Gut Microbiome Enhances Immunotherapy Response

Gut bacteria may help our immune system battle cancerous tumors, according to researchers from the Snyder Institute for Chronic Diseases at the Cumming School of Medicine. Their study—published in Science—provides a new understanding of why immunotherapy is not equally effective for every patient.  

Their findings demonstrate that combining immunotherapy with specific microbial therapy boosts the ability of the immune system to recognize and attack cancer cells in some colorectal, bladder, and melanoma cancers. "Recent studies have provided strong evidence that gut microbiota can positively affect anti-tumor immunity and improve the effectiveness of immunotherapy in treating certain cancers, yet, how the bacteria were able to do this remained elusive, " says principal investigator Kathy McCoy. "We've been able to build on that work by showing how certain bacteria enhance the ability of T-cells, the body's immunity soldiers that attack and destroy cancerous cells."

In order to study how bacteria could the ability of T-cells, they identified bacterial species that had been previously associated with colorectal cancer tumors treated with immunotherapy. Then, they introduced these strains along with immune checkpoint blockade into germ-free mice. Their data showed that specific bacteria were essential to immunotherapy working, causing the tumors to shrink drastically. At the same time, in the mice that weren’t exposed to the beneficial bacteria, immunotherapy had no effect. 

Specifically, the team identified that all these T-cell supportive bacteria produce a small molecule called inosine, "Inosine interacts directly with T-cells and together with immunotherapy, it improves the effectiveness of that treatment, in some cases destroying all the colorectal cancer cells,"  first author Lukas Mager says. 

"Identifying how microbes improve immunotherapy is crucial to designing therapies with anti-cancer properties, which may include microbial," says McCoy. "We are in the early stage of fully understanding how we can use this new knowledge to improve the efficacy and safety of anti-cancer therapy and improve cancer patient survival and well-being."