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Measuring Growth and Gene Expression Dynamics of Tumor-Targeted S. Typhimurium Bacteria
Published on: July 6, 2013
In tumors Salmonella migrate away from vasculature toward the transition zone and induce apoptosis
S Ganai1, R B Arenas, J P Sauer
1Department of Surgery, Baystate Medical Center, Tufts University School of Medicine, Springfield, MA, USA.
Abstract:
Motile bacteria can overcome diffusion resistances that substantially reduce the efficacy of standard cancer therapies. Many reports have also recently described the ability of Salmonella to deliver therapeutic molecules to tumors. Despite this potential, little is known about the spatiotemporal dynamics of bacterial accumulation in solid tumors. Ultimately this timing will affect how these microbes are used therapeutically. To determine how bacteria localize, we intravenously injected Salmonella typhimurium into BALB/c mice with 4T1 mammary carcinoma and measured the average bacterial content as a function of time. Immunohistochemistry was used to measure the extent of apoptosis, the average distance of bacteria from tumor vasculature and the location of bacteria in four different regions: the core, transition, body and edge. Bacteria accumulation was also measured in pulmonary and hepatic metastases. The doubling time of bacterial colonies in tumors was measured to be 16.8 h, and colonization was determined to delay tumor growth by 48 h. From 12 and 48 h after injection, the average distance between bacterial colonies and functional vasculature significantly increased from 130 to 310 microm. After 48 h, bacteria migrated away from the tumor edge toward the central core and induced apoptosis. After 96 h, bacteria began to marginate to the tumor transition zone. All observed metastases contained Salmonella and the extent of bacterial colocalization with metastatic tissue was 44% compared with 0.5% with normal liver parenchyma. These results demonstrate that Salmonella can penetrate tumor tissue and can selectively target metastases, two critical characteristics of a targeted cancer therapeutic.
Insights
Salmonella typhimurium bacteria can penetrate solid tumors and target metastases, offering a novel approach to cancer therapy. Their accumulation dynamics and spatiotemporal distribution within tumors are crucial for therapeutic timing.
Area of Science:
- Oncology
- Microbiology
- Biotechnology
Background:
- Motile bacteria can overcome diffusion limitations in solid tumors, enhancing cancer therapy efficacy.
- Salmonella species show potential for delivering therapeutic molecules to tumors.
- Understanding bacterial spatiotemporal dynamics in tumors is key for therapeutic application.
Purpose of the Study:
- To investigate the spatiotemporal dynamics of Salmonella typhimurium accumulation in solid tumors.
- To determine bacterial localization patterns and their relationship with tumor vasculature and apoptosis.
- To assess Salmonella's efficacy in targeting pulmonary and hepatic metastases.
Main Methods:
- Intravenous injection of Salmonella typhimurium into BALB/c mice bearing 4T1 mammary carcinoma.
- Measurement of bacterial content over time using immunohistochemistry.
- Analysis of bacterial distance from vasculature, apoptosis extent, and location within tumor regions (core, transition, body, edge).
- Quantification of bacterial accumulation in pulmonary and hepatic metastases.
Main Results:
- Salmonella typhimurium exhibited a doubling time of 16.8 h in tumors, delaying tumor growth by 48 h.
- Bacterial colonies significantly increased their distance from vasculature (130 to 310 µm) between 12 and 48 h post-injection.
- Bacteria migrated towards the tumor core, induced apoptosis after 48 h, and localized to the tumor transition zone after 96 h.
- Salmonella effectively targeted metastases, with 44% colocalization in metastatic tissue versus 0.5% in normal liver parenchyma.
Conclusions:
- Salmonella typhimurium demonstrates the ability to penetrate tumor tissue and selectively target metastases.
- The spatiotemporal dynamics of Salmonella accumulation are critical for its therapeutic potential in cancer.
- These findings support Salmonella's role as a targeted cancer therapeutic agent, particularly for metastatic disease.
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