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 proinflammatory cytokine cascade, including IL-1 alpha, IL-1 beta, TNF-alpha, IL-6, and IL-8, is activated in response to infection or immunologic insult. Besides their immunologic effects, several of these mediators stimulate bone resorption and inhibit bone formation. Osteocalcin, the most abundant noncollagenous protein present in bone, is an osteoblast-specific product whose production closely correlates with bone formation, and which has also been implicated in control of bone resorption. IL-1 and TNF have previously been shown to down-regulate osteocalcin production in vitro and in vivo, although the mechanism of this inhibition is unknown. In the present studies, IL-1 beta and TNF-alpha both inhibited 1,25-dihydroxyvitamin D3-stimulated production of osteocalcin protein and mRNA by ROS 17/2.8 osteosarcoma cells, whereas IL-6 had no effect on protein and only weakly inhibited mRNA. To determine if down-regulation was exerted at the transcriptional level, an osteocalcin promoter-chloramphenicol acetyltransferase (CAT) fusion gene was constructed (PHOC-CAT). After transient transfection of PHOC-CAT into ROS 17/2.8 osteosarcoma cells, reporter CAT activity was up-regulated by vitamin D at concentrations above 10(-12) M. In screening studies, TNF-alpha (-57%) and IL-6 (-37%) inhibited vitamin D-stimulated osteocalcin transcription, whereas IL-1 alpha, IL-1 beta, and IL-8 had no effect. Other immune cytokines and growth factors, including IL-2, IL-3, IL-7, and M-CSF, also failed to regulate osteocalcin transcription. Despite their lack of promoter regulation, IL-1 alpha and IL-1 beta also stimulated PGE2 production by ROS 17/2.8, further confirming the ability of the host cell to respond to these mediators. In dose-response experiments, down-regulation by TNF-alpha was significant at concentrations as low as 0.14 pM (0.1 U/ml), whereas approximately 10(4)-fold higher concentration of IL-6 was required to exert a similar effect. TNF-alpha-mediated down-regulation was unaffected by indomethacin. These data demonstrate that of these cytokines, TNF-alpha alone potently down-regulates osteocalcin promoter function, whereas IL-1 acts post-transcriptionally, possibly by reducing mRNA stability. Heterogeneity therefore exists among the proinflammatory cytokines with respect to the level at which control of osteocalcin expression is exerted.
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PMID:Proinflammatory cytokines tumor necrosis factor-alpha and IL-6, but not IL-1, down-regulate the osteocalcin gene promoter. 130 41

The observation that vitamin D-mediated enhancement of osteocalcin (OC) gene expression is dependent on and reciprocally related to the level of basal gene expression suggests that an interaction of the vitamin D responsive element (VDRE) with basal regulatory elements of the OC gene promoter contributes to both basal and vitamin D-enhanced transcription. Protein-DNA interactions at the VDRE of the rat OC gene (nucleotides -466 to -437) are reflected by direct sequence-specific and antibody-sensitive binding of the endogenous vitamin D receptor present in ROS 17/2.8 osteosarcoma nuclear protein extracts. In addition, a vitamin D-responsive increase in OC gene transcription is accompanied by enhanced non-vitamin D receptor-mediated protein-DNA interactions in the "TATA" box region (nucleotides -44 to +23), which also contains a potential glucocorticoid responsive element. Evidence for proximity of the VDRE with the basal regulatory elements is provided by two features of nuclear architecture. (i) Nuclear matrix attachment elements in the rat OC gene promoter that bind nuclear matrix proteins with sequence specificity may impose structural constraints on promoter conformation. (ii) Limited micrococcal nuclease digestion and Southern blot analysis indicate that three nucleosomes can be accommodated in the sequence spanning the OC gene VDRE, the OC/CCAAT box (nucleotides -99 to -76), and the TATA/glucocorticoid responsive element, and thereby the potential distance between the VDRE and the basal regulatory elements can be reduced. A model is presented for the contribution of both the VDRE and proximal promoter elements to the enhancement of OC gene transcription in response to vitamin D. The vitamin D receptor plus accessory proteins may function cooperatively with basal regulatory factors to modulate the extent to which the OC gene is transcribed.
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PMID:Vitamin D-responsive protein-DNA interactions at multiple promoter regulatory elements that contribute to the level of rat osteocalcin gene expression. 132 35

We have previously shown that one of the rapid nongenomic actions of 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25-(OH)2D3), the increase in intracellular calcium (Ca2+), accompanies the increased osteocalcin (OC) mRNA steady-state levels in rat osteosarcoma cells. To determine the functional significance of the nongenomic actions, we have measured changes in intracellular Ca2+ as an indicator of the rapid effects and have assessed the effect of inhibition of the rapid increase in cellular Ca2+ by the inactive epimer, 1 beta, 25-dihydroxyvitamin D3 (1 beta,25-(OH)2D3), on OC mRNA steady-state levels and transcription. 1 beta,25-dihydroxyvitamin D3 inhibited 1 alpha,25-(OH)2D3 induced increases in intracellular Ca2+ and OC mRNA transcription at 1 hr and OC mRNA steady state levels at 3 hr. 1 beta,25-Dihydroxyvitamin D3 did not alter the binding of the vitamin D receptor complex to the vitamin D responsive element of the OC gene. The results demonstrate the functional importance of the rapid, nongenomic actions of 1 alpha,25-(OH)2D3 in the genomic activation of the OC gene by the hormone in rat osteoblast-like cells, perhaps by modifying subtle structural and/or functional properties of the vitamin D-receptor DNA complex or by affecting other protein DNA interactions that support OC gene transcription.
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PMID:The rapid nongenomic actions of 1 alpha,25-dihydroxyvitamin D3 modulate the hormone-induced increments in osteocalcin gene transcription in osteoblast-like cells. 142 79

Rabbit and chicken antibodies were raised against two peptides synthesized according to the structure of human 1,25-dihydroxyvitamin D3 receptor (hVDR): rabbit alpha hVDR-103 against the N-terminal amino acids 5-18 and alpha hVDR-104 against the amino acids 172-186 in the hinge region and chicken alpha hVDR-cab11 against the amino acids 172-186, respectively. The specificity of the antibodies was tested by peptide saturation, SDS-PAGE immunoblotting, gel shift assay and sucrose gradient centrifugation. Immunoblotting of a soluble extract (cytosol) from osteosarcoma cell line MG-63 showed a single band with an M(r) of about 48,000 and human intestine cytosol a broad band (50-63,000) for both antibodies. The antibodies recognized activated (3.2S) hVDR by shifting the centrifugation sedimentation profile to 5-6S. The antibodies showed nuclear immunostaining of unoccupied VDR in human osteosarcoma cells MG-63, U2-Os and SaOs-2. The immunoreaction could be saturated with the corresponding synthetic peptide. In immunoblot alpha hVDR-103 reacted with human and rat VDR, whereas alpha hVDR-104 recognized human VDR only. Similarly in immunohistochemistry, alpha hVDR-103 showed staining with hVDR and rVDR, whereas alpha hVDR-104 reacted only with hVDR. All antibodies recognized the native hVDR as verified with sucrose gradient centrifugation or immunoprecipitation but only alpha hVDR-103 and alpha hVDR-cab11 in gel shift assay of hVDR associated with the vitamin D-responsive element of human osteocalcin gene promoter.
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PMID:Characterization of human 1,25-dihydroxyvitamin D3 receptor anti-peptide antibodies. 147 57

Protein-S is a vitamin K (Vit K)-dependent protein synthesized by hepatocytes, megakaryocytes, and endothelial cells and plays an important role in the regulation of hemostasis. Two cases of free protein-S congenital deficiency were recently reported to be associated with osteopenia. We hypothesized that this osteopenia could be the result of a bone deficit of protein-S synthesized by bone cells. Using enzyme-linked immunoassay, immunocytochemistry, immunoblotting, and immunoprecipitation after labeling with [35S]methionine, we have shown that this protein is secreted by three human osteosarcoma cell lines and by human adult osteoblast-like cells. In addition, protein-S was present in protein extracts of human bone matrix. Protein-S secreted by MG 63 cells increased linearly from 1-7 days of culture, was biologically active, and was regulated by warfarin, as previously described for the other cell types secreting protein-S. Vit K had no direct effect on protein-S secretion or activity, but could overcome the effects of warfarin. In conclusion, in addition to osteocalcin and matrix gamma-carboxyglutamic acid (Gla) protein, osteoblasts secrete another Vit K-dependent protein, which is a constituent of the bone matrix. Our data suggest that osteopenia occurring in patients with congenital protein-S deficiency might be related to a deficiency of protein-S secretion by the osteoblasts. This finding raises the intriguing possibility that protein-S might play a role in bone turnover and bone mass.
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PMID:Protein-S, a vitamin K-dependent protein, is a bone matrix component synthesized and secreted by osteoblasts. 153 28

Osteocalcin is initially synthesized as an 11 kD molecule consisting of a 23-residue translocation signal peptide that is cleaved during translation, a 26-residue propeptide that targets the protein for gamma-carboxylation, and the 49-residue mature protein. Although the majority of newly synthesized osteocalcin is deposited into bone matrix, a small amount can be detected in blood, and it is this characteristic that has led to its current clinical use as a specific index of osteoblastic activity. Nothing is known, however, about the fate of the propeptide. If osteocalcin and the propeptide are cosecreted, then the concentration of the propeptide could also be useful as a marker of osteoblastic function and, further, may be superior to osteocalcin because it would be unaffected by binding to bone. To test this hypothesis, we synthesized a peptide corresponding to 21 residues of the osteocalcin propeptide from humans and produced a polyclonal antibody to this peptide. Human sera were screened for the presence of the propeptide, and the human osteosarcoma cell line MG-63 was tested for secretion of the propeptide. We could not detect any osteocalcin propeptide in sera from normal adults or individuals with renal failure or primary hyperparathyroidism or those on long-term coumadin therapy. Likewise there was no propeptide present in media from cells grown in the presence of vitamin K, 1,25-(OH)2D3, warfarin, or warfarin plus 1,25-(OH)2D3. In contrast, the cell extract, characterized by high-performance liquid chromatography, contained mature osteocalcin, free propeptide, and the proosteocalcin precursor when cells were grown in the presence of 1,25-(OH)2D3 alone.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The osteocalcin propeptide is not secreted in vivo or in vitro. 154 60

Transforming growth factor beta (TGF beta) and 1,25-dihydroxyvitamin D3 (1,25D3), when added simultaneously to a human osteosarcoma cell line, MG-63, induce alkaline phosphatase activity 40-70-fold over basal levels, 6-7-fold over 1,25D3 treatment alone, and 15-20-fold over TGF beta treatment alone. TGF beta and 1,25D3 synergistically increased alkaline phosphatase specific activity in both matrix vesicles and plasma membrane isolated from the cultures, but the specific activity was greater in and targeted to the matrix vesicle fraction. Inhibitor and cleavage studies proved that the enzymatic activity was liver/bone/kidney alkaline phosphatase. Preincubation of MG-63 cells with TGF beta for 30 min before addition of 1,25D3 was sufficient for maximal induction of enzyme activity. Messenger RNA for liver/bone/kidney alkaline phosphatase was increased 2.1-fold with TGF beta, 1.7-fold with 1,25D3, and 4.8-fold with the combination at 72 h. Human alkaline phosphatase protein as detected by radioimmunoassay was stimulated only 6.3-fold over control levels with the combination. This combination of factors was tested for their effect on production of three other osteoblast cell proteins: collagen type I, osteocalcin, and fibronectin. TGF beta inhibited 1,25D3-induced osteocalcin production, whereas both factors were additive for fibronectin and collagen type I production. TGF beta appears to modulate the differentiation effects of 1,25D3 on this human osteoblast-like cell and thereby retain the cell in a non-fully differentiated state.
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PMID:Effects of combining transforming growth factor beta and 1,25-dihydroxyvitamin D3 on differentiation of a human osteosarcoma (MG-63). 157 31

A novel monoclonal antibody against human osteocalcin, recently established in our laboratory, was shown by immunoblotting and immunohistochemistry to react specifically with human osteoblasts. In the present study, the antibody was applied to the immunohistochemical diagnosis of human bone tumours, especially osteoblastic tumours. The antibody reacted with all 27 osteosarcomas. No positive reaction was found either in chondrosarcoma, giant cell tumours of bone, soft tissue tumours or epithelial tumours. A positive reaction was found preferentially in the cytoplasm of most of the osteosarcoma cells, but not in the extracellular matrix. Since the antibody reacted with formalin-fixed and paraffin-embedded tissues, it will be a useful tool for routine immunohistochemical diagnosis of osteoblastic lesions.
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PMID:Usefulness of a novel monoclonal antibody against human osteocalcin in immunohistochemical diagnosis. 160 11

Primary cultures of calvarial derived normal diploid osteoblasts undergo a developmental expression of genes reflecting growth, extracellular matrix maturation, and mineralization during development of multilayered nodules having a bone tissue-like organization. Scanning electron microscopy of the developing cultures indicates the transition from the uniform distribution of cuboidal osteoblasts to multilayered nodules of smaller cells with a pronounced orientation of perinodular cells towards the apex of the nodule. Ultrastructural analysis of the nodule by transmission electron microscopy indicates that the deposition of mineral is confined to the extracellular matrix where cells appear more osteocytic. The cell body contains rough endoplasmic reticulum and golgi, while these intracellular organelles are not present in the developing cellular processes. To understand the regulation of temporally expressed genes requires an understanding of which genes are selectively expressed on a single cell basis as the bone tissue-like organization develops. In situ hybridization analysis using 35S labelled histone gene probes, together with 3H-thymidine labelling and autoradiography, indicate that greater than 98% of the pre-confluent osteoblasts are proliferating. By two weeks, both the foci of multilayered cells and internodular cell regions have down-regulated cell growth associated genes. Post-proliferatively, but not earlier, initial expression of both osteocalcin and osteopontin are restricted to the multilayered nodules where all cells exhibit expression. While total mRNA levels for osteopontin and osteocalcin are coordinately upregulated with an increase in mineral deposition, in situ hybridization has revealed that expression of osteocalcin and osteopontin occurs predominantly in cells associated with the developing nodules. In contrast, proliferating rat osteosarcoma cells (ROS 17/2.8) concomitantly express histone H4, along with osteopontin and osteocalcin. These in situ analyses of gene expression during osteoblast growth and differentiation at the single cell level establish that a population of proliferating calvarial-derived cells subsequently expresses osteopontin and osteocalcin in cells developing into multilayered nodules with a tissue-like organization.
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PMID:Expression of cell growth and bone specific genes at single cell resolution during development of bone tissue-like organization in primary osteoblast cultures. 164 67

Osteoblast-like osteosarcoma cells (ROS 17/2.8) display a rapid transmembrane influx of extracellular calcium after stimulation by 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] that is mediated largely by the opening of voltage-gated calcium channels. These cells also constitutively express high numbers (greater than 18,000/cell) of nuclear receptors for this seco-steroid hormone that are involved in the modulation of genomic activity in the osteoblast and in the up-regulation of transcript ion of osteoblast-specific genes such as osteocalcin. The objective of this study was to determine the structural hierarchy of vitamin D3 analogs with regard to their efficacy as molecular transducers of the genomic and nongenomic pathways that are activated upon treatment of osteoblasts with 1,25-(OH)2D3. To test the structural features of the agonist required for initiation of these distinct pathways, a series of ligand analogs and naturally occurring metabolites of 1,25-(OH)2D3 were used that contain A-ring, D-ring, and side-chain modifications. The abilities of these analogs/metabolites to 1) bind to nuclear receptors and 2) stimulate transmembrane calcium influx were measured. Several analogs (25-hydroxy-16-ene-23-yne-D3 and 25-hydroxy-23-yne D3) were found to stimulate Ca2+ channel opening, but bind only poorly to the 1,25-(OH)2D3 nuclear receptor. Conversely, other analogs (1,24-dihydroxy-22-ene-24-cyclopropyl D3 and 1,25-dihydroxy-16-ene-23-yne,26,27 F6-D3) were found to bind very well to the nuclear receptor, but displayed little or no activity in opening Ca2+ channels. Pertussis toxin, which interferes with coupling of certain ligand-gated receptors to ion channels, failed to block the activation of calcium channels by 1,25-(OH)2D3 or active agonist analogs. Our results indicate that there are likely to be distinct nuclear and plasma membrane-associated forms of the 1,25-(OH)2D3 receptor that are involved in genomic and nongenomic activation of osteoblast activity, respectively. The membrane-associated receptors do not appear to be coupled to pertussis toxin-sensitive G-proteins.
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PMID:Nongenomic actions of 1,25-dihydroxyvitamin D3 in rat osteosarcoma cells: structure-function studies using ligand analogs. 165 87


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