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Published on: February 22, 2015
Generating Shigella that internalize into glioblastoma cells
Austin Shipley1, Gabriel Frampton1, Bryan W Davies2,3
1Department of Neurosurgery, Dell Medical School, The University of Texas at Austin, Austin, TX, United States.
Introduction:
The use of microorganisms as drug delivery systems to treat cancer has expanded recently, including FDA approval of certain viruses as oncolytics. Microorganisms have several unique benefits compared to traditional pharmacologic agents including dose independence, the ability to produce therapeutic proteins locally within the tumor, and simplicity of administration. However, current microbial delivery systems such as AAV9 and herpes virus have limited cassette sizes, minimal cancer cell selectivity, and low innate cytotoxicity. To address these issues, we sought to generate a strain of Shigella flexneri to selectively internalize into glioblastoma (GBM) brain tumor cells as an initial step to generating a bacterial-based drug delivery system.
Methods:
We generated S. flexneri that selectively internalize into GBM cells using iterative co-cultured assays.
Results:
After 50 rounds of co-culture, the new strain infected 95 percent of GBM cells in 2 hours. GBM-infecting Shigella demonstrate a 124-fold preference for internalizing in nine different GBM cell lines compared to Normal Astrocytes (NA) controls. Additionally, we developed an in-cell western to identify GBM-infecting Shigella clones that preferentially internalize in patient samples without iterative co-culture. Finally, we demonstrate internalization into GBM cells is mediated via a factor modified by myristoylation.
Discussion:
In conclusion, here we present a novel bacterial platform that preferentially internalizes in brain tumor cells. This system provides numerous potential benefits over current interventions and other microbial strategies for treating brain tumors.
Insights
Researchers engineered Shigella flexneri bacteria to selectively target and enter glioblastoma (GBM) brain tumor cells. This novel bacterial platform offers a promising new approach for brain cancer drug delivery systems.
Area of Science:
- Microbiology
- Oncology
- Biotechnology
Background:
- Microorganisms are emerging as viable drug delivery systems for cancer, offering advantages like localized therapeutic protein production.
- Current microbial systems, such as AAV9 and herpes virus, face limitations including small payload capacity, poor cancer cell selectivity, and low inherent toxicity.
- Glioblastoma (GBM) presents a significant challenge due to its aggressive nature and limited treatment options.
Purpose of the Study:
- To develop a novel bacterial strain of *Shigella flexneri* capable of selective internalization into glioblastoma (GBM) cells.
- To establish a foundation for a new generation of bacterial-based drug delivery systems for brain tumors.
Main Methods:
- Iterative co-culture assays were employed to select for *S. flexneri* strains with enhanced GBM cell internalization.
- An in-cell western assay was developed to identify high-affinity GBM-infecting clones from patient samples without iterative co-culture.
- Mechanism of internalization was investigated, identifying a myristoylation-modified factor.
Main Results:
- A modified *S. flexneri* strain demonstrated selective internalization into GBM cells after 50 rounds of co-culture, infecting 95% of cells within 2 hours.
- The engineered Shigella exhibited a 124-fold preference for GBM cell lines over normal astrocytes.
- Internalization was confirmed to be mediated by a myristoylation-modified factor.
Conclusions:
- A novel bacterial platform using *Shigella flexneri* has been successfully engineered for preferential internalization into brain tumor cells.
- This platform presents significant advantages over existing therapeutic strategies and other microbial delivery systems for brain tumor treatment.
