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)

Cyclic AMP production by freshly isolated cells, from a 32P-induced transplantable rat osteogenic sarcoma, was stimulated by PGE1, PGE2 and to a less extent by PGF2alpha and PGA2. In the case of PGE2, the cyclic AMP content of cells was maximal within 5 min. The 13,14-dihydroderivatives of PGE1, PGE2 and PGF2alpha had approximately 40% of the activity of the parent prostaglandin whilst, in every case, the metabolites (15-keto and 13,14-dihydro-15-keto) had very little activity. Two prostaglandin endoperoxide analogues (U44069 and U46619) had only 10% of the activity of an equimolar dose of PGE2. The data presented in this paper demonstrates similarities between the responses of these cells and cells derived from bony tissue in terms of the ability of prostaglandins to stimulate bone resorption in tissue culture.
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PMID:Rat osteogenic sarcoma cells:effects of some prostaglandins, their metabolites and analogues on cyclic AMP production. 19 86

Adenylate cyclase activity in particulate fractions from a transplantable rat osteogenic sarcoma was stimulated in a dose-dependent manner by prostaglandins E1 and E2 (PGE1 and PGE2) and parathyroid hormone (PTH). Prostaglandin F2alpha was active at a high concentration (3 x 10(-4) mol/l). Pretreatment of membranes with collagenase plus hyaluronidase reduced the magnitude of the PTH effect but did not affect the size of the PGE1 effect. Guanosine 5'-triphosphate and its synthetic analogue 5'-guanylylimidodiphosphate (Gpp(NH)p) activated adenylate cyclase in particulate preparations from the osteogenic sarcoma. The latter agent produced much larger effects, although the concentrations required for half-maximal enzyme activation were the same for both agonists (approximately 2 x 10(-6) mol/l). The effects of PTH and Gpp(NH)p were supra-additive at some concentrations of hormone. The effects of PGE1 and Gpp(NH)p were supra-additive at all hormone concentrations tested. Pre-incubation of membrane particles for 6 min with PTH produced an enzyme activation which was not reversed by dilution through washing; pre-incubation with PGE1 did not produce this effect. The response of membrane adenylate cyclase to Gpp(NH)p (10(-4) mol/l) was 75% greater in preparations pre-incubated with PTH than in membranes pre-incubated in buffer alone or in buffer containing PGE1. The basal rate of cyclic AMP production in the adenylate cyclase assay system decreased over a 35 min incubation period. This decrease was prevented by addition of PTH or PGE1. Addition of NaF or Gpp(NH)p produced a steady increase in the rate of production of cyclic AMP with time. Membrane preparations did not reduce the biological activity of PTH and did not degrade 125I-labelled PTH. The results demonstrate that the PTH- and PGE-responsive adenylate cyclases of the osteogenic sarcoma have distinctly different properties and that particulate preparations of the tumour do not metabolize PTH.
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PMID:Membranes from a transplantable osteogenic sarcoma responsive to parathyroid hormone and prostaglandins: regulation of adenylate cyclase and of hormone metabolism. 27 36

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

Prostaglandin E2 (PGE2), PTH, and epidermal growth factor (EGF) are potent regulators of osteoblast proliferation. In UMR 106-01 rat osteosarcoma cells with osteoblast-like features, PGE2 and PTH inhibit, while EGF stimulates, mitogenesis. Both PGE2 and PTH increase intracellular cAMP levels, cytosolic calcium, and inositol phosphate turnover. In a variety of cell types, EGF mediates its effects in part via activation of receptor protein-tyrosine kinase and other protein kinases, such as protein kinase-C. The nuclear mechanisms of PGE2, PTH, and EGF regulation of osteoblast proliferation are unknown. Accordingly, we have examined the effects of these agents on mitogenesis, second messenger generation, and primary response genes, which may link second messenger activation to subsequent alterations in gene expression. Northern blot analysis of mRNA from UMR 106-01 cells treated for 3 h with 2 microM PGE2, 10 nM PTH, or 10 ng/ml EGF in the presence of cycloheximide demonstrated that all three agents induced the expression of c-fos and c-jun mRNA. In contrast, only EGF stimulated cellular proliferation and induced Egr-1 mRNA. Also, unlike PGE2 and PTH, EGF did not increase intracellular cAMP levels. c-fos mRNA was induced by treatment with 50 ng/ml tetradecanoyl phorbol acetate or by 40 ng/ml forskolin, while induction of Egr-1 mRNA was stimulated by treatment with tetradecanoyl phorbol acetate, but not forskolin. Thus, EGF signal transduction differs from that of PGE2 and PTH in UMR 106-01 osteoblast-like cells, in that EGF does not stimulate the protein kinase-A second messenger system, but causes activation of Egr-1, a primary response gene that may play a role in the mitogenic effect of EGF.
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PMID:The effects of prostaglandin E2, parathyroid hormone, and epidermal growth factor on mitogenesis, signaling, and primary response genes in UMR 106-01 osteoblast-like cells. 133 Apr 91

We present evidence that the regulation of osteocalcin secretion by PTH and PGE2 in normal human bone cells can be produced in the human osteoblast-like cell line MG-63. Both cell cultures showed time- and dose-dependent stimulation of osteocalcin secretion in response to 1,25(OH)2D3. Bovine parathyroid hormone (PTH) amino acid fragment 1-34 (40 nM) and prostaglandin E2 (PGE2, 5 nM) significantly inhibited 1,25(OH)2D3-induced osteocalcin secretion by these cells. The inhibition reached 20 and 36%, respectively. In contrast, PTH 3-34 had no effect on osteocalcin secretion. Both cell cultures produced cAMP in response to PTH. Dexamethasone (Dex) (100 nM) potentiated PTH-induced (40 nM) cAMP synthesis in subconfluent MG-63 cells (1.5-fold increase, P less than 0.05). This treatment with Dex resulted in a greater inhibition of 1,25(OH)2D3-induced osteocalcin secretion (-30%, P less than 0.005) by PTH in MG-63 cells as compared to cells exposed to PTH and 1,25(OH)2D3 alone. Pretreatment of subconfluent MG-63 cells with Dex (100 nM) for 48 h also increased 1,25(OH)2D3-induced osteocalcin secretion by 40% (P less than 0.025). In contrast, treatments of confluent MG-63 cells with Dex inhibited osteocalcin secretion regardless of the 1,25(OH)2D3 doses used. Forskolin (10(-7)-10(-5) M) and dibutyryl cAMP (10(-6)-(10(-3) M) both reproduced the effects observed with PTH and PGE2 in the two cell cultures. Forskolin's action was time-dependent: addition of forskolin (10(-6) M) 12 h after 1,25(OH)2D3 (50 nM) resulted in a progressively weaker inhibition of osteocalcin secretion. Increasing the extracellular calcium concentration of the incubation media resulted in a dose-dependent increase in osteocalcin secretion (P less than 0.01). These results indicate that PTH and PGE2 inhibit osteocalcin secretion by a mechanism involving cAMP production. In contrast, an increase in extracellular calcium stimulated osteocalcin release. Thus the human osteosarcoma cell line MG-63 is a useful osteoblast-like cell model to study the regulation of osteocalcin secretion. Furthermore, a factor (or factors) between hormone-receptor coupling and gene induction can regulate the expression of the osteocalcin gene or affect pre- or posttranslational mechanisms implicated in osteocalcin synthesis and secretion.
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PMID:Regulation of osteocalcin secretion by human primary bone cells and by the human osteosarcoma cell line MG-63. 165 56

Production of proteolytic enzymes by osteoblasts is considered to be important for the initiation of osteoclastic bone resorption. We examined the production of tissue-type (tPA) and urokinase-type plasminogen activator (uPA) activity by three types of osteoblast-like cells (normal rat osteoblasts, rat and human osteosarcoma cells) using a quantitative spectrophotometric assay and a qualitative gel overlay technique. All 3 types of cells released both types of PA-activity into the medium, but normal rat osteoblasts released uPA probably in an inactive form. Treatment with different concentrations of the bone resorbing factors bovine Parathyroid Hormone [1-84], synthetic human Parathyroid Hormone-Like Protein [1-34]. Prostaglandin E2, Interleukin-1 beta, Tumor Necrosis Factor alpha and 1,25-dihydroxyvitamin D3 increased in general the production of both PA's by all three cell types. However, there were differences in the relative potencies of these factors. In contrast, Transforming Growth Factor beta, which inhibits bone resorption, decreased PA-activity in osteoblast-like cells. In all three types of cells, under control as well as under stimulated conditions, a high molecular weight form of PA was demonstrated by the gel overlay technique, most likely a complex of tPA with the PA-inhibitor PAI-1. The uniform increase in production of PA's by osteoblast-like cells in response to bone resorbing factors and its decrease by TGF beta supports the notion that PA's are involved in bone resorption. The exact mechanism however, remains to be elucidated.
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PMID:Regulation of the production of plasminogen activators by bone resorption enhancing and inhibiting factors in three types of osteoblast-like cells. 193 92

IL-1 is a potent bone resorbing agent. Its mechanism of action is unknown, but the presence of osteoblasts was shown to be necessary for IL-1 stimulation of bone resorption by isolated osteoclasts. This study examines the presence of IL-1R and IL-1 effects in osteoblastic cells from a clonal human osteosarcoma cell line, Saos-2/B-10. We found that the binding affinity and the number of binding sites increases substantially during the postconfluent stage. Scatchard and curve-fitting analysis revealed one class of high affinity binding sites, with Kd/Ki's of 40 +/- 17 pM (mean +/- SD) for IL-1 alpha (n = 5) and 9 +/- 7 pM for IL-1 beta (n = 5) and 2916 +/- 2438 (n = 6) receptors/cell. Incubation of the cells with 125I-IL-1 alpha (100 pM) at 4 degrees C, followed by incubation at 37 degrees C up to 4 h, revealed internalization of receptor-bound IL-1 alpha. Chemical cross-linking studies showed that the IL-1R in Saos-2/B-10 cells had a molecular mass of approximately 80 kDa. To assess the biologic effect of IL-1 in Saos-2/B-10 cells, we determined PGE2 content and adenylate cyclase activity. Although IL-1 had no effect on PGE2 synthesis, both IL-1 alpha and IL-1 beta enhanced PGE2 stimulation of adenylate cyclase two- to four-fold in a dose-dependent manner. The half-maximal effect for IL-1 alpha was seen at 8 to 10 pM and for IL-1 beta at 0.6 to 1.8 pM. IL-1 did not enhance basal adenylate cyclase or stimulation by parathyroid hormone, isoproterenol, or forskolin. IL-1 enhancement of PGE2-stimulated adenylate cyclase was detected between 1 to 2 h, was maximal at 4 to 5 h, was not prevented by cycloheximide treatment, and was seen in membranes from IL-1 pretreated cells. These data show effects of IL-1 on a human osteoblast-like cell line that are mediated by high affinity receptors. These IL-1 effects could contribute to the biologic action of IL-1 on bone.
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PMID:IL-1 binds to high affinity receptors on human osteosarcoma cells and potentiates prostaglandin E2 stimulation of cAMP production. 216 11

In order to segregate multiple activities ascribed to IL-1, various human IL-1 alpha derivatives were produced by recombinant DNA technology. A derivative substituted at the 151st Asp with Tyr(termed to be TN-55) showed unique characteristics. TN-55 lost the PGE2 inducing activity in a human osteosarcoma cell line (MG-63) and growth promoting activity for a human dermal fibroblast cell line (CCD-27Sk), but partially remained LAF activity in mouse thymocyte, cytostatic activity against a human melanoma cell line (A-375) and IL-2 inducing activity in a human T cell line (HSB.2). Although TN-55 bound to the receptor on MG-63 cells with a similar affinity as native IL-1 alpha, TN-55 not only failed in inducing PGE2 production but also antagonized the PGE2 inducing action of IL-1 alpha or IL-1 beta. Thus, TN-55 seems to work as a receptor antagonist. Moreover, TN-55 did not stimulate ACTH secretion in rats in vivo. On the other hand, TN-55 induced PGE2 production in a rabbit dermal fibroblast cell line (RAB-9) and exhibited pyrogenicity in rabbits in vivo. These data suggest that TN-55 has different species-cross reactivity from native IL-1 alpha. In conclusion, multiple biological activities of IL-1 alpha can be segregated by substituting one amino acid. TN-55 may be an ideal IL-1 agonist which lacks inflammatory characteristics of IL-1 (e.g. PGE2-dependent activities) in human but partially retained T lymphocyte stimulating activity and tumor cytostatic activity. In addition, TN-55 may also work as an IL-1 antagonist to block PGE2 production induced by IL-1 through receptor competition.
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PMID:A human IL-1 alpha derivative which lacks prostaglandin E2 inducing activity and inhibits the activity of IL-1 through receptor competition. 216 12

The human osteosarcoma cell line MG-63 has been used to study the production of the bone-specific protein, osteocalcin. In the absence of any stimuli, MG-63 cells secreted very low levels of osteocalcin. The secretion of osteocalcin started after a lag time of 10-12 h upon 1,25-(OH)2D3 treatment. Osteocalcin secretion was measured at doses as low as 0.03 nM (fourfold increase, p less than 0.05), and this activity increased further with higher doses of 1,25-(OH)2D3 to reach a plateau at 50 nM. The secretion increased transiently from very low levels in sparse cell cultures to peak values in subconfluent cultures (+/- 40%), two- to threefold above values obtained for confluent cells. Values for confluent cells average 55.9 +/- 2.0 ng/ml protein per 48 h. A similar behavior is observed for 1,25-(OH)2D3 receptor concentration under similar experimental conditions. Bmax increased transiently from sparse to subconfluent cell cultures (40-60% confluent) and reached values 50% lower in confluent cells. However, the receptor affinity was not affected by cell density. MG-63 cells also possessed an alkaline phosphatase isoenzyme of the bone-liver-kidney type that was stimulated by 1,25-(OH)2D3 treatment (two- to threefold) and inhibited by parathyroid hormone (40 nM, -25%, p less than 0.025). PTH and PGE2 increased cAMP production in a dose-dependent manner, but the cells were irresponsive to salmon calcitonin. Basal and PTH-responsive cyclic AMP production were also modulated by cell density. Dexamethasone pretreatment (100 nM, 48 h) stimulated the PTH-dependent cAMP production but failed to influence the response to PGE2.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Osteocalcin secretion by the human osteosarcoma cell line MG-63. 217 53

The recent demonstration of estrogen receptors in bone derived cells has stimulated the study of direct effects of sex steroids on bone. We have shown direct stimulation of proliferation by 17 beta-estradiol (E2) of ROS 17/2.8 rat osteogenic osteosarcoma cells, and other bone-derived cells in culture, as well as sex-specific stimulation of diaphyseal bone in vivo by estrogen and testosterone, using [3H]thymidine incorporation into DNA and stimulation of the specific activity of creatine kinase as markers. ROS 17/2.8 cells were used as models of osteoblast-like cells to study the reciprocal modulation of stimulation of bone cell proliferation by sequential treatment by sex steroid and calciotrophic hormones. Pretreatment with 1,25(OH)2D3 and PTH augmented stimulation by E2, while pretreatment with PGE2 followed by E2 resulted in no additional stimulation. Reciprocally, pretreatment with E2 significantly reduced the response to PGE2 while showing an insignificant effect on the response to the other hormones. Gonadectomized Wistar-derived rats provided a useful model system for study of postmenopausal osteoporosis. In diaphyseal bone, [3H]thymidine incorporation and creatine kinase activity decreased 4 weeks after gonadectomy. At that time, a single i.p. injection of E2 in females, and testosterone in males, resulted in a highly significant increase in both these parameters within 24 h.
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PMID:Hormonal stimulation of bone cell proliferation. 225 46


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