The microbiome-immune cell interaction network: Advancing tumor immunotherapy.

Tumor immunotherapy has achieved revolutionary advancements; however, owing to the complex interplay of multiple intrinsic and extrinsic tumor factors, the patient response rate remains suboptimal. Recent research has emphasized the pivotal role of microbiome in tumor progression. Under normal physiological conditions, microbiome enter orally and colonize sites such as the oral and intestinal mucosa, establishing a dynamic microbiome equilibrium that participates in essential physiological processes, including host metabolism and immune regulation. However, in pathological states, including dysbiosis, tumor initiation, or compromised mucosal barrier function, the microbiome can penetrate the mucosal barrier, infiltrate tumor tissues, and engage in intricate direct or indirect interactions with immune cells. These interactions play a pivotal role in reshaping the tumor immune microenvironment and modulating the host's anti-tumor immune response. This review elaborate the regulatory mechanisms involved in direct and indirect interactions between microbiome and immune cells within tumors, and their implications for tumor immunotherapy. We discuss the external factors that impact these interactions and outline the potential use of engineered bacteria in cancer treatment. From the perspective of the interaction network between microbiomes and immune cells, this review elucidates the mechanisms and potential of microbiomes in tumor immunotherapy, offering new insights and potential targets for innovative strategies in tumor prevention and treatment.