Insulin-like growth factor-I (IGF-I) antisense oligodeoxynucleotide mediated inhibition of DNA synthesis by WI-38 cells: evidence for autocrine actions of IGF-I.
Insulin-like growth factor-I (IGF-I) is elaborated into culture medium by WI-38 cells, a human embryonic lung fibroblast cell line, and may participate in the autocrine stimulation of DNA synthesis. We have confirmed the expression of IGF-I by these cells and documented that they express the type 1 IGF receptor and a number of IGF-binding proteins. In situ hybridization histochemistry demonstrated relatively uniform expression of IGF-I and type 1 IGF receptor transcripts among WI-38 cells. To determine whether WI-38-synthesized IGF-I exerted mitogenic effects, a 15-base oligodeoxynucleotide complementary to the 5'IGF-I mRNA sequence (IGF-I AS-Oligo), including the translation start site, was incubated with cultured cells in an attempt to inhibit IGF-I synthesis. The IGF-I AS-Oligo was stable in cell culture, formed intracellular duplexes with IGF-I mRNA, and at 2 microM reduced IGF-I in conditioned medium by 83%. The IGF-I AS-Oligo also inhibited [3H]thymidine incorporation into DNA in a dose-dependent fashion (by 77% at 2 microM and by 95% at 20 microM). This reduction in DNA synthesis was prevented when the medium was supplemented with 100 ng/ml IGF-I. The oligomer also decreased the abundance of IGF-binding proteins in conditioned medium. The IGF-I AS-Oligo appears to exert its effects by blocking IGF-I mRNA translation, rather than blocking transcription or initiating RNase-H activity, because the abundance of IGF-I transcripts was not decreased in its presence. These findings confirm an essential role for IGF-I in WI-38 cell DNA synthesis and are consistent with autocrine actions by WI-38 cell IGF-I.
Moats-Staats
B M
BM
Department of Pediatrics, University of North Carolina, Chapel Hill 27599-7596.
Retsch-Bogart
G Z
GZ
Price
W A
WA
Jarvis
H W
HW
D'Ercole
A J
AJ
Stiles
A D
AD
D001483:Base Sequence; D002352:Carrier Proteins / Q000096:biosynthesis; D002460:Cell Line; D004261:DNA Replication / Q000187:drug effects*; D016373:DNA, Antisense / Q000494:pharmacology*; D003864:Depression, Chemical; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D017526:Receptor, IGF Type 1 / Q000096:biosynthesis
D002352:Carrier Proteins; D016373:DNA, Antisense; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1