# Cutibacterium acnes: An Emerging Prostate Cancer Pathogen

## TL;DR

Cutibacterium acnes, a skin bacterium, may play a role in prostate cancer by causing inflammation and DNA damage, but its exact role is still unclear.

## Contribution

This review evaluates the potential role of C. acnes in prostate cancer and highlights its possible diagnostic and therapeutic implications.

## Key findings

- C. acnes is found in both healthy and cancerous prostate tissues, suggesting a possible link to cancer development.
- The bacterium may survive in the prostate due to low oxygen and acidic conditions, promoting inflammation and DNA damage.
- C. acnes has been detected in urine, gut, and blood, indicating potential for non-invasive early cancer detection.

## Abstract

Cutibacterium acnes is a bacterium which normally lives on the skin, and can contribute to the development of acne. Over the last 20 years, C. acnes has also been found in the prostate of people with prostate cancer. This review discusses research aiming to understand how often this bacterium is found in the prostate, how it survives there, and what effects it may have on prostate health. Studies show that C. acnes can be found in early-stage and advanced prostate tumours, as well as some healthy prostates. The bacteria may be able to survive in the prostate because of the low oxygen levels and acidic surroundings. Within this environment, C. acnes can trigger inflammation and change the body’s immune response. Evidence also suggests that the bacterium can contribute to DNA damage in healthy prostate cells, change how cells use energy, and affect the structure surrounding the cells. In these ways, C. acnes may influence the development of cancer. However, there are disagreements in study methods because C. acnes can also contaminate biological samples. This makes it difficult to understand whether the bacterium contributes to cancer or is found by coincidence. Using new genomic tools may help to tell the difference between the two in future research. Signs of C. acnes have also been found in urine, the gut, and in the blood, which suggests that it might be used to improve early detection of the disease. More research is needed to understand exactly what C. acnes is doing in prostate cancer, and whether there is a way to exploit it and help improve care for people with prostate cancer.

Cutibacterium acnes (C. acnes) has emerged as a potential contributor to prostate cancer (PCa) pathogenesis, yet the mechanistic basis remains unclear. This review explores the prevalence, persistence and mechanistic impact of C. acnes within the prostate to help decipher the functional consequence and diagnostic value of a C. acnes infection in this setting. We examine the evidence supporting C. acnes colonisation of both premalignant and malignant tissue, and critically evaluate how prostate tumour physiology, particularly hypoxia and low pH, may facilitate microbial persistence. Emerging data suggest that C. acnes modulates inflammatory and immune pathways, influencing macrophage activation, cytokine production, and the regulation of immune checkpoints. Additionally, we discuss studies demonstrating its involvement in DNA damage, host cell metabolism, and extracellular matrix remodelling. The identification of C. acnes in urinary and gut microbiomes, alongside the presence of its genomic DNA in extracellular vesicles in circulation indicate broad diagnostic potential. While discrepancies in methodology have hampered a consensus, recent genomic and functional studies provide new avenues to distinguish contamination from true pathogenicity. Ultimately, future research exploring whether C. acnes is a biomarker, bystander, or bona fide driver of PCa, and its potential role in personalised diagnostics are crucial to advance the field and unravel the predictive and therapeutic value of C. acnes. Clarifying this relationship will advance our understanding of microbiome-cancer dynamics and could help inform innovative early detection and screening strategies that improve patient care.