(56h) Inducible Cell Communication Amplifies Salmonella Gene Expression In Tumor Tissue

Bacterial anticancer therapies have the potential to overcome resistances that limit the efficacy of chemotherapy. Triggered production of anticancer agents by bacteria, which have penetrated into tumor tissue, would kill more cancer cells while damaging less normal tissue. However, the use of chemical triggers is hampered by uptake, clearance and diffusion, which reduce the number of activated bacteria. We have solved this problem by enabling bacteria to communicate. The engineered cell-communication system integrates the P_BAD promoter and components from the quorum-sensing machinery of V. fisheri. Cell communication enables activated bacteria to induce neighbors by producing a signaling molecule that can be ‘heard’ by responsive bacteria. The system was tested by connecting it to ZsGreen, a fluorescent reporter gene. Gene expression and sensitivity were measured by comparison with non-communicating controls that induce gene expression with direct induction of P_BAD. Function in three-dimensional tissue was tested in an in vitro tumor-on-a-chip device specifically designed to quantify the interaction of bacteria and cancer cells. Bacterial communication increased gene expression 40-fold and increased sensitivity to inducer molecules more than 10,000-fold. Tests with sensing bacteria showed that the AI-1 autoinducer was produced, secreted into the environment, and taken into bacterial cells. The system enabled individual bacteria to activate at least 100 neighbors and significantly increased the time-scale of protein production. Gene expression with this system was controllable and tightly regulated. In tissue, induction of protein production was possible with communicating Salmonella but not with control bacteria. At the optimal inducing signal, communicating bacteria produced 350 times more protein than non-communicating bacteria. The cell-communication system created in this study has numerous uses beyond cancer therapy, including protein manufacturing, bioremediation and biosensing. It would enable amplified induction of gene expression in any environment that limits availability of inducer molecules. Ultimately, because inducible cellular communication enables gene expression in tissue, it will be a critical component of every successful bacteria-based anticancer therapy.