Researchers at the University of Chicago transplanted a specific species of Bifidobacterium bacteria into the gastrointestinal (GI) tracts of mice suffering from melanoma. The bacteria dramatically increased the immune system, which proceeded to attack the cancerous cells. These increases have been comparable to other anti-cancer drugs like checkpoint inhibitors, including anti-PD-L1 antibodies.
Researchers reported that in combination, the bacteria, administered orally, and shots with anti-PD-L1 antibodies almost completely stopped tumor growth.
These results demonstrate a significant, albeit surprising, part for certain gut bacteria in in increasing the immune system's response to melanoma and potentially many other types of cancer, providing a novel way to exploit that connection to improve immunotherapy by selectively modulating intestinal bacteria.
Easton, John. "Gut Bacteria Can Dramatically Amplify Cancer Immunotherapy." University of Chicago. November 06, 2015. http://news.uchicago.edu/article/2015/11/06/gut-bacteria-can-dramatically-amplify-cancer-immunotherapy.
Sivan, Ayelet, et al. "Commensal Bifidobacterium promotes anti-tumor immunity and facilitates anti-PD-L1 efficacy." Science. November 27, 2015. www.sciencemag.org/lookup/doi/10.1126/science.aac4255