Enhanced targeting efficiency of bacteria-mediated cancer therapy using microbial surface engineering

Objectives We previously reported that certain strains of bacteria could target and proliferate in tumor. The bacteria has been applied for delivery of protein drugs tumor specifically. However, targeting efficiency showed variable depending on tumor types. Thus, it was necessary to enhance the bacterial targeting efficiency through bacterial surface engineering. In this study, we displayed RGD peptide sequence (ACDCRGDCFCG) in the external loop of outer membrane protein A (OmpA) of attenuated Salmonella typhimurium (SLΔppGpp) to explore the changes of bacterial adhesion and targeting to tumor cells.

Methods We constructed expression vector encoding fusion protein with OmpA and RGD which is controlled by Lac promoter to transform SLΔppGpp (SLΔppGpp-rgd).

Results The Western blot analysis showed successful expression of RGD-ompA in SLΔppGpp-rgd. Under the microscopic analysis, SLΔppGpp-rgd showed stronger adhesion to U87MG cells overexpressing αvβ3 integrin than to MCF-7 cells (negative control). In order to monitor in vivo distribution of the bacteria, the bacteria strain was further transduced with bacterial luciferase (Lux) operon using p22 bacteriophage (SLΔppGpp-rgdlux). In vivo bioluminescence imaging showed strong targeting efficiency of SLΔppGpp-rgdlux in U87MG-bearing nude mice as compared to SLΔppGpp-lux.

Conclusions We successfully engineered tumor-targeting bacterial strain that showed stronger targeting efficiency by using surface display of RGD in OmpA. The engineered bacteria may have a potential to deliver higher amount of protein drug in tumor tissue