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Scientists go with Gut to Fight Cancer

Two scientists in lab
Lukas Mager and Kathy McCoy have discovered how bacteria within our microbiome can help battle some forms of cancer. Kelly Johnston, Cumming School of Medicine

It is estimated that the human gastrointestinal tract contains around 100 trillion bacteria. Collectively known as your microbiome, recent studies have shown just how involved these bacteria are in our overall health. Research now indicates they may also dramatically impact the body’s ability to fight cancer.

Working out of the University of Calgary, researchers figured out that key bacteria found in the microbiome produce a small molecule called inosine, which can activate and enhance cancer immunotherapy—the science that uses the body’s immune system to recognize and destroy cancerous cells. 

Enhancing a Blockade

The researchers isolated three bacteria—Bifidobacterium pseudolongum, Lactobacillus johnsonii, and Olsenella species—and introduced them into germ-free mice along with a therapy known as immune checkpoint blockade. This treatment blocks specific proteins that can keep the body’s T-cells from attacking and killing cancer cells. They found that the combination of the bacteria with the immunotherapy dramatically shrunk or eliminated cancer cells in the mice. In mice that received the immunotherapy but no bacteria, the cancerous cells were not affected.

“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, ” said Kathy McCoy, Ph.D., director of the International Microbiome Centre at the University of Calgary and principal investigator on the study. “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.”

Early Stages

The combination therapy was shown effective against three types of cancer: colorectal, bladder, and melanoma, and the researchers believe their work points to the reason why cancer immunotherapy works on some patients, but not others. Those lacking the key bacteria in their guts might see no results from the treatment, while individuals possessing them might be the ones who see success.

“Identifying how microbes improve immunotherapy is crucial to designing therapies with anti-cancer properties, which may include microbials,” says McCoy. “The microbiome is an amazing collection of billions of bacteria that live within and around us every day. 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.”

The research was published in the peer-reviewed journal, Science.