Healthy populations of bacteria, called the microbiome, live in the mouths and gastrointestinal tracts of humans, and they have evolved right alongside them as well. These “good” bacteria help with digestion by absorbing nutrients from food and compete for resources and space with bad bacteria. Now, a new study from the University of Texas MD Anderson Cancer Center shows that gut bacteria also help fight cancer.
After looking at more than 200 mouth microbiome samples and more than 100 gut microbiome samples from individuals with advanced-stage melanoma, researchers saw a connection between healthy microbiome samples, which are more diverse, and the successful response to cancer immunotherapy.
Specifically, they saw there was a better response to immunotherapy treatment when an individual’s microbiome also appeared to be more diverse, compared to the gut bacteria of patients who did not respond as well to immunotherapy. There were also visible and meaningful differences in the types of bacteria found in the gut of individuals who responded well to immunotherapy. However, all of the significant results were seen in gut microbiota, not mouth microbiota.
This is one of the first studies comparing microbiomes and the response to immunotherapy, while past studies have focused their research on mice models of disease. “Our research shows a really interesting link that may mean the immune system is aided by gut bacteria when responding to these drugs,” said lead researcher Jennifer Wargo.
Immunotherapy stimulates the power that already exists in the human immune system to target and kill cancer cells. Sometimes this takes the form of enhancing the immune system’s strength or focus, and sometimes researchers add proteins or superpowered immune cells to help get the job done. However, Wargo said, “not all patients respond to immunotherapy drugs, and it's hard to know who will benefit from the treatment prior to it being given.”
This study has scientists interested in pre-immunotherapy alterations done to the gut microbiome. Providing antibiotics, probiotics, or a fecal transplant before treatment could change the content of an individual's microbiome to better fit the model that best responds to immunotherapy, as depicted by this study. Researchers plan on testing these options in clinical trials.
In 2009, the American Melanoma Foundation stated that melanoma was the most common form of cancer for young adults, saying that one American dies of melanoma every hour. Gut bacteria have been connected to conventional chemotherapy in past studies, and this research and its potential applications give great promise to the future of cancer treatment.
Sources:
Cancer Research UK,
American Cancer Society,
American Melanoma Foundation
