The Gut Microbiome and Immunotherapy: Researching the Connection

Dr. Sumanta (Monty) Pal and Dr. Arielle Elkrief discuss the clinical relevance of the gut microbiome in cancer immunotherapy and the importance of antibiotic stewardship, as well as interventions currently being explored to treat gut dysbiosis and optimize immunotherapy response. TRANSCRIPT Dr. Sumanta (Monty) Pal: Hi everyone, I'm Dr. Monty Pal, welcoming you to the ASCO Daily News Podcast. I'm a medical oncologist. I'm a professor and vice chair of academic affairs at the City of Hope Comprehensive Cancer Center in Los Angeles. Today we're here to discuss one of my favorite topics, which is the gut microbiome. It's almost hard to avoid the gut microbiome nowadays if you look at medical literature within oncology. It's an emerging phenomenon, but there are a couple of individuals that I would really define as pioneers in the field. And one of them is actually with me today, Dr. Arielle Elkrief, to discuss the clinical relevance of the gut microbiome, particularly amongst patients receiving immunotherapy, although I imagine our conversation today will take many twists and turns. Arielle is an assistant professor and clinician scientist in the Department of Oncology at the University of Montreal, and she is co-director of the CHUM Microbiome Center there. FYI for the listeners, we have our full disclosures in the transcript of this episode. Arielle, thank you so much for joining us today. Dr. Arielle Elkrief: Thanks so much, Monty. This is going to be amazing. Dr. Sumanta (Monty) Pal: Well, I have to tell you what sort of inspired me to bring you on as a guest. It was one of many things, but it was this really terrific ASCO Educational [Book] article that you wrote. Now, I have to tell you, I've read all the articles sort of cover to cover in the book, and they're always a wonderful primer, so if our audience is studying for board research or something of that sort, it's a terrific resource to go through. I have to tell you, this piece on the gut microbiome that you wrote is nothing short of a masterpiece. If you read this cover to cover, it's actually going to give you, I think, a sense of the current state and future state of the field. I wanted to start by just sort of beginning with sort of the origin story for a lot of this, which is this association between the gut microbiome and immunotherapy response. This takes us back several years to this pivotal series of papers in Science. Maybe you could walk our audience through that. Dr. Arielle Elkrief: Absolutely. Well, thank you so much for your kind words about the ASCO [Educational] Book. It was a team effort with a lot of key opinion leaders in the field, so I'm really glad to learn that you've liked it. Moving backwards in terms of how we came to understand that the gut microbiome is essential to priming a response to cancer immunotherapy actually goes back to 2015 and seminal papers that looked at what happens when we take mice that are germ-free mice that have never been exposed to a microbiome. These are mice that are born by cesarean section and essentially live in a bubble. And when we give those mice tumors and treat them, in the first papers with anti-CTLA-4 treatment, we realized that these antibodies don't work at all. And that was the first observation that the presence of a gut microbiome was essential to mounting an anti-cancer immune response. When we supplemented those same mice with beneficial bacteria or feces from responder patients, we were able to restore the response to immunotherapy. And so those were really the first preclinical observations that made us understand the critical role of the microbiome in immunotherapy response. Moving a little bit in the future, we examined the fecal microbiome composition using shotgun metagenomic sequencing in different cohorts of patients with solid tumors, namely lung cancers, kidney cancers, and also skin tumors like melanoma, and found that patients who responded to immunotherapy had a distinct m