Imaging and targeted therapy of pancreatic ductal adenocarcinoma using the theranostic sodium iodide symporter (NIS) gene

The theranostic sodium iodide symporter (NIS) gene allows detailed molecular imaging of transgene expression and application of therapeutic radionuclides. As a crucial step towards clinical application, we investigated tumor specificity and transfection efficiency of epidermal growth factor receptor (EGFR)-targeted polyplexes as systemic NIS gene delivery vehicles in an advanced genetically engineered mouse model of pancreatic ductal adenocarcinoma (PDAC) that closely reflects human disease. PDAC was induced in mice by pancreas-specific activation of constitutively active Kras(G12D) and deletion of Trp53. We used tumor-targeted polyplexes (LPEIPEG-GE11/NIS) based on linear polyethylenimine, shielded by polyethylene glycol and coupled with the EGFR-specific peptide ligand GE11, to target a NIS-expressing plasmid to high EGFR-expressing PDAC. In vitro iodide uptake studies in cell explants from murine EGFR-positive and EGFR-ablated PDAC lesions demonstrated high transfection efficiency and EGFR-specificity of LPEI-PEG-GE11/NIS. In vivo I-123 gamma camera imaging and three-dimensional high-resolution I-124 PET showed significant tumor-specific accumulation of radioiodide after systemic LPEI-PEG-GE11/NIS injection. Administration of I-131 in LPEI-PEG-GE11/NIS-treated mice resulted in significantly reduced tumor growth compared to controls as determined by magnetic resonance imaging, though survival was not significantly prolonged. This study opens the exciting prospect of NIS-mediated radionuclide imaging and therapy of PDAC after systemic non-viral NIS gene delivery

EGFR-Targeted Adenovirus Dendrimer Coating for Improved Systemic Delivery of the Theranostic NIS Gene

We recently demonstrated tumor-selective iodide uptake and therapeutic efficacy of combined radiovirotherapy after systemic delivery of the theranostic sodium iodide symporter (NIS) gene using a dendrimer-coated adenovirus. To further improve shielding and targeting we physically coated replication-selective adenoviruses carrying the hNIS gene with a conjugate consisting of cationic poly(amidoamine) (PAMAM) dendrimer linked to the peptidic, epidermal growth factor receptor (EGFR)-specific ligand GE11. In vitro experiments demonstrated coxsackie-adenovirus receptor-independent but EGFR-specific transduction efficiency. Systemic injection of the uncoated adenovirus in a liver cancer xenograft mouse model led to high levels of NIS expression in the liver due to hepatic sequestration, which were significantly reduced after coating as demonstrated by 123I-scintigraphy. Reduction of adenovirus liver pooling resulted in decreased hepatotoxicity and increased transduction efficiency in peripheral xenograft tumors. 124I-PET-imaging confirmed EGFR-specificity by significantly lower tumoral radioiodine accumulation after pretreatment with the EGFR-specific antibody cetuximab. A significantly enhanced oncolytic effect was observed following systemic application of dendrimer-coated adenovirus that was further increased by additional treatment with a therapeutic dose of 131I. These results demonstrate restricted virus tropism and tumor-selective retargeting after systemic application of coated, EGFR-targeted adenoviruses therefore representing a promising strategy for improved systemic adenoviral NIS gene therapy

Epidermal Growth Factor Receptor-targeted 131I-therapy of Liver Cancer Following Systemic Delivery of the Sodium Iodide Symporter Gene

We recently demonstrated tumor-selective iodide uptake and therapeutic efficacy of radioiodine in neuroblastoma tumors after systemic nonviral polyplex-mediated sodium iodide symporter (NIS) gene delivery. In the present study, we used novel polyplexes based on linear polyethylenimine (LPEI), polyethylene glycol (PEG), and the synthetic peptide GE11 as an epidermal growth factor receptor (EGFR)-specific ligand to target a NIS-expressing plasmid to hepatocellular carcinoma (HCC) (HuH7). Incubation of HuH7 cells with LPEI-PEG-GE11/NIS polyplexes resulted in a 22-fold increase in iodide uptake, which was confirmed in other cancer cell lines correlating well with EGFR expression levels. Using 123I-scintigraphy and ex vivo γ-counting, HuH7 xenografts accumulated 6.5–9% injected dose per gram (ID/g) 123I, resulting in a tumor-absorbed dose of 47 mGray/Megabecquerel (mGy/MBq) 131Iodide (131I) after intravenous (i.v.) application of LPEI-PEG-GE11/NIS. No iodide uptake was observed in other tissues. After pretreatment with the EGFR-specific antibody cetuximab, tumoral iodide uptake was markedly reduced confirming the specificity of EGFR-targeted polyplexes. After three or four cycles of polyplex/131I application, a significant delay in tumor growth was observed associated with prolonged survival. These results demonstrate that systemic NIS gene transfer using polyplexes coupled with an EGFR-targeting ligand is capable of inducing tumor-specific iodide uptake, which represents a promising innovative strategy for systemic NIS gene therapy in metastatic cancers

Imaging and targeted therapy of pancreatic ductal adenocarcinoma using the theranostic sodium iodide symporter (NIS) gene

The theranostic sodium iodide symporter (NIS) gene allows detailed molecular imaging of transgene expression and application of therapeutic radionuclides. As a crucial step towards clinical application, we investigated tumor specificity and transfection efficiency of epidermal growth factor receptor (EGFR)-targeted polyplexes as systemic NIS gene delivery vehicles in an advanced genetically engineered mouse model of pancreatic ductal adenocarcinoma (PDAC) that closely reflects human disease. PDAC was induced in mice by pancreas-specific activation of constitutively active KrasG12D and deletion of Trp53. We used tumor-targeted polyplexes (LPEI-PEG-GE11/NIS) based on linear polyethylenimine, shielded by polyethylene glycol and coupled with the EGFR-specific peptide ligand GE11, to target a NIS-expressing plasmid to high EGFR-expressing PDAC. In vitro iodide uptake studies in cell explants from murine EGFR-positive and EGFR-ablated PDAC lesions demonstrated high transfection efficiency and EGFR-specificity of LPEI-PEG-GE11/NIS. In vivo 123I gamma camera imaging and three-dimensional high-resolution 124I PET showed significant tumor-specific accumulation of radioiodide after systemic LPEI-PEG-GE11/NIS injection. Administration of 131I in LPEI-PEG-GE11/NIS-treated mice resulted in significantly reduced tumor growth compared to controls as determined by magnetic resonance imaging, though survival was not significantly prolonged. This study opens the exciting prospect of NIS-mediated radionuclide imaging and therapy of PDAC after systemic non-viral NIS gene delivery.Copyright: Schmohl et a