Intratumoral microbiota as a novel prognostic indicator in bladder cancer

Microbes are important components of the tumor microenvironment and have a close relationship with tumors. However, there is still a lack of research on the intratumoral microbiota in bladder cancer and its impact on the tumor immune microenvironment. In this study, we used fluorescence in situ hybridization (FISH) and observed a substantial presence of microbiota in bladder cancer tissues, with greater abundance compared to that in normal bladder tissues. Based on the BIC database, we found that the microbiome of bladder cancer is highly diverse and its structure is significantly different from that of other tumors. To investigate the relationships among the intratumoral microbiota, tumor immunity, and prognosis in bladder cancer patients, we analyzed bladder cancer-specific differentially expressed immune- and antimicrobial-related genes from the ImmPort, TISIDB, and TCGA databases. We identified 11 hub genes and constructed a prognostic risk model. Further analysis revealed differences at the family and genus levels between distinct groups. Using LEfSe analysis, we identified six hub biomarkers and developed a novel microbial-based scoring system. The scoring system allows subgrouping of bladder cancer patients, with significant differences in prognosis, immune cell infiltration, tumor mutation burden, and immune checkpoints among different groups. Further FISH and immunofluorescence co-staining experiments initially verified that the specific distribution of microorganisms and M2 macrophages in bladder cancer may be closely related to the poor prognosis of patients. In conclusion, this study revealed the characteristics of the intratumoral microbiota in bladder cancer and identified potential prognostic targets for clinical application.