Related Experiment Video
Updated: Aug 5, 2026
Measuring Growth and Gene Expression Dynamics of Tumor-Targeted S. Typhimurium Bacteria
Published on: July 6, 2013
Controlling intracellular protein delivery, tumor colonization and tissue distribution using flhDC in clinically
Vishnu Raman1, Christopher L Hall1, Victoria E Wetherby2
1Department of Chemical Engineering, University of Massachusetts, Amherst, Amherst, MA 01003, USA; Ernest Pharmaceuticals, Inc., Hadley, MA 01035, USA.
Abstract:
Effectively targeting intracellular pathways in cancers requires a system that specifically delivers to tumors and internalizes into cancer cells. To achieve this goal, we developed intracellular-delivering (ID) Salmonella with controllable expression of flhDC to regulate flagella production and cell invasion. We hypothesized that controlling flhDC would overcome the poor colonization seen in prior clinical trials. To test this hypothesis, we incorporated the aspirin-responsive Psal promoter and tuned flhDC expression with ssra degradation tags. In tumor-bearing mice, controlling flhDC increased protein release, tissue dispersion, and tumor colonization more than 10 million times. We discovered that inducing flhDC increases escape from intracellular vacuoles; however, deleting sseJ prevented escape and further increased protein delivery. Delivering constitutively active caspase-3 with ID-f-s Salmonella (ΔsseJ and induced Psal-flhDC) induced cell death in pancreatic, breast, and liver cancer cells and reduced the growth of breast tumors. This clinically ready strain preferentially colonized metastatic breast tissue 280 and 800 times more than surrounding healthy tissue in the lung and liver, respectively. By precisely controlling tumor colonization and cell invasion, this strain overcomes critical limitations of bacterial therapy and will enable treatment of many hard-to-treat cancers.
Insights
Engineered Salmonella bacteria, using controlled flhDC expression, significantly enhance tumor colonization and cancer cell invasion. This breakthrough in bacterial therapy improves targeted delivery for treating difficult-to-treat cancers.
Area of Science:
- Microbiology
- Oncology
- Biotechnology
Background:
- Targeting intracellular cancer pathways requires specific tumor delivery and cellular internalization.
- Previous bacterial therapy trials faced limitations due to poor tumor colonization.
Purpose of the Study:
- To develop an intracellular-delivering (ID) Salmonella system with controllable flhDC expression for enhanced tumor targeting and internalization.
- To overcome limitations in bacterial therapy by improving colonization and invasion.
Main Methods:
- Engineered Salmonella with controllable flhDC expression using an aspirin-responsive promoter (Psal) and ssra degradation tags.
- Tested ID-Salmonella in tumor-bearing mice, manipulating flhDC expression and sseJ deletion.
- Delivered constitutively active caspase-3 using engineered Salmonella to assess cancer cell death and tumor growth reduction.
Main Results:
- Controlled flhDC expression increased protein release, tissue dispersion, and tumor colonization over 10 million-fold.
- Inducing flhDC enhanced vacuolar escape; deleting sseJ prevented escape and improved protein delivery.
- Engineered Salmonella (ID-f-s) induced cancer cell death and reduced tumor growth, with preferential colonization of metastatic tissue.
Conclusions:
- Controllable flhDC expression in ID-Salmonella significantly enhances tumor colonization and invasion.
- Modulating bacterial escape mechanisms (e.g., sseJ deletion) further optimizes protein delivery for cancer therapy.
- This engineered bacterial strain offers a promising platform for treating challenging cancers by overcoming critical delivery limitations.
