| Intratumoral bacteria, as an important component of the tumor microenvironment, have been shown to be closely associated with tumor initiation and progression. As tumors metastasize, treatment complexity and mortality increase markedly, and intratumoral bacteria play critical biological roles throughout this process. This review summarizes the origins, diversity, and heterogeneity of intratumoral bacteria, evaluates the technical features and limitations of major detection methodologies, and outlines the protumorigenic mechanisms attributed to these microorganisms. We further highlight the roles of intratumoral bacteria at different stages of tumor metastasis, including epigenetic regulation, exosome-mediated effects, bacterial phenotypic features, tumor angiogenesis, metabolic reprogramming, and immune modulation. In addition, we discuss the potential clinical value of intratumoral bacteria in tumor diagnosis, prognostic assessment, and therapeutic intervention. Looking ahead, emerging research directions—such as high-resolution spatial microbiomics, multi-omics integration, targeted bacterial therapies, and microbiota-based interventions—will deepen our understanding of the biological functions of intratumoral bacteria and promote their application in precision oncology. |
