FIGURE 1.

Potential mechanisms employed by gut and breast microbiomes to influence breast cancer metastases to the bone. Figure highlights the multifaceted roles of gut and breast microbiomes in promoting breast cancer metastasis to bones, emphasizing the interplay between microbial communities, cancer, and bone microenvironment. Gut and breast microbiome dysbiosis: An imbalance in the gut and breast microbiomes can lead to the production of certain microbial fermentation products that affect cancer progression. Microbial fermentation products in circulation: These products can promote epithelial–mesenchymal transition (EMT), a critical step in cancer metastasis. EMT: EMT involves changes in cancer cells that enhance their ability to migrate and invade other tissues. Microbial products and microbes themselves play a key role in EMT. Cytoskeletal remodeling: Microbes influence changes in the cytoskeleton of cancer cells that facilitate their migration, invasion, and escape into circulation. Reduced shear stress: Intracellular bacteria reduce effect of shear stress on cancer cells and help their survival in circulation, and thus, cancer cells can eventually invade distant organs, including the bone. Immunomodulation: Microbiome‐induced changes in the immune system can either support or hinder cancer metastasis. Altered bone microenvironment: Microbiome dysbiosis can alter the bone microenvironment, making it more conducive for colonization of cancer cells. Impaired bone remodeling: Disruptions in normal bone remodeling processes, induced by microbial products, can facilitate the establishment of metastases in the bone. Steroid hormone dysregulation: Microbiome dysbiosis can dysregulate steroid hormone levels, further impacting cancer progression and metastasis.