Microbiome Interactions in Breast Cancer Pathogenesis

The human microbiome, encompassing diverse microbial communities across body sites, has emerged as a critical factor in breast cancer development and progression. Within the breast tissue itself, resident bacteria may influence local immune surveillance, produce genotoxins and modulate inflammatory pathways, thereby shaping the tumour microenvironment. Simultaneously, gut microbes regulate systemic levels of oestrogens, short-chain fatty acids and other bioactive metabolites that can reach the mammary gland, altering cell proliferation, apoptosis and response to therapy. Dysbiosis, or disruption of microbial balance, is linked to aberrant oestrogen recycling, increased pro-inflammatory cytokines and impaired antitumour immunity. Intratumoral bacterial signatures have been associated with distinct histological subtypes and prognostic features, suggesting that specific taxa may promote or inhibit malignant transformation. Together, these findings point to a complex network of local and systemic microbial–host interactions that contribute to breast carcinogenesis and therapy response, and which may yield novel biomarkers and therapeutic targets.*

Research from Nature Portfolio

Investigations into aseptically obtained breast tissue have confirmed the presence of a unique mammary microbiome distinct from skin and oral flora. Comparisons between malignant and benign breast samples revealed enrichment of low‐abundance genera such as Fusobacterium and Atopobium in cancerous tissue, while potentially protective taxa were more abundant in non-cancerous specimens. These foundational data demonstrate that microbial communities differ by disease state and provide a platform for examining mechanisms of microbe-driven carcinogenesis. In a complementary study of nipple aspirate fluid, women with a history of breast cancer exhibited higher levels of Alistipes and lower representation of Sphingomonadaceae relatives compared with healthy controls. Notably, many of the bacteria associated with disease shared β-glucuronidase activity, implicating microbial modulation of oestrogen conjugates in local ductal fluid. This work establishes for the first time a link between ductal microbiota and breast cancer history, underscoring the potential for fluid-based microbial biomarkers.*

Microbiome Interactions in Breast Cancer Pathogenesis publication trend

The graph below shows the total number of articles in microbiome interactions in breast cancer pathogenesis across all publications each year (not limited to Nature Index journals).

Technical terms

Dysbiosis: An imbalance in microbial community composition that disrupts host–microbe homeostasis and can promote disease.

16S rRNA gene sequencing: A molecular technique for identifying and comparing bacterial taxa by targeting a conserved region of the ribosomal RNA gene.

Intratumoral microbiome: Microbial communities residing within tumour tissue that may influence cancer biology and immune responses.

Metagenomics: The study of genetic material recovered directly from environmental or clinical samples to profile microbial diversity and function.

Bioactive metabolites: Compounds produced by microbes, such as short-chain fatty acids or secondary bile acids, that modulate host cellular pathways.

References

1. The Microbiome of Aseptically Collected Human Breast Tissue in Benign and Malignant Disease. Scientific Reports (2016).
2. Characterization of the microbiome of nipple aspirate fluid of breast cancer survivors. Scientific Reports (2016).
3. Human breast microbiome correlates with prognostic features and immunological signatures in breast cancer. Genome Medicine (2021).
4. Distinct Microbial Signatures Associated With Different Breast Cancer Types. Frontiers in Microbiology (2018).
5. Multiomics-based molecular subtyping based on the commensal microbiome predicts molecular characteristics and the therapeutic response in breast cancer. Molecular Cancer (2024).
6. Navigating the complex relationship between human gut microbiota and breast cancer: Physiopathological, prognostic and therapeutic implications. Cancer Treatment Reviews (2024).
7. Investigating the oral microbiome in retrospective and prospective cases of prostate, colon, and breast cancer. npj Biofilms and Microbiomes (2023).