Obligate and facultative anaerobic bacteria in targeted cancer therapy: Current strategies and clinical applications

Traditional methods for cancer therapy, including radiotherapy, chemotherapy, and immunotherapy are characterized by inherent limitations. Bacteria-mediated tumor therapy is becoming a promising approach in cancer treatment due to the ability of obligate or facultative anaerobic microorganisms to penetrate and proliferate in hypoxic regions of tumors. It is widely known that anaerobic bacteria cause the regression of tumors and inhibition of metastasis through a variety of mechanisms, including toxin production, anaerobic lifestyle and synergy with anti-cancer drugs. These features have the potential to be used as a supplement to conventional cancer treatment. To the best of our knowledge, no reports have been published regarding the most common tumor-targeting bacterial agents with special consideration of obligate anaerobes (such as Clostridium sp., Bifidobacterium sp.) and facultative anaerobes (including Salmonella sp., Listeria monocytogenes, Lactobacillus sp., Escherichia coli, Corynebacterium diphtheriae and Pseudomonas sp). In this review, we summarize the latest literature on the role of these bacteria in cancer treatment.