Poly(I:C)-Mediated Tumor Growth Suppression in EGF-Receptor Overexpressing Tumors Using EGF-Polyethylene Glycol-Linear Polyethylenimine as Carrier
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To develop a novel polyethylenimine (PEI)-based polymeric carrier for tumor-targeted delivery of cytotoxic double-stranded RNA polyinosinic:polycytidylic acid, poly(I:C). The novel carrier should be chemically less complex but at least as effective as a previously developed tetra-conjugate containing epidermal growth factor (EGF) as targeting ligand, polyethylene glycol (PEG) as shielding spacer, 25 kDa branched PEI as RNA binding and endosomal buffering agent, and melittin as endosomal escape agent.
Novel conjugates were designed employing a simplified synthetic strategy based on 22 kDa linear polyethylenimine (LPEI), PEG spacers, and recombinant EGF. The efficacy of various conjugates (different PEG spacers, with and without targeting EGF) in poly(I:C)-mediated cell killing was evaluated in vitro using two human U87MG glioma cell lines. The most effective polyplex was tested for in vivo activity in A431 tumor xenografts.
Targeting conjugate LPEI-PEG2 kDa-EGF was found as most effective in poly(I:C)-triggered killing of tumor cells in vitro. The efficacy correlated with glioma cell EGFR levels. Repeated intravenous administration of poly(I:C) polypexes strongly retarded growth of A431 human tumor xenograft in mice.
The optimized LPEI-PEG2 kDa-EGF conjugate displays reduced chemical complexity and efficient poly(I:C)-mediated killing of EGFR overexpressing tumors in vitro and in vivo.
KEY WORDSepidermal growth factor polyplex receptor-mediated delivery RNA delivery tumor targeting
Hepes buffered glucose (5% (w/v) glucose, 20 mM Hepes, pH 7.4)
N-2-hydroxyethylpiperazine-N′-2-ethane sulfonic acid
linear polyethylenimine with an average molecular weight of 22 kDa
poly inosinic acid
poly inosinic-cytidylic acid
size exclusion chromatography
We thank Olga Brück for assistance in preparing the manuscript and Miriam Sindelar for skillful assistance with the syntheses. This work was supported by EC project GIANT, the DFG projects SFB 486, and SPP1230, and the excellence cluster Nanosystems Initiative Munich (NIM). AS and AL are supported by grants from the ERC : ERC/B3/JM/NL/MW/gk/D(2009) 600950 and the National Cancer Institute (USA): 1R01CA125500.
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