title: Transcriptional regulation of osteopontin production in rat osteosarcoma cells by type beta transforming growth factor.
abstract: Type beta transforming growth factor (TGF beta) was shown to regulate the production of several extracellular matrix proteins. Osteopontin (OP) is a recently discovered bone matrix protein which was shown to promote the attachment of osteoblastic rat osteosarcoma ROS 17/2.8 cells to their substrate. We examined the effects of TGF beta on OP production and OP mRNA in ROS 17/2.8 cells. Four-day treatment with 4 ng/ml TGF beta 1 increased substantially the level of osteopontin in the cell culture media, as estimated by immunoblotting. Metabolic labeling showed that this effect was associated with a 3-4-fold increase in OP biosynthesis. TGF beta 1 also increased, in a dose-dependent manner starting at 0.4 ng/ml, the steady-state level of OP mRNA. The increase in OP mRNA was first detected 48 h after the addition of TGF beta 1 and lasted at least until 120 h. The half-life of OP mRNA, estimated in the presence of 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole, was about 10 h and was not altered by TGF beta 1. On the other hand, the increase in OP mRNA was blocked by actinomycin D. Nuclear run-on assays indicated that TGF beta 1 increased the rate of transcription of the OP gene. Examination of hormonal interactions showed that TGF beta 1 opposed or compensated for the reduction in OP mRNA produced by dexamethasone and that TGF beta 1 did not further augment OP mRNA levels which had been increased by 1,25-dihydroxyvitamin D3 treatment. TGF beta 2 had similar effects on OP gene expression as TGF beta 1. In conclusion, TGF beta promotes the production of osteopontin in the osteoblastic osteosarcoma cells through a pathway which is at least in part mediated by transcriptional events.
authors.affiliation: Department of Bone Biology and Osteoporosis Research, Merck Sharp and Dohme Research Laboratories, West Point, Pennsylvania 19486.
authors.forename: M
authors.initials: M
authors.lastname: Noda
authors.forename: K
authors.initials: K
authors.lastname: Yoon
authors.forename: C W
authors.initials: CW
authors.lastname: Prince
authors.forename: W T
authors.initials: WT
authors.lastname: Butler
authors.forename: G A
authors.initials: GA
authors.lastname: Rodan
mesh_terms: D000818:Animals; D002117:Calcitriol / Q000494:pharmacology; D003094:Collagen / Q000235:genetics; D003609:Dactinomycin / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005353:Fibronectins / Q000235:genetics; D006207:Half-Life; D007700:Kinetics; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism; D053495:Osteopontin; D012516:Osteosarcoma / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D012795:Sialoglycoproteins / Q000096:biosynthesis* / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects*; D015291:Transforming Growth Factors; D014407:Tumor Cells, Cultured
chemical_list: D005353:Fibronectins; D010455:Peptides; D012333:RNA, Messenger; D012795:Sialoglycoproteins; C506897:Spp1 protein, rat; D053495:Osteopontin; D003609:Dactinomycin; D015291:Transforming Growth Factors; D003907:Dexamethasone; D003094:Collagen; D002117:Calcitriol