How gut microbes are joining the fight against cancer

[Andy]

Bertrand Routy earned a lamentable reputation with Parisian oncologists in 2015. A doctoral student at the nearby Gustave Roussy cancer centre, Routy had to go from hospital to hospital collecting stool samples from people who had undergone cancer treatments. The doctors were merciless. “They made fun of me,” Routy says. “My nickname was Mr Caca.”

But the taunting stopped after Routy and his colleagues published evidence that certain gut bacteria seem to boost people’s response to treatment1. Now, those physicians are eager to analyse faecal samples from their patients in the hope of predicting who is likely to respond to anticancer drugs. “It was an eye-opener for a lot of people who couldn’t see the clinical relevance of gut microbes,” says Routy, who is now at the University of Montreal Health Centre in Canada.

https://www.nature.com/articles/d41586-018-05208-8

From same article

Zitvogel’s team found that the chemotherapy drug cyclophosphamide damages the mucus layer that lines the intestine, allowing some gut bacteria to travel into the lymph nodes and spleen, where they activate specific immune cells. For mice raised without microbes in their guts or given antibiotics, the drug largely lost its anticancer effects.

Following this observation, Zitvogel decided to explore whether bacteria in the gut might influence responses to a class of immunotherapy drugs called checkpoint inhibitors. These drugs, typically antibodies to cell-surface molecules such as CTLA4 and PD1, unleash a person’s immune system against tumour cells, and are used to treat several types of cancer (see ‘A little help from their friends’). But only 20–40% of people respond to treatment4.