Suppression of insulin-like growth factor type I receptor by a triple-helix strategy inhibits IGF-I transcription and tumorigenic potential of rat C6 glioblastoma cells.
Homopurine (AG) and homopyrimidine (CT) oligodeoxyribonucleotides predicted to form triple-helical (triplex) structures have been shown to specifically suppress gene expression when supplied to cultured cells. Here we present evidence that homopurine RNA (effector) sequences designed to form a triplex with a homopurine. homopyrimidine sequence 3' to the termination codon of the insulin-like growth factor type I receptor (IGF-IR) structural gene can efficiently suppress IGF-IR gene transcription. Transfection vectors were constructed to drive transcription of either AG or CT variant triplex-forming strands. To increase the probability of obtaining stable transfectants with adequate expression of effector sequences, these were designed to be transcribed together with cDNA sequences conferring neomycin resistance as a fusion transcript. Rat C6 glioblastoma cells transfected with the AG variant showed dramatic reduction of IGF-IR transcripts compared with untransfected cells. The AG transfectants also exhibited marked down-regulation of the IGF-I, and an enhanced accumulation of serine protease inhibitor nexin-I mRNA. Similar changes in gene expression were observed following transfection of C6 cells with constructs transcribing antisense RNA to IGF-IR transcripts, but were not observed in C6 cells transfected with either the CT triplex variant or with vector lacking triplex-forming sequences. Moreover, C6 cells transfected with AG triplex variant displayed a dramatic inhibition of tumor growth when injected into nude mice. The results suggest that a triple-helix strategy can be used to inhibit transcription elongation of the IGF-IR gene, and emphasize the efficacy of triplex-mediated gene inhibition in an animal model.
Rininsland
F
F
Department of Pathology, Case Western Reserve University, Cleveland, OH 44106, USA.
Johnson
T R
TR
Chernicky
C L
CL
Schulze
E
E
Burfeind
P
P
Ilan
J
J
D016564:Amyloid beta-Protein Precursor; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis; D002455:Cell Division; D015536:Down-Regulation; D005909:Glioblastoma / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology*; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D051379:Mice; D008819:Mice, Nude; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry / Q000494:pharmacology*; D011336:Probability; D058255:Protease Nexins; D016372:RNA, Antisense / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017526:Receptor, IGF Type 1 / Q000096:biosynthesis*; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins / Q000096:biosynthesis; D015842:Serine Proteinase Inhibitors / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects*; D014162:Transfection; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
D016564:Amyloid beta-Protein Precursor; D002352:Carrier Proteins; D009838:Oligodeoxyribonucleotides; D058255:Protease Nexins; D016372:RNA, Antisense; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1