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)

The relationship between histone acetylation and induction of gene expression was studied in Ros 17/2.8 rat osteosarcoma cells transfected with the pCH110 plasmid. This plasmid is commonly used in cotransfections as a measure of transfection efficiency. Cells were incubated for 48 hours with sodium butyrate, phenylbutyrate, 3-bromopropionate or trichostatin A. There was an approximate relationship between the extent of beta-galactosidase induction and the degree of histone hyperacetylation. Trichostatin A was the most effective agent followed by sodium butyrate and then phenylbutyrate. The toxicity of 3-bromopropionate made it difficult to compare its action with the other agents. Phenylbutyrate was less effective than sodium butyrate in causing induction of gene expression and histone hyperacetylation but this action may be a factor in the growth-inhibitory and differentiating activity of phenylbutyrate which has also been attributed to glutamine depletion.
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PMID:Induction of reporter gene expression by inhibitors of histone deacetylase. 970 34

The effects of natural lipid-soluble antioxidant, alpha-tocopherol (alpha-TP), and the synthetic water-soluble antioxidant, phenosan potassium salt (Ph-K), in a broad range of concentrations down to ultralow doses (10(-4)-10(-20) M) on the activity of protein kinase C (PKC) have been studied. It was shown that alpha-TP is a potent inhibitor of the rabbit heart enzyme: the maximum extent of inhibition is 80%. The effects of alpha-TP on the main kinetic parameters of the PKC activity differ at the alpha-TP physiological (10(-4) M) and ultralow (10(-14) M) concentrations: at 10(-14) M, alpha-TP acts as an allosteric inhibitor with Hill's coefficient about 2 and doubles the PKC affinity to the substrate (histone H-1). It was concluded that alpha-TP is more efficient inhibitor at ultralow concentration. Ph-K added to normal (A7r5 rat vascular smooth muscle cells, VSMC) and tumor cells (Saos-2 human osteosarcoma) growing in a culture has been found to be a PKC superactivator. The maximum activation is 400-500%, which is more than two times as high as the effect of the best activator of this enzyme, phorbol ester (TPA). It was demonstrated that irrespective of the effector action (activation or inhibition), the dose-effect curves are of the bimodal type with two maxima at the high (or physiological) (10(-4)-10(-7) M) and ultralow (10(-14)-10(-19) M) concentrations of the antioxidants and the so-called "silence zones" between them, in which the effect of antioxidants is significantly reduced or absent (tumor cells). For the first time, these bimodal curves were observed at the enzyme level. The results obtained are discussed considering various hypotheses of the effect of ultralow doses of biologically active compounds and the PKC activity regulation in normal and tumor cells by the antioxidants.
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PMID:Natural (alpha-tocopherol) and synthetic (phenosan potassium salt) antioxidants regulate the protein kinase C activity in a broad concentration range (10(-4)-10(-20) M). 987 48

Although quantitative measurement of skeletal alkaline phosphatase (sALP) activity in serum can provide an index of the rate of bone formation, the metabolic process that determines the release of sALP - from the surface of osteoblasts, into circulation-is unknown. The current studies were intended to examine the hypothesis that the release of sALP from human osteoblasts is a consequence of apoptotic cell death. We measured the release of sALP activity from human osteosarcoma (SaOS-2) cells and normal human bone cells, under basal conditions and in response to agents that increased apoptosis (TNF-a, okadiac acid) and agents that inhibit apoptosis (IGF-I, calpain, and caspase inhibitors). Apoptosis was determined by the presence of nucleosomes (histone-associated DNA) in the cytoplasm of the cells by using a commercial kit. The results of these studies showed that TNF-a and okadiac acid caused dose- and time-dependent increases in apoptosis in the SaOS-2 cells (r = 0.78 for doses of TNF-a and r = 0.93 for doses of okadiac acid, P <0.005 for each), with associated decreases in cell layer protein (P <0.05 for each) and concomitant increases in the release of sALP activity (e.g., r = 0.89 for TNF-a and r = 0.75 for okadiac acid, P <0.001 for each). In contrast, caspase and calpain inhibitors reduced apoptosis, increased cell layer protein, and decreased the release of sALP activity (P <0.05 for each). Exposure to IGF-I also decreased apoptosis, in a time- and dose-dependent manner (e.g., r = 0.93, P <0.001 for IGF-I doses), with associated proportional effects to increase cell layer protein (P <0.001) and decrease the release of sALP activity (P <0.001). IGF-I also inhibited the actions of TNF-a and okadiac acid to increase apoptosis and sALP release. The associations between apoptosis and sALP release were not unique to osteosarcoma (i.e., SaOS-2) cells, but also seen with osteoblast-line cells derived from normal human bone. Together, these data demonstrate that the release of sALP activity from human osteoblast-line cells in vitro is associated with, and may be a consequence of, apoptotic cell death. These findings are consistent with the general hypothesis that the appearance of sALP activity in serum may reflect the turnover of osteoblast-line cells.
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PMID:Apoptosis may determine the release of skeletal alkaline phosphatase activity from human osteoblast-line cells. 1203 23

The cytoskeleton, mainly composed of actin filaments, microtubules, and intermediate filaments, is involved in cell proliferation, the maintenance of cell shape, and the formation of cellular junctions. The organization of the intermediate filaments is regulated by phosphorylation and dephosphorylation. We examined cell population growth, apoptotic cell death, and the morphology of cytoskeletal components in myoblast cultures derived from patients with the 3243A-->G mutation in mitochondrial DNA (mtDNA) and from control subjects by means of assays detecting cellular nucleic acids, histone-associated DNA fragments and by immunolabeling of cytoskeletal components. Population growth was slower in the 3243A-->G myoblast cultures, with no difference in the amount of apoptotic cell death. The organization of vimentin filaments in myoblasts with 3243A-->G was disturbed by randomization of filament direction and length, whereas no disturbances were observed in the other cytoskeletal proteins. Vimentin filaments formed large bundles surrounding the nucleus in mtDNA-less (rho(0)) osteosarcoma cells and in osteosarcoma cells after incubation with sodium azide and nocodazole. We conclude that defects in oxidative phosphorylation lead to selective disruption of the vimentin network, which may have a role in the pathophysiology of mitochondrial diseases.
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PMID:Cytoskeletal structure of myoblasts with the mitochondrial DNA 3243A-->G mutation and of osteosarcoma cells with respiratory chain deficiency. 1221 Nov 4

The antitumor efficacy of the synthetic benzamide derivative MS-27-275 (MS-275), an inhibitor of histone deacetylation [T. Suzuki et al., J. Med. Chem., 42: 3001-3003, 1999], was evaluated in a series of pediatric solid tumor cell lines, including neuroblastoma, rhabdomyosarcoma, Ewing's sarcoma (EWS), retinoblastoma, medulloblastoma, undifferentiated sarcoma (US), osteosarcoma, and malignant rhabdoid tumors. Treatment with MS-275 results in an increase in acetylation of histones within 4 h of drug exposure. The cell lines were treated with various concentrations of MS-275 for 3 days and incubated with [(3)H]thymidine for 20 h before cell harvest. MS-275 inhibited [(3)H]thymidine uptake in a dose-dependent manner in all tumor cell lines examined. The IC(50) ranged from 50 nm in the D283 medulloblastoma cell line to 1.3 micro M in the US. A common feature of MS-275 treatment of pediatric tumor cell lines was induction of p21mRNA. However, the effects on cell cycle were diverse because in some cases MS-275 induced an increase in G(1) or G(2), whereas in others, there was an induction of apoptosis. In EWS, the EWS/fli chimeric transcription factor created by the t(11;22) suppresses transforming growth factor (TGF) betaRII transcription, however, MS-275 was able to induce an increase in TGF-betaRII mRNA and restore TGF-beta signaling. Using xenograft orthotopic models of US, EWS, and neuroblastoma, we find that the growth of established tumors is inhibited in mice treated with MS-275.
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PMID:MS-27-275, an inhibitor of histone deacetylase, has marked in vitro and in vivo antitumor activity against pediatric solid tumors. 1241 35

Efficient gene delivery of a baculovirus-derived vector (BV-p53-lacZ) to a human osteogenic sarcoma cell line, Saos-2, was serendipitously found while evaluating the vector for gene delivery to human p53-null tumour cells in a previous study. Therefore, we investigated other human, rat and mouse osteogenic sarcoma and other types of tumour cell lines for transduction efficiency via baculovirus vectors containing a lacZ reporter gene under the control of either a cytomegalovirus or Rous sarcoma virus promoter. The expression of beta-galactosidase protein, assessed by X-Gal staining and beta-galactosidase ELISA, demonstrated an extremely high level of transduction efficiency in some osteogenic sarcoma cell lines, such as U-2OS, Saos-2 and Saos-LM2. These human osteogenic sarcoma cell lines showed levels of beta-galactosidase expression 5-40 times greater than HepG2 cells, which were previously thought to be the mammalian cells most susceptible to baculovirus-mediated gene delivery. The level of acetylated histone proteins in these tumour lines did not correlate well with the high level of reporter gene expression. These results strongly suggest that some osteogenic sarcoma cells are highly susceptible to baculovirus-mediated gene delivery and that a baculovirus-derived vector is an efficient gene delivery vehicle into human osteogenic sarcoma cells.
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PMID:Effective transduction of osteogenic sarcoma cells by a baculovirus vector. 1260 22

The dihydrofolate reductase (dhfr) promoter contains cis-acting elements for Sp1 and E2F. Here we examined the cooperative regulation of dhfr gene transcription by Sp1 and E2F in human osteosarcoma cells, U2OS. Trichostatin A, an inhibitor of histone deacetylases, markedly stimulated dhfr promoter activity, a response that was enhanced by the deletion of an E2F element. In contrast, deletion of the dhfr Sp1 binding sites completely abolished promoter stimulation by trichostatin A. Cotransfection assays showed that activation of dhfr transcription by expression of E2F1/DP1 requires the reiterated Sp1 elements, whereas activation by Sp1 was enhanced by the deletion of the E2F element. Expression of HDAC1 with Sp1 suppressed promoter activity and suppression was not alleviated by coexpression of E2F1/DP1. These results suggest that HDAC1 acts through Sp1 to repress dhfr promoter activity, and that the E2F element modulates the activity of Sp1 at the dhfr promoter through a cis-acting mechanism.
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PMID:Modulation of Sp1-dependent transcription by a cis-acting E2F element in dhfr promoter. 1278 94

Although histone deacetylase (HDAC) inhibitors are emerging as a promising new treatment strategy in malignancy, how they exert their effect on osteosarcoama cells is as yet unclear. This study was undertaken to investigate the underlying mechanism of a HDAC inhibitor Trichostatin A (TSA)-induced apoptosis in a osteosarcoma cell line HOS. We observed that TSA treatment decreased the viability of the cells and prominently increased acetylation of histone H3. Evidence was obtained indicating that TSA induced apoptosis of HOS cells as follows: (1) Generation of DNA fragmentation; (2) activation of procaspase-3; (3) cleavage of PARP; and (4) increase of DNA hypoploidy. The reduction of MMP and the release of cytochrome c to cytosol were also shown, indicating that TSA induces apoptosis in HOS cells in a histone acetylation- and mitochondria-dependent fashions. We also examined whether TSA can sensitize HOS cells to the action of an antitumor agent genistein. The combination therapy of TSA and genistein showed synergistic anticancer effect indicating that TSA can be considered as a novel therapeutic strategy for osteosarcoma not only from its direct apoptosis-inducing activity but also from the possibility of sensitization to other antitumor agents.
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PMID:Mechanism of histone deacetylase inhibitor Trichostatin A induced apoptosis in human osteosarcoma cells. 1531 86

Cyclin-dependent kinases (Cdk) promote cell proliferation, are often deregulated in human cancers, and are targets of ongoing cancer chemotherapy trials. We show here that Cdk activity is also required in human cells to maintain function of the Chk1 pathway, a key component of the response to DNA damage or stalled replication. Chk1 expression was markedly reduced in primary fibroblasts and U2OS osteogenic sarcoma cells by treatment with small molecule Cdk inhibitors or induction of a dominant-negative mutant of Cdk2. The findings of decreased Chk1 activity and accumulation of Cdc25A, a protein targeted for degradation by Chk1, confirmed that Chk1 function was impaired. Furthermore, Cdk inhibition triggered a DNA damage response, characterized by the accumulation of activated forms of ATM and Chk2 as well as nuclear foci containing phosphorylated substrates of ATM/ATR, including histone H2AX (gammaH2AX). Time course experiments showed that the bulk of ATM activation followed Chk1 down-regulation. Chk1 RNA interference combined with partial inhibition of DNA replication was sufficient to evoke the DNA damage response. Conversely, ectopic expression of Chk1 blunted induction of gammaH2AX foci by Cdk inhibitors, indicating that Chk1 down-regulation was necessary to elicit the full phenotype. Finally, both Cdk and Chk1 inhibitors enhanced the cytotoxity of etoposide, a DNA-damaging agent. These results define a pathway through which Cdk inhibition can mediate DNA damage and potentially enhance the efficacy of extant cancer chemotherapies.
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PMID:Cdk inhibition in human cells compromises chk1 function and activates a DNA damage response. 1570 74

The retinoblastoma tumor suppressor protein (Rb) affects gene transcription both negatively and positively and through this regulates distinct cellular responses. Although cell cycle regulation requires gene repression, Rb's ability to promote differentiation and part of its antiproliferative activity appears to rely on the activation of gene transcription. We present evidence here that the RET finger protein (RFP)/tripartite motif protein 27 (TRIM 27) inhibits gene transcription activation by Rb but does not affect gene repression. RFP binds to Rb and prevents the degradation of the EID-1 inhibitor of histone acetylation and differentiation. Furthermore, ablation of RFP in U2OS osteosarcoma cells augments a transcriptional program indicative of lineage-specific differentiation in response to Rb. These findings provide precedent for a regulatory pathway that uncouples different Rb-dependent activities and thus silences specific cellular responses to Rb in a selective way.
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PMID:Selective ablation of retinoblastoma protein function by the RET finger protein. 1583 24


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