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)

Procollagen and proteoglycan biosynthesis was defined in long-term culture of a human osteogenic sarcoma cell line, SAOS-2. An osteoblast phenotype was maintained by these cells up to 40 days post-confluent in the presence of ascorbic acid. Under these conditions, cells deposited around them an extensive collagenous matrix that was able to mineralize in the presence of an exogenous phosphate donor (beta-glycerophosphate). The collagenous matrix was comprised predominantly of collagen type I with significant amounts of collagen type V, and greater than 80% of the collagen in the matrix was involved in covalent crosslinkages. With increasing time in culture there was a decrease in the collagen synthetic rate, although the collagenous matrix was maintained. The proteoglycans synthesized by nonmineralizing and mineralizing cultures were purified after biosynthetic labeling with [35S]sulfate and [3H]glucosamine. Two major species were apparent: a large chondroitin sulfate proteoglycan (CSPG), and a small chondroitin sulfate proteoglycan, decorin. In nonmineralizing cultures, decorin partitioned equally between the cell layer and culture medium, whereas the large CSPG species partitioned exclusively into the cell layer-associated matrix. In the presence of extensive mineral deposition, greater than 90% of the newly synthesized proteoglycans were secreted into the medium. Northern blot hybridization indicated that SAOS-2 cells express mRNA encoding a range of bone proteins, including decorin, osteonectin, and bone sialoprotein.
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PMID:Matrix deposition by a calcifying human osteogenic sarcoma cell line (SAOS-2). 760 1

The small proteoglycan decorin is known to interact with type I collagen fibrils, thereby influencing the kinetics of fibril formation and the distance between adjacent collagen fibrils. The structurally related proteoglycan biglycan has been proposed not to bind to fibrillar collagens. However, when osteosarcoma cells were cultured on reconstituted type I collagen fibrils, both decorin and biglycan were retained by the matrix. Immunogold labeling at the electron microscopic level showed that both proteoglycans were distributed along collagen fibrils not only in osteosarcoma cell-populated collagen lattices but also in human skin. Reconstituted type I collagen fibrils were able to bind in vitro native and N-glycan-free biglycan as well as recombinant biglycan core protein. From Scatchard plots dissociation, constants were obtained that were higher for glycanated biglycan (8.7 x 10(-8) mol/liter) than for glycanated decorin (7 x 10(-10) mol/liter and 3 x 10(-9) mol/liter, respectively). A similar number of binding sites for either proteoglycan was calculated. Recombinant biglycan and decorin were characterized by lower dissociation constants compared with the glycanated forms. Glycanated as well as recombinant decorin competed with glycanated biglycan for collagen binding, suggesting that identical or adjacent binding sites on the fibril are used by both proteoglycans. These data suggest that, because of its trivalency, biglycan could have a special organizing function on the assembly of the extracellular matrix.
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PMID:Interaction of biglycan with type I collagen. 785 49

Previous studies had shown that binding of TGF-beta to the small proteoglycan decorin results in its inactivation. Indeed, in osteosarcoma cells the addition of decorin prevented the TGF-beta 1-mediated up-regulation of biglycan synthesis. However, the down-regulation of proteoglycan-100 remained unaltered. Even in the presence of a 100,000-fold molar excess of decorin, TGF-beta 1 was fully active in U937 monocytes with respect to the inhibition of cell proliferation. There was no inhibition of the TGF-beta-mediated stimulation of the retraction of fibroblast-populated collagen lattices. Thus, the formation of TGF-beta/decorin complexes leads to the neutralization of distinct effects only.
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PMID:Selective inactivity of TGF-beta/decorin complexes. 795 66

The expression of the large chondroitin sulfate proteoglycan versican was studied in human adult skin. For this purpose, bacterial fusion proteins containing unique portions of the versican core protein were prepared. Polyclonal antibodies against the fusion proteins specifically reacted with versican from a proteoglycan fraction of MG63 osteosarcoma cells. In immunohistochemical experiments, the affinity-purified antibodies localized versican in the stratum basale of the epidermis, as well as in the papillary and reticular layers of the dermis. An apparent codistribution of versican with the various fiber forms of the elastic network of the dermis suggested an association of versican with microfibrils. Both dermal fibroblasts and keratinocytes expressed versican in culture during active cell proliferation. In line with the observation that versican is absent in the suprabasal layers of the epidermis where keratinocytes terminally differentiate, culture conditions promoting keratinocyte differentiation induced a down-regulation of versican synthesis. In Northern blots versican mRNA could be detected in extracts from proliferating keratinocytes and dermal fibroblasts. Comparison of RNA preparations from semi-confluent and confluent fibroblast cultures demonstrated decreasing amounts of versican mRNA at higher cell densities. This inverse correlation of versican expression and cell density was confirmed by indirect immunofluorescence staining of cultured fibroblasts and keratinocytes. The localization of versican in the basal zone of the epidermis as well as the density dependence of versican in cell cultures suggest a general function of versican in cell proliferation processes that may not solely be confined to the skin.
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PMID:Versican is expressed in the proliferating zone in the epidermis and in association with the elastic network of the dermis. 812 Jan 2

The expression of the core proteins and the co-polymeric structure of the glycosaminoglycan chains of three different small proteoglycans (biglycan, decorin, proteoglycan-100) have been examined in the human osteosarcoma cell line MG-63. The three proteoglycans, which are carrying either one or two chondroitin/dermatan sulphate chains, were synthesized in a similar molar ratio, as determined by [35S]methionine as well as by [35S]sulphate incorporation. After sulphate ester formation, they were secreted into the culture medium with similar kinetics. Immune staining with monospecific antibodies revealed that at least biglycan and proteoglycan-100 were present in all individual cells. However, in contrast to these similarities, the glycosaminoglycan moiety of proteoglycan-100 was composed exclusively of chondroitin 4- and 6-sulphate repeating units, whereas biglycan and decorin contained hybrid polymers of chondroitin and dermatan sulphate with approximately 90% 4-sulphated disaccharide repeating units. Treatment with transforming growth factor-beta resulted in a marked down-regulation of proteoglycan-100 synthesis without significant alteration of its glycosaminoglycan structure. Up-regulation of biglycan and moderate down-regulation of decorin were accompanied by a small decrease in the conversion of chondroitin to dermatan sulphate disaccharide units in both cases. The specific stimulation of the biosynthesis of proteoglycan-100 by tumour necrosis factor-alpha was without consequence for its glycosaminoglycan composition. Treatment with tumour necrosis factor-alpha had no influence on the synthesis and glycosaminoglycan structure of biglycan and decorin. These findings support the proposal of the importance of the core protein for the determination of the extent of glycosaminoglycan modification.
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PMID:Different galactosaminoglycan composition of small proteoglycans from osteosarcoma cells. 813 Mar 87

An osteoblast-like cell line (UMR 106-01 BSP), cloned from a transplantable osteosarcoma, was cultured in the presence of parathyroid hormone (PTH1-34) and metabolically labeled with [35S]sulfate, [3H]glucosamine, and [3H]tyrosine to determine proteoglycan, glycoconjugate, and protein synthesis, respectively. The synthesis of secreted proteins was substantially increased by PTH treatment. However, the synthesis of bone sialoprotein and proteoglycans was, at best, only moderately stimulated by PTH. Hyaluronan (HA) synthesis was dramatically stimulated by PTH in this cell line. A 5-6-fold increase in HA production was observed using 10(-8) M PTH, and even a 50% increase was detected using 10(-10) M PTH. The PTH-induced stimulation of HA synthesis was rapid and transient, reaching a maximum level (approximately 560 pmol of HA disaccharide equivalents/h/10(6) cells at 10(-8) M PTH) by 4-7 h after hormone exposure and returning to control levels by 12-15 h after the initial treatment. Lastly, the majority of this HA synthesis stimulated by PTH required only a short exposure (< 90 min) to the hormone. These data suggest (i) that normal osteoblasts (or a subpopulation of preosteoblasts) probably synthesize HA in response to PTH treatment, and (ii) that this PTH-induced synthesis of HA most likely involves some signal transduction mechanism(s).
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PMID:Parathyroid hormone stimulates hyaluronan synthesis in an osteoblast-like cell line. 817 49

Decorin is a leucine-rich, chondroitin/dermatan sulfate proteoglycan which binds collagen and growth factors. We have recently completed the genomic organization of human decorin and discovered two alternatively spliced leader exons, designated exon Ia and Ib, in the 5'-untranslated region. Initial analysis of the sequences upstream to these two exons showed that promoter Ia contained only two GC boxes while promoter Ib contained a CAAT and two TATA boxes in close proximity to the transcription start site. To determine if these 5'-flanking sequences exhibited promoter activity, chimeric chloramphenicol acetyltransferase expression plasmids containing the promoter region of either exon Ia or Ib were transfected into HeLa and MG-63 osteosarcoma cells. The results showed that only the region flanking exon Ib was functional. In vitro transcription assay generated two transcripts of 92 and 82 base pairs (bp) indicating that both TATA boxes could be used. Using stepwise 5' deletion analysis we found that the minimum promoter region at -140 bp from the transcription start site, which contained only the CAAT and the two TATA boxes, exhibited strong promoter activity. When a larger construct containing an additional 800 bp of upstream region was tested, a significant increase in transcriptional activity was observed. Interestingly, this promoter region contained several putative binding sites for ubiquitous factors (AP1, AP5, and NF-kappa B) and for transforming growth factor-beta and a 150-bp homopurine/homopyrimidine element with several mirror repeats. When contained in a supercoiled plasmid, this sequence exhibited sensitivity to endonuclease S1, an enzyme that preferentially digests single-stranded DNA. Precise S1 mapping, obtained by direct sequencing of nine distinct S1-generated clones, revealed that in all cases the borders of the sensitive sequence resided within the pur/pyr segment. We propose that this region of the promoter could adopt an intramolecular hairpin triplex structure in vivo and may play a role in the chromatin organization at the decorin gene locus. In addition, this region was able to up-regulate a minimal heterologous promoter in transient transfection assays. The results show that the structure of the decorin gene promoter is different from that of any other proteoglycan promoter characterized so far and indicate that the pur/pyr segment plays a role in the regulation of gene transcription.
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PMID:Structural and functional characterization of the human decorin gene promoter. A homopurine-homopyrimidine S1 nuclease-sensitive region is involved in transcriptional control. 827 54

Recently the high-mobility group protein gene HMGIC has been found to be rearranged in a variety of benign mesenchymal tumors with 12q13-q15 aberrations, such as angiomyxoma, fibroadenomas of the breast, lipomas, pleomorphic salivary gland adenomas, polyps of the endometrium, pulmonary chondroid hamartomas, and uterine leiomyomas. Here we report on HMGIC aberrations in the osteosarcoma cell line OsA-CI. In Northern blot studies, aberrant HMGIC transcripts were detected. Analysis of cDNA sequence data obtained after 3' rapid amplification of cDNA ends, indicated these to consist of 5' HMGIC sequences encoding the three DNA binding domains fused to ectopic sequences apparently derived from part of the human lumican (keratan sulphate proteoglycan) gene (LUM), which we mapped by fluorescence in situ hybridization (FISH) to chromosome 12q22-q23. Moreover, Southern blot analysis revealed amplification of this fusion gene but not of the 3'HMGIC sequences. This observation was independently confirmed by FISH analysis using yeast artificial chromosome (YAC) and cosmid clones, which furthermore indicated that the amplified 5'HMGIC sequences were contained within an amplicon of about 200 kb. Our results indicate that aberrations in HMGIC might not be restricted to benign mesenchymal tumors.
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PMID:Amplification of a rearranged form of the high-mobility group protein gene HMGIC in OsA-CI osteosarcoma cells. 890 60

The pericellular proteoglycan biglycan is among the major secretory products of osteoblasts and articular chondrocytes but the regulatory agents and signal transduction pathways that ultimately lead to alterations in biglycan gene expression are poorly defined. We report here on the transcriptional up-regulation of biglycan in MG-63 osteosarcoma cells by agents that increase intracellular cAMP levels. Transfection of these cells with biglycan promoter luciferase reporter fusion genes and subsequent treatment with forskolin or the cAMP analog 8-Bromo-cAMP resulted in an up to 3.8-fold stimulation of biglycan promoter activity. This effect could be prevented with the compound KT5720, a specific inhibitor of the cAMP-dependent protein kinase. Up-regulation of transcription is also reflected at the level of mRNA expression, since biglycan mRNA steady state levels in MG-63 cells increased approximately 2-fold after 24 hours of forskolin treatment. These data suggest that elevated levels of intracellular cAMP increase transcription from the biglycan promoter in bone cells and implicate for the first time the cAMP/protein kinase A signal transduction pathway in the regulation of biglycan gene expression.
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PMID:Biglycan gene promoter activity in osteosarcoma cells is regulated by cyclic AMP. 919 8

Osteosarcomas produce an extracellular matrix (ECM), called tumor osteoid, which is also the microscopic hallmark of these tumors. It can be difficult to differentiate tumor osteoid from other formations of ECM in intra-and extraskeletal soft tissue tumors, so that problems in differential diagnosis arise. Conventional special stainings provide a means to increase the reliability of the differential diagnosis, but do not identify the type of tumor conclusively as they only reflect physiochemical features and do not identify the molecular components of the matrix. The key to the solution of this problem is the immunohistochemical use of antibodies against bone matrix components. Matrix-immunohistochemistry using polyclonal and monoclonal antibodies against COL-I-C-peptide, Osteopontin, Osteonectin, Osteocalcin, and Decorin have proved to be a useful tool for the differentiation of osteoid in a series of 20 osteosarcomas with different variants of osteoid formation. For the detection of undifferentiated tumors, however, this method has not proved useful, since the cytoplasmatic immunoreactivity is variable. Molecular methods appear to be a more promising tool. Since the expression of Osteocalcin is known to be the last step of the osteoblastic differentiation, we have established a method to detect osteocalcin mRNA by RT-PCR. First studies of our group on the identification of the osteoblastic differentiation at the molecular level have revealed that Osteocalcin mRNA can be detected both in osteosarcoma cells and in non-skeletal tumor cell lines. In order to provide a reliable means of molecular tumor characterisation, thorough comparative studies on fresh and paraffin material of larger tumor series are in progress.
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PMID:[Bone matrix production in osteosarcoma]. 1009 26


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