Bacteria living deep in the digestive system appear to influence tumor shrinkage during cancer treatment, French and American researchers say. They tested the microbiome — the collection of microorganisms that live in the human gut — in cancer patients. Two studies, published in the journal Science, linked specific species and overall diversity of the microbiome to the effectiveness of immunotherapy drugs.
Bacteria living deep in the digestive system appear to influence tumor shrinkage during cancer treatment, French and American researchers say. They tested the microbiome — the collection of microorganisms that live in the human gut — in cancer patients. Two studies, published in the journal Science, linked specific species and overall diversity of the microbiome to the effectiveness of immunotherapy drugs.
Experts say the results are exciting and promising. Our bodies are home to trillions of microorganisms, and the relationship between the “gut” and the “microbiome” goes far beyond infectious diseases. Microbiome is involved in digestion, protecting against infections and regulating the immune system. Both studies were conducted on patients who were treated with immunotherapy, and this increased the body’s ability to protect against tumors. It doesn’t work for every patient, but in some cases it can clear up even late‐stage cancer.
Survival
A study at the Gustave Roussy University and Cancer Research Laboratory in Paris looked at 249 patients with lung or kidney cancer. The researchers found that those who had used antibiotics, for example for a dental infection, damaged the microbiota in their gut and were more likely to see tumour growth while being treated with immunotherapy.
One particular bacteria, Akkermansia muciniphila, responded in 69% of patients compared with just one‐third of those without it. Increasing the density of A. muciniphila in mice also appeared to enhance their response to immunotherapy.
Meanwhile, at the University of Texas MD Anderson Cancer Center, 112 patients with advanced melanoma had their microbiomes analyzed. Those who responded well to therapy tended to have a richer, more diverse microbiome than those who didn’t. And they had different bacteria, too. High levels of Faecalibacterium and Clostridiales appeared to be beneficial, while Bacteroidales were the harmful bacteria in the study.
‘Change the outcome’
Tissue samples showed that there were more cancer‐killing immune cells in the tumours of people with beneficial bacteria. The team then performed a trans‐poo‐sion, a faecal transplant, from humans into mice with melanoma. Mice given bacteria from these patients with a “good” mix of bacteria had slower growing tumours than mice with harmful bacteria. Dr Jennifer Wargo, from Texas, told the BBC: “If you disrupt a patient’s microbiome, you can reduce their response to cancer therapy.” She is planning clinical trials to modify the microbiome alongside cancer therapy.
“Our hypothesis is that if we change to a more favorable microbiome, you can just make patients respond better,” she said. “The microbiome is changing outcomes not just for cancer but for overall health, it definitely plays an important role.”
Brings much promise
Mark Fielder, president of the Society for Applied Microbiology and professor of biomedical sciences at Kingston University, said the research showed the importance of understanding the microorganisms that inhabit our bodies. “It’s exciting and it shows a lot of promise so we need to do more research because there are exciting glimmers here for treating some difficult diseases,” he told the BBC.
“Some people think that the microbiome is the answer to everything and I don’t think that’s the case. But once we understand more, it could be very important in changing human health.”
“It’s very exciting,” said Dr Emma Smith from Cancer Research UK. “One of the big challenges with using immunotherapy to treat cancer is understanding which patients will respond, and this study is a step forward in helping doctors identify these people.”
