Gram-negative bacteria actively secrete outer membrane vesicles, spherical nano-meter-sized
proteolipids enriched with outer
membrane proteins, to the surroundings. Outer membrane vesicles have gained wide interests as non-living complex
vaccines or delivery vehicles. However, no study has used outer membrane vesicles in treating
cancer thus far. Here we investigate the potential of bacterial outer membrane vesicles as therapeutic agents to treat
cancer via
immunotherapy. Our results show remarkable capability of bacterial outer membrane vesicles to effectively induce long-term antitumor immune responses that can fully eradicate established
tumors without notable adverse effects. Moreover, systematically administered bacterial outer membrane vesicles specifically target and accumulate in the
tumor tissue, and subsequently induce the production of antitumor
cytokines CXCL10 and
interferon-γ. This antitumor effect is
interferon-γ dependent, as
interferon-γ-deficient mice could not induce such outer membrane vesicle-mediated immune response. Together, our results herein demonstrate the potential of bacterial outer membrane vesicles as effective immunotherapeutic agent that can treat various
cancers without apparent adverse effects.Bacterial outer membrane vesicles (OMVs) contain immunogens but no study has yet examined their potential in treating
cancer. Here, the authors demonstrate that OMVs can suppress established tumours and prevent tumour
metastasis by an
interferon-γ mediated antitumor response.