Engineering of Escherichia coli for targeted delivery of transgenes to HER2/neu-positive tumor cells

Targeting of non‐phagocytic tumor cells and prompt release of gene cargos upon entry into tumors are two limiting steps in the bacterial gene delivery path. To tackle these problems, the non‐pathogenic Escherichia coli strain BL21(DE3) was engineered to display the anti‐HER2/neu affibody on the surface. After co‐incubation with tumor cells for 3 h, the anti‐HER2/neu affibody‐presenting E. coli strain was selectively internalized into HER2/neu‐positive SKBR‐3 cells. The invasion efficiency reached as high as 30%. Furthermore, the bacteria were equipped with the phage ϕX174 lysin gene E‐mediated autolysis system. Carrying the transgene (e.g., eukaryotic green fluorescent protein, GFP), the tumor‐targeting bacteria were subjected to the thermal shock to trigger the autolysis system upon entry into HER2/neu‐positive cells. Flow cytometric analysis revealed that 3% of infected cells expressed GFP 24 h post thermal induction. Overall, the results show a promise of the proposed approach for developing bacteria as a delivery carrier. Biotechnol. Bioeng. 2011; 108:1662–1672. © 2011 Wiley Periodicals, Inc.