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Query: UMLS:C0029463 (osteosarcoma)
 16,637 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The properties and regulation of insulin receptors on monolayers of cultured clonal osteoblastic rat osteosarcoma UMR-106 cells and human osteosarcoma U20S cells were studied. Confluent cultures of UMR-106 cells bound lactoperoxidase-labeled, HPLC-purified [125I]A-14-monoiodinated insulin in a reversible, saturable, and specific manner. Binding was related inversely to the incubation temperature. Prolonged period of steady-state binding was achieved at all temperatures studied. Competition curves demonstrated half-maximal inhibition of [125I]insulin binding at an unlabeled insulin concentration of about 1 nM. Scatchard analysis of the binding data was curvilinear, suggesting negative cooperativity, and revealed that UMR-106 osteoblasts contained about 87,000 receptor sites per cell according to a two-site model. Bound [125I]insulin dissociated from osteoblasts with a t1/2 of about 15 minutes at 22 degrees C. The dissociation curve was multiexponential, and the addition of native insulin accelerated the dissociation of intact but not degraded [125I]insulin. Preincubation with 125 nM insulin for 1 h induced 70% loss of binding sites and reduced total insulin bound by 30%. When monolayers were treated with the lysosomotropic agent chloroquine, a 40% increase in cell-associated radioactivity that could not be dissociable in fresh buffer was observed. The use of an energy depleter, sodium fluoride, completely inhibited the effects of chloroquine. Similar results were obtained for human osteosarcoma U20S cells except that the number of receptor sites was far less than that of UMR-106 cells. Insulin increased collagen synthesis at a half-maximal concentration of 1 nM. To conclude, cultured rat and human osteoblasts possess insulin receptors that exhibit kinetic properties and specificity similar to those of other insulin target cells. Receptor-bound insulin is internalized and degraded by a chloroquine-sensitive, energy-requiring reaction. Insulin receptor on bone cells modulates the synthesis of collagen and this role may be important in bone homeostasis.
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PMID:The characterization, regulation, and function of insulin receptors on osteoblast-like clonal osteosarcoma cell line. 269 4

UMR106 cells, a rat osteosarcoma derived clonal line, secreted insulin-like growth factors (IGF) in vitro. The IGF-II levels corrected for the cell numbers were 7-8 times higher than the IGF-I levels in the medium. Both growth factors were higher by 4-5 fold in medium conditioned by rapidly growing cells than in medium conditioned by confluent cells. The addition of 17-beta-estradiol (E) to the culture medium was associated with a statistically significant increase in the IGF concentrations. This increment was metabolite specific, not occurring with 17-alpha-E, the inactive epimer of E. 1,25(OH)2D3 also increased the IGF-I concentration but prior treatment with E blocked the response to 1,25(OH)2D3, demonstrating antagonistic actions of these two hormones on IGF secretion by osteoblast-like cells.
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PMID:Estradiol stimulates in vitro the secretion of insulin-like growth factors by the clonal osteoblastic cell line, UMR106. 291 89

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.
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PMID:The type II insulin-like growth factor receptor does not mediate deoxyribonucleic acid synthesis in human fibroblasts. 295 64

The processing of insulin-like growth factor I (IGF-I) by MG-63, an IGF-I-responsive human osteosarcoma cell line, has been investigated. At 37 C, the binding of [125I] IGF-I to monolayers of MG-63 cells reaches a maximum after about 1 h and slowly declines thereafter. The addition of the lysosomotropic agents methylamine, chloroquine, and monensin to the binding medium prevents the decline in [125I]IGF-I binding observed in the untreated cells and causes a 1.5- to 3-fold increase in cell-associated radioactivity after 4 h. Leupeptin, an inhibitor of lysosomal proteases, and colchicine, an inhibitor of endosomal transport, also increase cell-associated [125I]IGF-I. Three observations indicate that the increased radioactivity associated with the treated cells is the result of intracellular accumulation of the ligands and not the result of an increase in cell surface IGF binding. First, no increase in [125I]IGF-I binding is observed in cells preincubated with methylamine at 37 C but transferred to 4 C (where endocytosis is inhibited) before the addition of the radiolabeled ligands. Second, the increased radioactivity bound by methylamine-treated cells is not removed by washing the cells with dilute acid, a treatment that removes surface-bound [125I]IGF-I. Third, in leupeptin-treated cells [125I]IGF-I accumulates in a subcellular fraction with properties characteristic of lysosomes. Both alpha IR-3 (100 nM), an antibody that specifically inhibits binding to the type I IGF receptor, and high concentrations of insulin (900 nM) inhibit the accumulation of [125I]IGF-I by methylamine-treated cells, indicating that internalization of IGF-I occurs through the type I IGF receptor and not through the type II IGF receptor or the IGF-binding protein(s) that is also present on these cells. These results demonstrate that in MG-63 cells IGF-I is endocytosed via the type I IGF receptor and that the endocytosed hormone is degraded, at least in part, in lysosomes. These findings are similar to those described for the processing of insulin and other growth factors by their target cells and extend further the homology between IGF-I and these other agents.
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PMID:Receptor-mediated endocytosis and lysosomal processing of insulin-like growth factor I by mitogenically responsive cells. 296 62

Osteoporosis is a known complication of diabetes mellitus, suggesting a role for insulin in bone homeostasis. We studied insulin receptors and insulin action in the osteoblast-like rat osteogenic sarcoma cell line ROS 17/2.8. These cells share many common features with the osteoblast, such as 1,25-dihydroxyvitamin D3 receptors, PTH receptors, and 1,25-dihydroxyvitamin D3-induced modulation of alkaline phosphatase activity and osteocalcin. Competition binding studies revealed high affinity insulin receptors, with an ED50 for insulin of 1 nM. The receptors were highly specific for insulin, with 60% inhibition of insulin binding by an antireceptor antibody, no competition by epidermal growth factor, and an ED50 of 300 nM for proinsulin. Steady state maximal insulin binding was obtained by 40 min at 37 C, and insulin degradation, as measured by trichloroacetic acid solubility, was 1%/h at 37 C. ROS cells readily internalized insulin, and under steady state binding conditions at 37 C, 56% of the cell-associated radioactivity consisted of intracellular material. Chloroquine (100 microM) inhibited intracellular processing of insulin, leading to a 300% increase in cell-associated insulin by 2 h (37 C). Photoaffinity labeling of the insulin receptor with the photosensitive analog of insulin, B2 (2-nitro-4-azidophenyl-acetyl)des-pheB1-insulin, followed by solubilization and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, revealed specific bands of 125K and 430K mol wt under reducing and nonreducing conditions, respectively. Thus, the structure of insulin receptors in ROS cells appears comparable to that of insulin receptors of known target tissues. Insulin action was also examined. Insulin did not stimulate [2-3H]deoxyglucose uptake or [1-14C]leucine incorporation into protein. In contrast, physiological concentrations of insulin inhibited alkaline phosphatase activity in nonconfluent cells. After exposure to insulin for 24 h, alkaline phosphatase activity was decreased compared to basal by 39.5% and 50% with 5 and 50 ng/ml insulin, respectively. In conclusion, ROS cells bind insulin to specific receptors that are similar to insulin receptors on other target tissues; receptors internalize insulin, which is then processed through a chloroquine-sensitive pathway; insulin does not affect membrane substrate transport; and insulin does inhibit the activity of an enzyme that is important in bone metabolism. ROS cells represent a model for studying insulin effects on bone.
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PMID:Demonstration of insulin receptors and modulation of alkaline phosphatase activity by insulin in rat osteoblastic cells. 353 Jul 24

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.
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PMID:Production of an insulin-like growth factor by osteosarcoma. 638 81

Intravenous glucose tolerance, insulin response to glucose, the sensitivity of the periphery to insulin as well as growth hormone and somatomedin levels were determined in osteosarcoma patients and control subjects matched by age, sex, weight an length. The insulin response to glucose and the peripheral sensitivity to insulin were evaluated by using the individual blood glucose and plasma insulin curves for parameter identification in a mathematical model. The mean glucose tolerance was significantly decreased in the patients, most likely due to decreased peripheral insulin sensitivity. Plasma growth hormone levels were normal in all patients which was also the case with somatomedin levels determined by both radioreceptor- and radioimmunoassay.
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PMID:Glucose tolerance, growth hormone and somatomedin levels in osteosarcoma patients. 700 30

Protein degradation has been measured in confluent monolayers of eleven lines of contact-inhibited cells and ten transformed lines as the rate of release of trichloroacetic acid-soluble radioactivity after prelabeling cell protein with [3H]leucine. Insulin, at contrations from 10(-12) M to 10(-6) M, has been added at the beginning of the 4-hour degradation period to detect selective effects of this hormone as an inhibitor of the inducible proteolysis occurring in serum-free medium. In addition insulin binding measurements have been performed on selected cell lines in an attempt to relate receptor properties to insulin action. Substantial effects of insulin are found in most cells with a selective inhibition at low insulin concentrations noted in several of the transformed lines. The difference in insulin sensitivity is not entirely definitive because temperature-sensitive transformation mutants of NRK cells are not more sensitive to insulin at a temperature where they show the transformed phenotype. Although insulin receptors on different cell lines have similar binding properties, two of the hepatomas used, H35 and MH1C1, show inhibition of protein degradation at insulin concentrations where receptor occupancy is extremely low. Calvarial osteoblast-like cells have a high rate of protein degradation which can be reduced by growth factors but not by insulin. The lack of an insulin response is a consequence of poor insulin binding to the cells. Insulin binds to the osteogenic sarcoma cells in substantial amounts. However, its normal action to inhibit the induced proteolysis is restricted because with these cells no increase of proteolysis occurs in serum-free medium. Generally higher rates of protein degradation are observed in the contact-inhibited lines than the transformed cells. We suggest that this difference may provide a selective growth advantage to transformed cells.
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PMID:Insulin inhibition of protein degradation in cell monolayers. 700 98

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.
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PMID:Comparison of the type-2 insulin-like growth factor receptor in normal osteoblasts and osteosarcoma-derived osteoblast-like cells. 747 41

Insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) are thought to play an important role in the regulation of bone metabolism. In the present study, we investigated the effect of 1,25-dihydroxyvitamin D(3) [1,25-(OH)2D3] on the expression and secretion of IGFBPs in human osteoblast-like osteosarcoma cells (MG63) and untransformed human bone-derived cells in vitro. Northern blot analysis revealed that 1,25-(OH)2D3 (10(-8) mol/L) increased IGFBP-4 messenger RNA maximally 11-fold over control level in MG63 cells (after 24 h treatment) and 2.8-fold in human bone-derived cells (at 10(-10) mol/L). 1,25-(OH)2D3 increased secretion of IGFBP-4 2- and 3-fold, respectively, in MG63 cells and in human bone-derived cells. In normal human bone-derived cells, 1,25-(OH)2D3 also stimulated messenger RNA expression (3.9-fold) and the secretion of IGFBP-3 (2.2-fold). 1,25-(OH)2D3 also increased IGFBP-4 expression in skin fibroblasts but not in hepatocellular carcinoma cells. Consistent with these in vitro findings, treatment of human subjects with high doses of oral 1,25-(OH)2D3 (2-3 micrograms/day) for psoriasis resulted in a significant increase in serum IGFBP-4 concentration compared with pretreatment levels. Our observations present direct evidence that 1,25-(OH)2D3 plays an important role in the regulation of IGFBP secretion in vitro and in vivo.
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PMID:1,25-Dihydroxyvitamin D3 increases secretion of insulin-like growth factor binding protein-4 (IGFBP-4) by human osteoblast-like cells in vitro and elevates IGFBP-4 serum levels in vivo. 752 41


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