How gut microbes are joining the fight against cancer

By Giorgia Guglielmi

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.

Cancer has been a late bloomer in the microbiome revolution that has surged through biomedicine. Over the past few decades, scientists have linked the gut’s composition of microbes to dozens of seemingly unrelated conditions — from depression to obesity. Cancer has some provocative connections as well: inflammation is a contributing factor to some tumours and a few types of cancer have infectious origins. But with the explosive growth of a new class of drug — cancer immunotherapies — scientists have been taking a closer look at how the gut microbiome might interact with treatment and how these interactions might be harnessed.

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