Good gut bacteria could help in cancer treatment. The fact that a balanced gut microbiome is important for overall health is no secret. Over the past decade, scientists have linked gut bacteria to several illnesses, including depression and obesity. More recently, researches have turned their minds to studying the relationship between gut bacteria and how cancer patients respond (or don’t respond) to treatment. In summary, tests on mice and on humans have enabled scientists to determine that certain bacteria, when present in the intestines, can help cells fight tumors. A research published in 2013* showed that the presence of a specific type of gut bacteria helped an anti-cancer drug called cyclophosphamide achieve better results in mice that had this bacteria in their gut compared to those that had been given antibiotics. Somehow this specific bacteria triggered the mice’s immune system to fight tumors, while those mice that had their gut flora destroyed by antibiotics were not as fortunate. *(This study was carried out by a research group led by Laurence Zitvogel at Gustave Roussy and one led by immunologists Romina Goldszmid and Giorgio Trinchieri at the National Cancer Institute in Bethesda, Maryland). What scientists wish to find out is whether and how certain types of gut bacteria can influence the effect of a class of immunotherapy drugs called “checkpoint inhibitors”, and why only 20–40% of people respond to treatment. The possibilities of using bacteria to help treat cancer patients is very exciting, but there are several concerns around “faecal microbiome transplant”. As the name suggests, the process involves transferring “good” feacal bacteria from people who respond to treatment with a checkpoint inhibitor into the intestine of non-responders. This process would reshape the patient’s gut microbiome in a beneficial way. Gut bacteria transplant is no recent news. It’s been used for several years in the treatment of other illnesses instead of cancer. Read: How to regulate feacal transplants. But don’t wrinkl your nose in disgust just yet! This process does not take place as you might be imagining it. Pharmaceutical companies like Merck, Evelo Biosciences and Seres Therapeutics are working towards developing a pill that has a strain of the beneficial gut bacteria that’s been purified from the donor’s feaces. “Faecal transplants come with a lot of unknowns. They have proved safe and effective in many people without cancer. But they have also been associated with unexpected effects, including one case in which the procedure led to weight gain and obesity. Should we look for safety signals on these trials? Absolutely. But I strongly feel that we need to go into these trials. We need to design them well. We need to really learn from these trials.” says Jennifer Wargo, a surgeon–scientist at MD Anderson Cancer Center in Houston, Texas.