We have recently demonstrated induction of tumor-selective accumulation and therapeutic efficacy of radioiodine in neuroblastoma tumors after systemic non-viral polyplex-mediated sodium-iodide-symporter (NIS) gene delivery.
In the current study, we evaluated the efficacy of novel synthetic nanoparticle vectors based on linear polyethylenimine (LPEI), shielded by polyethylene glycol (PEG), and coupled with the synthetic peptide GE11 as an epidermal growth factor (EGF) receptor-specific ligand for systemic sodium-iodide-symporter (NIS) gene transfer in EGF-receptor-expressing human hepatocellular carcinoma (HCC) cells.
We used LPEI-PEG-GE11 to form targeted polyplexes with a NIS-expressing plasmid at two different conjugate/plasmid (c/p) weight ratios to transfect HCC (Huh7) cells in vitro and in vivo.
In vitro incubation of Huh7 cells with LPEI-PEG-GE11/NIS polyplexes resulted in an 11-fold increase in iodide uptake activity when using a c/p ratio of 0.8 as compared to a 3.5-fold increase when using a c/p ratio of 2. After establishment of subcutaneous Huh7 tumors in nude mice, LPEI-PEG-GE11/NIS polyplexes were injected via the tail vein followed by analysis of radioiodine distribution after injection of 18.5 MBq 123I using gamma camera imaging. After administration of LPEI-PEG-GE11/NIS polyplexes at c/p 0.8 and 2, Huh7 tumors showed a perchlorate-sensitive iodide uptake of 7.5 and 6.8% ID/g 123I with a biological half-life of 5 and 3 h, respectively. In mice receiving LPEI-PEG-GE11/NIS at c/p 0.8 non-target organs like liver, lungs and kidneys exhibited no significant iodide uptake, whereas at c/p 2 significant iodide uptake activity was induced in lungs and liver as shown by ex vivo biodistribution analysis.
These results indicate that optimization of conjugate/plasmid ratios has significant impact on specificity and efficacy of non-viral nanoparticle vectors. After individual optimization, EGF receptor targeted nanoparticles represent an effective gene delivery system for systemic NIS gene transfer opening the prospect of targeted NIS-mediated radionuclide therapy of EGF receptor-expressing tumors, even in metastatic disease.
Prague, Czech Republic
24 - 28 Apr 2010
European Society of Endocrinology