on understanding the possible role of these cells as well as looking into the effects of introducing probiotics into the experimental models we use.”
Dr Simon Vincent, director of research, support and influencing at Breast Cancer Now, said: “Whilst the link between antibiotics and breast cancer growth may sound alarming, we want to remind everyone affected by breast cancer that this is early stage research that has currently only been tested in mice.
“Much more work is needed to understand the complex relationship between gut bacteria and breast cancer.
“However, this research does provide crucial insight and we must now further investigate the effect of antibiotics in breast cancer treatment so that we can find the best way to stop tumours from growing.
“Excitingly, this research has already highlighted that by targeting mast cells, we could potentially halt antibiotic-induced breast cancer growth.”