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Somatostatin receptor type 2-based reporter expression after plasmid-based in vivo gene delivery to non-small cell
Abstract:
Plasmids tend to have much lower expression than viruses. Gene expression after systemic administration of plasmid vectors has not been assessed using somatostatin receptor type 2 (SSTR2)-based reporters. The purpose of this work was to identify gene expression in non-small cell lung cancer (NSCLC) after systemic liposomal nanoparticle delivery of plasmid containing SSTR2-based reporter gene. In vitro, Western blotting was performed after transient transfection with the plasmid cytomegalovirus (CMV)-SSTR2, CMV-TUSC2-IRES-SSTR2, or CMV-TUSC2. SSTR2 is the reporter gene, and TUSC2 is a therapeutic gene. Mice with A549 NSCLC lung tumors were injected intravenously with CMV-SSTR2, CMV-TUSC2-IRES-SSTR2, or CMV-TUSC2 plasmids in DOTAP:cholesterol-liposomal nanoparticles. Two days later, mice were injected intravenously with 111In-octreotide. The next day, biodistribution was performed. The experiment was repeated including single-photon emission computed tomography/computed tomography (SPECT/CT). Immunohistochemistry was performed. In vitro, SSTR2 expression was similar in cells transfected with CMV-SSTR2 or CMV-TUSC2-IRES-SSTR2. TUSC2 expression was similar in cells transfected with CMV-TUSC2 or CMV-TUSC2-SSTR2. Biodistribution demonstrated significantly greater 111In-octreotide uptake in tumors from mice injected with CMV-TUSC2-IRES-SSTR2 or CMV-SSTR2 than the control plasmid, CMV-TUSC2 (p < .05). Gamma-camera and SPECT/CT imaging illustrated SSTR2 expression in tumors in mice injected with CMV-TUSC2-IRES-SSTR2 or CMV-SSTR2 versus background with control plasmid. Immunohistochemistry corresponded with imaging. SSTR2-based reporter imaging can visualize gene expression in lung tumors after systemic liposomal nanoparticle delivery of plasmid containing SSTR2-based reporter gene or SSTR2 linked to a second therapeutic gene, such as TUSC2.
Insights
This study shows that somatostatin receptor type 2 (SSTR2)-based reporter gene imaging can effectively visualize gene expression in non-small cell lung cancer (NSCLC) tumors following systemic delivery of plasmid nanoparticles.
Area of Science:
- Biomedical engineering
- Molecular biology
- Oncology
Background:
- Plasmids generally exhibit lower gene expression compared to viruses.
- Assessing gene expression in non-small cell lung cancer (NSCLC) after systemic plasmid vector delivery using somatostatin receptor type 2 (SSTR2)-based reporters remains underexplored.
Purpose of the Study:
- To evaluate gene expression in NSCLC following systemic liposomal nanoparticle delivery of plasmids encoding an SSTR2-based reporter gene.
- To assess the utility of SSTR2-based reporter imaging for visualizing gene expression in lung tumors.
Main Methods:
- In vitro Western blotting was used to assess SSTR2 and TUSC2 expression after transfecting cells with various plasmids (CMV-SSTR2, CMV-TUSC2-IRES-SSTR2, CMV-TUSC2).
- Mice bearing A549 NSCLC lung tumors were intravenously injected with liposomal nanoparticle-encapsulated plasmids.
- Biodistribution studies, gamma-camera imaging, single-photon emission computed tomography/computed tomography (SPECT/CT), and immunohistochemistry were performed to evaluate SSTR2 expression and tumor uptake of 111In-octreotide.
Main Results:
- In vitro studies showed comparable SSTR2 expression for CMV-SSTR2 and CMV-TUSC2-IRES-SSTR2, and similar TUSC2 expression for CMV-TUSC2 and CMV-TUSC2-SSTR2.
- Biodistribution and imaging revealed significantly higher 111In-octreotide uptake in tumors injected with CMV-TUSC2-IRES-SSTR2 or CMV-SSTR2 compared to the control plasmid (CMV-TUSC2).
- SPECT/CT imaging and immunohistochemistry confirmed SSTR2 expression in tumors, correlating with biodistribution findings.
Conclusions:
- SSTR2-based reporter imaging successfully visualizes gene expression in lung tumors after systemic liposomal nanoparticle delivery of plasmids.
- This imaging approach can be used for plasmids containing an SSTR2-based reporter gene alone or linked to a therapeutic gene, such as TUSC2.
