Ligand substitution of receptor targeted DNA complexes affects gene transfer into hepatoma cells

Abstract

We have targeted the serpin enzyme complex receptor for luciferase expression measured 2 to 16 days after treatgene transfer in human hepatoma cell lines using peptides ment. All the protein conjugates in which 26% of the K resi-Ͻ30 amino acids in length which contain the five amino dues were modified with sulfo-LC SPDP were poor gene acid recognition sequence for this receptor, coupled to poly transfer reagents. Complexes containing less substituted K of average chain length 100 K, using the heterobifuncpoly K, averaged 17 ± 0.5 nm in diameter and gave peak tional coupling reagent sulfo-LC SPDP. The number of transgene expression of 3-4 × 10 6 ILU/mg which persisted sulfo-LC SPDP modified poly-L-lysine residues, as well as (Ͼ7 × 10 5 ILU) at 16 days. Of these, more substituted the degree of peptide substitution was assessed by nuclear polymers condensed DNA into complexes averaging magnetic resonance spectroscopy. Conjugates were pre-20 ± 0.7 nm in diameter and gave five-fold less luciferase pared in which 3.5%, 7.8% or 26% of the lysine residues than complexes containing less substituted conjugates. As contained the sulfo-LC SPDP moiety. Each of these conjufew as eight to 11 ligands per complex are optimal for DNA gates was then coupled with ligand peptides so that one delivery via the SEC receptor. The extent of substitution of in 370, one in 1039, or one in 5882 lysines were substituted receptor-mediated gene transfer complexes affects the with receptor ligand. Electron microscopy and atomic force size of the complexes, as well as the intensity and duration microscopy were used to assess complex structure and of transgene expression. These observations may permit size. HuH7 human hepatoma cells were transfected with tailoring of complex construction for the usage required. complexes of these conjugates with the plasmid pGL3 and

Defining strategies to extend duration of gene expression from targeted compacted DNA vectors

“…9 This chain length was selected based on earlier studies showing that the longer the chain length of poly K incorporated into the complex, the greater the duration of expression. The molar ratio of sulfo-LC SPDP to lysine residues was 1:10 in the reaction mix.…”

“…The molar ratio of sulfo-LC SPDP to lysine residues was 1:10 in the reaction mix. In subsequent nuclear magnetic resonance (NMR) spectroscopy, performed as previously described, 9 this ratio was determined to give an actual substitution rate of about 8.3%. Receptor ligand C105Y was then added at a molar ratio 1:200 (ligand/lysine residue).…”

“…9 However, even with long-chain poly K-containing complexes, expression returned to background levels after about 30 days in vivo. 9 Therefore, to achieve protracted expression, either the decline in expression must be prevented, or the complexes must be readministered.…”

“…8 The sec-R can be targeted by a short peptide sequence which was included in a peptide ligand, covalently coupled to poly-K, condensed by charge interaction with plasmid DNA under high salt conditions into unimolecular (with respect to DNA) complexes about 20-25 nm in diameter. 2,8,9 Earlier studies in human hepatoma cell lines in vitro determined that 10-11 receptor ligands per complex give optimal transfection, 8 and that longer chain length poly-L-lysine (poly K) favored longer duration of expression in vitro and in vivo. 9 However, even with long-chain poly K-containing complexes, expression returned to background levels after about 30 days in vivo.…”

“…2,8,9 Earlier studies in human hepatoma cell lines in vitro determined that 10-11 receptor ligands per complex give optimal transfection, 8 and that longer chain length poly-L-lysine (poly K) favored longer duration of expression in vitro and in vivo. 9 However, even with long-chain poly K-containing complexes, expression returned to background levels after about 30 days in vivo. 9 Therefore, to achieve protracted expression, either the decline in expression must be prevented, or the complexes must be readministered.…”