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)

Arsenic (As) is one of the most important environmental global toxicants. In various countries and for decades people have been and currently are exposed to inorganic As through geogenically contaminated drinking water. An increased incidence of diseases mediated by this toxic element is the consequence of long-term exposure. Despite past extensive research on the toxicology of As, many questions remained unanswered, making risk assessment difficult. For instance, it is still not known how the carcinogenicity of As is mechanistically operative. Moreover, there is an increasing debate on whether the metabolic methylation of As has to be considered a detoxification process. Furthermore, it is historically documented that long-term intake of small amounts of As can lead to an acquired increased tolerance to its acute toxicity. It is not known whether this tolerance may be associated with a reduced chronic toxicity as well. In contrast to nonhuman cells, the selection of As-induced self-tolerance in human cells in vitro had been unsuccessful until now. However, we recently selected As-resistant human hepatoma HepG2 sublines that have low-level tolerance to As. Besides an approximately twofold elevated resistance to As cytotoxicity, this tolerance was associated with a significantly suppressed induction of As-mediated genotoxicity, which was evident in the cytokinesis-block micronucleus test. Additional questions arise when we consider several factors suspected to modulate the long-term toxicity of arsenic in vitro, variables that may either enhance or suppress the environmental genotoxicity and carcinogenicity of the metalloid. Besides malnutrition, these are single nutritional factors such as selenium and possible drinking water co-contaminants such as antimony. For instance, in the case of selenium, we could show that antimony (III) is able to suppress As genotoxicity. Taken together, research answers in many fields of As toxicology are needed in order to reduce the uncertainties in risk assessment of environmental As.
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PMID:Unanswered questions in arsenic toxicology. 1179 39

This study was designed to investigate the influence of neonatal selenium (an anticarcinogenic agent) exposure on spontaneous liver tumor formation in adult mice. Pregnant CBA mice were administered selenium during the last week of pregnancy and for ten days following parturition. Selenium significantly reduced the incidence of spontaneous hepatomas in adult male progeny, while having no effect on the lower hepatoma incidence in adult females. The data indicate that neonatal selenium alters hepatoma incidence in a sex-dependent manner. This study represents the model of neonatal cancer prevention.
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PMID:Perinatal selenium exposure decreases spontaneous liver tumorogenesis in CBA mice. 1188 Jan 80

Selenium is a widely studied dietary anticancer agent. Among various selenium compounds, the methylated forms appear to be particularly effective in cancer prevention. Intracellular glutathione (GSH) is known to be involved in the metabolism of many methylated forms of selenium. In this study, we investigated the role of intracellular GSH in methylseleninic acid (MSeA)-induced apoptosis in human hepatoma (HepG(2)) cells. MSeA was shown to deplete intracellular GSH rapidly, preceding the typical apoptotic changes such as DNA fragmentation as measured by the TUNEL assay. When the intracellular GSH concentration was enhanced using N-acetylcysteiene (NAC) (a GSH synthesis precursor) and decreased using buthionine sufoxamine (BSO) (a GSH synthesis inhibitor), NAC markedly augmented MSeA-induced apoptosis, while BSO significantly inhibited MSeA-induced apoptosis. Different from the effect of sodium selenite, there was no measurable superoxide radical level in MSeA-treated cells. These observations suggest that intracellular GSH mainly acts as a cofactor to facilitate MSeA-induced apoptosis, while its antioxidant function becomes largely irrelevant. It is thus postulated that some cancer cells, such as liver cancer cells with higher level of intracellular GSH, would be more susceptible to MSeA cytotoxicity.
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PMID:Intracellular glutathione is a cofactor in methylseleninic acid-induced apoptotic cell death of human hepatoma HEPG(2) cells. 1216 Sep 37

Liver damage ranges from acute hepatitis to hepatocellular carcinoma, through apoptosis, necrosis, inflammation, immune response, fibrosis, ischemia, altered gene expression and regeneration, all processes that involve hepatocyte, Kupffer, stellate, and endothelial cells. Reactive oxygen and nitrogen species (ROS, RNS) play a crucial role in the induction and in the progression of liver disease, independently from its etiology. They are involved in the transcription and activation of a large series of cytokines and growth factors that, in turn, can contribute to further production of ROS and RNS. The main sources of free radicals are represented by hepatocyte mitochondria and cytochrome p450 enzymes, by endotoxin-activated macrophages (Kupffer cells), and by neutrophils. The consequent alteration of cellular redox state is potentiated by the correlated decrease of antioxidant and energetic reserves. Indices of free radical-mediated damage, such as the increase of malondialdehyde, 4-hydroxynonenal, protein-adducts, peroxynitrite, nitrotyrosine, etc., and/or decrease of glutathione, vitamin E, vitamin C, selenium, etc., have been documented in patients with viral or alcoholic liver disease. These markers may contribute to the monitoring the degree of liver damage, the response to antiviral therapies and to the design of new therapeutic strategies. In fact, increasing attention is now paid to a possible "redox gene therapy." By enhancing the antioxidant ability of hepatocytes, through transgene vectors, one could counteract oxidative/nitrosative stress and, in this way, contribute to blocking the progression of liver disease.
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PMID:Oxidative stress in viral and alcoholic hepatitis. 1249 74

We used an atomic absorption spectrophotometric method to determine the concentration of selenium, zinc, iron, copper and calcium in the whole blood of patients with hepatocellular carcinoma. The results demonstrate that these patients have a lower concentration of selenium (0.18 +/- 0.02 microg/ml vs. 0.28 +/- 0.06 microg/ml) and zinc (11.2 +/- 2.75 microg/ml vs. 18.2 +/- 7.33 microg/ml) than healthy controls (p < 0.05). On the other hand, the hepatocellular carcinoma patients have higher mean concentrations of iron (651.9+/-66.2 microg/ml vs.473.0 +/- 88.0 microg/ml; p < 0.05), copper (1.43 +/- 0.33 microg/ml vs. 0.95 +/- 0.19 microg/ml; p < 0.05) and calcium (75.0 +/- 13.1 microg/ml vs. 39.9 +/- 12.3 microg/ml; p < 0.01) than healthy controls. Thus, hepatocellular carcinoma seems to be associated with the changes in the whole blood concentrations of selenium, zinc, iron, copper and calcium.
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PMID:Blood concentrations of selenium, zinc, iron, copper and calcium in patients with hepatocellular carcinoma. 1252 Dec 29

Selenium (Se), a micronutrient, has a long history in chemoprevention of mammary and colon cancers in rodent models. Se is a current clinical trial, having shown promise in prevention of prostate and other human cancers. The mechanisms involved in the in vivo anti-carcinogenic activity of Se remain to be elucidated. In the present study, we examined the effect of sodium selenite supplementation in lymphocytes, obtained from hepatoma bearing rats on DNA damage in correlation with oxidative stress. In addition, this study examined the supplementation of Se at 4-ppm levels in the form of sodium selenite either before initiation or during initiation and/or promotion phase's increases lymphocyte Se concentrations. This in turn improves lymphocyte resistance to oxidative stress and protection against the lymphocytes DNA damage. Supplementation of Se increased lymphocyte Se concentration and reduced lymphocytes DNA damage as determined by single cell gel electrophoresis. The enzymatic antioxidants such as superoxide dismutase, glutathione peroxidase, and catalase were found to be decreased while the thiobarbituric acid reactive substances level was increased in the lymphocytes of hepatoma bearing rats. Furthermore, the reactive oxygen species such as superoxide radicals and hydroxyl radicals were also found to be high in lymphocytes. Our present results explain the understanding of unique association between anti-peroxidative effect of Se and ultimately the capability of Se to prevent cancer.
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PMID:Sodium selenite, dietary micronutrient, prevents the lymphocyte DNA damage induced by N-nitrosodiethylamine and phenobarbital promoted experimental hepatocarcinogenesis. 1253 33

Thioredoxin reductases (TrxRs) catalyse the NADPH-dependent reduction of thioredoxin and play an important role in multiple cellular events related to carcinogenesis including cell proliferation, apoptosis and cell signaling. We have used human hepatoma HepG2 cells to examine the regulation of TrxRs by isothiocyanate (sulforaphane) and selenium (Se). We show that TrxR1 mRNA, but not TrxR2 mRNA, is induced up to 4-fold by sulforaphane, and this increase was abolished by actinomycin D, a transcription inhibitor. Se, in the form of sodium selenite, induced TrxR1 at the translational level, as shown by an increase in protein (2.1-fold) and activity (4.8-fold), but not mRNA. In combination, sulforaphane and Se synergistically induced TrxR1 protein (5.5-fold), activity (13-fold) and mRNA (6.5-fold). Although Se does not induce TrxR1 mRNA, Se can delay the degradation of sulforaphane-induced TrxR1 mRNA. Modulation of TrxR1 mRNA by sulforaphane was glutathione and protein kinase C-dependent, as L-buthionine-S,R-sulfoximine (a specific inhibitor of glutathione synthesis), and the protein kinase C inhibitor 1-(5-isoquinolinesulfonyl)-2-methyl-piperazine, significantly reduced the induction. The combination of sulforaphane and Se also efficiently protected HepG2 cells from paraquat-induced cell death, whereas sulforaphane-only and Se-only treatments showed very little if any protective effect. These results demonstrate that synergy can result from a combination of induction at the levels of transcription and translation.
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PMID:Synergy between sulforaphane and selenium in the induction of thioredoxin reductase 1 requires both transcriptional and translational modulation. 1266 10

The stress response enzyme heme oxygenase (HO)-1 is induced in livers of selenium-deficient rodents, probably to compensate for loss of certain selenoproteins. We sought to identify those selenoproteins. Selenium-replete mice with genetic deletion of selenoprotein P or glutathione peroxidase-1 did not have elevated hepatic HO activity, thus ruling out involvement of those selenoproteins in HO-1 induction by selenium deficiency. However, inhibition of thioredoxin reductase (TrxR) by a low dose of gold in the form of aurothioglucose led to induction of hepatic HO activity. Moreover, further induction by phenobarbital was observed. This HO-1 induction pattern is also seen in selenium-deficient mice. In the rat hepatoma cell line H4IIE, inhibition of TrxR by aurothioglucose or by 1-chloro-2,4-dinitrobenzene led to induction of HO-1. We conclude that loss of TrxR is responsible for the induction of HO-1 by selenium deficiency.
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PMID:Loss of activity of the selenoenzyme thioredoxin reductase causes induction of hepatic heme oxygenase-1. 1270 24

Sulforaphane (SF), a glucosinolate-derived isothiocyanate found in cruciferous vegetables, is considered an anticarcinogenic component in broccoli. Sulforaphane induces a battery of detoxification enzymes, including quinone reductase (QR). Induction is thought to be mediated through a common regulatory region termed the antioxidant response element (ARE). To test the hypothesis that the antioxidant selenoprotein thioredoxin reductase (TR) may be induced as part of this coordinated host-defense response to dietary anticarcinogenic compounds, TR activity was measured in livers of rats pair-fed diets containing SF and/or broccoli (n = 6/group). At the doses used, neither SF nor broccoli alone significantly elevated TR activity, whereas treatments containing both broccoli and SF caused a significant increase in TR activity. Glutathione peroxidase (GSH-Px), a second selenium-dependant enzyme with antioxidant activity, was downregulated in rats fed both SF and broccoli, compared to the control diet.A second experiment, using mouse hepatoma Hepa1c1c7 cells, tested whether an interaction exists between selenium (Se) and SF in TR inducibility, since Se is known to induce TR activity. Selenium (2.5 &mgr;M) plus SF (2.0 &mgr;M) caused significantly greater TR activity than either treatment alone. All treatments with added Se or SF caused significantly greater TR activities than no Se or SF treatment. Glutathione peroxidase activity was elevated by Se, but not by SF. These data suggest that TR, known to be regulated by Se, is also upregulated as part of a host response to the dietary anticarcinogen SF, a trait not shared by another Se-dependent enzyme, GSH-Px.
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PMID:Induction of hepatic thioredoxin reductase activity by sulforaphane, both in Hepa1c1c7 cells and in male Fisher 344 rats. 1274 46

Selenium in the form of sodium selenite is an essential micronutrient, that acts as an antioxidant/anticancer agent by its numerous macromolecules associated with them. This study emphasizes further evidence on its role as anticancer agent in experimental rats with N-nitrosodiethylamine (DEN) initiated (200 mg kg(-1) body weight) and phenobarbital (PB) promoted hepatoma. Serum, whole liver tissue (control animals, n=6), hepatoma and surrounding liver tissue samples from DEN-treated rats and rats supplemented with selenite (n=6) were collected. Total protein, albumin, globulin and albumin/globulin ratio were investigated. Hexose, hexosamine and sialic acid were also quantified. Animals treated with DEN resulted in significantly decreased levels of total protein, albumin and albumin/globulin ratio; on the other hand, globulin content was increased significantly when compared to control rats. We have also observed significant increased levels of hexose, hexosamine and sialic acid in serum, whole liver tissue (control), hepatoma and surrounding liver tissue of control and experimental animals. Supplementation of selenite (4 ppm) either before initiation, during initiation and/or during promotion stages alters the above biochemical changes significantly. Thus, supplementations of selenite in cancer bearing animals reduce the adverse changes that occur during cancer condition. However, the chemopreventive/chemotherapeutic effect of selenite is more pronounced when it was supplemented before and/or during initiation of cancer when compared to promotion stage. Our results emphasize the role of sodium selenite in cancer and strongly indicate its role as an essential micronutrient in cancer chemoprevention and therapy.
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PMID:Influence of sodium selenite on glycoprotein contents in normal and N-nitrosodiethylamine initiated and phenobarbital promoted rat liver tumors. 1279 69


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