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)

In the present study, we have sought to determine whether a given signal transduction pathway can have diverse effects on subpopulations of cells of a lineage depending upon the stage of differentiation. To test this hypothesis, we selected the cyclic adenosine monophosphate (cAMP) signal transduction pathway because of its recognized importance in mediating the actions of many hormones, e.g., parathyroid hormone which acts on the bone-forming cells, the osteoblasts. Subpopulations of human osteosarcoma SaOS-2 cells with low (LSaOS) and high (HSaOS) alkaline phosphatase (ALP) content were chosen as model systems for preosteoblasts (pre-OB) and osteoblasts (OB), respectively. Dibutyryl cyclic AMP (DBcAMP) treatment of serum free cultures produced a differential effect on the proliferation of LSaOS cells (40 +/- 5% of control at 1 mM DBcAMP, P < 0.001) compared with HSaOS cells (no statistically significant effect). The finding supports the hypothesis. Next, we sought evidence for mediation, at least in part, by the insulin-like growth factor (IGF)-II regulatory system. We report that the basal expression of IGF-II, IGF binding protein (IGFBP)-3, and IGFBP-4 was higher in LSaOS cells than in HSaOS cells with the opposite true for type I IGF receptor. DBcAMP treatment of LSaOS cells decreased IGF-II and IGFBP-3 but increased IGFBP-4 and type I IGF receptor; no effect was observed for the type II IGF receptors. DBcAMP treatment of HSaOS cells had no detectable effect on IGF-II; IGFBP-3, or type I and type II IGF receptor expression; only IGFBP-4 expression increased with DBcAMP. These observations suggest that the differential regulation of cell proliferation by the cAMP signal transduction pathway may be mediated, at least in part, by the IGF-II regulatory system.
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PMID:Dibutyryl cyclic adenosine monophosphate differentially regulates cell proliferation in low and high alkaline phosphatase SaOS-2 human osteosarcoma cells: evidence for mediation by the insulin-like growth factor-II system. 768 70

1 alpha,25-Dihydroxycholecalciferol [1,25-(OH)2D3] is a potent differentiating agent in a variety of tumor cell lines. However, the induction of severe hypercalcemia has limited its clinical use. Several analogs have been synthesized that retain the antiproliferative differentiating effects of 1,25-(OH)2D3, but do not have the calcitropic effect of the parent compound. One such analog, 1 alpha,25(OH)2-16-ene-23-yne-26,27-hexafluorocholecalciferol (Ro24-5531), can induce differentiation in HL-60 cells and does not induce hypercalcemia in animal models. We, therefore, evaluated the effect of Ro24-5531 on a human osteosarcoma cell line, MG-63. Compared with 1,25-(OH)2D3, the analog Ro24-5531 is 10-100 times more potent as an inhibitor of MG-63 cell proliferation, as determined by [3H]thymidine incorporation and/or 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. The inhibition in cell growth is accompanied by a decrease in the expression of p34cdc2 (> 4-fold), a protein critically involved in cell cycle regulation. Ro24-5531 treatment of MG-63, at a concentration of 10(-8) mol/L, induced expression of the bone differentiation markers biglycan and osteocalcin, as determined by Northern analysis. These data suggest that Ro24-5531 treatment induces growth arrest coupled with differentiation. To begin to evaluate the mechanisms by which Ro24-5531 may exert an effect, we evaluated the effect of Ro24-5531 on components of the insulin-like growth factor I (IGF-I) signaling pathway, an important regulator of normal bone growth and differentiation. The expression of IGF-binding protein (IGFBP), IGFBP-3 messenger ribonucleic acid, and protein levels are increased 20-fold after 72 h of treatment with Ro24-5531 and are associated with a marked increase in detectable binding of ligand to binding protein, as measured by RRA. These data suggest an association between Ro24-5531-induced growth arrest and increased expression of IGFBP-3.
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PMID:1 alpha, 25-dihydroxy-16-ene-23-yne-26,27-hexafluorocholecalciferol (Ro24-5531) modulation of insulin-like growth factor-binding protein-3 and induction of differentiation and growth arrest in a human osteosarcoma cell line. 855 Aug 1

To begin delineating molecular mechanisms by which osteogenic protein-1 (OP-1) modulates its effect on the insulin-like growth factor (IGF) system in human skeletal cells, we evaluated time-course effects of OP-1 on the expression of IGFBP-3 messenger RNA (mRNA) in human SaOS-2 osteosarcoma cells and found that 100 ng/ml of OP-1 increased (maximum 10.7-fold at 24 h; P < 0.01) the level of IGFBP-3 mRNA in a time-dependent manner (from 3-36 h; treatment x time interaction, P < 0.001). The stimulatory effect of OP-1 on IGFBP-3 mRNA was not promoted by transcript stabilization; actually, OP-1 treatment selectively increased the decay of mRNA for IGFBP-3 (T1/2 = 5 h vs. 24 h for OP-1 and controls), but not for IGFBP-4 or beta-actin. Conversely, OP-1 acutely increased IGFBP-3 nuclear transcript abundance in total RNA samples ranging between 1-24 h of treatment. After 6 h of treatment, OP-1 produced an average 4-fold increase (P < 0.02; n = 4 experiments) in the level of IGFBP-3 nuclear transcripts vs. a 3-fold increase (P < 0.01; n = 2 experiments) in mRNA abundance. The OP-1 stimulated induction of IGFBP-3 nuclear transcript and mRNA expression was dependent on de novo protein synthesis. Transient transfection experiments were undertaken to isolate putative OP-1 stimulatory cis-elements within 1.8-kb of the IGFBP-3 5'-flanking region in SaOS-2 and TE-85 osteosarcoma cells. In these experiments, OP-1 did not stimulate IGFBP-3 proximal promoter activity in either cell line, thus suggesting that OP-1 reactive domains may be located either beyond the currently established 5'-flanking region, or within internal exon/intron regions of the IGFBP-3 gene. In conclusion, OP-1 treatment stimulates IGFBP-3 expression in human osteoblastic cells by a mechanism that largely promotes the production of IGFBP-3 nuclear transcripts, a process that requires de novo protein synthesis, and overrides an OP-1-induced targeted degradation of IGFBP-3 steady-state mRNA.
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PMID:Osteogenic protein-1 stimulates production of insulin-like growth factor binding protein-3 nuclear transcripts in human osteosarcoma cells. 932 36

A 6.5-year-old male with normal linear growth, despite septo-optic dysplasia, panhypopituitarism and a deficient GH/IGF axis, is presented. In addition to measuring IGF-I, IGF-II and IGFBP-3, serum IGFBP-1, -2, -4 and -5 were measured. A human osteosarcoma cell line was used to assess growth-promoting activity in the patient's serum. The role of leptin in linear growth in this case was investigated. There was no evidence for hyperinsulinism or hyperandrogenism. GH was undetectable upon multiple stimulation. GHBP was elevated. Serum IGF-I (25 microg/l), IGF-II (194 microg/l), IGFBP-3 (0.4 mg/l), and IGFBP-5 (87 microg/l) levels were low compared to age-matched prepubertal children. Serum IGFBP-4 level was normal. Molecular size of IGF-II in the patient's serum was normal, suggesting normal IGF-II bioavailability. Human osteosarcoma cell proliferation in response to the patient's serum was similar to sera from age-matched normal controls. Leptin levels were markedly elevated. Osteoblast cell proliferation was not stimulated by leptin. The data demonstrate that normal growth and osteoblast cell proliferation in this patient is not mediated by GH, total IGFs, insulin, or leptin, and suggest the presence of a yet unidentified growth factor or mechanism. The case offers a detailed picture of binding proteins in a case of growth without GH. It introduces osteoblast cell proliferation as a method of assessing serum growth-promoting activity in such cases. It adds IGF-II and leptin to the list of excluded growth-promoting candidates in GH-independent growth, and further demonstrates our incomplete understanding of the phenomenon of growth.
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PMID:Normal growth despite GH, IGF-I and IGF-II deficiency. 1051 93

Pregnancy-associated plasma protein-A (PAPP-A) has been identified as the insulin-like growth factor (IGF)-dependent IGF-binding protein-4 (IGFBP-4) protease produced by human fibroblasts. Recently, we found that serum proteases induced during human pregnancy cleaved IGFBP-4 in both an IGF-II-dependent and an IGF-II-independent fashion. This study sought to determine whether PAPP-A is the predominant IGFBP-4 protease in human pregnancy serum (PS) and to assess the in vitro role of serum PAPP-A. Immunoprecipitation with PAPP-A antibody effectively depleted PAPP-A from the PS and completely abolished both IGF-II-dependent and IGF-II-independent IGFBP-4 proteolytic activity in PS. Direct addition of PAPP-A antibody to PS completely blocked IGFBP-4 proteolysis and partially blocked IGFBP-5 proteolysis, but had no effect on IGFBP-3 proteolysis. To evaluate the role of serum PAPP-A, we tested whether PAPP-A in PS modulated the inhibitory activity of IGFBP-4 on IGF-II-induced cell proliferation in human osteosarcoma MG63 cells. The wild-type IGFBP-4 (WTBP-4; 200 ng/mL) failed to inhibit proliferation of the cells treated with PS (0.1% or 0.3%) alone or in combination with IGF-II (40 ng/mL), whereas the inhibitory effect of WTBP-4 was observed in the cells treated with nonpregnancy serum alone or in combination with IGF-II (P < 0.05). In contrast to WTBP-4, a protease-resistant IGFBP-4 was able to inhibit proliferation of the cells treated with PS alone or in combination with IGF-II (P < 0.05). In the presence of PAPP-A neutralizing antibody, the inhibitory effect of WTBP-4 on proliferation of the cells treated with IGF-II and PS was restored. In summary, these data demonstrate 1) that PAPP-A represents the predominant IGFBP-4 protease in PS; 2) that PAPP-A may in part contribute to IGFBP-5, but not IGFBP-3, proteolytic activity in PS; and 3) that PAPP-A enhances the bioactivity of IGFs in vitro by degrading IGFBP-4.
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PMID:Pregnancy-associated plasma protein-A accounts for the insulin-like growth factor (IGF)-binding protein-4 (IGFBP-4) proteolytic activity in human pregnancy serum and enhances the mitogenic activity of IGF by degrading IGFBP-4 in vitro. 1115 56

Growth Hormone (GH), Insulin-like Growth Factors (IGFs) and IGF-Binding Proteins which modulate the IGFs' bioavailability (e.g. IGFBP-3, -4, -5), are essential regulators of bone remodeling. In this study, MG-63 human osteosarcoma cells were used as a model system to investigate the mechanism(s) whereby IGF-I and GH control IGFBP-3 gene expression. Physiological concentrations of IGF-I (1-20 nM) induced a dose-dependent increase in the steady-state amount of IGFBP-3 mRNA (maximal stimulation: approximately 9-10-fold). This increase was detectable 3 h after the onset of IGF-I treatment, was enhanced over a 24 h period, then plateaued until at least 30 h. Consistently, a dose-dependent increase in IGFBP-3 secretion ( approximately 40-50-fold at IGF-I concentrations>/=16 nM) was observed by western ligand- and immuno-blot analysis of MG-63 cells conditioned medium, and its time course was similar to that observed for IGFBP-3 transcripts. IGFBP-3 mRNA stability (t(1/2) approximately 20 h) was identical in the presence or absence of IGF-I treatment. By contrast, human (h) GH treatment (24-72 h) of MG-63 cells did not increase IGFBP-3 secretion in the conditioned medium. Ectopic expression of recombinant rat GH-R resulted in hGH-enhanced expression of GH-responsive reporter gene constructs, but did not increase endogenous IGFBP-3 gene expression, suggesting that the GH unresponsiveness was not only due to the very low level of GH binding sites at the plasma membrane level. Altogether, these results support the conclusions that in MG-63 cells (i) transcriptional rather post-transcriptional mechanisms are involved in the IGF-I-induced increase of IGFBP-3; (ii) the abundance of GH-R is very low at the plasma membrane level; (iii) the dowstream GH-signaling cascade is fully functional in this human osteosarcoma cell line; and (iv) the endogenous IGFBP-3 gene is not responsive to hGH in human MG-63 osteosarcoma cells.
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PMID:The IGFBP-3 mRNA and protein levels are IGF-I-dependent and GH-independent in MG-63 human osteosarcoma cells. 1132 13

Recent studies using insulin-like growth factor I (IGF-I) knockout mice demonstrate that IGF-binding protein (IGFBP)-5, an important bone formation regulator, itself is a growth factor with cellular effects not dependent on IGFs. Because IGFBP-5 contains a nuclear localization sequence that mediates transport of IGFBP-5 into the nucleus, we propose that IGFBP-5 interacts with nuclear proteins to affect transcription of genes involved in bone formation. We therefore undertook studies to identify proteins that bind to IGFBP-5 using IGFBP-5 as bait in a yeast two-hybrid screen of a U2 human osteosarcoma cDNA library. Five related clones that interacted strongly with the bait corresponded to the FHL2 gene, which contains four and a half LIM domains. Co-immunoprecipitation studies with lysates from U2 cells overexpressing FHL2 and IGFBP-5 confirmed that interaction between IGFBP-5 and FHL2 occurs in whole cells. In vitro interaction studies revealed that purified FHL2 interacted with IGFBP-5 but not with IGFBP-3, -4, or -6. Northern blot analysis showed that FHL2 was strongly expressed in human osteoblasts. Nuclear localization of both FHL2 and IGFBP-5 was evident from Western immunoblot analysis and immunofluorescence. The role of FHL2 as an intracellular mediator of the effects of IGFBP-5 and other osteoregulatory agents in osteoblasts will need to be verified in future studies.
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PMID:Insulin-like growth factor-binding protein 5 (IGFBP-5) interacts with a four and a half LIM protein 2 (FHL2). 1182 1

All-trans -retinoic acid (atRA) inhibits osteoblast marker gene expression and markedly increases expression of insulin-like growth factor binding protein-6 (IGFBP-6) in human osteoblasts. The possibility that IGFBP-6 inhibits the osteoblast phenotype and also mediates the inhibitory effect of atRA on osteoblast marker gene expression was explored using an antisense approach. Stable human osteoblast-like osteosarcoma SaOS-2 cells were prepared that expressed antisense IGFBP-6 RNA under basal and atRA-stimulated conditions. The functional expression of IGFBP-6 antisense RNA was confirmed by measuring IGFBP-6 mRNA by Northern analysis or by measuring IGFBP-6 protein in the conditioned media (CM) by radioimmunoassay. Antisense clones produced less mRNA and had less IGFBP-6 protein in the CM than controls. IGFBP-6 protein levels in the CM were inversely correlated with alkaline phosphatase (ALP) activity, whereas IGFBP-3 and IGFBP-4 protein levels were not. We reasoned that atRA would have little or no effect on ALP activity in IGFBP-6 antisense clones if atRA mediated its inhibitory effects by recruiting IGFBP-6. In the majority of IGFBP-6 antisense clones with the lowest IGFBP-6 mRNA and CM protein levels and only modest changes in other IGF system components, atRA did not significantly decrease ALP activity. These findings provide evidence that atRA recruits IGFBP-6 to inhibit the human osteoblast phenotype.
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PMID:Inhibition of human osteoblast marker gene expression by retinoids is mediated in part by insulin-like growth factor binding protein-6. 1191 24

To further define the role of insulin-like growth factor-1 (IGF-1) and its receptor (IGF-1R) in osteosarcoma (OS), human OS cell lines with low (SAOS-2) and high (SAOS-LM2) metastatic potential and three canine OS-derived cell lines were studied. Cell lines were evaluated for: IGF-1R expression; expression of IGF binding proteins (IGFBPs); effect of IGF-1 on tumor cell growth, invasion, expression of urokinase plasminogen activator (uPA), and soluble uPA receptor (suPAR), and; ectopic and orthotopic tumorigenicity of the canine OS cells in athymic mice. All cell lines exhibited steady-state mRNA expression of IGF-1R. The SAOS-2 and SAOS-LM2 cells expressed 9,138 and 10,234 cell-associated binding sites, respectively. Canine OS cells expressed from 1,728 to 3,883 binding sites. Two IGF-1-treated cell lines displayed enhanced proliferation. Two cell lines formed colonies in semisolid media, and IGF-1 increased colony number. Matrigel invasion was enhanced in one cell line following IGF-1 treatment. uPA and suPAR were unchanged in SAOS-2 and SAOS-LM2 cells following IGF-1 treatment, but the highly metastatic OS line SAOS-LM2 expressed five times more suPAR and displayed enhanced invasion compared to the parental, low metastatic SAOS-2. IGFBP-5 was detected in four of five cell lines, and IGFBP-3 was detected in two canine OS cell lines. Two canine OS lines were tumorigenic, and one metastasized spontaneously. In conclusion, OS cells express IGF-1R, which can contribute to their growth and invasion. There is suggestive evidence that increasing receptor number may contribute to in vivo tumorigenesis. Additional studies are needed to determine how IGF-1/IGF-1R interactions contribute to the malignant phenotype of OS.
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PMID:IGF-1 receptor contributes to the malignant phenotype in human and canine osteosarcoma. 1509 5

In adolescent bone sarcoma patients, bone mass acquisition is potentially compromised at a time in which it should be at a maximum. To evaluate the problem we measured bone mineral density (BMD) and serum markers of bone formation and resorption in a series of pediatric patients with bone tumors. BMD was measured by dual-energy x-ray absorptiometry, at clinical remission, for lumbar spine and the neck of the femur in 38 osteosarcoma and 25 Ewing's sarcoma patients. Mean age was 20.65 and 19.13 y respectively. Serum markers of bone metabolism were: OC, PICP, ICTP, 25-OH vit D and 1,25-(OH)(2) vit D, IGF-I, IGFBP-3 and intact PTH. Serum was sampled throughout anti-tumoral treatments and follow-up. We analyzed 85 samples from 59 osteosarcoma patients and 54 samples from 36 Ewing's sarcoma patients. Patients had decreased lumbar and femoral BMD. The decrease was more pronounced in pubertal patients compared with those who had completed pubertal development at the time of disease diagnosis. Multivariate analysis indicated that sex, age, weight and BMI were significant in lumbar BMD depletion. Weight and BMI were significant in femoral BMD depletion. Serum markers of bone formation (PICP and OC) and resorption (ICTP) were, throughout, lower than reference values. Significant alterations in other markers were also observed. Up to a third of osteosarcoma and Ewing's sarcoma patients in clinical remission had some degree of BMD deficit. The corresponding increased risk of pathologic bone fractures constitutes a reduction in future quality of life.
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PMID:Bone mineral density and bone metabolism in children treated for bone sarcomas. 1664 Dec 12


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