title: Analysis of ribosyl-modified, mixed backbone analogs of a bcl-2/bcl-xL antisense oligonucleotide.
abstract: Progress in oligonucleotide chemistry has provided second-generation antisense oligonucleotides with increased efficacy and reduced non-antisense-related toxicity. The ability of the 2'-O-(2-methoxyethylribose) (2'-MOE)-modified phosphorothioate gapmer oligonucleotide 4625, which matches the bcl-2 mRNA and has three base-mismatches to bcl-xL, to inhibit bcl-2 and bcl-xL expression and induce tumor cell apoptosis has been described. Here we investigated the consequences of adding of 2'-MOE or 2'-Me modifications to ribonucleotides at either the two ends of the sequence, or the center region together with different combinations of phosphodiester/phosphorothioate backbones on the activity of oligonucleotide 4625. The ability of the various 4625 analogs, including the parental first-generation oligonucleotide 3005, to inhibit bcl-2 and bcl-xL expression, and diminish cell growth or induce tumor cell death was assessed in SW2 lung cancer cells using real-time PCR, Western blotting and cell viability assays. Only oligonucleotide 4625 exhibited a potent bispecific antisense activity against bcl-2 and bcl-xL, which effectively reduced tumor cell viability. The other antisense oligonucleotides were either uniquely active against bcl-2 or completely inactive. Our data suggest that the 2'-MOE modification in combination with the phophorothioate gapmer chemistry is the optimal format of the 4625 sequence in terms of antisense activity and biological efficacy.
authors.affiliation: Division of Medical Oncology, Department of Internal Medicine, University Hospital of Zürich, Haldiweg 4, CH-8044 Zurich, Switzerland.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Olie
authors.forename: Jonathan
authors.initials: J
authors.lastname: Hall
authors.forename: Francois
authors.initials: F
authors.lastname: Natt
authors.forename: Rolf A
authors.initials: RA
authors.lastname: Stahel
authors.forename: Uwe
authors.initials: U
authors.lastname: Zangemeister-Wittke
mesh_terms: D017209:Apoptosis; D018288:Carcinoma, Small Cell; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D008175:Lung Neoplasms; D009841:Oligonucleotides / Q000737:chemistry / Q000494:pharmacology; D016376:Oligonucleotides, Antisense / Q000737:chemistry* / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis / Q000096:biosynthesis; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein
chemical_list: D009841:Oligonucleotides; D016376:Oligonucleotides, Antisense; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; C423963:oligonucleotide 4625