4. Bladder Cancer and Urinary Microbiome
Limited research has been conducted on the bladder microbiome involvement in urological cancers. Recent studies indicate that the human microbiome can affect cancer formation, however the function of microbes in bladder cancer pathogenesis has not been investigated. According to a study comparing urine samples from healthy people to bladder cancer patients using 16S rRNA sequencing, an abundance of the genus
Streptococcus in bladder cancer patients was detected
[40]. Bladder urothelial carcinoma (UBC) is the sixth most common kind of cancer globally
[41]. UBC can be categorized as non-muscle invasive, muscle invasive, or locally advanced/metastatic
[42]. UBC is characterized by a heterogeneous tumor cell population and surrounding tumor microenvironment (TME). Given that the microbiota has been linked to the formation of cancer in a variety of tissues, urinary microbiome is also implicated in UBC. Only a few studies have examined the relevance of the microbiome in urologic malignancy.
Several studies were performed to define and compare the bladder cancer patients’ urine microbiota to that of healthy controls. The potential changes in the extracellular matrix caused by the microbiota and the subsequent inflammation may play a role in carcinogenesis
[43]. This study recruiting male bladder cancer patients and non-neoplastic controls collected midstream urine. Cancer patients’ urine samples were enriched with some bacterial genera (e.g.,
Acinetobacter,
Anaerococcus, and
Sphingobacterium), but showed a decrease in others (e.g.,
Serratia,
Proteus, and
Roseomonas)
[43]. Enrichment of
Herbaspirillum,
Porphyrobacter, and
Bacteroides was identified in cancer patients with a high risk of recurrence and progression, suggesting that these genera might serve as risk stratification biomarkers
[43]. Another study was performed to analyze bacterial populations using 16S sequencing in mid-stream urine specimens obtained from male patients diagnosed with bladder cancer and healthy, age-matched males
[44]. Although microbial diversity and overall microbiome composition did not change substantially between groups, the study detected more abundant operational taxonomic units (OTUs) belonging to the genus
Fusobacterium as a potential protumorigenic pathogen enriched in the bladder cancer group. OTUs from the genera
Veillonella,
Streptococcus, and
Corynebacterium were less prevalent in the bladder cancer group
[44]. An additional study reported that the midstream urine samples from bladder cancer patients exhibited a higher abundance of
Actinomyces than the control group. The study suggested that the increased prevalence of
Actinomyces europaeus in bladder cancer patient samples may be diagnostic of bladder cancer
[45]. More recently, bladder cancer patients’ urine microbiota was compared to that of healthy controls by utilizing 16S rRNA sequencing of voided urine samples. Bacterial populations were analyzed using 16S sequencing in urine specimens taken from bladder cancer patients and healthy, age-matched controls
[44]. While microbial diversity and overall microbiome composition did not vary substantially across groups, the genus
Fusobacterium was substantially enriched in the bladder cancer group and can be considered as a potential protumorigenic pathogen
[44]. In healthy urines, the genera
Veillonella,
Streptococcus, and
Corynebacterium were more prevalent
[44]. However, owing to the small sample size, more research is required to establish if the urine microbiota is linked with bladder cancer.
Although these studies performed on the bladder cancer patients suggest the potential relationship between the bladder microbiome and bladder cancer, these studies collected voided urine specimens (midstream urine samples) which mischaracterized the urinary bladder microbiome for the urogenital microbiota
[22][33]. A further comparative study of microbial communities in urine obtained via suprapubic aspiration or transurethral catheter should be performed in order to examine the contribution of the urinary bladder microbiome in bladder cancer. A recent study evaluated the need to carefully compare the microbiome profiles linked with the urine and bladder mucosa in bladder cancer patients. Tissue samples were obtained from patients after transurethral excision of cancer tissue
[46]. Simultaneously, urine samples were collected from the same individuals by transurethral resectoscopy. As “five suspicious genera,”
Akkermansia,
Bacteroides,
Clostridium sensustricto,
Enterobacter, and
Klebsiella were overrepresented in tissue samples compared to urine
[46]. This study discovered significant differences in some taxa, suggesting that the bladder tissue microbiota and the urine microbiota may differ to some extent
[2][46]. Greater knowledge of the microbiome’s function in the development and progression of bladder cancer may open the way for novel treatment approaches. The urine microbiota may serve as a biomarker for bladder cancer and as a therapeutic target. Finally,
Table 1 contains a description of the major bacterial genera found in individuals with urinary diseases.
Table 1. A summary of the bacterial genera reported in individuals with urinary disease.
Disorder |
Subjects |
Specimens |
More Abundant Microbiome than Control Group |
References |
UI/OAB |
Women with MUI |
Catheterized urine |
No difference in Lactobacilli, but six bacterial community types identified |
[47] |
Women undergoing POP/ SUI surgery |
Catheterized urine |
OAB group: Atopobium vaginae, Finegoldia magna |
[48] |
Women with OAB |
Midstream urine and vaginal swab |
OAB group: Proteus (Less: Lactobacillus) |
[49] |
Women undergoing SUI surgery |
Voided or catheterized urine |
Hormone-negative women: (Less Lactobacillus, Gardnerella) |
[45] |
Women with OAB |
Catheterized urine |
OAB group: Sneathia, Staphylococcus, Proteus, Helcococcus, Gemella, Mycoplasma, Aerococcus |
[50] |
Women with daily UUI |
Catheterized urine |
UUI group: Sphingomonadales, Chitinophaga, Brevundimonas, Cadidatus Planktoluna, Alteromonadaceae, Elizabethkingia, Methylobacterium, Caldicellulosiruptor, Stenotrophomonas(less: Prevotella, Comamonadaceae, Nocardioides, Mycobacterium) |
[51] |
Women seeking UUI treatment |
Catheterized urine |
UUI group: Actinobaculum, Actinomyces, Aerococcus, Arthrobacter, Corynebacterium, Gardnerella, Oligella, Staphylococcus, Streptococcus |
[52] |
IC/BPS |
Women with IC/BPS |
Midstream urine |
IC/BPS group: Lactobacillus gasseri (less Corynebacterium) |
[53] |
Women with IC/BPS |
Midstream urine |
No difference in genus |
[54] |
Women with IC/BPS |
Midstream urine and vaginal swab |
No difference in genus |
[55] |
Women with IC/BPS |
Catheterized urine |
IC group: (less Lactobacillus acidophilus) |
[56] |
Women with IC/BPS |
Stool and vaginalswab |
IC/BPS group: (less Eggerthella sinensis, Colinsella aerofaciens, F. prausnitzii, Odoribacter splanchnicus, Lactonifactor longoviformis) |
[57] |
Women with IC/BPS |
Midstream urine |
No difference in genus |
[58] |
Women with IC |
Midstream urine |
IC group: -more Lactobacillus |
[59] |
UTI |
Women with acute cystitis or recurrent cystitis |
Catheterized urine |
Acute cystitis group: Pseudomonas, Acinetobacter, Enterobacteriaceae Recurrent cystitis group: Sphingomonas, Staphylococcus, Streptococcus, Rothia spp |
[25] |
postoperative urinary tract infection patients |
Catheterized urine and vaginal swab |
Patient group: Escherichia coli, Klebsiella pneumoniae, P. aeruginosa (Less Lactobacillus iners) |
[60] |
Bladder cancer |
Bladder cancer patients |
Midstream urine |
Bladder cancer group: Actinomyces europaeus |
[61] |
Men with non-muscle invasive bladder cancer |
Midstream urine |
Bladder cancer group: Fusobacterium, Actinobaculum, Facklamia, Campylobacter |
[44] |
Men with bladder cancer |
Midstream urine |
Bladder cancer group: Acinetobacter, Anaerococcus, Sphingobacterium (Less: Serratia, Proteus, Roseomonas) |
[43] |
Urothelial carcinoma patients |
Midstream urine |
Bladder cancer group: Streptococcus, Pseudomonas, Anaerococcus |
[40] |