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

The mechanisms by which glucocorticoids (GC) inhibit some actions of vitamin D [1,25-(OH)2D3] are not well understood, but there is growing evidence that GC alter vitamin D receptor (VDR) number. We studied the effects of dexamethasone (DEX) on VDR number and mRNA in the human osteosarcoma cell line, MG-63. The effects of DEX on 1,25-(OH)2D3 binding were examined by incubating confluent cells overnight in media without or with 10(-6) M DEX. DEX decreased VDR number (B max) by approximately 70% (110 versus 32 fmol/mg cellular protein, p less than 0.001) without significantly changing the apparent affinity (K'D) of 1,25-(OH)2D3 for its receptor (3.8 versus 2.2 x 10(-10) M, p greater than 0.05). Overnight incubation of MG-63 cells with DEX produced a time- and dose-responsive decrease in VDR mRNA compared to untreated controls (p less than 0.01). To determine the mechanism of the DEX-mediated decrease in VDR mRNA, the effect of DEX on VDR mRNA stability was studied. We found that the half-life for the VDR mRNA was approximately 5.7 h and was not significantly changed when the cells were incubated with DEX (approximately 6.3 h). We conclude that DEX decreases both VDR number and mRNA in MG-63 osteosarcoma cells. Since the half-life of VDR mRNA was not significantly modified by dexamethasone, glucocorticoids appear to decrease VDR mRNA by inhibiting VDR gene transcription or by affecting the processing of VDR mRNA.
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PMID:Glucocorticoids decrease vitamin D receptor number and gene expression in human osteosarcoma cells. 131 60

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

We have used a monoclonal antibody (9A7) against the purified avian 1,25-dihydroxyvitamin D3 receptor to develop an immunocytochemical technique for visualization of the protein in fixed tissues and cultured cells. In Bouin's-fixed, chick intestine, 1,25-dihydroxyvitamin D3 receptor-like immunoreactivity was localized mainly in nuclei of epithelial cells and was more abundant in the crypt than in the villar cells. Receptor staining was low or undetectable in liver hepatocytes but was present in nuclei of cells lining the hepatic sinusoids. In rat brain, receptor-like immunoreactivity was abundant and widely distributed, but did not always coincide with the presence of vitamin D-dependent calcium-binding protein; 1,25-dihydroxyvitamin D3 receptor was absent from cerebellar Purkinje cells that contained abundant calcium-binding protein. In disaggregated rat bone cells, receptor immunoreactivity was present in mononuclear cells including osteoblasts and fibroblasts but was absent from osteoclasts. Two separate clones of osteoblast-like, rat osteosarcoma cells, shown in previous studies to be either receptor positive (17/2.8) or negative (24.1), demonstrated nuclear immunoreactivity in exact concordance with receptor levels as determined by ligand binding. The phenomenon of hormone-induced up-regulation of receptor was visualized in receptor-positive 3T6 fibroblasts by demonstration of markedly enhanced nuclear reactivity in cells treated with 10(-7) M 1,25-dihydroxyvitamin D3 for 48 h. Our studies demonstrate the feasibility of the immunocytochemical approach to visualize the 1,25-dihydroxyvitamin D3 receptor in target tissues and show that it is predominantly a nuclear protein in the relatively unoccupied and fully activated states. Moreover, the vitamin D-dependent calcium binding is not a universal marker for 1,25-dihydroxyvitamin D3 action. Rather, our observations suggest that the expression of the 1,25-dihydroxyvitamin D3 receptor may be connected with the state of cellular differentiation.
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PMID:Immunocytochemical localization of the 1,25-dihydroxyvitamin D3 receptor in target cells. 283 Oct 24

The effect of 1,25-dihydroxyvitamin D3 on adenylate cyclase responsiveness was studied in the clonal osteogenic sarcoma cell line, UMR 106-06, which responds to several bone active hormones. 1,25-dihydroxyvitamin D3 treatment had no consistent effect on basal formation of cyclic AMP in intact cells, but the responses to parathyroid hormone, isoproterenol, prostaglandin E2, salmon calcitonin and the plant diterpene, forskolin, were all attenuated, by up to 90%. The effect of 1,25-dihydroxyvitamin D3 was dose-dependent, with half-maximal effectiveness at 0.1 nM, and required 48 h treatment of cells before it became apparent. The relative potencies of other vitamin D3 compounds correlated closely with their relative affinities for the 1,25-dihydroxyvitamin D3 receptor and their biological activities in other systems. 1,25-dihydroxyvitamin D3 treatment had no effect on the kinetics of labelled calcitonin binding to UMR 106-06 cells. Furthermore, the fact that such a range of hormones was affected made a receptor mediated mechanism unlikely. Nucleotide stimulatory (Ns) unit activity was assayed after 1,25-dihydroxyvitamin D3 treatment and found to be unchanged. Islet activating protein, an inhibitor of nucleotide inhibitory unit (Ni) activity, failed to modify the 1,25-dihydroxyvitamin D3 effect. Thus the effect of 1,25-dihydroxyvitamin D3 appeared to be exerted beyond hormone receptor and nucleotide regulatory components of the adenylate cyclase complex. It is concluded that 1,25-dihydroxyvitamin D3 attenuates adenylate cyclase response to hormones by a direct or indirect action on the catalytic component of adenylate cyclase.
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PMID:Effect of 1,25-dihydroxyvitamin D3 on cyclic AMP responses to hormones in clonal osteogenic sarcoma cells. 299 36

The human T cell lymphotrophic virus type I (HTLV-I) has recently been identified in a T cell lymphoma associated with hypercalcemia and increased bone turnover. Since increased serum concentrations of 1,25-dihydroxyvitamin D have been reported in this disease, we have examined the capacity of HTLV-I-infected cord blood lymphocytes to metabolize 25-hydroxyvitamin D3. Our results demonstrate that HTLV-I-infected cells have the capacity to metabolize 25-hydroxyvitamin D3 to a substance that co-migrates with 1,25-dihydroxyvitamin D3 by high performance liquid chromatography over a silica column using either 12% isopropanol in hexane or 5% isopropanol in dichloromethane. The metabolite binds to the 1,25-dihydroxyvitamin D3 receptor in rat osteosarcoma cells and stimulates bone resorption in cultures of fetal rat long bones. Mass spectrometric analysis of the metabolite confirmed the presence of 1,25-dihydroxyvitamin D3. Production of 1,25-dihydroxyvitamin D by lymphoma cells may contribute to the pathogenesis of the hypercalcemia seen in patients with HTLV-I-associated T cell lymphomas.
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PMID:Production of 1,25-dihydroxyvitamin D3 by human T cell lymphotrophic virus-I-transformed lymphocytes. 301 32

The classic function of 1,25-dihydroxyvitamin D3, the hormonally active form of vitamin D, is the maintenance of normal levels of calcium and phosphorus in the blood. 1,25-Dihydroxyvitamin D3 binds to a specific receptor protein and exerts its biologic action by a mechanism analogous to that proposed for other steroid hormones, that is, the receptor-ligand complex acts on the chromatin to induce transcription of specific genes. Intracellular receptors that bind 1,25-dihydroxyvitamin D3 with high affinity have been found in a large number of tumor cell lines examined as melanoma, osteosarcoma, and human breast and colonic carcinoma cells. The 1,25-dihydroxyvitamin D3 receptor in these cells has characteristics similar to the receptor in bone and intestine, the known target tissues of the hormone. In fact, 1,25-dihydroxyvitamin D3 inhibits the proliferation of melanoma, osteosarcoma, and breast carcinoma cells. More recently, 1,25-dihydroxyvitamin D3 has been shown to suppress the growth and induce monocytic differentiation of murine and human myeloid leukemia cells in vitro. These results point to a previously unsuspected involvement of vitamin D in cell proliferation and differentiation and suggest that analogs of the vitamin D hormone may be of interest as possible therapeutic agents in the treatment of malignancy.
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PMID:The relationship between the vitamin D system and cancer. 303

Two 1,25-dihydroxyvitamin D3-controlled parameters in the osteoblastlike osteosarcoma cell line ROS 17/2, bone gamma-carboxyglutamic acid-containing protein (BGP) and collagen synthesis, were measured after pretreatments with either retinoic acid (RA), or triamcinolone acetate (TRM). RA and TRM both caused double the expected increase in BGP secretion at 16 hr after treatment with 1,25-dihydroxyvitamin D3. Triamcinolone acetate concentrations of 10(-8) and 10(-9) M or 10(-6) M retinoic acid were effective in enhancing the 1,25-dihydroxyvitamin D3 stimulation of BGP secretion. Treatment with RA or TRM alone did not stimulate BGP secretion. RA alone had no effect on BGP secretion, while TRM inhibited BGP secretion. Collagen synthesis is inhibited by 1,25-dihydroxyvitamin D3. Neither retinoic acid nor triamcinolone acetate enhanced the 1,25-dihydroxyvitamin D3-mediated inhibition of collagen synthesis. Retinoic acid by itself inhibited collagen synthesis but did not change the 1,25 dihydroxyvitamin D3-mediated inhibition of collagen synthesis. Triamcinolone acetate by itself or together with 1,25-dihydroxyvitamin D3 increased collagen synthesis. We conclude that, although both triamcinolone acetate and retinoic acid increase the 1,25-dihydroxyvitamin D3 stimulation of BGP secretion by ROS 17/2 cells, they have different effects on the regulation of collagen production. Thus, although both hormones increase the 1,25-dihydroxyvitamin D3 receptor concentration in these cells, their actions are not mediated solely by this mechanism.
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PMID:Retinoic acid and glucocorticoids enhance the effect of 1,25-dihydroxyvitamin D3 on bone gamma-carboxyglutamic acid protein synthesis by rat osteosarcoma cells. 348 2

The effects of steroid and thyroid hormones are mediated by intracellular hormone receptors. An important mechanism modulating target tissue responsiveness to hormones is homologous and heterologous regulation of the receptors. We have characterized the expression of steroid hormone receptors in human MG-63 osteosarcoma cells. The MG-63 cells express receptor mRNAs for glucocorticoids, estrogen, retinoic acid, and 1,25(OH)2D3. We found that only the vitamin D receptor (VDR) mRNA concentration was influenced by the hormones. The stability of the VDR message was identical in control, dexamethasone- and estradiol-treated cells. On the other hand, both 1,25(OH)2D3 and retinoic acid separately stabilized the VDR mRNA levels increasing the apparent half-life by 11 h and 6 h, respectively. The VDR protein levels, however, as measured by immunoprecipitation, increased only after the 1,25(OH)2D3 treatment.
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PMID:Steroid hormone modulation of vitamin D receptor levels in human MG-63 osteosarcoma cells. 780 48

1,25-(OH)2-Vitamin D3, the active metabolite of vitamin D, is a secosteroid hormone with known differentiating activity in leukemic cells. Studies have demonstrated the presence of vitamin D receptors (VDR) in a wide range of tissues and cell types. Antiproliferative activity of 1,25-(OH)2-vitamin D3 has been documented in osteosarcoma, melanoma, colon carcinoma, and breast carcinoma cells. This study was designed to analyze vitamin D receptor level in breast cancer cells as a marker of differentiation and as a predictor of growth inhibition by 1,25-(OH)2-vitamin D3. VDR messenger RNA was found to be present in relatively high levels in well-differentiated cells and in low levels in poorly differentiated cells. All cell lines had detectable VDR mRNA. Radiolabeled ligand binding assay showed a similar pattern. MCF-7 and T47D cells, which express VDR at moderate levels, showed significant growth inhibition by 10(-9) M1,25-(OH)2-vitamin D3 (p < 0.05). MDA-MB-231 cells, which have very low levels of VDR, demonstrated no growth inhibition by 1,25-(OH)2-vitamin D3 at concentrations up to 10(-6) M. Based on these results it can be stated that VDR expression is lost with de-differentiation and that receptor is essential for the antiproliferative response to 1,25-(OH)2-vitamin D3.
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PMID:Vitamin D receptors in breast cancer cells. 788 Oct 99

The binding of transcription factor AP-1 and vitamin D receptor (VDR) to the composite AP-1 plus vitamin-D-responsive promoter region (AP-1 + VDRE) of the human osteocalcin gene was characterized in osteocalcin-producing (MG-63) and non-producing (U2-Os, SaOs-2) human osteosarcoma cell lines. In mobility-shift assays with AP-1 + VDRE, AP-1, and VDRE probes and nuclear extracts from these cells, one AP-1-specific and two VDR-specific (fast and slow mobility) interactions were observed. Characterization of the complexes indicated that AP-1 and VDR do not bind simultaneously to the AP-1 + VDRE oligonucleotide. Intensity of the complexes was greatly influenced by cell density: in MG-63 and SaOs-2 cells, AP-1 binding was strong during the proliferative period disappearing at confluency whereas, in U2-Os cells, AP-1 binding was prominent also at the confluent stage. Furthermore, MG-63 cells possessed the faster migrating VDR complex at all stages of confluency whereas, in U2-Os and SaOs-2 cells, it was very weak or absent. There were no detectable differences in the levels of VDR protein between these cell lines. In U2-Os cells, the level of c-jun mRNA was higher than in the other two cell lines, whereas none of these cell lines exhibited detectable levels of c-fos mRNA at the confluent stage. Exogenous c-Jun protein effectively blocked the VDR-DNA interaction. Further, all these cell lines expressed mRNA for retinoid X receptor alpha (RXR alpha), the factor suggested to be required for the VDR-DNA interaction. The presence of an accessory factor in the VDR-DNA complexes was indirectly shown by treatment of the cells with 9-cis retinoic acid and by cycloheximide. Both treatments reduced VDR binding without affecting the VDR protein level. These results suggest that AP-1 interferes with VDR binding to the AP-1 + VDRE element and that the vitamin D responsiveness of the osteocalcin gene correlates with weak AP-1 binding and strong binding of the faster migrating VDR complex.
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PMID:Functional interference between AP-1 and the vitamin D receptor on osteocalcin gene expression in human osteosarcoma cells. 807 31


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