Overview of tumor-resident intratumoral microbiota in human bladder cancer

Background: There is increasing evidence supporting the association between urinary microbiota and bladder cancer (BCa). However, the understanding of the relationship between intratumoral microbiota and BCa remains limited. The objective of this study is to characterize the intratumoral microbiota potentially linked to BCa, and identify microbial differences among patients with different tumor grades. Methods: Surgical resection tissue samples were prospectively collected from BCa patients without preoperative therapy. The presence of bacteria within the tissue samples was assessed using fluorescence in situ hybridization (FISH). Following this, 16S rRNA sequencing and subsequent analyses were conducted, including microbial diversity, community composition, and gene function prediction. Results: After a rigorous pathological diagnosis and exclusion process, 15 BCa tissues and 12 adjacent normal tissues were collected. FISH analysis revealed the presence of bacteria in both BCa tissues and adjacent normal tissues. No significant differences in alpha and beta diversity were observed between two groups. Bacillus, Bacillaceae, Thermoomonas, Enterococcaceae and Enterococcus were significantly increased in BCa tissues versus adjacent normal tissues. Additionally, compared with low-grade BCa, enriched Ramlibacter and depleted Escherichia-Shigella, Bacteroides, Bifidobacterium, Parabacteroides, and Lactococcus were found in patients with high-grade BCa. Conclusions: Our study characterized the intratumoral microbiota characteristics of BCa and provided initial evidence of potential associations between specific bacteria and tumor grade. These findings suggest novel candidate biomarkers and potential therapeutic targets for BCa, but the exact application potential remains to be verified by functional experiments.