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)

The specific interaction of platelet-derived growth factor (PDGF) with the human osteosarcoma cell line MG-63 was studied. Scatchard analysis of 125I-PDGF binding to MG-63 cells indicated there were 32,000 specific PDGF-binding sites per cell with a Kd of 2.4 X 10(-11) M. Unlabeled PDGF blocked the specific binding of labeled PDGF to MG-63 cells at concentrations greater than 1 ng/ml. When assayed for phosphorylation of MG-63 membrane vesicles, PDGF was shown to stimulate a dose-dependent phosphorylation of a protein (phosphoprotein with a molecular weight of 185,000) which was stable in 1 M NaOH. In the absence of PDGF, a prominent alkali-stable phosphoprotein with a molecular weight of 116,000 was noted. PDGF also stimulated a dose-dependent increase in [3H]aminoisobutyric acid uptake, [3H]thymidine incorporation, and cell proliferation. When tested for secretion of PDGF-like factors, the mitogenic activity of MG-63-conditioned serum-free medium was not blocked by anti-PDGF antiserum. Concentrated MG-63-conditioned medium did not compete with 125I-PDGF for specific receptor sites on diploid fibroblasts. Therefore, MG-63 osteosarcoma cells have functional PDGF receptors and do not secrete PDGF-like mitogens.
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PMID:Evidence for functional platelet-derived growth factor receptors on MG-63 human osteosarcoma cells. 632 31

A human osteosarcoma-derived cell line, 2T, grows almost as well in medium supplemented with platelet-poor plasma (PPP) as it does in medium containing fetal bovine serum. Human diploid fibroblasts, in contrast, will not grow in medium containing PPP unless human platelet-derived growth factor (PDGF) is added. PPP treated with carboxymethyl-Sephadex at pH 7.4 was able to support 2T cell proliferation, although at a reduced rate compared to untreated PPP. Addition of PDGF to carboxymethyl-Sephadex-treated PPP did not restore the growth rate. However, insulin-like growth factor isolated from human plasma did partially restore the activity of carboxy-methyl-Sephadex-treated PPP. Medium conditioned by 2T cells was mitogenic for quiescent BALB/c3T3 cells and human diploid fibroblasts. Antiserum to human PDGF blocked the mitogenic activity of the conditioned medium. Partial characterization confirmed the biochemical similarity to PDGF. The data are consistent with the hypothesis that these osteosarcoma-derived cells have growth factor requirements similar to those of normal mesenchymal cells but are able to overcome the normal growth limitations by autocrine secretion of PDGF-like mitogens.
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PMID:Evidence that a human osteosarcoma cell line which secretes a mitogen similar to platelet-derived growth factor requires growth factors present in platelet-poor plasma. 633 4

A human osteosarcoma cell line, U-2 OS, cultured under serum-free conditions, was shown to produce a growth factor (osteosarcoma-derived growth factor, ODGF) for human-cultured glial cells, fibroblasts, and other cells. ODGF, collected from the spent medium of 2 OS cultures, was purified by a sequence involving heparin-Sepharose chromatography, hydrophobic chromatography, gel chromatography, and preparative gel electrophresis in SDS. Purified ODGF, at a concentration of 3 ng/ml, elicited a mitogenic response in human glial cells equivalent to 50% of that afforded by human serum at a final concentration of 1%. The preparation was estimated to be > 50% pure. The biological activity of ODGF resided in a cationic, relatively heat-resistant, reduction-susceptible protein with a molecular weight of 30,000 (by gel chromatography and SDS-gel electrophoresis). The electrophoretic behaviour of radioiodinated ODGF suggested that the protein was composed of two different polypeptide chains (about 13,000-14,00 and 16,000-17,000 daltons, respectively) linked via disulphide bonds. The molecular makeup of ODGF was thus similar to that of platelet-derived growth factor. 125I-ODGF could be precipitated by an antibody to platelet-derived growth factor, indicating that the two factors were immunologically related. Resemblance with platelet-derived growth factor was also indicated by the finding that the latter (but not, e.g., fibroblast growth factor or epidermal growth factor) competed with 125I-ODGF for binding to human-cultured glial cells.
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PMID:Chemical and biological properties of a growth factor from human-cultured osteosarcoma cells: resemblance with platelet-derived growth factor. 693

The replication of fibroblasts is thought to be controlled by exogenous growth factors mainly secreted by macrophages and epithelial cells. However, under standard culture conditions, lung fibroblasts are able to produce several growth factors, suggesting an autocrine pathway of proliferation. In this work, we examined the expression of platelet-derived growth factor (PDGF-A) and PDGF-B-messenger RNA (mRNAs) by fibroblasts derived from four human adult normal lungs and from two fibrotic lungs. Northern blot analysis showed that both normal and idiopathic pulmonary fibrosis (IPF)-derived fibroblasts expressed a 2.8 PDGF-B/c-sis mRNA. This transcript was also observed as a minor form in human osteosarcoma cell line, used as control, which predominantly expressed a 4.0-kb PDGF-B mRNA. In two fibroblast cell lines, one fibrotic and one normal, the 4.0-kb transcript was also observed but was always weaker than the 2.8-kb mRNA. PDGF-A mRNA was not detected. By immunofluorescence, lung fibroblasts exhibited intracytoplasmic PDGF-like protein. Likewise, conditioned media from normal and IPF lung fibroblasts stimulated 3H-thymidine incorporation in BALB/c-3T3 cells that was significantly inhibited by anti-PDGF antibody. These results show that in vitro, some human lung fibroblasts express PDGF-B/c-sis mRNA, mainly an alternate 2.8-kb transcript, and produce PDGF-like protein.
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PMID:Expression of a 2.8-kb PDGF-B/c-sis transcript and synthesis of PDGF-like protein by human lung fibroblasts. 760 65

Treatment of the U-2 OS human osteosarcoma cell line with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) dramatically decreased the rate of DNA synthesis. This decrease in proliferation as well as the change in morphology of the TPA-treated cells can be blocked by the protein kinase C inhibitor GF 109203X. The U-2 OS cells are known to express the c-sis oncogene [platelet-derived growth factor (PDGF) B-chain], PDGF-A, and receptors for PDGF, thus providing a potential autocrine loop of growth stimulation. TPA was found to induce the expression of both the PDGF-A and the PDGF-B chains. However, the levels of the PDGF receptor beta subunits and of the PDGF-BB inducable tyrosine phosphorylation of the PDGF receptor were markedly reduced. The TPA treatment of the U-2 OS cells also induced changes typical for maturing bone cells, such as increased expression levels of alkaline phosphatase and osteopontin. The expression levels of type I collagen and bone sialoprotein were reduced. The results show a TPA-dependent down-regulation of the PDGF receptor beta subunits that correlates with an increased expression of osteoblast phenotypic markers.
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PMID:Phenotypic modification of human osteosarcoma cells with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate. 779 13

Platelet-derived growth factor BB, encoded by the SIS/PDGF-B gene, is a potent mitogen for cells of mesenchymal origin, and the SIS/PDGF-B gene is expressed in a large percentage of human mesenchymal tumor cells establishing a growth-promoting, autocrine growth circuit. A 4-kb fragment, containing the SIS/PDGF-B promoter, was isolated from a human genomic library, and a series of 5'-nested deletions and linker-scanning mutants were used to identify positive regulatory elements that are necessary for the constitutive expression of this gene in human U2-OS osteosarcoma cells. A 250-bp fragment, lying immediately 5' to the SIS/PDGF-B mRNA initiation site (+1), retained full promoter activity, and positive regulatory elements at -228 to -219, -97 to -88 (SIS distal element) and -58 to -39 (SIS proximal element, SPE) were identified. Insertion of the 20-bp SPE into a heterologous, minimal promoter resulted in >5-fold transcriptional activation which was ablated by mutations to the SPE. High resolution mutagenesis within the 20-bp SPE, indicated the necessity of a CACCC motif for activity. Gel shift analysis of SPE-binding proteins in U2-OS nuclear extracts identified Sp1 and two additional binding factors that could be competed away from SPE binding by adding excess consensus Sp1 or CACC oligonucleotides. The individual and aggregate roles of the SPE and two weaker positive regulatory elements in regulating SIS/PDGF-B transcription in these tumor cells is considered.
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PMID:SIS/PDGF-B promoter isolation and characterization of regulatory elements necessary for basal expression of the SIS/PDGF-B gene in U2-OS osteosarcoma cells. 796 14

We have discovered a soluble form of the platelet-derived growth factor (PDGF) alpha receptor, designated sPDGF-R alpha, that is produced by and secreted into the conditioned medium of the human osteosarcoma cell line, MG-63. Additionally, sPDGF-R alpha activity has been detected in normal human blood plasma and serum. We have achieved partial purification of this protein by column chromatography using three different affinity matrices: anti-PDGF-R alpha monoclonal antibody (mAb) 292.15-Sepharose, PDGF-BB-Sepharose, and wheat germ agglutinin-agarose. All three matrices have been shown to purify a 90-kDa protein that is recognized by mAbs specific for the PDGF-R alpha extracellular domain. sPDGF-R alpha is capable of binding PDGF ligand in solution and can compete with cell-associated PDGF receptors for ligand binding. We provide three pieces of data suggesting that the sPDGF-R alpha is generated by proteolytic clipping of the full-length PDGF-R alpha protein. First, the conditioned medium of an expression cell line transfected with a cDNA construct designed to produce only full-length PDGF-R alpha exhibits sPDGF-R alpha activity. Second, a truncated intracellular fragment of the PDGF-R alpha, presumably representing the intracellular counterpart of the clipped sPDGF-R alpha, can be immunoprecipitated from the MG-63 osteosarcoma cell extracts using antiserum raised against an intracellular portion of PDGF-R alpha. Finally, we have been unable to detect alternative splicing in the PDGF-R alpha transcript using reverse transcription-polymerase chain reaction.
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PMID:Identification of a soluble receptor for platelet-derived growth factor in cell-conditioned medium and human plasma. 848 49

The expression of both epidermal growth factor (EGF) and platelet-derived growth factor (PDGF), and of their receptors (EGFR and PDGFR) was immunohistochemically examined in 37 cases of osteosarcoma. Furthermore, immunostaining for p53 protein and Ki-67 antigen by MIB-1 was carried out and compared with the above results. EGFR (81%) expressed more often than EGF (51%) and the expression of EGF and EGFR, and PDGF and PDGFR were recognized in 49% and 38%, respectively. In eleven cases (30%), the expression of both growth factors and their receptors was combined. Anaplastic osteosarcoma showed higher MIB-1 index than osteoblastic and fibroblastic subtypes (P < 0.05). High grade osteosarcomas (G3 and G4) revealed higher MIB-1 index compared with low grade tumors (G1 and G2). PDGF positive tumors (MIB-1 index: 20.0) showed significantly higher proliferation compared with PDGF negative tumors (MIB-1 index: 6.5) (P < 0.01). Five out of 37 cases (13.5%) showed positive immunoreaction for p53. There was no correlation of p53 status with MIB-1 index and the expression of growth factors or their receptors. Our results suggest that PDGF expression may be an important mediator of cell proliferation control, via an autocrine mechanism, in human osteosarcoma.
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PMID:Expression of growth factors and their receptors in human osteosarcomas. Immunohistochemical detection of epidermal growth factor, platelet-derived growth factor and their receptors: its correlation with proliferating activities and p53 expression. 854

Expression of PDGF-B, the gene encoding the platelet-derived growth factor B chain, has been implicated as a participant in an autocrine growth loop in the human osteosarcoma cell line U2-OS. In previous work, we identified a primary site in the PDGF-B promoter, the SIS proximal element (SPE), which is critical for transcription of the PDGF-B gene in U2-OS cells. We also identified Sp1 as one of the SPE-binding proteins in U2-OS nuclear extracts. In the present work, we have identified another SPE-binding protein to be Sp3. Gel mobility shift assays showed that both Sp1 and Sp3 require the CACCC motif within the SPE for binding. In vitro transcription assays showed that Sp1 or/and Sp3 is necessary for transcription of the PDGF-B gene. Cotransfection experiments functionally demonstrated that Sp1 and Sp3 can independently or additively activate the PDGF-B promoter through the SPE as well as a synthetic promoter. However, the CACCC motif within the SPE is not the only site within the minimal PDGF-B promoter through which Sp1/Sp3 acts; additional nested deletion analyses showed that multiple cis-acting elements within the minimal promoter are required for full level transcription of the PDGF-B gene in U2-OS cells.
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PMID:Transcriptional regulation of the SIS/PDGF-B gene in human osteosarcoma cells by the Sp family of transcription factors. 866 47

Studies on a platelet-derived growth factor (PDGF) responsive osteosarcoma cell line, MG-63, were initiated to determine the effects of phosphatidylinositol (Ptdlns) 3-kinase inhibitors on serum-stimulated cell proliferation and PDGF-stimulated DNA replication, actin rearrangements, or Ptdlns 3-kinase activity. In a dose-dependent manner, the fungal metabolite wortmannin and a quercetin derivative, LY294002 (2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one), inhibited serum-stimulated MG-63 cell proliferation. The mitogenic effects of PDGF on MG-63 cells, as determined by incorporation of [3H]-thymidine, were also substantially inhibited in the presence of 0.10 microM wortmannin or 10 microM Ly294002. Furthermore, MG-63 cells stimulated by PDGF form distinct actin-rich, finger-like membrane projections which are completely inhibited by either 0.10 microM wortmannin or 10 microM LY294002. At these same concentrations, wortmannin and LY294002 were also effective at reducing levels of phosphatidylinositol 3-phosphate in PDGF-stimulated MG-63 cells. Treatment of these cells with increasing concentrations of wortmannin reduced the level of PDGF stimulated tyrosine phosphorylation of the PDGF receptor but did not significantly affect the amount of the Ptdlns 3-kinase regulatory subunit, p85, associated with the receptor. Additionally, pretreatment of cells with 0.250 microM wortmannin followed by stimulation with PDGF resulted in a slightly reduced level of receptor autokinase activity; however, similar treatment with 50 microM LY294002 did not affect the level of autokinase activity. These results demonstrate the effects of two different Ptdlns 3-kinase inhibitors on serum- and PDGF-stimulated MG-63 cell proliferation and PDGF-stimulated morphological changes and suggest a greater role for Ptdlns 3-kinase in these processes.
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PMID:Inhibition of MG-63 cell proliferation and PDGF-stimulated cellular processes by inhibitors of phosphatidylinositol 3-kinase. 902 79


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