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Preparation and evaluation of tumor-targeting peptide-oligonucleotide conjugates
1Department of Nuclear Medicine, Universitätsklinikum Heidelberg, INF 400, 69120 Heidelberg, Germany. walter_mier@med.uni-heidelberg.de
Abstract:
Enormous progress has been made in the development of antisense oligodeoxynucleotides (ODNs) as therapeutic agents inhibiting gene expression. Unfortunately, the therapeutical application of ODNs is still held back because of the low cellular uptake and the lack of specific transport into particular cells. In this paper, we report a drug-targeting system using somatostatin receptors (SSTRs) which are overexpressed in various tumors. Phosphorothioate ODNs were covalently linked to Tyr(3)-octreotate, an analogue of somatostatin. The peptide was assembled by solid-phase synthesis, oxidized to form the cyclic disulfide, and subsequently derivatized with a N-terminal maleimido functionality. 5'-Thiol derivatized phosphorothioate-ODNs directed against the protooncogene bcl-2 were conjugated to this maleimido-modified peptide. Binding studies revealed that the conjugates retain specific binding with nanomolar affinities to SSTRs (IC(50)-values between 1.83 and 2.52 nM). Furthermore, melting studies with complementary DNA revealed that the terminal conjugation of the ODNs did not significantly affect their hybridization affinity.
Insights
Researchers developed a novel drug-targeting system by linking antisense oligodeoxynucleotides (ODNs) to a somatostatin analogue. This system enhances targeted delivery to tumor cells overexpressing somatostatin receptors (SSTRs), improving therapeutic potential.
Area of Science:
- Biotechnology
- Molecular Biology
- Oncology
Background:
- Antisense oligodeoxynucleotides (ODNs) show promise for inhibiting gene expression but face challenges in cellular uptake and targeted delivery.
- Overexpression of somatostatin receptors (SSTRs) in various tumors presents a potential target for drug delivery systems.
Purpose of the Study:
- To develop a novel drug-targeting system for antisense ODNs using SSTRs.
- To enhance the specific delivery of ODNs to tumor cells by conjugating them to a somatostatin analogue.
Main Methods:
- Covalent linkage of phosphorothioate ODNs targeting the bcl-2 protooncogene to Tyr(3)-octreotate, a somatostatin analogue.
- Solid-phase synthesis of the peptide, followed by oxidation and maleimido derivatization.
- Conjugation of 5'-thiol derivatized ODNs to the maleimido-modified peptide.
Main Results:
- The resulting conjugates demonstrated specific binding to SSTRs with nanomolar affinities (IC(50) values between 1.83 and 2.52 nM).
- Terminal conjugation of ODNs to the peptide did not significantly impact their DNA hybridization affinity, as confirmed by melting studies.
Conclusions:
- The developed SSTR-targeted ODN conjugates show potential for specific tumor cell targeting.
- This strategy may overcome limitations of cellular uptake and improve the therapeutic efficacy of antisense ODN-based gene silencing therapies.