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)

Bone sialoprotein (BSP) is a noncollagenous matrix glycoprotein localized predominantly in mineralized tissues but also detected in extraskeletal sites undergoing focal mineralization. We have previously characterized the human BSP gene and have shown that the upstream sequence contains inverted TATA and CCAAT motifs at the expected locations from the transcriptional start site (J. M. Kerr et al. [13]) and a potential YY1 binding motif located within the first 30 bp of intron 1 of the human gene. Deletion analyses of the human BSP promoter/exon 1 sequence fused to a CAT reporter gene indicate that CCAAT enhances basal transcription of BSP in transiently transfected rat UMR106-01 BSP osteosarcoma and rat skin fibroblasts. Though this enhancing activity was lost with inclusion of 68 bp of intron containing a YY1 motif in these constructs, reporter activity in the UMR106-01-BSP cells was elevated four- to seven-fold relative to that of rat fibroblasts. Gel electrophoretic mobility shift, UV-crosslinking, and south-western experiments indicate that YY1 is present only in the extracts of nuclei isolated from the UMR cells and may contribute to the elevated transcriptional activity of the human BSP promoter construct in UMR106-01-BSP.
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PMID:The human bone sialoprotein gene contains an NF-E1/YY1 cis-acting sequence with putative regulatory activity. 906 66

The regulation of osteocalcin gene transcription is complex, involving multiple positive and negative regulators. Previous studies have demonstrated that an intronic sequence, TTTCTTT (+118 to +124) is capable of mediating transcriptional repression of osteocalcin-CAT fusion genes in cells of the osteoblast lineage, by interacting with a specific nuclear protein. Further analyses of intronic sequences have identified a second silencer motif in this region. Two copies of a CCTCCT motif are present within the first intron of the rat osteocalcin gene (+106 to +111 and +135 to +140) and are capable of mediating transcriptional repression of osteocalcin-CAT fusion genes in rat osteosarcoma cells. Transient gene expression assays of wild-type and mutant osteocalcin-CAT fusion genes into ROS 17/2.8 cells demonstrate that mutagenesis of either of these CCTCCT motifs in isolation results in a 1.6-fold increase in CAT activity relative to the parent fusion gene. Moreover, a 5-fold increase in reporter gene activity is observed when both motifs are mutated together. These sequences are also capable of suppressing osteocalcin promoter activity when placed upstream to the osteocalcin promoter. Gel retardation and southwestern analyses demonstrate that the CCTCCT motifs interact with specific proteins present in nuclear extracts from ROS 17/2.8 and UMR 106 osteosarcoma cells but not COS-7 kidney cells. Mutations that abolish suppressor function of this motif markedly impair interactions with this specific nuclear protein. These data demonstrate that at least two different silencer motifs (TTTCTTT and CCTCCT) in the first intron of the rat osteocalcin gene contribute to its transcriptional repression.
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PMID:Transcriptional repression of the rat osteocalcin gene: role of two intronic CCTCCT motifs. 1046 84

Insulin-like growth factor-binding protein-5 (IGFBP-5) is produced by osteoblasts and potentiates insulin-like growth factor mitogenic stimulation in osteoblast cell cultures. Progesterone (PG) increased IGFBP-5 expression in normal human osteoblasts and increased IGFBP-5 transcription in U2 human osteosarcoma cells. We developed a chloramphenicol acetyltransferase reporter construct containing the human IGFBP-5 proximal promoter sequence, which includes TATA and CAAT boxes, and five putative PG response element half-sites. 10(-8) M PG increased promoter activity of this construct in U2 cells co-transfected with a PG receptor isoform A (PR(A)) expression vector. Analysis of 5' deletion constructs indicates that PG transactivation of IGFBP-5 promoter activity does not require the PG response element half-sites but does require the region -162 to -124 containing two tandem CACCC box sequences. Mutation of the proximal CACCC box at -139 eliminated PG transactivation. Gel shift assays using a -162 to -124 DNA fragment, U2 cell nuclear extracts, and purified PR(A) protein indicate that nuclear factors bind to a CACCC sequence at -139 and that PR(A) alters the pattern of transcription factor interaction with the CACCC sequence. Using a luciferase reporter construct containing base pairs -252 to +24 of the IGFBP-5 promoter, we found that both PR(A) and PR(B) isoforms mediated PG stimulation of promoter activity. These results suggest that PG may stimulate IGFBP-5 gene transcription via a novel mechanism involving PR and CACCC-binding factors.
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PMID:Progesterone stimulation of human insulin-like growth factor-binding protein-5 gene transcription in human osteoblasts is mediated by a CACCC sequence in the proximal promoter. 1047 2

Developmental control of bone tissue-specific genes requires positive and negative regulatory factors to accommodate physiological requirements for the expression or suppression of the encoded proteins. Osteocalcin (OC) gene transcription is restricted to the late stages of osteoblast differentiation. OC gene expression is suppressed in nonosseous cells and osteoprogenitor cells and during the early proliferative stages of bone cell differentiation. The rat OC promoter contains a homeodomain recognition motif within a highly conserved multipartite promoter element (OC box I) that contributes to tissue-specific transcription. In this study, we demonstrate that the CCAAT displacement protein (CDP), a transcription factor related to the cut homeodomain protein in Drosophila melanogaster, may regulate bone-specific gene transcription in immature proliferating osteoblasts. Using gel shift competition assays and DNase I footprinting, we show that CDP/cut recognizes two promoter elements (TATA and OC box I) of the bone-related rat OC gene. Overexpression of CDP/cut in ROS 17/2.8 osteosarcoma cells results in repression of OC promoter activity; this repression is abrogated by mutating OC box I. Gel shift immunoassays show that CDP/cut forms a proliferation-specific protein/DNA complex in conjunction with cyclin A and p107, a member of the retinoblastoma protein family of tumor suppressors. Our findings suggest that CDP/cut may represent an important component of a cell signaling mechanism that provides cross-talk between developmental and cell cycle-related transcriptional regulators to suppress bone tissue-specific genes during proliferative stages of osteoblast differentiation.
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PMID:The CCAAT displacement protein/cut homeodomain protein represses osteocalcin gene transcription and forms complexes with the retinoblastoma protein-related protein p107 and cyclin A. 1060 45

Studies performed at tissular (three-dimensional, 3-D) or cellular (two-dimensional, 2-D) levels showed that the loading pattern plays a crucial role in the osteoblastic physiology. In this study, we attempted to investigate the response of a 3-D osteoblastic culture submitted to either no external stress or static or dynamic stresses. Rat osteosarcoma cells (ROS 17/2.8) were embedded within collagen type I lattices and studied for 3 weeks. Entrapment and proliferation of cells within the hydrated collagen gel resulted in the generation of contractile forces, which led to contraction of the collagen gel. We used this ability to evaluate the influence of three modes of mechanical stresses on the cell proliferation and differentiation: (1) the freely retracted gels (FRG) were floating in the medium, (2) the tense gels (TG) were stretched statically and isometrically, with contraction prevented in the longitudinal axis, and (3) the dynamic gels (DG) were floating gels submitted to periodic stresses (50 or 25 rpm frequency). Gels showed maximum contraction at day 12 in 50 rpm DG, followed by 25 rpm DG, then FRG (88%, 81%, 70%, respectively) and at day 16 in TG (33%). The proliferation rate was greater in TG than in FRG (+52%) but remained low in both DGs. Gel dimensions were related to the collagen concentration and on a minor extent to cell number. Cells in DG appeared rounder and larger than in other conditions. In TG, cells were elongated and oriented primarily along the tension axis. Scanning electron microscopy (SEM) showed that tension exerted by cells in TG led to reorientation of collagen fibers which, in turn, determined the spatial orientation and morphology of the cells. Transmission electron microscopy (TEM) performed at maximum proliferation showed a vast majority of cells with a distended well-developed RER filled with granular material and numerous mitochondria. Alkaline phosphatase activity peaked close to the proliferation peak in FRG, whereas in TG, a biphasic curve was observed with a small peak at day 4 and the main peak at day 16. In DG, this activity was lower than in the two other conditions. A similar time course was observed for alkaline phosphatase gene expression as assessed by Northern blots. Regardless of the conditions, osteocalcin level showed a triphasic pattern: a first increase at day 2, followed by a decrease from day 4 to 14, and a second increase above initial values at day 18. Microanalysis-x indicated that mineralization occurred after 14 days and TEM showed crystals within the matrix. We showed that static and dynamic mechanical stresses, in concert with 3-D collagen matrices, played a significant role on the phenotypic modulation of osteoblast-like cells. This experimental model provided a tool to investigate the significance and the mechanisms of mechanical activity of the 3-D cultured osteoblast-like cells.
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PMID:Effects of static or dynamic mechanical stresses on osteoblast phenotype expression in three-dimensional contractile collagen gels. 1061 39

While sequencing the first intron of the rat heat shock protein 27 gene (hsp27), we identified a consensus heat shock regulatory element (HSE). This intronic HSE (i-HSE) is conserved among mammalian hsp27 genes. The aim of this study was to investigate possible effects of this intronic HSE (i-HSE) on transcription from the rat hsp27 promoter. Gel mobility shift assays indicated that the i-HSE bound heat shock transcription factor 1 (HSF1) in a manner equivalent to that of HSE present in hsp27 promoter (p-HSE). The effect of i-HSE on transcription from the hsp27 promoter was evaluated using reporter constructs transiently transfected in the osteosarcoma cell line ROS17/2.8. When inserted 5' to a 145 bp fragment of the hsp27 promoter not containing p-HSE, a 215 bp fragment of hsp27 intron 1 containing i-HSE enhanced CAT activity and conferred heat shock-inducible activity to the construct. This intronic fragment containing i-HSE also enhanced CAT activity in either normal or heat-shocked culture conditions when inserted 3' to the CAT open reading frame. However, in chimeric reporter constructs with a 273 bp hsp27 promoter containing p-HSE directly 5' to CAT reporter, and with a 215 bp fragment containing i-HSE inserted 3' to the CAT open reading frame, transcription from hsp27 promoter was reduced under normal and heat-stressed culture conditions. Mutation of the i-HSE reversed this effect. Further study is required to define the mechanism by which the i-HSE-containing region of the hsp27 promoter may mediate negative regulation of hsp27 transcription.
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PMID:Transcriptional regulation involving the intronic heat shock element of the rat hsp27 gene. 1068 80

Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are important growth factors for postnatal longitudinal bone growth. Although many effects of GH on bone growth are mediated by IGF-1, GH can directly influence bone cells. Limited knowledge exists regarding specific intracellular signaling pathways and genes activated by GH in bone cells. GH is known to activate several intracellular signaling pathways, among them the Janus kinase (JAK)/signal transducers and activators of transcription (STAT) pathway. GH mainly activates JAK2 and both isoforms of STAT5, A and B. STAT5 gene deletion experiments have shown the importance of these transcription factors for growth. To understand the molecular mechanism(s) behind this, different experimental models are needed. The UMR 106 cell line is a rat clonal osteosarcoma cell line with osteoblast-like phenotypic properties, one is the endogenous expression of GH receptor (GHR). The present study focused on whether these cells express a functional GH-responsive JAK2/STAT5 pathway. Analysis of cell extracts by immunoprecipitation and Western blot showed that physiological concentrations of GH activated JAK2. Western blot analysis of nuclear extracts from GH-stimulated UMR 106 cells showed that physiological concentrations of GH induced nuclear translocation of both STAT5 isoforms, but with STAT5A being predominant. Both isoforms displayed similar nuclear turnover after GH stimulation of cells. Gel electrophoretic mobility shift assay (GEMSA) of nuclear extract revealed that both STAT5A and STAT5B obtained DNA-binding capacity after GH stimulation. Thus, we have shown, for the first time, the expression and GH-induced activation of JAK2 and STAT5A/B in UMR 106 osteoblast-like cells. This study also shows that this cell line is a suitable experimental model to study unique GH effects in osteoblasts mediated by STAT5.
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PMID:Growth hormone-regulated intracellular signaling in UMR 106 osteosarcoma cells. 1109 11

Tumor necrosis factor-alpha (TNF-alpha) is a major mediator of inflammatory response in many diseases. It inhibits bone formation and stimulates bone resorption. To determine the molecular mechanisms involved in the regulation of gene expression of osteoblast-like cells, we analyzed the effects of TNF-alpha on the human osteosarcoma cell line Saos2. We used RT-PCR to examine the effects of TNF-alpha on bone sialoprotein (BSP), core binding factor a1 (Cbfa1), osterix, alpha 1 (I) collagen, cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), cathepsin B, cathepsin L and tissue inhibitors of metalloproteinase-1 (TIMP-1). TNF-alpha (10ng/ml) increased BSP, IL-6 and COX-2 mRNA levels after 3h, reaching maximal levels at 12 h. Cbfa1 mRNA levels increased after 3 h, but decreased by 24 h. Osterix, cathepsin B, cathepsin L and TIMP-1 mRNA levels did not change after stimulation with TNF-alpha. On the other hand, alpha 1 (I) collagen mRNA expression was suppressed by TNF-alpha at 24 h. Transient transfection analyses were performed using chimeric constructs of the rat BSP gene promoter linked to a luciferase reporter gene. TNF-alpha (10 ng/ml) had no effect on the promoter activities of BSP transfected into Saos2 cells. The results of gel mobility shift assays using radiolabeled double-stranded cAMP response element (CRE) and FGF2 response element (FRE) oligonucleotides in the proximal promoter of the rat BSP gene showed increased binding of nuclear proteins at 6 h. Gel mobility shift assays with radiolabelled COX-2-CRE and COX-2-NF kappa B oligonucleotides revealed an increase in the binding of nuclear proteins from TNF-alpha-stimulated Saos2 cells. These studies, therefore, showed that TNF-alpha indirectly increased BSP expression, and that it could be mediated through COX-2 and Cbfa1 expression in Saos2 osteoblast-like cells.
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PMID:Effect of TNF-alpha on human osteosarcoma cell line Saos2--TNF-alpha regulation of bone sialoprotein gene expression in Saos2 osteoblast-like cells. 1551 23

Osteoclasts (OCs) are involved in several pathologies associated with bone loss, including rheumatoid arthritis, osteoporosis, bone metastasis of myeloma, osteosarcoma, and breast cancer. In this review we determined the effects of natural compounds, including extracts from medicinal plants, on differentiation and survival of human primary OCs obtained from peripheral blood. We found that OCs from umbilical cord blood and peripheral blood behave differently in response to molecules inducing apoptosis in this experimental system. Apoptosis induced by decoy oligonucleotides was reproducibly obtained in OCs from peripheral blood but not in OCs derived from cord blood. With respect to effects of medicinal plants, we found that crude extracts of Emblica officinalis are able to induce specifically programmed cell death of mature OCs without altering the process of osteoclastogenesis. E. officinalis specifically increased the expression levels of Fas, a critical member of the apoptotic pathway. Gel shift experiments BioPharmaNet demonstrate that E. officinalis extracts specifically compete with the binding of a transcription factor involved in osteoclastogenesis NF-kappaB to its specific target DNA sequences. This might explain the observed effects of E. officinalis on the expression levels of IL-6, an NF-kappaB-specific target gene. We suggest the application of natural products as an alternative tool for therapy applied to bone diseases.
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PMID:Apoptosis of human primary osteoclasts treated with molecules targeting nuclear factor-kappaB. 1972 88

In recent years, in situ chemotherapy mediated by biodegradable polymer platforms has attracted increased attention. Herein, an advanced drug delivery system, combretastatin A-4 (CA4) and docetaxel (DTX)-loaded microsphere embedded in injectable thermosensitive polypeptide hydrogel (i.e., hydrogel-microsphere (Gel-MP) construct), was reported for sequential release of drugs with different mechanisms to treat osteosarcoma synergistically. The Gel-MP construct showed sequential biodegradability and excellent biocompatibility. CA4 was preferentially released from hydrogel with faster degradation to disturb the vascular structure of the tumor and reduce the exchange of nutrients between the tumor and surrounding tissues, which created interstitial space in the tissue for DTX penetration to inhibit tumor cell proliferation. The in vivo treatment with Gel/CA4-MP/DTX efficiently suppressed the growth of mouse K7 osteosarcoma compared to other formulations. More importantly, by systematical study of histopathology and immunohistochemistry, the Gel-MP construct can significantly upregulate antiproliferation effect and reduce toxicity of drugs. Therefore, this injectable and locally sequential delivery system has a bright prospect in clinical application of in situ synergistic chemotherapy.
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PMID:Injectable Hydrogel-Microsphere Construct with Sequential Degradation for Locally Synergistic Chemotherapy. 2806 93


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