Urinary microbiome (UM) has gained increasing interest in bladder cancer (BCa), trying to unveil its possible role in the onset and progression of tumor as well as predictive biomarker of treatment response. Moreover, the relationship urinary–bladder tissue microbiomes has not yet been investigated. Herein, we aimed to investigate the gender-specific UM of BCa patients compared to age-matched controls, and to establish how much the UM is representative of bladder tissues, profiling the microbiome of single-patient triplets (urine/BCa tissue/non-BCa tissue).
A total of 160 biological samples were analyzed: morning, mid-stream voided urines from 47 therapy-naïve patients (36 males, 11 females) undergoing radical cystectomy for MIBC and from 51 age-matched healthy controls (26 males, 25 females), plus bladder tissue specimens (paired BCa/non-BCa tissues) of 31 patients (21 males, 10 females). Microbiome was analyzed up to the species level by performing amplifications of the V3–V5 region of 16S rRNA. Sequences with a high-quality score and a length of >250 bp were used for the taxonomic analysis with QIIME version 1.9.1. All statistical tests and enrichments were considered significant for p-value <0.05. Bacterial categories below 1% at any depth of analysis (from phylum to species) were excluded.
In male UM, β-diversity did not show distinct clustering of BCa vs. control. Firmicutes were enriched in BCa males (26% vs. 11%, p=0.02). Notably, within this phylum, Enterococcaceae family was present only in patients (12% vs. 0%, p=0.04), with the increase of Enterococcus spp. (+12%, p=0.04). Instead, in female UM β-diversity showed distinct clustering of BCa vs. controls (p<0.001), mostly due to a >10-fold decrease in Lactobacillaceae (2% vs. 28%, p=0.02), along with an increase in Enterobacteriaceae (56% vs. 10%, p<0.01). Lactobacillus iners, an important species in preventing the colonization of vagina by potentially pathogenic bacteria, was absent in the UM of BCa female (0% vs. 18%, p<0.01). Considering the urine/BCa/non-BCa triplets, principal component analysis showed a distinct clustering of urine vs. tissues but did not discriminate BCa vs. non-BCa.
Our findings showed that UM is different in BCa patients and age-matched controls, and the relative changes in composition are gender-specific. Moreover, UM does not recapitulate the bladder microbiome in BCa patients, suggesting that UM cannot be used as a perfect surrogate of the bladder microenvironment. Future studies will test UM as a non-invasive biomarker to monitor BCa and response to therapy.