The urinary microbiota: towards a new prognostic tool for prostate cancer?

Prostate cancer is the second most common cancer in men and the fifth deadliest cancer in the world with more than 375,000 deaths in 2020². Despite these figures, prostate cancer is characterized by a very heterogeneous course (in the United States, the 5-year survival rate is estimated at 90%¹).
Today, it is the aggressiveness of the tumor that primarily guides treatment decisions. It is assessed inter alia by the Gleason histopathological score after biopsy, which is an invasive procedure. The identification of urinary markers, which, in combination with clinical data, allows the detection of aggressive forms of the disease, is therefore generating great interest among clinicians.

The urinary microbiota analyzed by molecular imaging and genomics

Studies had already revealed a link between prostate cancer and a specific urinary microbial profile, but also differences in the prostatic bacterial community according to the Gleason score. English researchers therefore turned to the prostate and urinary microbiome, still incompletely characterized, to explore its prognostic potential¹. Using tools such as fluorescence microscopy, anaerobic bacterial culture and genomic sequencing, they analyzed samples of urine and of prostate tissue secretions collected from more than 600 individuals examined in hospital for suspected prostate cancer or hematuria. The subjects were divided into clinical groups and patients diagnosed with prostate cancer stratified according to the D'Amico score.

Anaerobic bacteria linked to tumor progression 

Researchers have demonstrated a significant link between the presence of bacteria in urine and an increased risk of prostate cancer. They also discovered four new bacterial species in the urine samples, the prostatic secretions and the tissues, belonging to the phyla Firmicutes (Fenollariasp. nov. and Peptoniphilus sp.nov), Actinobacteria (Varibaculum sp.nov) and Bacteroidetes (Porphyromonas sp.nov). Five anaerobic species, including three of these new bacteria, were associated with a 2.6-fold increased risk of adverse disease progression, and could serve as potential prognostic biomarkers.

A prognostic, even therapeutic, potential which encourages continued research

The researchers arrived at a hypothesis: these anaerobic bacteria may act on certain metabolic processes.
Such as the conversion of cholesterol into androstenedione, a precursor of testosterone which stimulates tumor growth, or the degradation of citrate, a known marker of prostate cancer aggressiveness. But a causal link between the overrepresentation of these bacteria in patients and disease progression cannot be established at this stage. New research must therefore be undertaken in this respect: if this link is confirmed, a prognostic urine test that is very practical for clinics could be developed. More importantly, targeted antibiotic treatments could control, or even prevent, disease progression.