Introduction:

The role of microbiome in genitourinary cancer is an emerging field, with evidence implicating the important role of microbiome as causative factors or cofactors in tumorigenesis and drug metabolism. With the sexual dimorphism that exists within bladder cancer prevalence and survival, our study aims to characterize the role of microbiome in sex-based setting. In addition to characterization of microbiome, our study also aims to identify functional alterations using metagenomics data.

Methods:

This is a single site, non-randomized, prospective study of patients with the diagnosis of muscle invasive bladder cancer (MIBC) undergoing cystectomy from September 2020 to May 2021. Stool samples were collected during surgery using aseptic technique. Bacterial genomic DNA was isolated and purified with the QiaAmp DNA Mini Kit (Qiagen V3-V4 region of the 16S rRNA gene was amplified using16S-515F: GTGCCAG CMGCCGCGGTAA and 16s-806R: GGACTACHVGGGTWTCTAAT primers., The statistical programming language R and related packages were used for diversity and correlation analysis. Hierarchical clustering by Bray-Curtis distance was performed using hclust2. Linear discriminant analysis (LDA) effect size (LEfSe) was used to identify significant differences in metagenomic taxa between male and female patients. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analysis was performed to identify Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways.  

Results:

A total of 29 patients (17 males and 12 females) were enrolled. The median (IQR) age was 74 yo (63-77), males, and 68.5 yo (58-78), females. Per figure 1, Bacteroidales dominated the bacterial community at order level with mean relative abundance of 43.45%, males, and 49.42%, females (Figure 1D). Clostridiales was the second most notable order, composing 31.34% and 34.33% of male and female samples. While there were no differences overall in diversity (Figure 1F) and similarity (Figure 1C), greatest difference between sexes in LDA were noted in Burkholderia (log change -1.71,p=0.004/p_adj=0.082), Campylobacterales (log change 2.18,p=0.007/p_adj=0.082), Actinomycetales (log change 1.39,p=0.036/p_adj=0.208), and Enterobacteriales (log change -1.54,p=0.017/p_adj=0.132) (Figure 1E). Regarding functional analysis, 57 modules were differently expressed across genders, with KO00039 (isocitrate dehydrogenase (log change 3.12,p_adj=0.051) and KO00050 (glucose-6-phosphase-1-dehydrogenase (log change 3.12,p_adj=0.049) noted to be exaggerated in males.

Conclusion:

Crosstalk between the natural host microbiome and immune system modulates the local and systemic inflammatory response, oncogenic signaling, and tumor progression. Characterization of how microbiomes alter cellular activity, induce tumorigenesis, or predict response to treatment may represent the first step in understanding sex-based differences in Bca. Our study highlighted key functional and metabolic differences between males and females Bca patients, with goal for future translational studies aimed to validate functional pathways and novel “personalized” therapeutic targets.

Funding: P30CA043703 Case Comprehensive Cancer Center Microbiome Grant