Gut bacteria may help treat cancer

According to two new reports, the communities of bacteria that live in our gut can help determine the effectiveness of certain anti-cancer therapies, including those drugs which were previously thought to act directly on tumor cells. In both cases, it appears that the gut microbiota may modulate the immune system's response triggered by these treatments. The researchers found that these therapies were less effective in attacking tumors in mice with sterile intestines. Noriho Iida and his colleagues found that both cancer immunotherapy and a platinum-based chemotherapy were less effective in mice without gut microbiota. In this case, bacteria are needed to activate a certain kind of anti-tumor innate immune response.

Sophie Viaud and her colleagues used mice to demonstrate that the cytotoxic drug cyclophosphamide drives certain bacteria from the gut into the secondary lymphoid system, where they trigger the production of specific T "helper" cells and other components of the adaptive immune system that then attack the tumor. This anti-cancer defense is poorly activated in mice without gut bacteria. Whether these data from the two mouse studies reflect what happens in cancer patients undergoing chemotherapy remains to be determined. If it does, the research suggests that manipulating the gut microbiota could enhance the efficacy of some anti-cancer treatments. It also highlights the potential risks of using antibiotics during certain cancer treatments.