Construction of an inducible cell‐communication system that amplifies Salmonella gene expression in tumor tissue

Abstract

Bacterial therapies have the potential to overcome resistances that cause chemotherapies to fail. When using bacteria to produce anticancer agents in tumors, triggering gene expression is necessary to prevent systemic toxicity. The use of chemical triggers, however, is hampered by poor delivery of inducing molecules, which reduces the number of activated bacteria. To solve this problem, we created a cell-communication system that enables activated bacteria to induce inactive neighbors. We hypothesized that introducing cell communication into Salmonella would improve direct triggering strategies by increasing protein production, increasing sensitivity to inducer molecules, and enabling expression in tumor tissue. To test these hypotheses we integrated the PBAD promoter into the quorum-sensing machinery from Vibrio fischeri. The expression of a fluorescent reporter gene was compared to expression from non-communicating controls. Function in three-dimensional tissue was tested in a tumor-on-a-chip device. Bacterial communication increased fluorescence 40-fold and increased sensitivity to inducer molecules more than 10,000-fold. The system enabled bacteria to activate neighbors and increased the time-scale of protein production. Gene expression was controllable and tightly regulated. 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 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 bacterial anticancer therapies.

Genetically modified bacteria as a tool to detect microscopic solid tumor masses with triggered release of a recombinant biomarker

“…In humans, antibiotics could not be used, and the ZsGreen construct would have to be maintained with a balanced lethal system or be incorporated into the Salmonella genome. 46,47 …”

Salmonella-Mediated Cancer Therapy: Roles and Potential

“…Anderson et al inserted the inv gene downstream of the lux quorum system, which showed that invasiveness depended on the multiplicity of infection and was comparable to that of the constitutive construct [72]. A recent publication reported integration of the pBAD promoter into the quorum sensing system, which enabled bacteria to activate neighbors and increased the time scale of protein production [73].…”

“…Overcoming these obstacles is important to move BMCT closer to clinical application in the future. [7,10,71,72] pTet Tetracylin [30] RecA Radiation [12] Quorum sensing Bacterial density [72,73] Hypoxia-inducing promoters Low oxygen condition [11,20,72,74,75] …”

Engineered bacteria as therapeutic agents

“…A similar strategy has also been employed to amplify the expression of the desired protein induced with small molecules (e.g. L-arabinose) that diffuse poorly within the tumor mass [39]. Bacteria have also been engineered to silence the expression of important genes related to tumor development through RNA interference.…”