New research highlights just how important our gut bacteria are to overall health—and even to how cancer patients respond to treatment.
Scientists studying patients with advanced melanoma have found that the composition of the gut microbiome—the community of bacteria living in the intestines—can strongly influence how well patients respond to immunotherapy.
“We got strong evidence that the intestinal flora largely shapes how patients respond to treatment,”
— Jennifer Wargo, M.D., University of Texas, co-author of the study published in Science
Immunotherapy works by activating the body’s own immune system to attack cancer cells. However, researchers have long been puzzled by the fact that many patients do not respond to this treatment. The new findings suggest that differences in gut bacteria may help explain why.
By mapping the bacterial composition in patients’ intestines, researchers at the University of Texas discovered that those who responded best to immunotherapy had a more diverse gut microbiome and higher levels of certain beneficial bacterial species.
“The difference in the intestinal flora between those who became healthier and those who became sicker was like night and day,”
— Jennifer Wargo
To test whether gut bacteria were actually causing the difference in treatment outcomes, the researchers transplanted fecal samples from patients into mice with tumors. The results were striking: mice that received microbiome samples from patients who had responded well to treatment showed stronger anti-tumor responses than mice that received samples from non-responding patients.
Immune profiling further revealed enhanced systemic and anti-tumor immune activity in both responding patients and germ-free mice that received transplants from those patients.
In recent years, growing research has demonstrated the crucial role the microbiome plays in health and disease. This study adds to that evidence, suggesting that gut bacteria may directly influence the effectiveness of cancer therapies.
“We still do not know what mechanisms make these bacteria beneficial for treatment, but it raises important questions. It may be time to try to influence the intestinal flora of our cancer patients,”
— Jennifer Wargo
The findings suggest that the microbiome could one day help predict which melanoma patients are likely to benefit from immunotherapy. In the future, it may even become possible to modify or transplant beneficial gut bacteria to improve treatment outcomes.
Reference:
Wargo, J. A., Gopalakrishnan, V., Spencer, C. N., et al. “Gut microbiome modulates response to anti–PD-1 immunotherapy in melanoma patients.” Science. DOI: 10.1126/science.aan4236