Oral Combined Probiotics Clostridium butyricum and Akkermansia muciniphila Inhibits the Progression of 4T1 Breast Cancer by Activating Bcl-2/Bax Pathway.

BACKGROUND: Breast cancer is the most common malignant tumor among women. Recent studies have found that gut probiotics and their metabolic products play a significant role in activating the immune system, reshaping the tumor microenvironment, and inhibiting cancer progression. METHODS: We established a 4T1 tumor-bearing mice model and analyzed the proportions of CD4(+) T and CD8(+) T cells in the spleen using flow cytometry and immunohistochemistry. The expression levels of TNF-α, IL-6, and IL-10 were measured by enzyme-linked immunosorbent assay. Hematoxylin-eosin staining was used to observe the tumor morphology. Selective protein blotting and quantitative real-time PCR were used to analyze the expression of Bax, Bcl-2, and Caspase-3. Cell proliferation was evaluated using the MTT assay, and apoptosis was detected by flow cytometry. RESULTS: The results indicated that oral administration of CB and AKK possesses the capability to inhibit the progression of 4T1 breast cancer; however, the combined treatment with both strains (CB-AKK) exhibited significantly superior effects compared to each individual strain. Further mechanistic analysis revealed that the CB-AKK combination could activate the antitumor immunity in mice and reshape the tumor microenvironment. Additionally, it was found that the live bacteria and their metabolites derived from CB-AKK could inhibit cell proliferation and promote tumor apoptosis by activating the Bcl-2/Bax signaling pathway. CONCLUSION: This study is the first to demonstrate that orally administered live bacteria CB-AKK can inhibit the progression of 4T1 breast cancer, providing a promising new strategy for the development of innovative biotherapies for breast cancer.