Gut bacteria boost chemotherapy drugs in a research trial

Two bacterial species that inhabit the human gut activate immune cells to boost the effectiveness of a commonly prescribed anticancer drug, researchers report in Immunity.The study identifies a new role for Enterococcus hirae and Barnesiella intestinihominis in activating cancer-fighting T cell immune responses, thereby enhancing the effects of the chemotherapy drug cyclophosphamide.

“The anti-cancer drug’s efficacy relies on a complex interplay between the microbiome of cancer patients and their ability to mount an efficient immune memory response against some bacteria of the gut microbiota,” says co-senior study author Mathias Chamaillard, Inserm research director of the Center for Infection and Immunity of Lille.

In a few cases, the antitumor effects of intestinal bacteria can also contribute to the effectiveness of chemotherapy drugs.It has not been clear which specific bacterial species activate antitumor immune responses in response to chemotherapy, and exactly how they do so.

In the new study, Chamaillard and senior study author Laurence Zitvogel of the Institut de Cancérologie Gustave Roussy Cancer Campus showed that two intestinal bacteria, E. hirae and B. intestinihominis, both act to orchestrate the anticancer therapeutic effects of cyclophosphamide-an immunosuppressive chemotherapy drug used to treat a wide range of cancers.

Using mouse models, the researchers showed that oral treatment with E. hirae activated antitumor T cell responses in the spleen in parallel with the direct toxic effects of cisplatin on the tumor, thereby curbing tumor growth. On the other hand, oral treatment with B. intestinihominis achieved a similar effect by promoting the infiltration of T cells in various mouse tumors.

Press release: How gut microbes help chemotherapy drugs