title: Sequence-specific DNA strand cleavage by 111In-labeled peptide nucleic acids.
abstract: Peptide nucleic acids (PNAs) bind tightly and sequence-specifically to single- and double-stranded nucleic acids, and are hence of interest in the design of gene-targeted radiotherapeutics that could deliver the radiodamage to designated DNA and/or RNA sites. As a first step towards this goal, we developed a procedure for incorporation of Auger electron-emitting radionuclide (indium-111) into PNA oligomers and studied the efficiency of PNA-directed cleavage of single-stranded DNA targets. Accordingly, diethylene triamine penta-acetic acid (DTPA) was conjugated to the lysine-appended mixed-base PNAs and sequence-homologous DNA oligomer with a proper linker for comparative studies. By chelation of PNA-DTPA and DNA-DTPA conjugates with (111)In(3+) in acidic aqueous solutions, (111)In-labeled PNA and DNA oligomers were obtained. Targeting of single-stranded DNA with PNA-DTPA-[(111)In] conjugates yielded highly localized DNA strand cleavage; the distribution of breaks along the target DNA strand has two maxima corresponding to both termini of PNA oligomer. After 10-14 days, the overall yield of breaks thus generated within the PNA-targeted DNA by (111)In decay was 5-7% versus < or =2% in the case of control oligonucleotide DNA-DTPA-[(111)In]. The estimated yield of DNA strand breaks per nuclear decay is ~0.1 for the PNA-directed delivery of (111)In, which is three times more than for the DNA-directed delivery of this radionuclide. This in vitro study shows that (111)In-labeled PNAs are much more effective than radiolabeled DNA oligonucleotides for site-specific damaging of DNA targets. Accordingly, we believe that PNA oligomers are promising radionuclide delivery tools for future antisense/antigene radiotherapy trials.
authors.affiliation: Department of Nuclear Medicine, Warren G. Magnuson Clinical Center, National Institutes of Health, Bethesda, MD 20892-1180, USA.
authors.forename: Yujian
authors.initials: Y
authors.lastname: He
authors.forename: Igor G
authors.initials: IG
authors.lastname: Panyutin
authors.forename: Alex
authors.initials: A
authors.lastname: Karavanov
authors.forename: Vadim V
authors.initials: VV
authors.lastname: Demidov
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Neumann
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000737:chemistry* / Q000528:radiation effects*; D004249:DNA Damage / Q000528:radiation effects*; D005240:Feasibility Studies; D020868:Gene Silencing; D018390:Gene Targeting / Q000379:methods*; D015316:Genetic Therapy / Q000379:methods*; D007205:Indium Radioisotopes / Q000737:chemistry*; D007553:Isotope Labeling / Q000379:methods; D008969:Molecular Sequence Data; D020135:Peptide Nucleic Acids / Q000737:chemistry*; D012680:Sensitivity and Specificity
chemical_list: D007205:Indium Radioisotopes; D020135:Peptide Nucleic Acids; D004247:DNA