Gold digging: Searching for gut microbiota that enhances antitumor immunity

Programmed cell death protein-1/programmed cell death-ligand 1 and cytotoxic T-lymphocyte antigen-4 are two immune checkpoint inhibitors (ICIs), exhibiting significant antitumor effects on multiple types of cancers in clinical practice. However, only some patients respond to ICI agents, which limits their widespread application. Recent findings revealed that the gut microbiota is relevant to host health through the modulation of host physical and immune functions. Therefore, the modulation of gut microbiota to achieve the desired taxa may be a potential strategy to improve the efficacy of immunotherapies. In this review, we classified the relative microbes according to their taxonomic information and aimed to clarify their modulatory functions and potent effects on ICI immunotherapy by focusing on recent trials investigating the relationships between the gut microbiota and ICIs.