It was almost seven years ago that we published a blog about the role of the gut microbiome in breast cancer (© Gene Online). We commented that this ecological community of trillions of bacteria which inhabit our bodies and outnumber our own cells by three to one had caught the imagination of biological scientists. Researchers had shown that these micro-organisms found within the breast tissues of women with benign lesions were distinctly different from women with malignant tumours. Well, in the first half of 2023 more studies exploring the relationship between the gut microbiome and breast cancer have been published.

Xia Ji et al. from Huizhou in China have just published a paper in PLOS ONE in which they constructed an animal model to explore the intestinal microbiome for detection of breast cancer. They induced the genesis of breast cancer tumours in mice and then, over time, collected faeces samples which were analysed for various intestinal microbiota and concluded that their research results could perhaps be used as an important biomarker for the diagnosis of breast cancer in humans.

A group from Taiwan, in a preprint, sought to determine the relationship of distress and quality of life with microbial composition among newly diagnosed breast cancer patients. They enrolled 82 patients in a prospective, observational study and found that microbiota levels were significantly correlated with distress levels, thus providing useful information for potentially finding probiotics for improving the quality of life for patients. Interestingly, the authors acknowledged that the English version of their paper was partially assisted by the AI algorithm, ChatGPT.

In a wide-ranging review article, Viswanathan et al. discussed the impact of microbiota on breast cancer, with a primary focus on the gut microbiota’s regulation of the micro-environment that influences breast cancer. They recognised that an understanding of how immunotherapy can affect the microbiome of breast cancer, together with further clinical trials, might be an important part of the clinical puzzle in predicting both the risk and prognosis of breast cancer.

As illustrated in the diagram at right (© Pathogens), the authors speculated that multiple factors such as stress, aging or smoking could lead to increased levels of deconjugated oestrogen which in turn would lead to chronic inflammation within the breast. These changes would then precipitate DNA damage, genetic instability, angiogenesis and, ultimately, invasion and metastasis. Their hope is that by understanding the mechanisms by which the gut microbiome cause breast cancer could lead to novel methods of drug therapy.