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)

TGF beta 1 from porcine platelets increased alkaline phosphatase (AP) activity in the rat osteoblastic cell line ROS 17/2.8 about three-fold. This effect was dose-dependent with an ED50 of about approximately 0.2 ng/ml and was larger during logarithmic growth than at confluence. TGF beta 1 inhibited cell growth by about 30% with similar dose dependence. Thirty min exposure to TGF beta 1 was sufficient to increase AP activity 3 days later by about two-fold but did not affect cell growth, suggesting dissociation between effects on proliferation and differentiation. The rise in AP activity started 6 h after TGF beta 1 addition and was blocked by cycloheximide and actinomycin D. TGF beta 1 also increased AP mRNA by two- to three-fold and this effect was not blocked by cycloheximide. The half-life of AP mRNA, estimated following the addition of 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole was about ten h in both control and TGF beta 1-treated cells. The mRNAs for type I procollagen and osteonectin were also increased by TGF beta 1 but fibronectin mRNA was decreased. TGF beta 2 effects on AP and cell growth were similar to those of TGF beta 1, except for lack of activity following transient exposure. At saturating concentrations, TGF beta 2 (2 ng/ml) or dexamethasone (10(-7) M), which has similar effects on these cells, did not further augment the effects of TGF beta 1 (at 2 ng/ml). Above findings suggest that TGF beta promotes osteoblastic differentiation in rat osteosarcoma cells at least in part by acting at the pretranslational level.
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PMID:Type beta transforming growth factor (TGF beta) regulation of alkaline phosphatase expression and other phenotype-related mRNAs in osteoblastic rat osteosarcoma cells. 348 Feb 88

We compared the procollagen synthetic properties of MG-63 osteosarcoma cells with those of cultured human skin fibroblasts. In both cells, the expressions of type I and III procollagens are largely dependent on the constant presence of ascorbate and coordinately decreased by the neutral polymer dextran T-40. The amino-terminal propeptides of pro-alpha 1 and pro-alpha 2 chains of type I procollagen are phosphorylated and those of the pro-alpha 1 and pN-alpha 1 chains of type III procollagen both phosphorylated and sulfated, there being no difference in net charge in the propeptides between these cell types. The major differences between MG-63 and normal fibroblasts are the exceptionally high relative synthesis of type III procollagen by MG-63 cells, up to about 40% of the total of types I and III (6% in cultured skin fibroblasts), and the inability of ascorbate-supplemented MG-63 cells to deposit collagens into an insoluble pericellular matrix. A longer dextran treatment shifts up to one-fourth of the proline-labeled extracellular macromolecules into the matrix fraction within 4 days (in control 4%). Despite processing of the procollagens to the respective collagens in the matrix, neither control matrices nor those induced by dextran induced increased production of alkaline phosphatase. In cultures up to 4 days postconfluence the proportion of type III collagen produced tended to increase over that in early confluent cultures. With respect to collagen production, the MG-63 cell line is not a representative of the osteoblast lineage but rather resembles a proliferative wound fibroblast.
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PMID:Procollagen synthesis and extracellular matrix deposition in MG-63 osteosarcoma cells. 832 6

Although numerous studies have shown potent antiproliferative and differentiation-inducing effects of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) and its analogs on cells not directly related to bone metabolism, only few reports focussed on the effects of these analogs on bone. We compared the action of several recently developed analogs with that of 1,25-(OH)2D3 on human (MG-63) and rat (ROS 17/2.8) osteoblast-like cells and on in vitro bone resorption. In MG-63 cells the analogs EB1089 and KH1060 were about 166,000 and 14,000 times more potent than 1,25-(OH)2D3 in stimulating type I procollagen and 100 and 6,000 times more potent in stimulating osteocalcin production, respectively. Also in ROS 17/2.8 cells EB1089 and KH1060 were most potent in inducing osteocalcin synthesis. In vitro bone resorption was 2.3 and 17.5 times more potently stimulated by EB1089 and KH1060, respectively. In MG-63 cells, 1,25-(OH)2D3 and the analogs inhibited cell proliferation, whereas both 1,25-(OH)2D3 and the analogs stimulated the growth of ROS 17/2.8 cells. Differences in potency could neither be explained by affinity for the vitamin D receptor nor by a differential involvement of protein kinase C in the action of the analogs. Together, these data show that also in bone the analogs EB1089 and KH1060 are more potent than 1,25-(OH)2D3 but that the potency of the analogs compared to 1,25-(OH)2D3 is dependent on the biological response. On the basis of these observations it can be concluded that the reported reduced calcemic effect in vivo is not the result of a decreased responsiveness of bone to these analogs. Lastly, in view of eventual clinical application of 1,25-(OH)2D3-analogs, the observed stimulation of in vitro bone resorption and growth of an osteosarcoma cell line warrant in vivo studies to further examine these effects.
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PMID:Differential effects of 1,25-dihydroxyvitamin D3-analogs on osteoblast-like cells and on in vitro bone resorption. 854 Dec 30

The kinetics of type I procollagen synthesis in a human osteosarcoma cell line, MG 63, were investigated after treatment with 1,25-dihydroxyvitamin D3 (1,25-(OH)2 D3), a hormonal inducer of phenotypic differentiation. Pulse label and chase experiments demonstrated greatly enhanced production and more rapid reduction of intracellular procollagen molecules in the 1,25-(OH)2 D3-treated cells as compared to the nontreated case. After a chase for 1 h, labeled procollagen was reduced by nine-tenths in 1,25-(OH)2 D3-treated cells, while half of the radioactivity still remained in nontreated cells. The expression rate of type I collagen, which was examined by pulse label experiment, was elevated in association with an increase in the mRNA coding for the type I collagen alpha 1 chain by 1,25-(OH)2 D3 treatment. However, the amount of intracellular procollagen present after 4 h continuous labeling was almost the same, independent of the 1,25-(OH)2 D3 treatment. Thus, we conclude that strage of the molecule was not affected. The results therefore suggest an increase in both the synthesis and secretion of type I collagen. The 1,25-(OH)2 D3 treatment was also found to induce the alpha subunit of prolyl 4-hydroxylase and to be associated with an elevated level of hydroxyproline in the procollagen. Moreover, gelatinase B-resistant procollagen molecules, indicative of intracellular procollagen molecules in the stable triple helical form, were detected only in the 1,25-(OH)2 D3-treated cells. These data suggest more efficient proline hydroxylation is involved in rapid secretion of procollagen after hormone administration. The present evidence points to posttranslational control of procollagen synthesis.
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PMID:Alteration of the kinetics of type I procollagen synthesis in human osteosarcoma cells by 1,25-dihydroxyvitamin D3. 917 3

Change in the synthesis of type I collagen, the major extracellular matrix component of skin and bone, are associated with normal growth, tissue repair processes, and several pathological conditions. Expression of the COL 1A1 gene is regulated by transcriptional and post-transcriptional mechanisms. However, the hormonal regulation of type I collagen synthesis in human bone has not been well characterized. We have studied the influence of calcitriol, dexamethasone, retinoic acid, and estradiol on the COL 1A1 gene expression by determining the secretion of the C-terminal propeptide (PICP) and the levels of alpha 1(I) procollagen mRNA in cultured human MG-63 and SaOs-2 osteoblast-like osteosarcoma cells. Similar experiments were also performed with respect to expression of the nuclear proto-oncogenes, c-fos and c-jun, in MG-63 cells. In MG-63 cells, calcitriol stimulated the synthesis and secretion of PICP. The alpha 1(I) procollagen mRNA level was elevated with no effect on message stability, indicating a transcriptional mechanism of regulation. In contrast, dexamethasone treatment was accompanied by an accelerated rate of alpha 1(I) procollagen mRNA turnover, observed as decreased amounts of the message and the secreted PICP, implying a posttranscriptional regulation. Retinoic acid, in turn, decreased the levels of alpha 1(I) procollagen mRNA and secreted PICP by slowing down transcription of the COL1A1 gene without any effect on message stability. The ability of these hormones to regulate the alpha 1(I) transcripts was sensitive to puromycin treatment, suggesting an involvement of an induced mediator protein in the action of the hormones on the COL1A1 gene. Both dexamethasone and calcitriol rapidly but transiently increased the expression of the c-fos and c-jun proto-oncogenes. Neither proto-oncogene responded to retinoic acid treatment with significant changes in mRNA levels. Estradiol treatment was found to have no influence on type I procollagen synthesis. In SaOs-2 cells, which are not as well differentiated as the MG-63 cells, calcitriol and dexamethasone did not influence type I procollagen synthesis. Retinoic acid as well as estradiol reduced collagen gene expression in these cells. These findings suggest that hormonal effects on type I procollagen synthesis may depend on the maturational state of the osteoblastic cells that express different regulatory factors and receptors, resulting in, in each case, a finely adjusted rate of gene expression.
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PMID:Type I procollagen synthesis is regulated by steroids and related hormones in human osteosarcoma cells. 944 71

Insulin-like growth factor binding protein (IGFBP)-6 has been reported to inhibit differentiation of myoblasts and osteoblasts. In the current study, we explored the mechanisms underlying IGFBP-6 effects on osteoblast differentiation. During MC3T3-E1 osteoblast differentiation, we found that IGFBP-6 protein was down-regulated. Overexpression of IGFBP-6 in MC3T3-E1 and human bone cells inhibited nodule formation, osteocalcin mRNA expression and ALP activity. Furthermore, accumulation of IGFBP-6 in the culture media was not required for any of these effects suggesting that IGFBP-6 suppressed osteoblast differentiation by an intracellular mechanism. A yeast two-hybrid screen of an osteosarcoma library was conducted to identify intracellular binding partners to account for IGFBP-6 inhibitory effects on osteoblast differentiation. LIM mineralizing protein (LMP-1) was identified as a high affinity IGFBP-6 binding partner. Physical interaction between IGFBP-6 and LMP-1 was confirmed by co-immunoprecipitation. Fluorescent protein fusion constructs for LMP-1 and IGFBP-6 were transiently transfected into osteoblasts to provide evidence of subcellular locations for each protein. Coexpression of LMP-1-GFP and IGFBP-6-RFP resulted in overlapping subcellular localization of LMP-1 and IGFBP-6. To determine if there was a functional association of IGFBP-6 and LMP-1 as well as a physical association, we studied the effect of IGFBP-6, LMP-1 and their combination on type I procollagen promoter activity. LMP-1 increased promoter activity while IGFBP-6 reduced promoter activity, and coexpression of LMP-1 with IGFBP-6 abrogated IGFBP-6 suppression. These studies provide evidence that overexpression of IGFBP-6 suppresses human and murine osteoblast differentiation, that IGFBP-6 and LMP-1 physically interact, and supports the conclusion that this interaction may be functionally relevant.
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PMID:Potential involvement of the interaction between insulin-like growth factor binding protein (IGFBP)-6 and LIM mineralization protein (LMP)-1 in regulating osteoblast differentiation. 1839 33