Two types of bacteria commonly found in the gut work together to fuel the growth of colon tumors, researchers reported on Thursday.
Their study, published in the journal Science, describes what may be a hidden cause of colon cancer, the third most common cancer in the United States. The research also adds to growing evidence that gut bacteria modify the body’s immune system in unexpected and sometimes deadly ways.
The findings suggest that certain preventive strategies may be effective in the future, like looking for the bacteria in the colons of people getting colonoscopies.
If the microbes are present, the patients might warrant more frequent screening; eventually people at high risk for colon cancer may be vaccinated against at least one of the bacterial strains.
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Gut Microbes Combine to Cause Colon Cancer, Study Suggests
Anticancer immunotherapy by CTLA-4 blockade relies on the gut microbiota
Science. Author manuscript; available in PMC 2016 Jan 21.
Published in final edited form as:
Science. 2015 Nov 27; 350(6264): 1079–1084.
Published online 2015 Nov 5. doi: 10.1126/science.aad1329
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4721659/
Abstract
Antibodies targeting CTLA-4 have been successfully used as cancer immunotherapy. We find that the antitumor effects of CTLA-4 blockade depend on distinct Bacteroides species. In mice and patients, T cell responses specific for B. thetaiotaomicron or B. fragilis were associated with the efficacy of CTLA-4 blockade. Tumors in antibiotic-treated or germ-free mice did not respond to CTLA blockade. This defect was overcome by gavage with B. fragilis, by immunization with B. fragilis polysaccharides, or by adoptive transfer of B. fragilis–specific T cells. Fecal microbial transplantation from humans to mice confirmed that treatment of melanoma patients with antibodies against CTLA-4 favored the outgrowth of B. fragilis with anticancer properties. This study reveals a key role for Bacteroidales in the immunostimulatory effects of CTLA-4 blockade.
Published in final edited form as:
Science. 2015 Nov 27; 350(6264): 1079–1084.
Published online 2015 Nov 5. doi: 10.1126/science.aad1329
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4721659/
Abstract
Antibodies targeting CTLA-4 have been successfully used as cancer immunotherapy. We find that the antitumor effects of CTLA-4 blockade depend on distinct Bacteroides species. In mice and patients, T cell responses specific for B. thetaiotaomicron or B. fragilis were associated with the efficacy of CTLA-4 blockade. Tumors in antibiotic-treated or germ-free mice did not respond to CTLA blockade. This defect was overcome by gavage with B. fragilis, by immunization with B. fragilis polysaccharides, or by adoptive transfer of B. fragilis–specific T cells. Fecal microbial transplantation from humans to mice confirmed that treatment of melanoma patients with antibodies against CTLA-4 favored the outgrowth of B. fragilis with anticancer properties. This study reveals a key role for Bacteroidales in the immunostimulatory effects of CTLA-4 blockade.
Debbie