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)

DNA topoisomerase II is an essential nuclear enzyme for proliferation of eukaryotic cells and plays important roles in many aspects of DNA processes. In this report, we have demonstrated that the catalytic activity of topoisomerase IIalpha, as measured by decatenation of kinetoplast DNA and by relaxation of negatively supercoiled DNA, was stimulated approximately 2-3-fold by the tumor suppressor p53 protein. In order to determine the mechanism by which p53 activates the enzyme, the effects of p53 on the topoisomerase IIalpha-mediated DNA cleavage/religation equilibrium were assessed using the prototypical topoisomerase II poison, etoposide. p53 had no effect on the ability of the enzyme to make double-stranded DNA break and religate linear DNA, indicating that the stimulation of the enzyme catalytic activity by p53 was not due to alteration in the formation of covalent cleavable complexes formed between topoisomerase IIalpha and DNA. The effects of p53 on the catalytic inhibition of topoisomerase IIalpha were examined using a specific catalytic inhibitor, ICRF-193, which blocks the ATP hydrolysis step of the enzyme catalytic cycle. Clearly manifested in decatenation and relaxation assays, p53 reduced the catalytic inhibition of topoisomerase IIalpha by ICRF-193. ATP hydrolysis assays revealed that the ATPase activity of topoisomerase IIalpha was specifically enhanced by p53. Immunoprecipitation experiments revealed that p53 physically interacts with topoisomerase IIalpha to form molecular complexes without a double-stranded DNA intermediary in vitro. To investigate whether p53 stimulates the catalytic activity of topoisomerase II in vivo, we expressed wild-type and mutant p53 in Saos-2 osteosarcoma cells lacking functional p53. Wild-type, but not mutant, p53 stimulated topoisomerase II activity in nuclear extract from these transfected cells. Our data propose a new role for p53 to modulate the catalytic activity of topoisomerase IIalpha. Taken together, we suggest that the p53-mediated response of the cell cycle to DNA damage may involve activation of topoisomerase IIalpha.
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PMID:The p53 tumor suppressor stimulates the catalytic activity of human topoisomerase IIalpha by enhancing the rate of ATP hydrolysis. 1076 86

In human osteosarcoma MG63 cells, the effect of the neuroprotective drug riluzole on the intracellular Ca(2+) concentration ([Ca(2+)](i)) was measured using fura-2. Riluzole (50-500 micromol/l) caused a rapid and sustained plateau increase in [Ca(2+)](i) in a concentration-dependent manner (EC(50) = 150 micromol/l). The riluzole-induced rise in [Ca(2+)](i) was prevented by 58 and 20% by extracellular Ca(2+) removal and nifedipine, respectively, but was not changed by La(3+) and verapamil. In Ca(2+)-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum (ER) Ca(2+)-ATPase, caused a monophasic increase in [Ca(2+)](i), after which the increasing effect of riluzole on [Ca(2+)](i) was attenuated by 84%; also, pretreatment with riluzole abolished the thapsigargin-induced [Ca(2+)](i) increase. U73122, an inhibitor of phospholipase C, abrogated the ATP (but not riluzole)-induced rise in [Ca(2+)](i). A low concentration (6 micromol/l) of riluzole selectively potentiated the bradykinin (but not ATP and histamine)-induced increase in [Ca(2+)](i). These results suggest that riluzole rapidly increases [Ca(2+)](i) by stimulating both the extracellular Ca(2+) influx via a nifedipine-sensitive pathway and intracellular Ca(2+) release from the ER via an as yet unidentified mechanism(s).
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PMID:Effect of riluzole on cytosolic Ca2+ increase in human osteosarcoma cells. 1237 1

In human osteosarcoma MG63 cells, the effect of desipramine, an antidepressant, on intracellular Ca(2+) concentration ([Ca(2+)](i)) was measured by using fura-2. Desipramine (>10 micromol/l) caused a rapid and sustained rise of [Ca(2+)](i) in a concentration-dependent manner (EC(50) = 200 micromol/l). Desipramine-induced [Ca(2+)](i) rise was prevented by 80% by removal of extracellular Ca(2+) but was not altered by voltage-gated Ca(2+) channel blockers. In Ca(2+)-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum (ER) Ca(2+)-ATPase, caused a monophasic [Ca(2+)](i) rise, after which the increasing effect of desipramine on [Ca(2+)](i) was abolished; also, pretreatment with desipramine partly reduced thapsigargin-induced [Ca(2+)](i) increase. U73122, an inhibitor of phospholipase C, did not affect desipramine-induced [Ca(2+)](i) rise. Overnight incubation with 10 micromol/l desipramine did not alter cell proliferation, but killed 32 and 89% of cells at concentrations of 100 and 200 micromol/l, respectively. These findings suggest that desipramine rapidly increases [Ca(2+)](i) in osteoblasts by stimulating both extracellular Ca(2+) influx and intracellular Ca(2+) release, and is cytotoxic at high concentrations.
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PMID:Effect of the antidepressant desipramine on cytosolic Ca(2+) movement and proliferation in human osteosarcoma cells. 1462 59

The molecular mechanism of cisplatin uptake remains poorly defined and impaired drug accumulation may be implicated in the acquisition of resistance to cisplatin. Thus, we used cell lines of different tumor types (ovarian carcinoma A2780 and IGROV-1, osteosarcoma U2-OS, cervix squamous cell carcinoma A431) and stable cisplatin-resistant sublines, exhibiting variable levels of resistance (between 2.5 and 18.4), to investigate the mechanisms of cellular accumulation of cisplatin. Among the resistant lines we found that reduced cisplatin uptake was a common feature and ranged between 23 and 76%. In an attempt to examine the role of human copper transporter 1 (CTR1) in cisplatin accumulation by human cells, we selected the well characterized A431 cell line and the resistant variant A431/Pt. As compared with A431/Pt cells, A431/Pt transfectants overexpressing CTR1 (3.4-fold) exhibited increased uptake of copper, thereby supporting the expression of a functional transporter. However, no changes in cisplatin uptake and cellular sensitivity to drug were observed. Also overexpression of CTR1 in A431 cells did not produce modulation of cisplatin accumulation. An analysis of the expression of other factors that could affect drug accumulation indicated that A431/Pt cells displayed increased expression of ATPase, Cu(2+) transporting, alfa polypeptide. In conclusion, our results indicate that the overexpression of a functional CTR1 in a human cell line characterized by impaired cisplatin uptake fails (a) to restore cellular drug accumulation to the level of the parental cell line and (b) to modulate cisplatin sensitivity. Our data are consistent with the interpretation that the defects in cellular accumulation by resistant cells are not mediated by expression of CTR1, that plays a marginal role, if any, in cisplatin transport.
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PMID:Cellular pharmacology of cisplatin in relation to the expression of human copper transporter CTR1 in different pairs of cisplatin-sensitive and -resistant cells. 1519

The key role of mitochondria in the apoptotic process is well understood, but not many data are available regarding the specific role of mitochondrial DNA mutations in determining cell fate. We investigated whether two mitochondrial DNA mutations (L217R and L156R) associated with maternally-inherited Leigh syndrome may play a specific role in triggering the apoptotic cascade. Considering that different nuclear genetic factors may influence the expression of mtDNA mutations, we used a 143BTK(-) osteosarcoma cell line deprived from its own mtDNA in order to insert mutated mtDNAs. Analysis of mitochondrial features in these cybrids indicated that both mitochondrial DNA mutations produced evidence of biochemical, functional and ultrastructural modifications of mitochondria, and that these modifications were associated with an increased apoptotic proneness. Cybrids were highly susceptible to two different apoptotic stimuli, tumour necrosis factor-alpha and Staurosporin. The mechanism involved was the mitochondrial 'intrinsic' pathway, i.e. the caspase 9-driven cascade. More importantly, our results also indicated that the polarization state of the mitochondrial membrane, i.e. a constitutive hyperpolarization detected in cybrid clones, played a specific role. Interestingly, the different effects of the two mutations in terms of susceptibility to apoptosis probably reflect the deeper bioenergetic defect associated with the L217R mutation. This work provides the first evidence that hyperpolarization of mitochondria may be a 'risk factor' for cells with a deep ATPase dysfunction, such as cells from patients with maternally-inherited Leigh syndrome.
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PMID:Maternally-inherited Leigh syndrome-related mutations bolster mitochondrial-mediated apoptosis. 1522 5

Capsazepine is thought to be a selective antagonist of vanilloid type 1 receptors; however, its other in vitro effect on different cell types is unclear. In human MG63 osteosarcoma cells, the effect of capsazepine on intracellular Ca(2+) concentrations ([Ca(2+)](i)) and cytotoxicity was explored by using fura-2 and tetrazolium, respectively. Capsazepine caused a rapid rise in [Ca(2+)](i) in a concentration-dependent manner with an EC(50) value of 100 microM. Capsazepine-induced [Ca(2+)](i) rise was partly reduced by removal of extracellular Ca(2+), suggesting that the capsazepine-induced [Ca(2+)](i) rise was composed of extracellular Ca(2+) influx and intracellular Ca(2+). In Ca(2+)-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca(2+)-ATPase, caused a monophasic [Ca(2+)](i) rise, after which the increasing effect of capsazepine on [Ca(2+)](i) was inhibited by 75%. Conversely, pretreatment with capsazepine to deplete intracellular Ca(2+) stores totally prevented thapsigargin from releasing more Ca(2+). U73122, an inhibitor of phospholipase C, abolished histamine (an inositol 1,4,5-trisphosphate-dependent Ca(2+) mobilizer)-induced, but not capsazepine-induced, [Ca(2+)](i) rise. Overnight treatment with 1-100 microM capsazepine inhibited cell proliferation in a concentration-dependent manner. These findings suggest that in human MG63 osteosarcoma cells, capsazepine increases [Ca(2+)](i) by stimulating extracellular Ca(2+) influx and also by causing intracellular Ca(2+) release from the endoplasmic reticulum via a phospholiase C-independent manner. Capsazepine may be mildly cytotoxic.
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PMID:Capsazepine elevates intracellular Ca2+ in human osteosarcoma cells, questioning its selectivity as a vanilloid receptor antagonist. 1536 57

The effect of the antidepressant nortriptyline, on bone cells is unknown. In human osteosarcoma MG63 cells, the effect of nortriptyline on intracellular Ca2+ concentration ([Ca2+]i) and proliferation was measured by using fura-2 and tetrazolium, respectively. Nortriptyline (> or = 10 microM) caused a [Ca2+]i rise in a concentration-dependent manner (EC50 = 200 microM). Nortriptyline-induced [Ca2+]i rise was prevented by 60% by removal of extracellular Ca2+ but was not altered by voltage-gated Ca2+ channel blockers. In Ca2+ -free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+ -ATPase, caused a monophasic [Ca2+]i rise, after which the increasing effect of nortriptyline on [Ca2+]i was abolished; also, pretreatment with nortriptyline abolished thapsigargin-induced [Ca2+]i increase. U73122, an inhibitor of phospholipase C, did not affect nortriptyline-induced [Ca2+]i rise; however, activation of protein kinase C decrease nortriptyline-induced [Ca2+]i rise by 32%. Overnight incubation with 50 and 100 microM nortriptyline killed 78% and 97% of cells, respectively; while 10 microM nortriptyline had no effect. These data suggest that nortriptyline rapidly increases [Ca2+]i in human osteosarcoma cells by stimulating both extracellular Ca2+ influx and intracellular Ca2+ release, and is cytotoxic at high concentrations.
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PMID:Effect of nortriptyline on intracellular Ca2+ handling and proliferation in human osteosarcoma cells. 1544 36

In human MG63 osteosarcoma cells, the effect of calmidazolium on [Ca(2+)](i) and proliferation was explored using fura-2 and ELISA, respectively. Calmidazolium, at concentrations greater than 0.1 micromol/L, caused a rapid increase in [Ca(2+)](i) in a concentration-dependent manner (EC(50) = 0.5 micromol/L). The calmidazolium-induced [Ca(2+)](i) increase was reduced by 66% by removal of extracellular Ca(2+). In Ca(2+)-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca(2+)-ATPase, caused a monophasic increase in [Ca(2+)](i), after which the effect of calmidazolium to increase [Ca(2+)](i) was completely inhibited. U73122, an inhibitor of phospholipase C (PLC), abolished histamine (but not calmidazolium)-induced increases in [Ca(2+)](i). Pretreatment with phorbol 12-myristate 13-acetate to activate protein kinase C inhibited the calmidazolium-induced increase in [Ca(2+)](i) in Ca(2+)-containing medium by 47%. Separately, it was found that overnight treatment with 2-10 micromol/L calmidazolium inhibited cell proliferation in a concentration-dependent manner. These results suggest that calmidazolium increases [Ca(2+)](i) by stimulating extracellular Ca(2+) influx and also by causing release of intracellular Ca(2+) from the endoplasmic reticulum in a PLC-independent manner. Calmidazolium may be cytotoxic to osteosarcoma cells.
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PMID:Effect of calmidazolium on Ca(+2) movement and proliferation in human osteosarcoma cells. 1555 16

In human osteosarcoma MG63 cells, the effect of Y-24180, a presumed specific platelet-activating factor (PAF) receptor antagonist, on intracellular Ca(2+) concentration ([Ca(2+)](i)) and proliferation was measured by using fura-2 and tetrazolium as fluorescent dyes, respectively. Y-24180 (1-5 microM) caused a rapid and sustained [Ca(2+)](i) rise in a concentration-dependent manner. The [Ca(2+)](i) rise was inhibited by 35% by dihydropyridines or removal of extracellular Ca(2+), but was not altered by verapamil and diltiazem. In Ca(2+)-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca(2+)-ATPase, caused a monophasic [Ca(2+)](i) rise, after which 5 microM Y-24180 failed to increase [Ca(2+)](i); conversely, depletion of Ca(2+) stores with 5 microM Y-24180 abolished thapsigargin-induced [Ca(2+)](i) rise. U73122, an inhibitor of phoispholipase C, inhibited histamine-induced, but not 5 microM Y-24180-induced [Ca(2+)](i) rise. Overnight treatment with 0.1-5 microM Y-24180 inhibited cell proliferation in a concentration-dependent manner. Together, these findings suggest that Y-24180 acts as a potent and cytotoxic Ca(2+) mobilizer in human osteosarcoma cells, by inducing both extracellular Ca(2+) influx and intracellular Ca(2+) release. Alterations in cytosolic Ca(2+) regulation may lead to interferences of various cellular functions; thus, attention should be exercised in using Y-24180 as a selective PAF receptor antagonist.
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PMID:Novel effect of Y-24180, a presumed specific platelet-activating factor receptor antagonist, on Ca2+ levels and growth of human osteosarcoma cells. 1566 67

Econazole is an antifungal drug with different in vitro effects. However, econazole's effect on osteoblast-like cells is unknown. In human MG63 osteosarcoma cells, the effect of econazole on intracellular Ca2+ concentrations ([Ca2+]i) was explored by using fura-2. At a concentration of 0.1 microM, econazole started to cause a rise in [Ca2+]i in a concentration-dependent manner. Econazole-induced [Ca2+]i rise was reduced by 74% by removal of extracellular Ca2+. The econazole-induced Ca2+ influx was mediated via a nimodipine-sensitive pathway. In Ca2+ -free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca+ -ATPase, caused a [Ca2+]i rise, after which the increasing effect of econazole on [Ca2+]i was abolished. Pretreatment of cells with econazole to deplete Ca2+ stores totally prevented thapsigargin from releasing Ca2+. U73122, an inhibitor of phospholipase C, abolished histamine (an inositol 1,4,5-trisphosphate-dependent Ca2+ mobilizer)-induced, but not econazole-induced, [Ca2+]i rise. Econazole inhibited 76% of thapsigargin-induced store-operated Ca2+ entry. These findings suggest that in MG63 osteosarcoma cells, econazole increases [Ca2+]i by stimulating Ca2+ influx and Ca2+ release from the endoplasmic reticulum via a phospholipase C-independent manner. In contrast, econazole acts as a potent blocker of store-operated Ca2+ entry.
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PMID:Econazole induces increases in free intracellular Ca2+ concentrations in human osteosarcoma cells. 1623 34


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