Potential mechanisms of intestinal microbes in bone metastasis of breast cancer

Breast cancer (BRCA) is the most common type of cancer in women worldwide, with distant metastases most frequently occurring in the skeleton. Bone metastasis in BRCA often leads to severe bone pain, pathological fractures, spinal cord compression, and other complications, significantly reducing the patients' quality of life. Recently, the role of intestinal microbes in BRCA bone metastasis has gained increasing attention. As a complex ecosystem, the intestinal microbiota influences the occurrence and progression of BRCA bone metastasis through immune regulation, metabolite production (such as short-chain fatty acids), systemic inflammation, and modulation of intestinal permeability barrier function. On the one hand, gut microbiota can facilitate cancer cell colonization in bones by regulating the balance of Treg/Th17 cells and osteoclast activity. Conversely, probiotics and microbial metabolites exhibit potential anticancer and bone-protective effects, making them promising therapeutic targets. However, the specific regulatory mechanisms of intestinal microbes in BRCA bone metastasis require further investigation. This review provides a comprehensive overview of the potential mechanisms by which intestinal microorganisms contribute to bone metastasis in BRCA and explores their clinical translational potential, offering new strategies for the prevention and management of bone metastases in BRCA.