Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A number of N-alkylated-1,3-diaminopropane derivatives [H2N-(CH2)3-NH-(CH2)nH, where n = 1-9] have been tested as potential inhibitors of partially purified rat hepatoma (HTC) cell or pure bovine spleen spermine synthase. Among the compounds described in this paper, the most potent competitive inhibitor of spermine synthase, with respect to spermidine, is N-butyl-1,3-diaminopropane with Ki values of 11.9 nM and 10.4 nM for the HTC cell and bovine spleen enzymes respectively. Inhibition of spermine synthase by this alkylated amine is selective since spermidine synthase activity is not affected up to 100 microM N-butyl-1,3-diaminopropane at a range of 5-200 microM putrescine. Added to the culture medium of growing HTC cells, N-butyl-1,3-diaminopropane causes the expected changes in the polyamine levels with a marked decrease of spermine and an increase of spermidine. Under these conditions cell growth continues unabated. Such N-alkylated-1,3-diaminopropane derivatives may have considerable potential as tools for studying the role of polyamines and in particular the functions of spermine in cell multiplication and differentiation.
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PMID:Inhibition of mammalian spermine synthase by N-alkylated-1,3-diaminopropane derivatives in vitro and in cultured rat hepatoma cells. 291 58

Dicyclohexylamine, a spermidine synthase inhibitor, was evaluated for its ability to alter specific polyamine levels in rat hepatoma HTC cells in culture. Media concentrations of 0.5 and 1.0 mM reduced the production of spermidine from putrescine and enhanced the conversion of existing spermidine to spermine. This created a very interesting change in polyamine levels such that after 24 h putrescine content was almost 3-times control values and spermine was about twice, while spermidine was lowered to about 10% of control cultures. This pattern of polyamines is quite distinct from that induced by the common polyamine biosynthetic inhibitors like methylglyoxal bis(guanylhydrazone) and difluoromethylornithine and replicates the pattern induced by S-adenosyl-1,8-diamino-3-thiooctane, a transition-state analog designed as a specific inhibitor of spermidine synthase. When cells were stimulated by serum addition, the presence of dicyclohexylamine caused an extraordinarily large induction in ornithine decarboxylase in spite of the abnormally high levels of both putrescine and spermine. The concomitant depression of spermidine levels induced a 4-fold increase in the stability of this enzyme that could be reversed by the addition of exogenous spermidine. The data suggest that spermidine induces, perhaps at the transcriptional level, a protein that is necessary for the characteristically very rapid inactivation of ornithine decarboxylase.
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PMID:Dicyclohexylamine effects on HTC cell polyamine content and ornithine decarboxylase activity. 400 90

Exposure of mammalian cells (transformed mouse fibroblasts or rat hepatoma cells) to S-adenosyl-1,8-diamino-3-thiooctane produced profound changes in the intracellular polyamine content. Putrescine was increased and spermidine was decreased, consistent with the inhibition of spermidine synthase by this compound, which is a potent and specific "transition-state analogue inhibitor" of the isolated enzyme in vitro. The spermine content of the cells was increased by exposure to this drug presumably since spermine synthase was able to use a greater proportion of the available decarboxylated S-adenosylmethionine when spermidine synthase was inhibited. The decarboxylated S-adenosylmethionine content rose substantially because the activity of S-adenosylmethionine decarboxylase was increased in response to the decline in spermidine. These results indicate that S-adenosyl-1,8-diamino-3-thiooctane is taken up by mammalian cells and is an effective inhibitor of spermidine synthase in vivo and that S-adenosylmethionine decarboxylase is regulated by the content of spermidine, but not of spermine. The growth of SV-3T3 cells was substantially reduced in the presence of S-adenosyl-1,8-diamino-3-thiooctane at concentrations of 50 microM or greater. Such inhibition was reversed by the addition of spermidine but not by putrescine. When SV-3T3 cells were exposed to 5 mM alpha-(difluoromethyl)ornithine and 50 microM S-adenosyl-1,8-diamino-3-thiooctane, the content of all polyamines was reduced. Putrescine and spermidine declined by more than 90% and spermine by 80%. Such cells grew very slowly unless spermidine was added.
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PMID:Effects of S-adenosyl-1,8-diamino-3-thiooctane on polyamine metabolism. 629

1. Direct or indirect inhibitors of l-ornithine decarboxylase (EC 4.1.1.17), structurally related or unrelated to l-ornithine, including dl-alpha-difluoromethylornithine, alpha-methylornithine and 1,3-diaminopropane, used alone or in combination, decreased polyamine concentrations in rat hepatoma tissue culture (HTC) cells and increased S-adenosyl-l-methionine decarboxylase activity (EC 4.1.1.50). 2. Comparison of the catalytic properties of S-adenosyl-l-methionine from cells with elevated and normal activities revealed no apparent modification of the catalytic site as judged by affinity for the substrate, stimulation by di- and tri-amines and inhibition by methylglyoxal bis-(guanylhydrazone). 3. Actinomycin D and cycloheximide, and RNA and a proteinsynthesis inhibitor respectively, blocked the increase of S-adenosyl-l-methionine decarboxylase activity elicited by alpha-difluoromethylornithine. In polyamine-depleted cells the apparent half-life of elevated S-adenosyl-l-methionine decarboxylase activity, determined by inhibition of protein synthesis, was 2.5-fold longer than in control cells. The present results suggest that elevation of S-adenosyl-l-methionine decarboxylase activity by alpha-difluoromethylornithine is due to stabilization of the enzyme. 4. Restoration of the normal intracellular putrescine content, by addition of putrescine to the medium of polyamine-deficient cells, transiently increased S-adenosyl-l-methionine decarboxylase activity. Thereafter, intracellular conversion of putrescine into spermidine was accompanied by inactivation of the enzyme at a rate that was similar to that found on addition of spermidine itself. No relationship between total intracellular spermine content and S-adenosyl-l-methionine decarboxylase activity could be established. 5. Addition of 1mm-1,3-diaminopropane to polyamine-deficient cells did not cause a decrease in the activity of S-adenosyl-l-methionine decarboxylase, whereas addition of 1,5-diaminopentane (cadaverine) did. 1,3-Diamino-N-(3-aminopropyl)propane did not accumulate in cells treated with alpha-difluoromethylornithine and 1,3-diaminopropane, whereas addition of 1,5-diaminopentane led to the accumulation of 1,5-diamino-N-(3-aminopropyl)pentane. 1,3-Diamino-N-(3-aminopropyl)propane (10mum) was as effective as spermidine in decreasing S-adenosyl-l-methionine decarboxylase activity. Thus effectiveness of a diamine in decreasing enzyme activity is related to its capability of being converted into a closely structurally related homologue of spermidine by spermidine synthase. 6. The spermidine site of action appears to be post-translational since (a) the spermidine-induced decrease of S-adenosyl-l-methionine activity was not prevented by actinomycin D and (b) spermidine in the presence of cycloheximide led to a synergistic inactivation of the enzyme with a decay rate that progressively approached control values. Altogether these results are indirect evidence for a strict negative control of S-adenosyl-l-methionine decarboxylase by spermidine and substantiate previous findings [Mamont, Duchesne, Grove & Tardif (1978) Exp. Cell Res.115, 387-393]. Spermidine appears to act on some processes involved in denaturation and/or degradation of the enzyme protein. Putrescine appears to decrease the rate of these processes. The physiological significance of the regulatory control of S-adenosyl-l-methionine decarboxylase is discussed.
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PMID:Indirect evidence for a strict negative control of S-adenosyl-L-methionine decarboxylase by spermidine in rat hepatoma cells. 679 4

Biological transmethylation reactions and polyamine biosynthesis share the substrate S-adenosyl-L-methionine. Under normal conditions, decarboxylated S-adenosyl-L-methionine, the aminopropyl donor for polyamine biosynthesis, does not accumulate because of its rapid utilization in spermidine and spermine synthesis. Alteration of polyamine synthesis by DL-alpha-difluoromethylornithine, an enzyme-activated irreversible inhibitor of L-ornithine decarboxylase, leads to a striking accumulation of decarboxylated S-adenosyl-L-methionine in rat hepatoma cells cultured in vitro and in rat ventral prostate. This increase is due both to lack of putrescine and spermidine for the aminopropyltransferase reactions and to the elevation of S-adenosyl-L-methionine decarboxylase activity. The biological implications of accumulation of decarboxylated S-adenosyl-L-methionine are discussed with regard to the regulation of S-adenosyl-L-methionine decarboxylase activity and to the antiproliferative effects of DL-alpha-difluoromethylornithine.
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PMID:Accumulation of decarboxylated S-adenosyl-L-methionine in mammalian cells as a consequence of the inhibition of putrescine biosynthesis. 680 35

The effects of a potent spermidine synthase inhibitor, trans-4-methylcyclohexylamine (4MCHA), and a spermine synthase inhibitor, N-(3-aminopropyl)cyclohexylamine (APCHA), on polyamine biosynthesis and cell growth have been studied in rat hepatoma cells (HTC cells) in culture. Treatment of HTC cells with 4MCHA or APCHA caused a marked decrease of spermidine or spermine with a compensatory increase of putrescine and spermine or spermidine, respectively, in a dose-dependent manner, suggesting specific and potent inhibition of each target enzyme. When 250 microM 4MCHA or APCHA was administered to the cells for 8 days, spermidine was decreased to 2% of control culture or spermine below 1%, respectively, while total polyamine (sum of putrescine, spermidine, and spermine) remained almost unchanged during the culture. There were no significant changes in the growth rate during treatment with the inhibitors at 250 microM concentration. The results suggest that in the growth of HTC cells, putrescine and spermine can be substituted for most of the fraction of cellular spermidine, and spermidine for most of the fraction of cellular spermine. Of five enzymatic activities involved in polyamine biosynthesis and interconversion, S-adenosylmethionine decarboxylase activity increased 8-fold with 250 microM 4MCHA, and 3-fold with 250 microM APCHA during the treatment. This increase was partially due to the increase of half-life of the enzyme. Separate roles for spermidine and spermine in the biosynthesis of the enzyme protein were also suggested.
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PMID:Specific depletion of spermidine and spermine in HTC cells treated with inhibitors of aminopropyltransferases. 760 22

Two unusual aminopropyl acceptors found in a survey of putrescine binding sites of mammalian spermidine synthase, N-methylputrescine (I) and 4-aminomethylpiperidine (II), were examined for their aminopropyl derivatives. Studies under in vitro incubation conditions suggested that the aminopropyl derivatives of the secondary amine of I and II, N4-methylspermidine (Is) and 1-N-(3-aminopropyl)-4-aminomethylpiperidine (IIs), and of the primary amine of I and II, N8-methylspermidine (Ip) and 4-[N-(3-aminopropyl)aminomethyl]piperidine (IIp), respectively, were biosynthesized by rat spermidine synthase. Studies on the cell culture system of cultured rat hepatoma (HTC) cells treated with alpha-difluoromethylornithine, an ornithine decarboxylase inhibitor, clearly showed the presence of Is and Ip when I was administered, and IIs and IIp when II was administered, with no detection of putrescine or spermidine. These results suggested that mammalian spermidine synthase can transfer the aminopropyl moiety of decarboxylated S-adenosylmethionine to certain secondary amines in living cells.
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PMID:Enzymatic aminopropylation of certain secondary amines. 774 12

We screened genes responsive to transforming growth factor-beta (TGF-beta 1) protein in a human hepatoma cell line (Hep3B) using a PCR-mediated differential display technique, in order to investigate the mechanisms involved in TGF-beta-induced growth suppression. We found a gene that was down-regulated by TGF-beta 1 to be completely identical in an approx. 620 bp segment to the gene for the enzyme spermidine synthase, which mediates the conversion of putrescine into spermidine. Both spermidine synthase mRNA expression and its enzyme activity were decreased after TGF-beta 1 treatment of Hep3B cells. The inhibition of spermidine synthase gene expression by TGF-beta 1 protein was also observed in other hepatoma cell lines. The expression of genes for other biosynthetic enzymes in polyamine metabolism (ornithine decarboxylase and S-adenosylmethionine decarboxylase) was also inhibited to the same extent as for spermidine synthase, while the gene expression of spermidine/spermine N1-acetyltransferase, a catabolic enzyme, was relatively resistant to TGF-beta 1. Spermine levels in Hep3B cells were decreased by TGF-beta 1 treatment, although the levels of spermidine and putrescine were unchanged, probably due to compensation by remaining spermidine/spermine N1-acetyltransferase activity. Exogenously added spermidine or spermine, but not putrescine, partially antagonized the growth-inhibitor effects of TGF-beta 1 on Hep3B cells. Our data suggest that down-regulation of gene expression of the enzymes involved in polyamine metabolism, including spermidine synthase, may be associated with the mechanism of TGF-beta-induced growth suppression.
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PMID:Inhibition of spermidine synthase gene expression by transforming growth factor-beta 1 in hepatoma cells. 902 Aug 92