c-fos protooncogene is involved in the mitogenic effect of transforming growth factor-beta in osteoblastic cells.
We investigated the contribution of c-fos protooncogene in the mitogenic effect of transforming growth factor-beta (TGF beta) in serum-deprived, confluent rat calvaria osteoblastic cells. The TGF beta-induced growth in these cells was associated with an immediate and transient c-fos mRNA accumulation, similar to the inductive effect of fetal calf serum. To assess the role of c-fos in the response to TGF beta, we used a c-fos antisense (AS) oligonucleotide displaying duplex formation with rat c-fos mRNA. Studies of AS and sense (S) uptake by osteoblastic cells demonstrated that incorporation of labeled oligomers was maximal at 2 h, and the incorporated AS oligonucleotide remained intact for 24 h. Immunofluorescence analysis of c-Fos-labeled cells demonstrated that AS, but not S, oligonucleotide reduced c-Fos protein expression, suggesting specific efficient inhibition of c-fos translation by the AS oligomer. Proliferation assays showed that cell growth induced by fetal calf serum was inhibited by the AS, but not by the S oligonucleotide, in both normal rat osteoblasts and ROS 17/2.8 osteosarcoma cells, demonstrating efficient and specific blockage of cell growth by the AS oligomer. The mitogenic effect of TGF-beta was abolished in cells cultured in the presence of AS, whereas S had no effect, showing that c-fos is required for TGF beta-induced osteoblast cell growth. The results show that the induction of c-fos is implicated in the mitogenic effect of TGF beta in osteoblastic cells and provide a cellular mechanism involved in the response of these cells to TGF beta.
Machwate
M
M
INSERM Unit 349, Cell and Molecular Biology of Bone and Cartilage, Lariboisiere Hospital, Paris, France.
Jullienne
A
A
Moukhtar
M
M
Lomri
A
A
Marie
P J
PJ
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002455:Cell Division; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation; D016762:Genes, fos; D006133:Growth Substances / Q000494:pharmacology; D008969:Molecular Sequence Data; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects; D012516:Osteosarcoma; D016760:Proto-Oncogene Proteins c-fos / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D016372:RNA, Antisense / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D006133:Growth Substances; D016760:Proto-Oncogene Proteins c-fos; D016372:RNA, Antisense; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta