Application of Invasive Bacteria for the Delivery of Anti-Cancer Therapeutics

Bacterial vectors for biomolecule delivery to targeted organelles, facilitating temporary or continuous protein production, have emerged as a promising approach for treating acquired and inherited diseases. This method offers a selective cancer eradication and targeting strategy with minimal side effects. Bacterial vectors provide an alternative to viral gene delivery, given their capacity to deliver large genetic materials while inducing minimal immunogenicity and cytotoxicity. Bacteria such as Bifidobacterium, Salmonella, Clostridium, and Streptococcus have demonstrated potential for tumor-targeted biomolecule delivery or serve as oncolytic bacteria. These vectors have also been used to transfer and amplify genes encoding biomolecules such as pro-drug-converting enzymes, toxins, angiogenesis inhibitors, and cytokines. The microenvironment of necrotic tumors offers a unique opportunity for targeted therapy with the non-pathogenic anaerobic bacterium. For example, Clostridium sporogenes can germinate selectively in the necrotic regions upon injection as endospores, which helps to enhance the specificity of Clostridium sporogenes, resulting in tumor-specific colonization. Also, E. coli and Salmonella sp. can be capacitated with a hypoxic sensing promotor gene for specificity delivery into the core region of solid tumors. The uniqueness of the tumor microenvironment, including hypoxia, immunosuppression, metabolite deficiency or enrichment, and necrosis, selectively enables bacteria in the tumor. Combining traditional cancer therapy with bacterial therapy will significantly complement and cover the limitations of other treatments. This review provides an overview of the use of the bacteria vector in cancer therapy, discussing strategies to maximize delivery efficiency and address potential challenges. In this review, we discuss the potential of bacteria vectors as anti-cancer therapeutics while focusing on therapeutic delivery strategies. We highlight the complementary use of bacteria therapy with other cancer therapies and the mechanism of bacteria cancer immunotherapy with limitations and perspectives for future use.