Robust inducible gene expression in intracellularListeria monocytogenes in vivo

Abstract

AbstractAttenuated strains of the intracellular pathogenListeria monocytogenescan deliver genetically encoded payloads inside tumor cells.L. monocytogenespreferentially accumulates and propagates inside immune-suppressed tumor microenvironments. To maximize the payload impact in tumors and minimize damage to healthy tissues, it is desirable to induce payload synthesis when bacteria are eliminated from the healthy tissues but are grown to high numbers intratumorally. Here, we have engineered a tightly controlled gene expression system for intracellularL. monocytogenesinducible with a cumin derivative, cumate. Upon cumate addition, expression of a reporter gene is increased inL. monocytogenesgrowingin vitroby 80-fold, and in intracellularL. monocytogenesin murine tumors by 10-fold. This study demonstrates the feasibility of activating gene expression in intracellular bacteria in live animals using an edible inducer. The system is expected to enhance the efficacy and safety of the attenuatedL. monocytogenesstrains as antitumor payload delivery bacterial drones.