E. coli Membrane Vesicles as a Catalase Carrier for Long-Term Tumor Hypoxia Relief to Enhance Radiotherapy.

Hypoxia is one of the most important factors that limit the effect of radiotherapy, and the abundant H2O2 in tumor tissues will also aggravate hypoxia-induced radiotherapy resistance. Delivering catalase to decompose H2O2 into oxygen is an effective strategy to relieve tumor hypoxia and radiotherapy resistance. However, low stability limits catalase's in vivo application, which is one of the most common limitations for almost all proteins' internal utilization. Here, we develop catalase containing E. coli membrane vesicles (EMs) with excellent protease resistance to relieve tumor hypoxia for a long time. Even treated with 100-fold of protease, EMs showed higher catalase activity than free catalase. After being injected into tumors post 12 h, EMs maintained their hypoxia relief ability while free catalase lost its activity. Our results indicate that EMs might be an excellent catalase delivery for tumor hypoxia relief. Combined with their immune stimulation features, EMs could enhance radiotherapy and induce antitumor immune memory effectively.