Bacterial Microbiome DE in Bladder Cancer: Implications for Progression and Treatment

Bladder cancer (BC) is a prevalent disease, with an estimated 570,000 people diagnosed globally in 2020. Recent studies have highlighted the presence of communities of bacteria, known as the bacterial microbiome, in both normal and cancerous tissues and their potential impact on treatment efficacy. A team of researchers from the University of Surrey, Guildford, UK, conducted a study that delved into the microbiome of formalin-fixed paraffin-embedded (FFPE) tumor tissue across various stages of BC, as well as adjacent normal tissue to identify differentially expressed (DE) bacteria. The study also sought to investigate the differences in bacteria between responders and non-responders of Bacillus Calmette Guerin (BCG) treatment. The research team also linked the findings to the differential host immune gene expression, the profiles of immune cells infiltrating the tumor, as well as the spatial relationships within the tumor microenvironment (TME).

To determine the bacterial signatures present in urine and formalin-fixed paraffin-embedded (FFPE) tissue samples, researchers utilized 16s rRNA sequencing (V3-V4) on a total of 56 urine and 66 FFPE samples taken from 44 matching patients. After collection, the sequencing data was further analyzed by processing it through QIIME2 and grouping it into operational taxonomic units (OTUs). Alpha diversity analysis (Shannon and observed) and Beta diversity analysis (Bray-Curtis, weighted and unweighted uniFrac) were performed, with non-parametric statistics used to determine significance.

The researchers also extracted RNA from the FFPE BC tissue samples to get gene expression data using the Nanostring IO360 panel (a 770 gene CodeSet). Subsequently, they compared the gene expression data with the tumor microbiome profiles using SparCC analysis. To further investigate and spatially define the immune cell types, 9-color multiplex immunohistochemistry (mIHC) using Phenoimager HT (Akoya Biosciences) was performed on 71 tumor tissue samples.

The findings revealed that the bacterial microbiome of bladder cancer (BC) exhibited decreased diversity and composition as the disease progressed, with a significance level of P<0.01. Additionally, the bacterial profiles between urine and FFPE cancer tissues revealed independent groups (P<0.01), indicating that urine is not an accurate proxy for the bacterial makeup of the cancerous tissue. It also showed that the bacterial microbiome of cancerous and normal tissue, as well as between responders and non-responders, displayed a high degree of similarity. However, some variations in the bacterial populations were identified. The immune cell profiles and spatial relationships, as determined via multiplex immunohistochemistry (mIHC), revealed distinctions between stromal and tumor regions, as well as between low-grade and high-grade disease. The researchers also uncovered connections between the bacterial populations, the expression of immune genes, and the presence of immune cells within the tumor microenvironment (TME).

The results showed a clear progression of differentially expressed bacteria from low-grade to high-grade bladder cancer (BC). Further research is ongoing to investigate these bacteria’s influence on the immune cell phenotype. The potential impact of these bacteria on the tumor immune microenvironment, and consequently on disease and treatment outcomes, will offer a strong foundation for exploring the modulation of the tumor microbiome for improved therapeutic results.

Source: https://jitc.bmj.com/content/10/Suppl_2/A1526

Clinical Trial: https://clinicaltrials.gov/ct2/show/NCT02834013

Wooldridge T, Rayner C, Sunshine S, et al. 1467 An holistic and integrated approach for investigating the bacterial microbiome, gene expression profile and immune cell profile in the non-muscle invasive bladder cancer tumor microenvironmentJournal for ImmunoTherapy of Cancer 2022;10:doi: 10.1136/jitc-2022-SITC2022.1467