Efficacy and regulatory strategies of gut microbiota in immunotherapy: a narrative review

Background and Objective: With advances in gut microbiome research, it has been recognized that the gut microbiome has an important and far-reaching impact on many human diseases, including cancer. Therefore, more and more researchers are focusing on the treatment of gut flora in tumors. In this article, we present a review of the mechanisms of gut microbes in tumor immunotherapy and related studies to provide reference for further research and insights into the clinical application of gut microbes. Methods: Between April 25, 2023, and November 25, 2023, we searched for articles published only in English between 1984 and 2023 using the databases PubMed, American Medical Association and Elsevier ScienceDirect using the keywords "gut microbiology" and "tumor" or "immunotherapy". Key Content and Findings: The gastrointestinal tract contains the largest number of microorganisms in the human body. Microorganisms are involved in regulating many physiological activities of the body. Studies have shown that gut microbes and their derivatives are involved in the occurrence and development of a variety of inflammations and tumors, and changes in their abundance and proportion affect the degree of cancer progression and sensitivity to immunotherapy. Gut microbiota-based drug research is ongoing, and some anti-tumor studies have entered the clinical trial stage. Conclusions: The abundance and proportion of intestinal microorganisms influence the susceptibility of tumors to tumor immunotherapy. This article reviewed the effects and mechanisms of gut microbes on tumor immunotherapy to further explore the medical value of gut microbes in tumor immunotherapy.