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Query: UMLS:C0017638 (glioma)
 30,880 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cholesterol in animals is a major structural component of cell membranes. It may therefore play a functional role in the modulation of cell osmolarity, the process of pinocytosis and the activities of membrane-associated proteins such as ionic pumps, immune responses, etc. A major relationship exists between the cell-growth processes and the cholesterol biosynthetic pathway. The cholesterol needed for new membranes may be derived either from endogenous synthesis or from exogenous sources, principally plasma low-density-lipoproteins (LDL) which enter the cells by receptor-mediated endocytosis. Both these pathways are enhanced in rapidly growing cells. Conversely, if synthesis is inhibited and no exogenous cholesterol is available, cell growth is blocked. The 3-hydroxy-3-methylglutaryl CoA (HMGCoA) reductase (the rate-limiting reaction in cholesterol biosynthesis) is the enzyme which catalyzes the conversion of HMGCoA to mevalonic acid. It has been suggested that mevalonate may play an important role in cell proliferation. All cells need at least two products synthesized from mevalonate in order to proliferate, and the only one yet identified is cholesterol. Other melavonate-derived potential candidates as cell-cycle and cell-survival products include the dolichols ubiquinone side chains, isopentenyladenosine derivatives, etc. Furthermore, it has recently been shown that membrane association appears to be an important function in mevalonate-derive modifications of several important proteins such as cellular membrane G proteins, those coded for by oncogenes (ras proteins) and lamins (nuclear proteins). In recent years the development of cholesterol-synthesis-inhibiting drugs, for lowering plasma cholesterol levels has mainly been centred on the control of HMGCoA reductase activity (vastatins). However, because mevalonic acid is the precursor of numerous metabolites, any reduction of such activity may potentiate pleiotropic effects. Vastatins are now, therefore, receiving increased attention as potential pharmacological tools for the control of abnormal cell growth in pathological situations, i.e. tumours and vascular smooth muscle cell proliferation under atherogenic conditions. In our laboratories, we have demonstrated that simvastatin can prevent arterial myocyte proliferation both in vivo and in vitro. Simvastatin can also inhibit in vitro the rate of human glioma cell growth, since it shows a strong synergistic inhibitory effect on cell proliferation when used in association with anticancer agents such as Carmustine or beta-interferon. Both simvastatin-induced cell growth inhibition and the synergy observed with these drugs can be completely reversed by incubating cells with mevalonate. This shows that the effect of simvastatin of cell proliferation is due to its specific inhibitory activity on intracellular mevalonate synthesis.
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PMID:Cholesterol and mevalonic acid modulation in cell metabolism and multiplication. 147 Nov 62

Naturally occurring sesquiterpene lactones and their semisynthetic derivatives, such as the O = C-C = CH-bearing helenalin and its esters, have been shown to demonstrate potent cytotoxicity against the growth of murine L1210 lymphoid leukemia and human Tmolt3 leukemia, colon adenocarcinoma, HeLaS3, lung bronchogenic, KB, osteosarcoma, and glioma cells. The modes of action of helenalin in L1210 cells are the inhibition of DNA, RNA, and protein syntheses. This study confirms that thiol bearing enzymes of nucleic acid metabolism were significantly inhibited, e.g. DNA polymerase alpha, IMP hydrogenase, and ribonucleoside reductase. The addition of GSH to the reaction medium demonstrated total recovery of L1210 ribonucleoside reductase activity. Helenalin reduced cellular GSH levels in L1210 cells. Helenalin also reduced all four pool levels of d(NTP)s which would account for part of the observed inhibition of DNA synthesis. Reductions in the ribonucleotide pool levels were also generally evident after drug treatment. Thus, the sesquiterpene lactones appear to have more than one mode of action in L1210 cells. All of the modes of actions of helenalin are feasible mechanisms to lower nucleic acid synthesis and cause cell death of the L1210 leukemia cells.
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PMID:The cytotoxicity of helenalin, its mono and difunctional esters, and related sesquiterpene lactones in murine and human tumor cells. 152 2

Although plasma lipoproteins have been demonstrated to have a major role in regulating cholesterol biosynthesis in extraneural cells, no data concerning such regulation are available for developing brain, when cholesterol synthesis is especially active. Glial primary cultures derived from neonatal rat brain and by morphological and biochemical criteria essentially exclusively composed of astrocytes were utilized to examine such regulation. When the primary cultures, which had been maintained in 10% fetal calf serum, were placed in 10% lipoprotein-poor serum on day 7 of culture, an induction of sterol synthesis (1.6-2.2-fold) and of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase-specific activity (1.5-2-fold) resulted after 24 hr. Addition of low-density lipoprotein (LDL) to the 10% lipoprotein-poor serum prevented the induction of both sterol synthesis and HMG-CoA reductase. However, addition of high-density lipoprotein (HDL) to the 10% lipoprotein-poor serum caused a 1.5-2-fold further induction of sterol synthesis relative to that in cultures containing 10% lipoprotein-poor serum alone. In contrast to the glial primary cultures, cultures of C-6 glioma cells responded to replacement of 10% fetal calf serum with 10% lipoprotein-poor serum with much more marked increases of sterol synthesis and HMG-CoA reductase. Although, as with the primary cultures, addition of LDL to the C-6 glioma cell cultures prevented the increases in sterol synthesis and reductase activity, addition of HDL had no effect. Thus, these results indicate that in developing glial cells in primary culture, cholesterol synthesis and HMG-CoA reductase are capable of responsiveness to both LDL and HDL.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regulation of sterol synthesis and of 3-hydroxy-3-methylglutaryl coenzyme A reductase by lipoproteins in glial cells in primary culture. 288 63

C-6 glioma cells, grown in medium supplemented with 5% delipidated foetal calf serum, were induced to enter a quiescent state by removing serum from the medium. Within 24h there was a 75-80% decline in the rate of incorporation of [(14)C]acetate or (3)H(2)O into digitonin-precipitable sterols. Experiments with [(3)H]mevalonolactone as a labelled sterol precursor suggested that the decline in sterol synthesis was regulated primarily at a point in the pathway before the formation of mevalonate. The specific activities of 3-hydroxy-3-methylglutaryl-CoA synthase and 3-hydroxy-3-methylglutaryl-CoA reductase decreased sharply in conjunction with the decline in sterol synthesis in the serum-free cultures; however, the activity of acetoacetyl-CoA thiolase was altered only slightly. The magnitude of the initial decline in reductase activity was not affected when 50-mm-NaF was included in the preincubation and assay buffers to prevent activation of physiologically inactive enzyme. However, after 6h of serum deprivation the decline in 3-hydroxy-3-methylglutaryl-CoA reductase activity was due to a decrease in the amount of latent activity. The sterol concentration in C-6 cells was unchanged after 24h in serum-free medium, although a 20% decrease in the sterol/fatty acid molar ratio occurred as a result of a small increase in the fatty-acid concentration. Incorporation of (3)H(2)O into fatty acids was inhibited in the serum-deprived glial cells; however, this inhibition developed more slowly and was not as pronounced as the diminution in sterol synthesis. The results suggest that in C-6 glia, which resemble the glial stem cells of the developing brain, the decreased demand for membrane sterols in the quiescent state results in a decline in sterol synthesis, mediated primarily through co-ordinate changes in the activities of 3-hydroxy-3-methylglutaryl-CoA synthase and 3-hydroxy-3-methylglutaryl-CoA reductase.
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PMID:Changes in sterol biosynthesis accompanying cessation of glial cell growth in serum-free medium. 723 34

The mixed function oxidase system consists of NADPH-cytochrome P450 reductase (P450 reductase) and various isoforms of cytochrome P450 (P450), which can catalyze the oxidation of a broad range of endogenous and exogenous compounds. In this study, we examined the rat glioma C6 cell line for the presence of P450 reductase and three isozymes of cytochrome P450, 1A1, 2B1, and 2B2, by reverse transcription followed by PCR (RT-PCR). Rat glioma C6 cells were treated with hepatic P450 inducers phenobarbital (PB) or benzo(a)anthracene (BA). Cytochromes P450 1A1, P450 2B1, and P450 2B2, and P450 reductase, were detected in all the different treatment groups. Restriction digestion was used to confirm the PCR fragments and the expected digestion products were obtained. The induction of P450 1A1 and 2B was quantified using competitive PCR. Ten- and five-fold inductions of P450 1A and 2B mRNA after BA or PB treatments, respectively, were detected by competitive PCR. Microsomes prepared from rat glioma C6 cells showed cytochrome P450 spectra with absorption at 450 nm. Ethoxyresorufin O-deethylase activity (11.5 +/- 1.7 pmol/min/mg of microsomal protein) and pentoxyresorufin O-dealkylation activity (8.9 +/- 1.4 pmol/min/mg of microsomal protein) confirmed the induction of P450 1A and 2B at the protein level in response to BA or PB treatments, respectively. These experiments provide further evidence that the rat glioma C6 cell line contains an active mixed function oxidase system that can be induced by hepatic P450 inducers.
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PMID:Identification of inducible mixed function oxidase system in rat glioma C6 cell line. 761 9

The 1-acyl- and 1,2-diacyl-4,4-diethyl-3,5-pyrazolinediones proved to be cytotoxic against the growth of a number of cell lines, including murine and human leukemias. HeLa suspended carcinoma, colon adencarcinoma SW480, KB nasopharynx and glioma tumors. Selected compounds were also active in the human lung bronchogenic MB-9812, and osteosarcoma TE418 screens. These derivatives were active in vivo in the Ehrlich ascites carcinoma screen in CF-1 mice at 8 mg/kg/day I.P. The mode of action in Tmol3 leukemia cells showed that the compounds reduced de novo synthesis of purines and pyrimidines and inhibited dihydrofolate reductase and ribonucleoside reductase activities. The DNA molecule was not a target although limited DNA strand scission may be possible.
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PMID:The cytotoxic activity of 1-acyl- and 1,2-diacyl-4,4-diethyl-3,5-pyrazolidinediones. 773 34

The proliferation of normal non-tumourigenic mouse fibroblasts is stringently controlled by regulatory mechanisms located in the postmitotic stage of G1 (which we have designated G1pm). Upon exposure to growth factor depletion or a lowered de novo protein synthesis, the normal cells leave the cell cycle from G1pm and enter G0. The G1 pm phase is characterized by a remarkably constant length (the duration of which is 3 h in Swiss 3T3 cells), whereas the intercellular variability of intermitotic time is mainly ascribable to late G1 or pre S phase (G1ps) (Zetterberg & Larsson (1985) Proc. Natl. Acad. Sci. USA 82, 5365). As shown in the present study two tumour-transformed derivatives of mouse fibroblasts, i.e. BPA31 and SVA31, did not respond at all, or only responded partially, respectively, to serum depletion and inhibition of protein synthesis. If the tumour cells instead were subjected to 25-hydroxycholesterol (an inhibitor of 3-hydroxy-3 methyglutaryl coenzyme A reductase activity), their growth was blocked as measured by growth curves and [3H]-thymidine uptake. Time-lapse analysis revealed that the cells were blocked specifically in early G1 (3-4 h after mitosis), and DNA cytometry confirmed that the arrested cells contained a G1 amount of DNA. Closer kinetic analysis revealed that the duration of the postmitotic phase containing cells responsive to 25-hydroxycholesterol was constant. These data suggest that transformed 3T3 cells also contain a 'G1pm program', which has to be completed before commitment to mitosis. By repeating the experiments on a large number of tumour-transformed cells, including human carcinoma cells and glioma cells, it was demonstrated that all of them possessed a G1pm-like stage. Our conclusion is that G1pm is a general phenomenon in mammalian cells, independent of whether the cells are normal or neoplastic.
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PMID:Existence of a commitment program for mitosis in early G1 in tumour cells. 783 84

Heterocyclic thiosemicarbazones, thioureas and 2-substituted pyridine N-oxides as well as representative nickel, cobalt and copper complexes were shown to be potent antineoplastic/cytotoxic agents. The cytotoxicity was demonstrated against single cell leukemia as well as cell lines derived from solid tissue (colon adenocarcinoma, HeLa, KB, skin, bronchogenic lung, bone osteosarcoma and glioma). In L1210 cells, DNA synthesis and subsequently RNA synthesis were particularly inhibited by the agents. IMP dehydrogenase activity and thus purine de novo synthesis was reduced significantly by the agents. Dihydrofolate reductase, ribonucleoside reductase, nucleoside kinase and DNA polymerase alpha activities were inhibited by the agents. d(NTP) pool levels were reduced by most of the agents. DNA strand scission was present with all of the derivatives; however, there was no evidence of intercalation, cross linking or alkylation/binding to bases of DNA. This new group of compounds may offer novel exploratory derivatives for future investigations in the treatment of cancer.
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PMID:The cytotoxicity of heterocyclic thiosemicarbazones and their metal complexes on human and murine tissue culture cells. 849 Feb 2

The 3,5-isoxazolidinediones and 2-isoxazolin-5-ones demonstrated potent cytotoxicity against the growth of human Tmolt3 T cell leukemia, murine P388 and L1210 leukemias, as well as human HeLa-S3 uterine carcinoma and glioma tumor cell growth. The specificity of the 3,5-isoxazolidinedione and 2-isoxazoline-5-one derivatives as cytotoxic agents varied with the histological type of tumor cell. Selected compounds were active against solid HeLa uterine. KB nasopharynx, skin A431, SW-480 adenocarcinoma, osteosarcoma and glioma growth. Selected compounds demonstrated in vivo antineoplastic activity against Ehrlich ascites carcinoma growth. In L-1210 leukemia cells, the agents blocked DNA and protein synthesis at 25, 50 and 100 microM over 60 min. The agents were effective in reducing rate limiting enzymes in the de novo purine and pyrimidine pathways. In addition they suppressed dihydrofolate reductase and ribonucleoside reductase activities with moderate inhibition of DNA and RNA polymerase activities. DNA itself was not a target of the agents.
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PMID:Synthesis and cytotoxic action of 3,5-isoxazolidinediones and 2-isoxazolin-5-ones in murine and human tumors. 916 49

We analyzed the antiproliferative effect of simvastatin (SV), an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, on human glioma cell lines. Inhibition of cell growth with SV was observed in all cell lines tested. Different culture conditions altered this inhibition of growth: the lower the concentration of fetal bovine serum (FBS) in the medium, the higher the inhibitory effect of SV on glioma cells. On morphological examination, we found that most of the cells exposed to SV became rounded and the proportion of floating cells was increased in a time-dependent manner. Then we examined whether exogenously added mevalonic acid reversed the growth inhibitory effect of SV. Exogenous mevalonic acid suppressed the inhibitory effect of SV on glioma cells in a dose-dependent manner. SV also enhanced the expression of low-density lipoprotein (LDL) receptor on glioma cells. We also found that peroxidized LDL (p-LDL) was cytotoxic to glioma cells and that SV had additive effects on pLDL-induced cytotoxicity. In a mouse model, growth of glioma cells inoculated into nude mice was inhibited by intratumoral injection of both SV and peroxidized LDL. These results indicate that mevalonic acid or a metabolite in the cholesterol synthesis pathway is necessary for the growth of glioma cells and that simvastatin and/or peroxidized LDL should be examined further as potential therapeutic agents for gliomas.
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PMID:In vitro and in vivo antiproliferative effects of simvastatin, an HMG-CoA reductase inhibitor, on human glioma cells. 925 15


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