Bifidobacterium -derived membrane vesicles inhibit triple-negative breast cancer growth by inducing tumor cell apoptosis

Background Bacterial outer membrane vesicles have gained increasing attention for its antitumor effect and application in drug delivery. However, the bacterial membrane vesicles (MVs) that are secreted by Gram-positive bacteria are rarely mentioned. Bifidobacterium has a certain anti-tumor effect, but there is a certain risk when injected into human body. Here we investigated the potential of Bifidobacterium -derived membrane vesicles (B-MVs) as therapeutic agents to treat triple-negative breast cancer. Methods and results Firstly, we discovered that B ifidobacterium can produce B-MVs and isolated them. In vivo, we found that B-MVs can inhibit tumor growth in mice and the mice were in good state. H&E staining displayed extensive apoptotic cells in tumor tissues. Western blotting and immunohistochemistry showed that B-MVs increased the expression of Bax, while decreased the expression of Bcl-2. These results suggested that B-MVs may induce apoptosis of tumor cells in vivo. Furthermore, to further confirm this phenomenon, we conducted experiments in vitro. Hoechst 33,258 staining assay, flow cytometry and western blotting also demonstrated B-MVs promoted cell apoptosis in vitro. Conclusions We speculate B-MVs may inhibit tumor growth by inducing tumor cell apoptosis in triple-negative breast cancer, which provided a new direction in the treatment of TNBC. Graphical abstract