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

ABSTRACT 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.