Insights into the Interplay between the Urinary Microbiome and Bladder Cancer: A Comprehensive Review

New insights in the urinary microbiome have led to a better understanding being built of the shifts in bacterial representations from health to disease; these hold promise as markers for diagnosis and therapeutic responses. Although several efforts have been made to identify a "core urinary microbiome", different fingerprints have been identified in men and women that shift with age. The main bacterial groups overall include Firmicutes, Actinobacteria, Fusobacteria, and Bacteroidetes. Although patients with bladder cancer have a microbiome that is similar to that of healthy individuals, differences have been observed at the species level with Fusobacterium nucleatum and Ralstonia, and at the genus level with Cutibacterium. Different bacterial representations may influence extracellular matrix composition, affecting tumor metastatic spreading and tumorigenic metalloproteinase expression. Furthermore, gene expression affecting targets of immune therapy, such as PD-L1, has been associated with changes in bacterial representations and therapeutic response to BCG. This comprehensive review aims to examine the influence of the urinary microbiome in bladder cancer.