The microbiome’s critical role in bladder cancer has gained recognition over the past decade, but the complex dynamics between the microbiome and tumors have yet to be fully understood. To assess the current understanding of that relationship, Ilaha Isali, M.D., MSc, a urology resident at NewYork-Presbyterian and Weill Cornell Medicine, recently published a state-of-the-art review in Urologic Oncology with Dr. Laura Bukavina of the Cleveland Clinic, with whom she has is currently doing research on the urinary microbiome of bladder cancer patients.
Below, Dr. Isali summarizes the current evidence and discusses best practice guidelines for collecting samples for use in bladder cancer research.
How Understanding Microbes Can Provide Insight Into Cancer Biology
The relationship between the urinary tract microbiome and bladder cancer (BCa) progression remains an open question in research. Some evidence suggests that BCa may alter the bladder's extracellular matrix, potentially influencing inflammation, but more studies are needed to understand these effects.
Our review examined how microbiomes could help develop new biomarkers and treatment strategies for BCa patients. Modulating the microbiome might enhance treatment outcomes. Notably, research shows that the gut microbiome can influence how patients respond to immunotherapies such as pembrolizumab in BCa. This highlights the potential for microbiome-based approaches to improve cancer care.
We highlighted recent microbiome studies in BCa research, such as Bukavina et al., which provided a global assessment of the urinary microbiome in BCa patients. This study compared microbiome profiles in 129 BCa patients and 60 healthy controls across four countries and three continents, carefully evaluating the influence of environmental factors versus direct associations with BCa. This study revealed that urine collection methods significantly influenced many of these taxonomic differences (voided vs. catheterized). Additionally, researchers identified an increased presence of polycyclic aromatic hydrocarbon (PAH)-degrading bacteria-including Sphingomonas, Acinetobacter, Micrococcus, Pseudomonas, and Ralstonia-which remained consistently more abundant in BCa patients even after controlling for contamination associated with voided urine. These findings suggest a potential microbial biomarker or a microbial role in BCa pathogenesis, warranting further investigation. Even so, some outcomes provided useful insights for treatment.
Another study also examined the urine microbiome as a potential predictor for recurrence. It found nine specific genera that were more prevalent in patients experiencing recurrence, including Anoxybacillus, Massilia, Thermomonas, Brachybacterium, Micrococcus, Nocardioides, Larkinella, Bacillus Jeotgali, and Geomicrobium. These findings suggest that, in the future, microbiome profiling could help stratify patients and improve early detection of BCa recurrence.
Best Practice Guidelines for Sample Collection
This state-of-the-art review underscores the critical role of collection methods in advancing microbiome research. Key challenges such as contamination risks, variability in sample storage, and methodological inconsistencies continue to hinder progress, particularly in studying bladder cancer microbiome. Relevant to this, my colleagues and I recently published best practice guidelines for collecting microbiome samples. Our work explores essential strategies, including adopting standardized nomenclature, using techniques such as catheterization to minimize external contamination, and optimizing storage methods to preserve microbiome stability. By advocating for the widespread adoption of standardized protocols, we aim to enhance the accuracy, reproducibility, and overall reliability of urinary microbiome research.
