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)

Inhibitory insulin-like growth factor binding protein (In-IGF-BP) has been purified to homogeneity from medium conditioned by TE89 human osteosarcoma cells by two different methods using Sephadex G-100 gel filtration, FPLC Mono Q ion-exchange, HPLC C4 reverse-phase, HPLC CN reverse-phase, and affinity chromatographies. In-IGF-BP thus purified appeared to be homogeneous and unique by the following criteria. (i) N-terminal sequence analysis yielded a unique sequence (Asp-Glu-Ala-Ile-His-Cys-Pro-Pro-Glu-Ser-Glu-Ala-Lys-Leu-Ala). (ii) Amino acid composition of In-IGF-BP revealed marked differences with the amino acid compositions of other known BPs. (iii) In-IGF-BP exhibited a single band with a molecular mass of 25 kDa under reducing conditions on sodium dodecyl sulfate/polyacrylamide gels. IGF-I and IGF-II but not insulin displaced the binding of 125I-labeled IGF-I or 125I-labeled IGF-II binding to In-IGF-BP. In-IGF-BP inhibited basal, IGF-stimulated bone cell proliferation and serum-stimulated bone cell proliferation. Forskolin increased synthesis of In-IGF-BP in TE85 human osteosarcoma cells in a dose-dependent manner. Based on these findings, we conclude that In-IGF-BP is a protein that has a unique sequence and significant biological actions on bone cells.
 ...
PMID:Isolation of an inhibitory insulin-like growth factor (IGF) binding protein from bone cell-conditioned medium: a potential local regulator of IGF action. 247 22

Two insulin-like growth factor (IGF) receptors, the type I and type II IGF receptors, have been described. While substantial evidence indicates that the type I receptor is involved in the regulation of cell division, it is uncertain if the type II receptor also mediates this response. Similarly, the role of the insulin receptor in mediating DNA synthesis remains controversial. To address these questions, we used a monoclonal antibody (alpha IR-3) to specifically inhibit type I IGF receptor activity and examined the effects of this inhibition on IGF- and insulin-stimulated DNA synthesis in human fibroblasts. WI-38 human embryonic lung fibroblasts have both type I and type II IGF receptors, as determined by cross-linking [125I] IGF-I and [125I]IGF-II to monolayers of these cells. In serum-free medium both IGF-I and IGF-II stimulate DNA synthesis in WI-38 fibroblasts, with half-maximal effects occurring at 1.5 +/- 0.3 (+/- SD) and 3.4 +/- 1.4 nM, respectively. At maximally effective concentrations, however, both hormones stimulate DNA synthesis to equal levels. alpha IR-3 binds to the type I, but not the type II, IGF receptor on WI-38 cells. It also inhibits IGF binding to the type I receptor on these cells. alpha IR-3 competitively inhibited both IGF-I- and IGF-II-stimulated DNA synthesis in WI-38 cells, but had no effect on either epidermal growth factor- or platelet-derived growth factor-stimulated DNA synthesis. These results indicate that in WI-38 fibroblasts the mitogenic effects of both IGF-I and IGF-II are mediated through the type I receptor and that the type II IGF receptor is not directly involved in this response. To define the role of the insulin receptor in mediating DNA synthesis we compared the effects of alpha IR-3 on insulin-stimulated DNA synthesis in a variety of human cell lines under identical experimental conditions. With WI-38 and HEL, another human embryonic lung fibroblast cell line, alpha IR-3 competitively inhibited the mitogenic effect of insulin. However, in two other fibroblast cell lines (GM498 and HES) and an osteogenic sarcoma cell line (MG63), alpha IR-3 inhibited IGF, but not insulin-stimulated DNA synthesis. These results indicate that human cell lines differ in the receptor type through which insulin stimulates DNA synthesis and that these differences are intrinsic properties of the cell lines and are not artifacts resulting from differences in experimental conditions.
 ...
PMID:The type II insulin-like growth factor receptor does not mediate deoxyribonucleic acid synthesis in human fibroblasts. 295 64

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.
 ...
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

To test the possibility that osteosarcoma cells produce their own growth factors, we measured levels of insulin and somatomedin C (SMC), an insulin-like growth factor, in culture media of two cell lines derived from patients with that disease. SMC but not insulin levels increased three- to ten-fold over a period of 7 days paralleling the increases in cell number. Production of SMC was inhibited by cycloheximide.
 ...
PMID:Production of an insulin-like growth factor by osteosarcoma. 638 81

Insulin-like growth factor-II is known to stimulate the proliferation and differentiation of osteoblasts in part through activation of the type-2 insulin-like growth factor receptor. The present study examined the type-2 insulin-like growth factor receptors of three normal osteoblast-like cells and three osteosarcoma-derived osteoblast-like cells (OGA, SU, and IMAI) from humans. [125I]insulin-like growth factor-II was used for the binding studies. All of the cell types had high affinity binding sites for insulin-like growth factor-II (dissociation constants [Kd] < or = 1 nM). The concentration of these sites was 10 to 24-fold higher in normal osteoblasts than in the osteosarcoma cells studied. Unlabeled insulin-like growth factor-II inhibited the binding of [125I]insulin-like growth factor-II to the cells in a dose-dependent manner; however, unlabeled insulin-like growth factor-I and insulin were less effective. Covalent crosslinking of insulin-like growth factor-II binding sites gave molecular mass estimates of M(r) 250,000 in human osteoblast cells, 250,000 and 130,000 in OGA cells, 240,000 in SU cells, and 250,000 and 130,000 in IMAI cells. Unlabeled insulin-like growth factor-II inhibited all affinity labeling. In Northern blot analysis, the type-2 insulin-like growth factor receptor mRNA of normal osteoblasts was seen in greater abundance than it was in osteosarcoma cells. These results indicate that the numbers of type-2 insulin-like growth factor receptors differ between normal and transformed osteoblasts and that the differential expression of the receptor may be due to the differentiation of osteoblasts.
 ...
PMID:Comparison of the type-2 insulin-like growth factor receptor in normal osteoblasts and osteosarcoma-derived osteoblast-like cells. 747 41

Previous studies have shown that the actions of insulin-like growth factor-II (IGF-II) in bone are determined by both its concentration and the concentrations of the IGF-binding proteins (IGFBPs). As IGFBP concentrations may be regulated not only at the level of production, but also at the level of degradation, IGFBP proteases may be an important component of the IGF-II regulatory system. In this study, we have identified IGFBP-4 and IGFBP-5 protease activity in the conditioned medium (CM) of the human osteosarcoma U2 cell line (U2OS) and untransformed normal human bone cell (HBC) derived from skull. Proteolysis of the 29-kilodalton (kDa) [125I]IGFBP-5 produced an 18- to 20-kDa fragment of IGFBP-5, and 25 kDa [125I]IGFBP-4 yielded two lower mol wt fragments in the presence of IGF-II. CM from IGF-II-treated U2OS and normal HBC cultures exhibited decreased IGFBP-5 proteolytic activity compared to control cultures. In contrast, CM from IGF-II-treated HBC cultures had increased proteolytic activity against IGFBP-4. To determine the mechanisms by which IGF-II modulates IGFBP-4 and -5 proteolytic activity, CM from control U2OS cell culture was incubated with [125I]IGFBP-4 or -5 in the presence of various concentrations of IGF-II and IGF analogs under cell-free conditions. It was found that exogenous IGF-II stimulated IGFBP-4 proteolysis, but IGF analogs that had no or extremely low affinity to IGFBP-4 failed to induce IGFBP-4 proteolysis. On the contrary, exogenous IGF-II had no effect on IGFBP-5 proteolysis in cell-free U2OS CM. Both IGFBP-4 and IGFBP-5 proteolytic activities were inhibited by aprotinin, zinc chloride, and EDTA and eluted as a single major peak between mol wt markers of 160 and 67 kDa upon gel filtration. Based on the findings that HBCs in culture produce a protease(s) capable of cleaving both IGFBP-4 and IGFBP-5 and that IGF-II can promote or inhibit proteolytic degradation of IGFBP-4 and IGFBP-5, respectively, it is proposed that IGFBP protease(s) may be an important modulator of IGF activity in bone.
 ...
PMID:Evidence that human bone cells in culture produce insulin-like growth factor-binding protein-4 and -5 proteases. 750 11

Bone morphogenetic proteins (BMPs) have the unique ability to convert mesenchymal cells into matrix-producing osteoblasts. To understand the mechanism(s) by which a BMP produces a multitude of effects on bone cells, we examined the effects of recombinant human osteogenic protein (OP)-1 (referred to as BMP-7) on the insulin-like growth factor (IGF) regulatory system, an important growth factor system in bone. After 48 h of treatment, OP-1 increased the level of IGF-II (3- and 2-fold, respectively, at 100 ng/ml) in the conditioned medium (CM) of SaOS-2 and TE85 human osteosarcoma cells with osteoblastic characteristics, whereas IGF-I levels were low to undetectable in the CM of either cell type. OP-1 treatment had no significant effect on the messenger RNA (mRNA) level for type 1 and type 2 IGF receptors. In TE85 and SaOS-2 cells, 100 ng/ml OP-1 increased the level of IGF binding protein (BP)-3 more than 10-fold, decreased the IGFBP-4 level by 50%, and increased the level of the 29-32.5 kDa IGFBP-5 3-fold in the CM as determined by analysis with Western ligand blot, Western immunoblot, and RIA. The effect of OP-1 on IGFBP production was time and dose dependent. The OP-1 induced changes in the levels of IGFBPs were associated with decreased IGFBP-3 and -5 protease activity (29% and 71%, respectively) and proportional changes in IGFBP mRNA levels. OP-1 increased the level of IGFBP-3 mRNA (2- and 10-fold, respectively, after 4 and 24 h of treatment at 100 ng/ml) and of IGFBP-5 mRNA (more than 5-fold after 24 h of treatment) but decreased the level of IGFBP-4 mRNA (> 50% after 24 h at 100 ng/ml). OP-1 treatment had no effect on IGFBP-4 protease activity. These results collectively demonstrate that OP-1 can act locally by modulating the IGF regulatory system, suggesting that the mitogenic/differentiative effect of OP-1 on human bone cells may in part be mediated via IGF-II by increasing its secretion, and by regulating the balance between the stimulatory (e.g. IGFBP-5) and inhibitory (e.g. IGFBP-4) classes of IGFBPs both at the level of production (mRNA) and at the level of degradation but not by up-regulating the IGF receptor.
 ...
PMID:Regulation of insulin-like growth factor system components by osteogenic protein-1 in human bone cells. 753 81

Human osteosarcoma-derived osteoblast-like cells, TE-85, were used to assess the effect of a low frequency alternating magnetic field in combination with a controlled static magnetic field (combined magnetic fields, CMF) on insulin-like growth factor receptor regulation. In our culture system, application of a 15.3 Hz CMF induces a calculated maximum electrical potential in the culture media of 10(-5) V/m. Initial characterization of TE-85 cells demonstrated that (a) TE-85 cells contain both type I insulin-like growth factor (IGF-I) and IGF-II receptors and (b) dose dependence for IGF-stimulated cell proliferation were comparable to the affinities of the IGF's binding to membrane binding sites (i.e., receptors had dissociation constants in the low nanomolar concentration range). The studies with CMF exposure revealed that CMF treatment for 30 minutes increased the number of IGF-II receptors in a frequency-dependent manner without affecting the number of IGF-I receptors. The CMF-dependent increase in IGF-II receptor number was associated with a significant increase in the IGF-II dissociation constant. These results indicate that a membrane receptor levels can be altered by short-term exposure to low-energy, low-frequency electromagnetic fields and suggest a potential biochemical mechanism for electromagnetic effects on bone formation and remodeling.
 ...
PMID:IGF-II receptor number is increased in TE-85 osteosarcoma cells by combined magnetic fields. 763 17

U-2 human osteosarcoma cells secrete a 29/32/34 kilodalton (kDa) insulin-like growth factor binding protein (IGFBP) identified as O-glycosylated IGFBP-5. Treatment of U-2 cells with IGF-I markedly increased medium levels of IGFBP-5 in a concentration- and time-dependent manner; other skeletal regulatory factors (GH, insulin, PTH, dexamethasone, beta-estradiol, 1,25-dihydroxyvitamin D3, transforming growth factor-beta) had no effect. IGF-I increased IGFBP-5 levels in the culture medium 10-fold without influencing IGFBP-5 messenger RNA abundance. IGF-I, IGF-II, and the IGF-I analog [1-27Gly(4)38-70] IGF-I bound IGFBP-5 with high affinity and, when added to U-2 cultures, effectively promoted IGFBP-5 accumulation in the medium. On the other hand, des(1-3)IGF-I and [QAYL]IGF-I, IGF-I analogs that did not bind IGFBP-5, failed to elicit an increase in medium IGFBP-5. Cell-free incubation of recombinant human (rh) IGFBP-5 in U-2 conditioned medium resulted in a marked reduction of detectable rhIGFBP-5; the presence of IGF-I or IGF-II peptide partially prevented this decrease. By immunoblot analysis, loss of intact rhIGFBP-5 (29-kDa unreduced, 34-kDa reduced) coincided with the appearance of a 16-kDa proteolytic fragment. U-2 conditioned medium contained immunoreactive IGFBP-5 at 29-34-kDa, 20-kDa, 17-kDa, and 16-kDa. Endogenous IGFBP-5 inhibited IGF-I but not des(1-3)IGF-I-stimulated U-2 cell proliferation. In conclusion, IGF peptides can regulate the availability of IGFBP-5 in osteoblast-like cells by impeding IGFBP-5 proteolysis. The biological consequence of increased medium IGFBP-5 appears to be decreased cell responsiveness to IGF-I stimulation.
 ...
PMID:Regulation and biological effect of endogenous insulin-like growth factor binding protein-5 in human osteoblastic cells. 768 91

PTH treatment of UMR 106-01 rat osteosarcoma cells increased 20- to 100-fold medium levels of a discrete insulin-like growth factor binding protein (IGFBP) with M(r) of 29K. Northern analysis of UMR cellular RNA hybridized with a specific IGFBP-5 complementary DNA probe indicated a 6.0-kilobase transcript induced within 2 h in PTH-treated cells. IGFBP-5 messenger RNA (mRNA) abundance was maximal around 6 h and remained elevated after 24 h of treatment. Another rat osteosarcoma cell line (ROS 17/2.8) did not express IGFBP-5 mRNA and did not secrete 29K IGFBP. Induction of IGFBP-5 mRNA by PTH was blocked when RNA synthesis in UMR cells was inhibited by actinomycin D (Bu)2cAMP mimicked the effect of PTH on IGFBP-5 mRNA expression and protein secretion. In addition, a monoclonal antibody against IGF-I (Sm 1.2) inhibited the PTH-induced increase in medium IGFBP-5 without influencing IGFBP-5 transcript levels. Direct addition of IGF-I to UMR cell cultures increased medium IGFBP-5 levels approximately 14-fold, with a modest effect on IGFBP-5 mRNA levels. Studies comparing IGF-I, IGF-II, different IGF-I analogs, and insulin indicated that the predominant IGF effect on IGFBP-5 accumulation was type I IGF receptor independent. Thus, in UMR 106-01 cells, PTH and IGF-I increase extracellular concentrations of IGFBP-5 via distinct but coordinate mechanisms; PTH acts primarily to induce IGFBP-5 mRNA expression through a cAMP-mediated mechanism, and IGF-I appears to interact directly with IGFBP-5 protein to promote its accumulation.
 ...
PMID:Regulation of insulin-like growth factor binding protein-5 messenger ribonucleic acid expression and protein availability in rat osteoblast-like cells. 768 79


<< Previous 1 2 3 4 5 6 7 8 9 Next >>