Expressing cytotoxic compounds in Escherichia coli Nissle 1917 for tumor-targeting therapy.

Abnormal blood vessels and hypoxic and necrotic regions are common features of solid tumors and related to the malignant phenotype and therapy resistance. Certain obligate or facultative anaerobic bacteria exhibit inherent ability to colonize and proliferate within solid tumors in vivo. Escherichia coli Nissle 1917 (EcN), a non-pathogenic probiotic in European markets, has been known to proliferate selectively in the interface between the viable and necrotic regions of solid tumors. The objective of this study was to establish a tumor-targeting therapy system using the genetically engineered EcN for targeted delivery of cytotoxic compounds, including colibactin, glidobactin and luminmide. Biosynthetic gene clusters of these cytotoxic compounds were introduced into EcN and the corresponding compounds were detected in the resultant recombinant EcN strains. The recombinant EcN showed significant cytotoxic activity in vitro and in vivo as well, and significantly suppressed the tumor growth. Together, this study confirmed efficient tumor-targeting colonization of EcN and demonstrated its potentiality in the tumor-specific delivery of cytotoxic compounds as a new tumor-targeting therapy system.