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)

Two human osteosarcoma cell lines, Hu09 and OST, were suspended in Matrigel (Becton Dickinson Labware, Bedford, Massachusetts) and implanted subcutaneously in the backs of nude mice. To study phenotypic changes of tumor cells and host cells, expression of mRNA for osteopontin (OPN), osteocalcin (OC), and osteonectin (ON) was analyzed by in situ hybridization. Bone tissue was formed in the tumors derived from Hu09 cells. OPN mRNA was transcribed predominantly in osteocyte-like cells within the bone, whereas OC mRNA was transcribed in osteoblast-like cells that surrounded the bone. ON mRNA was detected in both types of cells. The similarity of the expression pattern of OPN, OC, and ON during osteogenesis of Hu09 cells to that of normal skeletal development suggests that the bone formed in Hu09-implanted mice is the same as normal bone tissue. By DNA-DNA in situ hybridization using a human-specific Alu probe and a mouse-specific m-L1 probe, osteoblast-like cells in Hu09 tumorous bone were, however, of human origin, whereas osteocyte-like cells were of mouse origin. In the tumors derived from OST cells, no osteogenesis was observed during the experimental period, and the expression of OPN, OC, and ON was not detected in tumor cells. An endochondral bone formation was not evident when these cells were simply implanted into muscle tissue. An endochondral bone was, however, reactively induced in the host mUscle tissue either when 1 alpha-hydroxyvitamin D3 and all-transretinoic acid were administered to OST-implanted mice or when Hu09 cells were pretreated with dexamethasone before implantation. Hu09 implantation seems to be a useful tool not only for the study of the differentiation of osteosarcoma cells but also for the investigation of the mechanism of bone formation. This system, using Hu09 and OST, may provide us with a new tool for the isolation of the unidentified factors that induce or inhibit osteogenesis in vivo.
 ...
PMID:In vivo implantation of human osteosarcoma cells in nude mice induces bones with human-derived osteoblasts and mouse-derived osteocytes. 894 Dec 16

Monoclonal antibody HTP IV-#1 specifically recognizes a complexation-dependent neoepitope on bone acidic glycoprotein-75 (BAG-75) and a Mr = 50 kDa fragment. Complexes of BAG-75 exist in situ, as shown by immunofluorescent staining of the primary spongiosa of rat tibial metaphysis and osteosarcoma cell micromass cultures with monoclonal antibody HTP IV-#1. Incorporation of BAG-75 into complexes by newborn growth plate and calvarial tissues was confirmed with a second, anti-BAG-75 peptide antibody (#503). Newly synthesized BAG-75 immunoprecipitated from mineralizing explant cultures of bone was present entirely in large macromolecular complexes, while immunoprecipitates from monolayer cultures of osteoblastic cells were previously shown to contain only monomeric Mr = 75 kDa BAG-75 and a 50 kDa fragment. Purified BAG-75 self-associated in vitro to form large spherical aggregate structures composed of a meshwork of 10 nm diameter fibrils. These structures have the capacity to sequester large amounts of phosphate ions as evidenced by X-ray microanalysis and by the fact that purified BAG-75 preparations, even after extensive dialysis against water, retained phosphate ions in concentrations more than 1,000-fold higher than can be accounted for by exchange calculations or by electrostatic binding. The ultrastructural distribution of immunogold-labeled BAG-75 in the primary spongiosa underlying the rat growth plate is distinct from that for other acidic phosphoproteins, osteopontin and bone sialoprotein. We conclude that BAG-75 self-associates in vitro and in vivo into microfibrillar complexes which are specifically recognized by monoclonal antibody HTP IV-#1. This propensity to self-associate into macromolecular complexes is not shared with acidic phosphoproteins osteopontin and bone sialoprotein. We hypothesize that an extracellular electronegative network of macromolecular BAG-75 complexes could serve an organizational role in forming bone or as a barrier restricting local diffusion of phosphate ions.
 ...
PMID:Bone acidic glycoprotein-75 self-associates to form macromolecular complexes in vitro and in vivo with the potential to sequester phosphate ions. 909 4

We studied the expression of estrogen-related receptor ERR-1 during mouse embryonic development. ERR-1 mRNA is present in bones formed by both the endochondral and intramembranous routes, and the onset of its expression coincides with bone formation. By RT-PCR experiments, we found that ERR-1, but not the related receptor ERR-2, is expressed in osteoblastic osteosarcoma cell lines as well as in primary osteoblastic cell populations derived from normal human bone. By gel shift analysis we found that ERR-1 binds as a monomer specifically to the SFRE sequence (SF-1-responsive-element; TCAAGGTCA). Mutation analysis revealed that both the core AGGTCA motif and the TCA 5'-extension are required for efficient ERR-1 binding. In transient transfection assays, ERR-1 acts as a potent transactivator through the SFRE sequence. This effect is cell-specific since ERR-1 activates transcription in the rat osteosarcoma cell line ROS 17.2/8 as well as in HeLa, NB-E, and FREJ4 cells but not in COS1 and HepG2 cells. Notably, the osteopontin (a protein expressed by osteoblasts and released in the bone matrix) gene promoter is a target for ERR-1 transcriptional regulation. Our findings suggest a role for ERR-1 in bone development and metabolism.
 ...
PMID:The ERR-1 orphan receptor is a transcriptional activator expressed during bone development. 917 50

Tamoxifen is a synthetic estrogen analog which may regulate osteogenesis in vivo by virtue of its antiglucocorticoid properties. We have examined tamoxifen regulation of glucocorticoid-induced osteogenesis in two different in vitro bone systems: the chicken periosteal osteogenesis model (CPO) and rat bone marrow stromal cells (RBMC). Hormone uptake studies were conducted with the osteosarcoma cell line, ROS 17/2.8. In the CPO model, alkaline phosphatase (AP) activity and collagen synthesis were stimulated by the glucocorticoid dexamethasone (Dex; 0.1 microM). These Dex-mediated effects were inhibited by increasing concentrations of tamoxifen (10-100 microM). Similarly, in the RBMC model, Dex-dependent (0.01 microM Dex) mineralized tissue formation and AP activity were blocked by tamoxifen (0.1 microM). Although tamoxifen inhibited Dex-mediated increases of AP activity in ROS 17/2.8 cells, it did not inhibit uptake of 3H-Dex or of 3H-estrogen. Northern analyses showed that tamoxifen did not affect messenger RNAs (mRNAs) for AP. Tamoxifen did seem to reduce mRNA for collagen type I, but not bone sialoprotein, osteopontin, and osteocalcin. Dex-induced increases for all proteins mRNAs in the RBMC model were not reduced by tamoxifen. Similarly, tamoxifen had no effects on cellular proliferation. We conclude that tamoxifen has no direct effect on gene expression of bone-related proteins of osteoblastic cells. Further, in the ROS 17/2.8 cell line, the antiglucocorticoid properties of tamoxifen do not appear to be mediated through either Dex or estrogen receptors.
 ...
PMID:Tamoxifen attenuates glucocorticoid actions on bone formation in vitro. 923 77

Human prostatic carcinoma frequently metastasizes to bone tissue and activates bone metabolism, especially bone formation, at the site of metastasis. It has been reported that an extract of prostatic carcinoma and conditioned medium (CM) of a human prostatic carcinoma cell line, PC-3, established from a bone metastastic lesion, stimulate osteoblastic cell proliferation. However, there is little information about the effect of PC-3 CM on the differentiation of osteoblastic cells. In this study, we investigated the effect of PC-3 CM on the differentiation of two types of osteoblastic cells, primary fetal rat calvaria (RC) cells containing many undifferentiated osteoprogenitor cells, and ROS 17/2.8, a well-differentiated rat osteosarcoma cell line. PC-3 CM inhibited bone nodule formation and the activity of alkaline phosphatase (ALPase), an osteoblastic marker enzyme, on days 7, 14, and 21 (RC cells) or 3, 6, and 9 (ROS 17/2.8 cells) in a dose-dependent manner (5-30% CM). However, the CM did not affect cell proliferation or cell viability. PC-3 CM was found to markedly block the gene expression of ALPase and osteocalcin (OCN) mRNAs but had no effect on the mRNA expression of osteopontin (OPN), the latter two being noncollagenous proteins related to bone matrix mineralization. These findings suggest that PC-3 CM contains a factor that inhibits osteoblastic cell differentiation and that this factor may be involved in the process of bone metastasis from prostatic carcinoma.
 ...
PMID:Inhibition of osteoblastic cell differentiation by conditioned medium derived from the human prostatic cancer cell line PC-3 in vitro. 932 30

Bone is an estradiol-responsive tissue. Estrogen withdrawal during the menopause causes loss of bone mass and clinically relevant osteoporosis in a third of all women. Sufficient or impaired local production, as well as degradation of estradiol in cells present in the bone microenvironment might be an important mechanism of rescue or might contribute to the development of osteoporosis, respectively. We therefore investigated aromatase and 17beta-hydroxysteroid dehydrogenase type IV (17beta-HSD IV) expression in osteoblast- and osteoclast-like cells. Aromatase mRNA was increasingly expressed in myeloid THP 1 cells differentiated along the monocyte/phagocyte pathway exploiting vitamin D and either granulocyte-macrophage-stimulating factor (GMCSF) or macrophage-stimulating factor (MCSF). In long-term cultures, when sequentially exposed to vitamin D (days 0-21) and GMCSF (days 5-10) and plated on collagen, the amount of expression of aromatase mRNA steadily increased along with the increasing expression of osteopontin mRNA, alpha(v) integrin mRNA, c-fms (MCSF-receptor) mRNA and multinucleated cells developing. The conversion of estradiol from testosterone (10(-7) M/l) in the supernatants of dishes mirrored changes in aromatase mRNA expression and by day 21 rose to 30,000 ng/10(7) cells/24 h. 17Beta-HSD IV mRNA expression was abundant in undifferentiated THP 1 cells and was decreased to approximately 50% by day 21. Unstimulated SV-40 immortalized fetal osteoblasts did not express aromatase mRNA, but the expression was stimulated by the addition of the phorbol ester phorbol myristate acetate (PMA). Unstimulated osteoblasts from primary cultures did not express aromatase mRNA. Osteoblast-like osteosarcoma cells MG 63 expressed faint levels of aromatase mRNA in contrast to the osteosarcoma cell line HOS 58. 17Beta-HSD IV mRNA was expressed in fetal osteoblasts as well as in osteoblasts from primary culture, MG 63 and HOS 58 cells. In summary, we can show the expression of estradiol metabolizing enzymes in cells which are present in the bone microenvironment. Impaired aromatase expression and/or enhanced expression of 17beta-HSD IV may contribute to the pathogenesis of osteoporosis.
 ...
PMID:Local estradiol metabolism in osteoblast- and osteoclast-like cells. 936 87

Cultured rodent osteoblastic cells reiterate the phenotypic maturation of osteoblasts seen in vivo. Under appropriate culture conditions this maturation is a stepwise sequence of phenotypic changes culminating in the production of a mineralised matrix. Although individual components of the osteoblast phenotype are apparent in transformed osteosarcoma cell lines, the co-ordination of the maturation sequence appears to be compromised. Because to date no comparable human cell differentiation system has been developed we investigated the recently introduced HOS 58 osteosarcoma cell line up to 3 months in culture. Proliferation, the secretion of osteoblast specific proteins, gene expression and mineralisation were analysed at different time points. Low-density HOS 58 cultures exhibit rapid proliferation and high levels of c-myc, collagen type I and osteopontin mRNAs. This phenotypic stage was maximum between the 4th and 5th days of culture. As cell density increased expression of these genes declined and by day 14 the predominant mRNAs was alkaline phosphatase. Osteocalcin secretion was detected after confluence at an increasing level. In the presence of ascorbate and beta-glycerophosphate the production of alkaline phosphatase and collagen type I increased coincident with the elaboration of a Von Kossa staining matrix. Nevertheless no proper mineralisation of the collagenous matrix was detectable by electron microscopy. Hence, the human osteosarcoma cell line HOS 58 expressed a rather differentiated phenotype with further maturation during a culture period of 21 days. We conclude that the developmental sequence exhibited by the HOS 58 human osteosarcoma cell line is comparable to that described for primary rat osteoblasts. However, in detailed analysis considerable differences to other species are evident. Further evaluation of the HOS 58 system and comparison to other human osteoblast cell lines will be necessary to establish the most appropriate differentiation model for human bone cell cultures.
 ...
PMID:In vitro differentiation potential of a new human osteosarcoma cell line (HOS 58). 967 17

The effects of three immunosuppressants (rapamycin, FK506 and cyclosporin A) on the proliferation and differentiation of rat osteoblasts-like osteosarcoma cell line, ROS 17/2.8 (ROS) cells were examined in vitro. All immunosuppressants showed a direct inhibition on the proliferation of ROS cells with different potencies. Growth inhibition by rapamycin was stronger than that by FK506 or cyclosporin A. Rapamycin caused a significant increase in alkaline phosphatase (ALP) activity and in the expression of osteopontin and osteocalcin mRNAs. FK506 caused a moderate increase in ALP activity and a decreased expression of osteopontin mRNA. Cyclosporin A caused a decrease in ALP activity and in the expression of type 1 alpha 1 collagen mRNA. Our study indicates that rapamycin directly acts on ROS cells and induces osteoblastic differentiation, however, the effect of FK506 and cyclosporin A is weak. Rapamycin significantly enhances the differentiation induced by 1,25(OH)2-vitaminD3.
 ...
PMID:Osteoblastic differentiation is enhanced by rapamycin in rat osteoblast-like osteosarcoma (ROS 17/2.8) cells. 970 62

The 9,000 Mr calcium-binding protein calbindin-D9k (CaBP9k) is markedly induced by 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] in mammalian intestine. However, although a vitamin D response element (VDRE) has been reported in the promoter of the rat CaBP9k gene (at -490/-472), the CaBP9k promoter is weakly transactivated by 1,25-(OH)2D3. Previous studies indicated that when MCF-7 cells are transfected with the rat CaBP9k VDRE ligated to the thymidine kinase promoter and treated with both 1,25-(OH)2D3 and T3 there is an enhancement of the response observed with 1,25-(OH)2D3 alone, suggesting direct cross-talk between thyroid hormone and the vitamin D endocrine system and activation via the formation of vitamin D receptor (VDR)-thyroid hormone receptor (TR) heterodimers. To determine whether the weak response of the rat CaBP9k natural promoter to 1,25-(OH)2D3 could be enhanced by T3, CaBP9k promoter/reporter chloramphenicol acetyltransferase constructs were transfected in MCF-7 cells, and the cells were treated with the two hormones alone or in combination. No induction with T3 alone and no enhancement of reporter activity in the presence of both hormones was observed. To determine whether a lack of effect by T3 was specific for the CaBP9k promoter and to further examine the possibility of cross-talk between the TR- and VDR-signaling pathways, the 1,25-(OH)2D3-responsive rat 24 hydroxylase [24(OH)ase] promoter and the rat osteocalcin VDRE (-457/-430), both fused to reporter genes were similarly examined in MCF-7 cells. Again, no enhancement of the response to 1,25-(OH)2D3 was observed in the presence of T3. In addition, a similar lack of response to T3 but responsiveness to 1,25-(OH)2D3 was observed when UMR106-01 osteosarcoma cells [which, like MCF-7 cells, express VDR, TR, and the retinoid X receptor (RXR) endogenously] were transfected with a 1,25-(OH)2D3 responsive mouse osteopontin promoter reporter. In vitro DNA binding assays were carried out using purified human VDR, human RXRalpha, and chick T3Ralpha and 24(OH)ase, osteocalcin, osteopontin, and CaBP9k VDRE oligonucleotide probes. No VDR-TR heterodimer binding on any of these VDREs was observed, although, as expected, there was binding by the VDR-RXR complex and strong TR-RXR binding to a consensus thyroid hormone response element. Simultaneous gel retardation assays using similar and lower concentrations of TR with RXR showed strong binding of TR-RXR on a 32P-labeled thyroid response element. Studies using the yeast two-hybrid system also did not provide evidence for the formation of a VDR-TR protein-protein interaction. In addition, in vivo data showed that transfection of TR, in fact, repressed VDR-mediated transcription and that the repression could be reversed by the addition of RXR. Thus, in vitro and in vivo experiments do not support ligand-sensitive transactivation mediated by VDR-TR heterodimer formation but rather suggest that TR expression can repress 1,25-(OH)2D3-induced transcription predominantly by sequestering RXR.
 ...
PMID:Thyroid hormone receptor does not heterodimerize with the vitamin D receptor but represses vitamin D receptor-mediated transactivation. 973 5

We have previously shown that an exogenous type I collagen matrix can regulate expression of mRNA for parathyroid hormone (PTH)-related protein (PTHrP) and its receptor, the PTH/PTHrP receptor, in the UMR106-06 osteogenic sarcoma cell line, which is considered to be representative of a relatively mature osteoblast phenotype. Consistent with those data, we show here that growth of UMR106-06 cells on type I collagen increased PTH/PTHrP receptor-binding capacity. Analysis of the binding data showed that the number of PTH/PTHrP receptors expressed by cells cultured on collagen was at least 2-fold greater than that of cells cultured on plastic. Expression of mRNA encoding alkaline phosphatase (ALP) and osteopontin (OP) was also upregulated in cells cultured on collagen, suggesting that interaction with collagen promotes the osteoblast phenotype in this cell line. Retinoic acid (RA), which has also been shown to promote osteoblastic differentiation, synergized with type I collagen to cause super-induction of OP mRNA. In contrast, RA abolished the collagen-induced increase in ALP mRNA and PTH/PTHrP receptor mRNA. The collagen-mediated increase in the expression of OP and PTH/PTHrP receptor mRNA, but not that of ALP, was perturbed by prior covalent modification of the collagen by non-enzymatic glycation. The collagen effects did not occur via interaction with RGD amino acid domains in type I collagen, but evidence was obtained for involvement of the DGEA amino acid cell-binding domain. The mechanism by which plating of UMR106-06 cells on a type I collagen substrate affects PTH/PTHrP receptor mRNA levels was investigated. Inhibition of cytoskeletal organization using cytochalasin D, and inhibitors of protein phosphatases, protein kinase C, phospholipase C and cyclooxygenase, did not abrogate the collagen-mediated effects. In contrast, treatment of cells with the protein tyrosine kinase inhibitor genistein, but not herbimycin A, dose-dependently abolished the collagen effects on the expression of PTH/PTHrP receptor, ALP and OP mRNA. These results show that a type I collagen substrate influences the expression of osteoblast-associated genes in a cell model of mature osteoblasts and suggests that this involves, at least in part, changes in intracellular tyrosine phosphorylation.
 ...
PMID:Type I collagen influence on gene expression in UMR106-06 osteoblast-like cells is inhibited by genistein. 984 67


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>