Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0029463 (osteosarcoma)
 16,637 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A murine mRNA (provisionally called 2ar) is described whose abundance is greatly increased by the tumor promoter 12-O-tetradecanoylphorbol 13-acetate both in JB6 epidermal cells in vitro and in epidermis in vivo. We have previously shown induction of 2ar in epidermal or fibroblast cell lines by tumor promoters, growth factors, and transformation with H-ras. The 2ar mRNA appears to be derived from a single copy gene. It encodes the mouse homolog of rat osteopontin, a 41.5-kDa glycosylated bone phosphoprotein that binds to fibroblasts and osteosarcoma cells and to hydroxylapatite (bone matrix). The rat and mouse sequences are 84% identical at the amino acid level and 87% identical at the nucleotide level. Many of the primary structural features are conserved, including a run of 9-10 aspartic residues and a Gly-Arg-Gly-Asp-Ser cell adhesion sequence. Antiserum raised against portions of the predicted polypeptide immunoprecipitated proteins of apparent Mr 55,000-70,000 both from reticulocyte lysates containing the translation products of hybrid-selected mRNA and from cell culture medium containing metabolically labeled proteins secreted by JB6 cells. The results presented here demonstrate that osteopontin is identical to a transformation-associated phosphoprotein whose level of expression by cultured cells and abundance in human sera has been correlated with tumorigenicity. These results suggest a role for osteopontin in carcinogenesis. The murine version of osteopontin has been given the formal name "secreted phosphoprotein 1" and the designation spp.
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PMID:Osteopontin, a transformation-associated cell adhesion phosphoprotein, is induced by 12-O-tetradecanoylphorbol 13-acetate in mouse epidermis. 272 55

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.
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PMID:Transcriptional regulation of osteopontin production in rat osteosarcoma cells by type beta transforming growth factor. 316 60

We investigated the effects of 1,25-dihydroxyvitamin D3 on the synthesis of osteopontin, a phosphorylated cell attachment glycoprotein, in ROS 17/2.8 cells, a clonal osteoblast-like rat osteosarcoma cell line. We observed a dose dependent increase in uptake of [32PO4] into osteopontin secreted into the medium. An increased incorporation of [35S]-methionine into secreted osteopontin suggested the effect was that of increased protein biosynthesis. Using a radioimmunoassay we demonstrated a dose dependent increase in the amount of secreted osteopontin, an increase which could be blocked by Actinomycin D, in response to 1,25-dihydroxyvitamin D3. These results suggest that the hormonal form of vitamin D regulates the biosynthesis of osteopontin, possibly at the level of transcription.
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PMID:1,25-Dihydroxyvitamin D3 regulates the biosynthesis of osteopontin, a bone-derived cell attachment protein, in clonal osteoblast-like osteosarcoma cells. 347 71

Intratypic osteosarcoma hybrids were constructed by fusing the human osteoblast-like osteosarcoma SaOS-2 with the rat osteoblast-like osteosarcoma UMR-106. Both of these osteosarcomas express liver/bone/kidney alkaline phosphatase (ALPL), but only the UMR-106 cell line expresses osteopontin (OPN), a gene expressed during later stages of osteoblast differentiation. Analysis of osteoblast gene expression in these hybrids demonstrated that ALPL continued to be expressed; however, OPN steady-state mRNA levels were dramatically reduced in four hybrids. Quantitative measurements indicated that OPN steady-state mRNA levels were extinguished by a factor of 20- to 1000-fold. Since SaOS-2 chromosomes are preferentially lost from these hybrids, subclones of extinguished hybrids were isolated that reexpressed OPN mRNA at levels similar to the UMR-106 parental line. These data indicate that trans-acting negative regulatory factors, expressed from the SaOS-2 genome, are responsible for OPN extinction. This report provides the first demonstration of the negative regulation of OPN gene expression and also provides additional evidence that extinction plays a role in the regulation of osteoblast gene expression.
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PMID:Regulation of osteoblast gene expression in intratypic osteosarcoma hybrid cells. 749 36

Exposure of osteosarcoma cell lines to chronic intermittent strain increases the activity of mechano-sensitive cation (SA-cat) channels. The impact of mechano-transduction on osteoblast function has not been well studied. We analyzed the expression and production of bone matrix proteins in human osteoblast-like osteosarcoma cells, OHS-4, in response to chronic intermittent mechanical strain. The OHS-4 cells exhibit type I collagen production, 1,25-Dihydroxyvitamin D-inducible osteocalcin, and mineralization of the extracellular matrix. The matrix protein message level was determined from total RNA isolated from cells exposed to 1-4 days of chronic intermittent strain. Northern analysis for type I collagen indicated that strain increased collagen message after 48 h. Immunofluorescent labeling of type I collagen demonstrated that secretion was also enhanced with mechanical strain. Osteopontin message levels were increased several-fold by the application of mechanical load in the absence of vitamin D, and the two stimuli together produced an additive effect. Osteocalcin secretion was also increased with cyclic strain. Osteocalcin levels were not detectable in vitamin D-untreated control cells. However, after 4 days of induced load, significant levels of osteocalcin were observed in the medium. With vitamin D present, osteocalcin levels were 4 times higher in the medium of strained cells compared to nonstrained controls. We conclude that mechanical strain of osteoblast-like cells is sufficient to increase the transcription and secretion of matrix proteins via mechano-transduction without hormonal induction.
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PMID:Human osteoblast-like cells respond to mechanical strain with increased bone matrix protein production independent of hormonal regulation. 753 Jun 47

The 1,25-dihydroxyvitamin D3 (vitamin D) receptor (VDR) is a key trans-activating protein that mediates calcium regulation as well as cellular proliferation and differentiation. Phosphorylation of the VDR contributes significantly to its functional activity, but the specific mechanisms that mediate this regulation are not well understood. Phosphorylation may influence DNA binding, ligand binding, and protein-protein interactions, including heterodimerization and/or transactivation functions. We used a protein kinase C inhibitor, staurosporine (ST), and an inhibitor of serine-threonine phosphatases, okadaic acid (OA), to elucidate the contribution of VDR phosphorylation to vitamin D-mediated transcription of the osteocalcin (OC) gene. Vitamin D-induced transcription was assayed in transfected ROS 17/2.8 osteosarcoma cells using chloraminphenicol acetyltransferase constructs containing the vitamin D-responsive element (VDRE) at its native locus in the rat OC promoter as well as fused to a heterologous promoter. Both ST and OA inhibit VDRE-mediated and vitamin D-dependent enhancement of OC gene transcription as well as OC biosynthesis, as assessed by RIAs. Results from gel mobility shift and Western blot analyses using nuclear proteins from ROS 17/2.8 cells show that binding of the VDR-retinoid-X receptor heterodimer complex to the OC VDRE is not inhibited in the presence of ST. In contrast, OA does inhibit the formation of complexes interacting with both the OC and osteopontin VDREs; immunoprecipitation studies using 32P-labeled ROS 17/2.8 cells reveal that OA treatment result in ligand-independent hyperphosphorylation of the VDR. Our results suggest that two distinct phosphorylation events modulate rat VDR function. One event is related to transactivation, and the other is also critical to the VDRE-binding activity of VDR-retinoid X receptor-DNA complexes with consequential effects on transactivation.
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PMID:Control of 1,25-dihydroxyvitamin D3 receptor-mediated enhancement of osteocalcin gene transcription: effects of perturbing phosphorylation pathways by okadaic acid and staurosporine. 758 24

1 alpha,25-Dihydroxyvitamin D3 (D3), T3, and retinoids are necessary for normal skeletal development, and their actions are interdependent due to the heterodimerization capabilities of their receptors. We investigated the hypothesis that these hormones act on osteoblasts directly to produce complex target gene responses resulting from multiple hormone interactions. Physiological interactions among D3, T3, and retinoid signaling were analyzed in serum-free cultures of the osteosarcoma cell lines ROS 25/1, UMR106, and ROS 17/2.8. These cells express distinct stages of the osteoblast phenotype and coexpress appropriate hormone receptors. Regulation of collagen I alpha 1 and alpha 2, alkaline phosphatase, osteopontin, and osteocalcin messenger RNAs was dependent on the dose and duration of hormone stimulation and modified by cell confluence. Retinoids were required for comprehensive expression of phenotypic responses to D3 and T3 in each cell type and hormone interactions were both cell and target gene specific. Differing responses of target genes in each cell line may provide a molecular basis for discrete hormone actions seen at specific stages of osteoblast differentiation or skeletal development.
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PMID:Retinoids modify regulation of endogenous gene expression by vitamin D3 and thyroid hormone in three osteosarcoma cell lines. 766 49

We have studied the role of retinoid X receptor alpha (RXR alpha) in vitamin D receptor (VDR) responsive interactions using nuclear extracts from human osteoblast-like MG-63 osteosarcoma cells and its specific response element from human osteocalcin gene (OC-VDRE). An RXR alpha-specific antibody was not capable of recognizing the two VDR responsive complexes formed with the OC-VDRE. Addition of in-vitro-produced RXR alpha to the binding reaction resulted in decreased binding of the two VDR-responsive interactions and, simultaneously, formation of a new complex, which was identified with RXR alpha- and VDR-specific antibodies. A similarly migrating RXR alpha- and VDR-responsive complex was also formed when baculovirus-expressed VDR was used with the in-vitro-produced RXR alpha in the absence of a nuclear extract or when VDRE from mouse osteopontin gene (OP-VDRE) was used as a binding site. Characterization of DNA binding properties for this VDR-RXR alpha complex revealed that both half sites of OC-VDRE are required for DNA binding. These results indicate that RXR alpha is probably not the physiological accessory factor in the MG-63 osteosarcoma cells needed for the VDR-VDRE interactions within the human osteocalcin gene promoter, although it is capable of dimerizing with recombinant VDR and the native VDR from these cells and although these dimers are capable of binding in vitro to the OC-VDRE.
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PMID:Retinoid-X-receptor-alpha-independent binding of vitamin D receptor to its response element from human osteocalcin gene. 770 32

Treatment of the U-2 OS human osteosarcoma cell line with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) dramatically decreased the rate of DNA synthesis. This decrease in proliferation as well as the change in morphology of the TPA-treated cells can be blocked by the protein kinase C inhibitor GF 109203X. The U-2 OS cells are known to express the c-sis oncogene [platelet-derived growth factor (PDGF) B-chain], PDGF-A, and receptors for PDGF, thus providing a potential autocrine loop of growth stimulation. TPA was found to induce the expression of both the PDGF-A and the PDGF-B chains. However, the levels of the PDGF receptor beta subunits and of the PDGF-BB inducable tyrosine phosphorylation of the PDGF receptor were markedly reduced. The TPA treatment of the U-2 OS cells also induced changes typical for maturing bone cells, such as increased expression levels of alkaline phosphatase and osteopontin. The expression levels of type I collagen and bone sialoprotein were reduced. The results show a TPA-dependent down-regulation of the PDGF receptor beta subunits that correlates with an increased expression of osteoblast phenotypic markers.
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PMID:Phenotypic modification of human osteosarcoma cells with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate. 779 13

Establishing regulatory mechanisms that mediate proliferation of osteoblasts while restricting expression of genes associated with mature bone cell phenotypic properties to post-proliferative cells is fundamental to understanding skeletal development. To gain insight into relationships between growth control and the developmental expression of genes during osteoblast differentiation, we have examined expression of three classes of genes during the cell cycle of normal diploid rat calvarial-derived osteoblasts and rat osteosarcoma cells (ROS 17/2.8): cell cycle and growth-related genes (e.g., histone), genes that encode major structural proteins (e.g., actin and vimentin), and genes related to the biosynthesis, organization, and mineralization of the bone extracellular matrix (e.g., alkaline phosphatase, collagen I, osteocalcin, and osteopontin). In normal diploid osteoblasts as well as in osteosarcoma cells we found that histone genes, required for cell progression, are selectively expressed during S phase. All other genes studied were constitutively expressed both at the transcriptional and posttranscriptional levels. Alkaline phosphatase, an integral membrane protein in both osteoblasts and osteosarcoma cells, exhibited only minimal changes in activity during the osteoblast and osteosarcoma cell cycles. Our findings clearly indicate that despite the loss of normal proliferation-differentiation interrelationships in osteosarcoma cells, cell cycle regulation or constitutive expression of growth and phenotypic genes is maintained.
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PMID:Expression of cell growth and bone phenotypic genes during the cell cycle of normal diploid osteoblasts and osteosarcoma cells. 782 87


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