Mass-produced gram-negative bacterial outer membrane vesicles activate cancer antigen-specific stem-like CD8+ T cells which enables an effective combination immunotherapy with anti-PD-1.

Despite the capability of extracellular vesicles (EVs) derived from Gram-negative and Gram-positive bacteria to induce potent anti-tumour responses, large-scale production of bacterial EVs remains as a hurdle for their development as novel cancer immunotherapeutic agents. Here, we developed manufacturing processes for mass production of Escherichia coli EVs, namely, outer membrane vesicles (OMVs). By combining metal precipitation and size-exclusion chromatography, we isolated 357 mg in total protein amount of E. coli OMVs, which was equivalent to 3.93 × 1015 particles (1.10 × 1010 particles/µg in total protein amounts of OMVs) from 160 L of the conditioned medium. We show that these mass-produced E. coli OMVs led to complete remission of two mouse syngeneic tumour models. Further analysis of tumour microenvironment in neoantigen-expressing tumour models revealed that E. coli OMV treatment causes increased infiltration and activation of CD8+ T cells, especially those of cancer antigen-specific CD8+ T cells with high expression of TCF-1 and PD-1. Furthermore, E. coli OMVs showed synergistic anti-tumour activity with anti-PD-1 antibody immunotherapy, inducing substantial tumour growth inhibition and infiltration of activated cancer antigen-specific stem-like CD8+ T cells into the tumour microenvironment. These data highlight the potent anti-tumour activities of mass-produced E. coli OMVs as a novel candidate for developing next-generation cancer immunotherapeutic agents.

Indoor dust extracellular vesicles promote cancer lung metastasis by inducing tumour necrosis factor-α.

Indoor pollutants are important problems to public health. Among indoor pollutants, indoor dust contains extracellular vesicles (EVs), which are associated with pulmonary inflammation. However, it has not been reported whether indoor dust EVs affect the cancer lung metastasis. In this study, we isolated indoor dust EVs and investigated their roles in cancer lung metastasis. Upon intranasal administration, indoor dust EVs enhanced mouse melanoma lung metastasis in a dose-dependent manner in mice. Pre-treatment or co-treatment of indoor dust EVs significantly promoted melanoma lung metastasis, whereas post-treatment of the EVs did not. In addition, the lung lysates from indoor dust EV-treated mice significantly increased tumour cell migration in vitro. We observed that tumour necrosis factor-α played important roles in indoor dust EV-mediated promotion of tumour cell migration in vitro and cancer lung metastasis in vivo. Furthermore, Pseudomonas EVs, the main components of indoor dust EVs, and indoor dust EVs showed comparable effects in promoting tumour cell migration in vitro and cancer lung metastasis in vivo. Taken together, our results suggest that indoor dust EVs, at least partly contributed by Pseudomonas EVs, are potential promoting agents of cancer lung metastasis.