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Intestinal microbes influence cancer patients before immunotherapy

The composition of intestinal bacteria can influence the response of cancer patients to immunotherapy, according to two new studies published today by the journal Science.

Antibiotics, according to one study, make these immunotherapy treatments less effective, which reinforce the patient’s immune response or reactivate it by infusing modified cells in the laboratory.

In addition, “good bacteria” are more abundant in patients who respond well to immunotherapy, according to the second research.

“Together, these studies suggest that maintaining a healthy intestinal flora could help fight cancer,” says the scientific journal.

In the first study, Bertrand Routy and colleagues at the Gustave Roussy Cancer Institute (France) analyzed how antibiotics can influence the outcomes of patients with lung or kidney cancer undergoing immunotherapy with PD-1 inhibitors, a type of therapy which activates the immune system to attack tumors.

Patients who had previously taken antibiotics (for urinary or dental infections, for example) had a reduced survival compared to those who did not take antibiotics.

The examination of the intestinal microbes of the patients revealed that the abundance of the bacterium Akkermansia muciniphila was associated with the best clinical result.

This bacterium could be detected in 69% and 58% of the patients who presented a partial response or a stable disease, respectively, but it was only detectable in 34% of the patients who did not respond to the therapy.

In mice treated with antibiotics, the oral supply of the bacteria increased the effectiveness of the immune cells of the mice, thus driving their response to the therapy, according to experts.

In the second study, Vancheswaran Gopalakrishnan and colleagues at the MD Anderson Cancer Center at the University of Texas (USA) indicate that patients with melanoma who respond better to the same PD-1 inhibitors have a greater diversity of intestinal microbes and abundance of certain bacteria.

These researchers collected and analyzed microbiome samples from 112 patients with advanced melanoma who were also taking PD-1 inhibitors.

Patients whose microbiomes were enriched with the bacteria Faecalibacterium and Clostridiales were more likely to respond to treatment and experience greater survival.

The experts detected the opposite for patients whose microbiomes were enriched more with Bacteroidales bacteria.

The analysis of the patients’ immune responses revealed that those with the beneficial microbes tended to have more immune cells, which may be more prone to infiltrate and kill tumors.

Transplanting the microbes of these patients that offered response to germ-free mice and analyzing their response to PD-1 inhibitors yielded results similar to those observed in humans
“The results of the two studies have important implications for the treatment of cancer patients with immune control inhibitors,” the specialized journal concluded.

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