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)

The effect of modulation of protein kinase C (PKC) activity by 12-O-tetradecanoylphorbol-13-acetate (TPA) on cisplatin cytotoxicity was examined in a human osteosarcoma U2-OS cell line and in a U2-OS variant (U2-OS/Pt) selected after continuous exposure to increasing concentrations of cisplatin. U2-OS/Pt cells showed a 7.5-fold resistance to the drug. A 24 h exposure of cells to TPA caused a potentiation of cisplatin cytotoxicity in sensitive and in resistant cells; under these conditions, PKC activity was shown to be down-regulated. In contrast, a short-term exposure of cells to TPA did not affect cisplatin cytotoxicity in U2-OS or in U2-OS/Pt cells. These results support the involvement of PKC in cellular response to cisplatin. However, this enzyme is probably not directly implicated in the mechanisms of acquired resistance in this cell system.
 ...
PMID:Effect of modulation of protein kinase C activity on cisplatin cytotoxicity in cisplatin-resistant and cisplatin-sensitive human osteosarcoma cells. 840 75

Immunocytochemistry revealed an association between growth inhibition and a translocation of retinoblastoma protein (pRB) to the nucleoli of U-2 osteosarcoma cells inhibited in their growth by the negative growth factor NCPI (natural cell proliferation inhibitor). Similar phenomenon was demonstrated by Western blot analysis and immunocytochemistry in U937 leukemic cells inhibited in their growth and induced to differentiate by 12-O-tetradecanoylphorbol acetate (TPA). Total nuclear extract of control U937 cells gave an intense 110 KD band, while total nuclear extract of TPA treated cells produced an intense 60 KD band and a weak 110 KD band. No bands were observed for the purified nucleoli of control cells, but the purified nucleoli of TPA treated cells produced a 60 KD band. These results suggest that in the process of cell growth inhibition and differentiation, specific proteolysis of pRB and its translocation to the nucleolus may occur.
 ...
PMID:Translocation of retinoblastoma protein associated with tumor cell growth inhibition. 850 87

Leukemia inhibitory factor (LIF) is a recently characterized glycoprotein with complex biologic activities on bone cells. We tested various rodent and human immortalized and malignant bone cell lines and primary osteoblast-enriched cell cultures from fetal rat calvarial digests for expression of LIF mRNA and LIF protein. Both human and rodent immortalized and malignant cells expressed a single 4.4 kb mRNA transcript that hybridized to a human LIF cDNA probe in Northern blots. LIF mRNA was undetectable in unstimulated rodent osteoblast-like cells lines MC3T3-E1 and Py1a. However, treatment with LPS (10 micrograms/ml), TGF-beta (1 ng/ml), TNF-alpha (100 ng/ml) or inhibitors of protein synthesis (cycloheximide, emetine, puromycin, and anisomycin) induced the expression of LIF message in these cells. In contrast, primary osteoblast-enriched cells did not express LIF mRNA in Northern blot assays either constitutively or after treatment with TNF-alpha or cycloheximide. The human osteosarcoma cells lines U-2 OS and Saos-2 constitutively expressed LIF mRNA and did not respond to LPS treatment. However, phorbol myristate acetate (PMA), an activator of protein kinase C, was a potent stimulator of LIF message in Saos-2 but not U-2 OS cells. The effects of PMA (0.5 ng/ml) on LIF mRNA in Saos-2 cells were detectable at 1 h and maximal at 6 h. TNF-alpha (100 ng/ml) and inhibitors of protein synthesis also increased LIF mRNA in both Saos-2 and U-2 OS cells. LIF protein was also detected constitutively in the conditioned medium from both Saos and U-2 OS cells.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Production of leukemia inhibitory factor mRNA and protein by malignant and immortalized bone cells. 851 89

The closely related cytokines bFGF and aFGF regulate the function of bone cells and mineralization. Osteoblasts express PPi-generating nucleoside triphosphate pyrophosphohydrolase (NTPPPH)/nucleotide phosphodiesterase I activity. bFGF and aFGF (10 ng/ml) up-regulated NTPPPH in human SaOS-2 and U2OS osteosarcoma cells, which express osteoblast-like features in culture. The induction was selective as alkaline phosphatase activity was down-regulated and specific as insulin-like growth factor-1 (IGF-1) and interleukin-1 beta (IL-1 beta) were not active. Furthermore, IL-1 beta but not IGF-1 inhibited bFGF-induced up-regulation of NTPPPH. The induced NTPPPH remained predominantly associated with cells. bFGF can induce signaling through pathways including protein kinase A (PKA) and protein kinase C (PKC)-mediated transduction. An activator of the PKA pathway (8-bromo cyclic adenosine monophosphate [cAMP]) induced NTPPPH. Furthermore, pretreatment with the PKC activator phorbol myristate acetate (PMA) (80 nM) markedly increased subsequent NTPPPH induction by both bFGF and cAMP. The PMA effect was associated with morphologic changes characterized by long, thin intercellular extensions. PKC desensitization also potentially contributed to this effect because the PKC inhibitors staurosporine and H-7 enhanced bFGF-induced and cAMP-induced NTPPPH expression in the absence of morphologic changes. We observed that bFGF induced expression of PC-1, a member of the NTPPPH gene family. The majority of NTPPPH activity was depleted by immunoadsorption using a monoclonal antibody to native human PC-1. bFGF- and aFGF-induced production of PC-1/NTPPPH in osteoblastoid cells may contribute to the effects of FGFs on bone metabolism.
 ...
PMID:Expression of the nucleoside triphosphate pyrophosphohydrolase PC-1 is induced by basic fibroblast growth factor (bFGF) and modulated by activation of the protein kinase A and C pathways in osteoblast-like osteosarcoma cells. 882 42

Bone sialoprotein (BSP), a protein which has been implicated in the initial mineralization of newly-formed bone, provides an early phenotypic marker for differentiated osteoblasts. BSP expression is induced by glucocorticoids in association with osteoblast differentiation, and a glucocorticoid response element (GRE) overlapping a putative TRE (TPA, 12-O-tetradecanoyl-phorbol 13-acetate, response element) site has been identified in the rat BSP promoter (Ogata et al., 1995). Since AP-1 and the glucocorticoid receptor have a central role in regulating cell proliferation and differentiation, we have studied AP-1 activity, stimulated by 100 ng/ml TPA in normal fetal rat calvarial cells and in transformed rat osteosarcoma cells (ROS 17/2.8). A transient induction of both c-fos and c-jun mRNAs by TPA was observed in both cell populations, together with an associated suppression of BSP mRNA in the fetal rat calvarial cells. Rat BSP promoter constructs, transiently transfected into ROS 17/2.8 cells, were used to show that TPA suppressed transcription of a luciferase construct (-938/+60; pLUC6) that included the GRE/TRE, but not transcription of shorter contructs lacking this element. Notably, suppression of pLUC6 transcription by TPA was abrogated in the presence of the synthetic glucocorticoid, dexamethasone. Gel mobility shift analyses were performed using two double-stranded synthetic oligonucleotides. These encompassed the TRE and either the distal pair of GRE half-sites (-936/ -910; GRE3) or the proximal pair of GRE half-sites (-925/-899; GRE 4) that comprise the GRE/AP-1 element. The assay showed binding of both AP-1 complexes and recombinant c-Jun homodimers. Additionally, either the c-Jun or glucocorticoid receptor could displace its counterpart from the GRE/TRE but not from consensus GRE and TRE oligonucleotides, indicating that the abrogation of AP-1-mediated gene suppression by glucocorticoids could involve competitive binding. These studies, therefore, have identified a glucocorticoid response unit through which c-Fos and c-Jun can suppress the expression of BSP in proliferating pre-osteoblastic cells and through which glucocorticoids can ameliorate the effects of AP-1 and promote osteoblast differentiation and the associated expression of BSP.
 ...
PMID:AP-1 regulation of the rat bone sialoprotein gene transcription is mediated through a TPA response element within a glucocorticoid response unit in the gene promoter. 883 13

The inositol 1,4,5-trisphosphate (InsP3) receptor is essential for signal Ca2+ release from intracellular stores and for capacitative Ca2+ entry. We have isolated the promoter and proximal DNA segments of the human type I InsP3 receptor gene. Transcription initiation in human G-292 osteosarcoma and HL-60 promyelocytic leukemia cells was shown to occur predominantly from an adenine residue located 39 base pairs downstream of a consensus TATA box element. Upstream DNA including the TATA box promoted directional transcription of a chloramphenicol acetyltransferase reporter gene when transfected into G-292 cells. A negative regulatory element in the distal promoter and a positive element in the proximal region were identified by deletion mapping and transcription assays. The proximal region enhanced transcription in response to 12-O-tetradecanoylphorbol-13-acetate or serum, but conferred transcriptional repression in response to 1,25-dihydroxyvitamin D3 or 17beta-estradiol. The repressive effect of 17beta-estradiol was mediated by the nuclear estrogen receptor, as estrogen-dependent transcriptional repression was inhibited by the antiestrogen tamoxifen and the estrogen receptor antagonist ICI 182,780. This is the first study of the type I InsP3 receptor gene promoter, and the results suggest a mechanism by which chronic estrogen treatment of osteoblasts affects type I InsP3 receptor gene expression, signal transduction, and secretion.
 ...
PMID:Cloning and characterization of the type I inositol 1,4,5-trisphosphate receptor gene promoter. Regulation by 17beta-estradiol in osteoblasts. 927 93

Parathyroid hormone (PTH) functions in part by regulating osteoblast cytokine expression. We recently demonstrated that PTH induced a rapid and transient increase in interleukin-6 (IL-6) mRNA expression in rat bones in vivo. To determine the molecular basis of this effect, we analyzed the human IL-6 promoter fused (-1,179 to +9) with the chloramphenicol acetyltransferase (CAT) reporter gene in stable transfections into human osteoblast-like osteosarcoma SaOS-2 cells. We compared the effects of PTH on IL-6 expression with adenylate cyclase activator forskolin, PKC activator phorbol 12-myristate 13-acetate (PMA), calcium ionophore A23187, interleukin-1 alpha (IL-1 alpha), prostaglandin E-2 (PGE-2), RS-66271 (a parathyroid hormone-related peptide analog), and platelet-derived growth factor-BB (PDGF-BB). Analyses of cell clones showed that IL-6 promoter expression was extremely low in the unstimulated state. Exposure to PTH (0.001-100 nM) for 12 h stimulated CAT expression in a dose-dependent manner (200-500% of control). Treatment with IL-1 alpha was more potent than PTH in inducing transcription of the IL-6 promoter (900-1,000%). Activation of the cAMP-PKA pathway by treatment with forskolin induced a comparable level of induction with PTH. Together, the effects of PTH and forskolin were additive. RS-66271, previously shown to have PTH-like effects, induced a comparable level of IL-6 promoter expression. When examined together, PTH+RS-66271 effects were comparable to PTH effects alone. Exposure to PGE-2, PMA, PDGF-BB, or A23187 for 12 h did not significantly alter IL-6 promoter expression. These results demonstrate PTH, forskolin, the PTHrP analog RS-66271, and IL-1 alpha stimulate IL-6 expression by stimulating gene transcription. The response to forskolin suggests that the messenger system mediated by PKA is sufficient to induce IL-6 expression.
 ...
PMID:Parathyroid hormone (1-34)-mediated interleukin-6 induction. 932 32

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

In this study, we examined the effect of activation of protein kinase C (PKC) pathways on the regulation of 1,25-dihydroxyvitamin D receptors (VDR) in rat osteosarcoma (ROS) 17/2.8 cells. Activation of PKC with phorbol 12-myristate 13-acetate (PMA) resulted in a time- and dose-dependent increase in VDR expression in ROS cells. Treatment of ROS cells with 4alpha-phorbol 12,13-dedeconate, a PKC-inactive phorbol ester, had no effect on VDR expression. Oleoyl acetyl glycerol (OAG), a synthetic diacylglycerol, stimulated VDR up-regulation in ROS cells. The PKC inhibitors (H-7, staurosporin, and sphingosine) all blocked PMA-mediated up-regulation of VDR in a dose-dependent manner. We next examined the interaction of 1,25(OH)2D3 and PKC activation by PMA on the regulation of VDR in ROS cells. We found that PMA or 1,25(OH)2D3 treatment alone resulted in a 50 and 200% increase in VDR, respectively. PMA treatment alone resulted in a 50% increase in VDR protein and a marginal 20% increase in VDR mRNA. 1,25(OH)2D3 up-regulation of VDR was associated with a 2-fold increase in VDR mRNA. In contrast, co-treatment of ROS cells with PMA and 1,25(OH)2D3 resulted in a synergistic 10-fold induction of VDR mRNA and the appearance of a 7.2 kb VDR transcript. VDR protein was also synergistically up-regulated by combined PMA and 1,25(OH)2D3 treatment of ROS cells. Scatchard analysis demonstrated that the synergistic effect of PMA and 1,25(OH)2D3 on VDR protein expression was not associated with any change in the affinity of VDR for 1,25(OH)2D3. The synergistic effect of 1,25(OH)2D3 and PMA on VDR expression supports a link between PKC signal pathways and the function of VDR.
 ...
PMID:Phorbol 12-myristate 13-acetate and 1,25-dihydroxyvitamin D3 regulate 1,25-dihydroxyvitamin D3 receptors synergistically in rat osteosarcoma cells. 939 48

Human cartilage glycoprotein 39 (HC gp-39) has been described as a major secreted product of cultured articular chondrocytes, synovial fibroblasts, and the osteosarcoma line MG63. However, its expression in these cells types has not been directly linked to corresponding cell types in vivo. In this report, expression of HC gp-39 is demonstrated from peripheral blood-derived macrophages in association with their differentiation from monocytes to macrophages. Consistent with macrophage specificity, HC gp-39 expression is also induced upon selective stimulation of the pluripotent promyelocytic leukemia cell line HL-60 toward the monocyte/macrophage lineage with vitamin D3 or phorbol 12-myristate 13-acetate (PMA), while treatments stimulating granulocyte and eosinophilic pathways do not induce expression. Furthermore, HC gp-39 expression levels correlate with the degree of morphological differentiation induced by PMA and vitamin D3 treatments. PMA-induced mRNA expression occurs by 36 h and is a secondary transcriptional response since its synthesis is inhibited by cycloheximide. Apparently, HC gp-39 expression is tied to later events in the differentiation of monocytes into macrophages. The in vivo significance of these results is validated by the in situ detection of HC gp-39 mRNA in inflammatory macrophages associated with rheumatoid synovium. Thus, macrophages appear to be an important source of HC gp-39, which has been shown to be present at elevated levels in the blood and synovium of rheumatoid arthritis patients. The implications of this extend well beyond the previously restricted observations in cell types associated with the joint and suggest a potential involvement of macrophage-derived HC gp-39 in other aspects of inflammation, tissue remodeling, and host defense.
 ...
PMID:Induction and expression of human cartilage glycoprotein 39 in rheumatoid inflammatory and peripheral blood monocyte-derived macrophages. 941 65


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