title: Pseudo-cyclic oligonucleotides: in vitro and in vivo properties.
abstract: We have designed and studied antisense oligodeoxynucleotides (oligonucleotides; oligos) which we call 'pseudo-cyclic oligonucleotides' (PCOs). PCOs contain two oligonucleotide segments attached through their 3'-3'- or 5'-5'-ends. One of the segments of the PCO is an antisense oligo complementary to a target mRNA, and the other is a short protective oligo that is 5-8 nucleotides long and complementary to the 3'- or 5'-end of the antisense oligo. As a result of complementarity between the antisense and protective oligo segments, PCOs form intramolecular pseudo-cyclic structures in the absence of the target RNA. The antisense oligo segment of PCOs used for the studies described here is complementary to an 18-nucleotide-long site on the mRNA of the protein kinase A regulatory subunit RIalpha (PKA-RIalpha). Thermal melting studies of PCOs in the absence and presence of the complementary RNA suggest that the pseudo-cyclic structures formed in the absence of the target RNA dissociate, bind to the target RNA, and form heteroduplexes. The results of RNase H cleavage assays suggest that PCOs bind to complementary RNA and activate RNase H in a manner similar to that of an 18-mer conventional antisense PS-oligo. In snake venom (a 3'-exonuclease) or spleen (a 5'-exonuclease) phosphodiesterase digestion studies, PCOs are more stable than conventional antisense oligos because of the presence of 3'-3'- or 5'-5'-linkages and the formation of intramolecular pseudo-cyclic structures. PCOs with a phosphorothioate antisense oligo segment inhibited cell growth of MDA-MB-468 and GEO cancer cell lines similar to that of the conventional antisense PS-oligo, suggesting efficient cellular uptake and target binding. The nuclease stability studies in mice suggest that PCOs have higher in vivo stability than antisense PS-oligos. The studies in mice showed similar pharmacokinetic and tissue distribution profiles for PCOs to those of antisense PS-oligos in general, but rapid elimination from selected tissues.
authors.affiliation: Hybridon, Inc., Milford, MA 01757, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Jiang
authors.forename: E R
authors.initials: ER
authors.lastname: Kandimalla
authors.forename: Q
authors.initials: Q
authors.lastname: Zhao
authors.forename: L X
authors.initials: LX
authors.lastname: Shen
authors.forename: A
authors.initials: A
authors.lastname: DeLuca
authors.forename: N
authors.initials: N
authors.lastname: Normano
authors.forename: M
authors.initials: M
authors.lastname: Ruskowski
authors.forename: S
authors.initials: S
authors.lastname: Agrawal
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry* / Q000493:pharmacokinetics / Q000494:pharmacology*; D001483:Base Sequence; D002455:Cell Division / Q000187:drug effects; D015195:Drug Design; D004355:Drug Stability; D006801:Humans; D008297:Male; D051379:Mice; D009691:Nucleic Acid Denaturation; D020319:Oligodeoxyribonucleotides, Antisense / Q000737:chemistry* / Q000235:genetics / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D013696:Temperature; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
chemical_list: D000970:Antineoplastic Agents; D020319:Oligodeoxyribonucleotides, Antisense; D012333:RNA, Messenger