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Abstract
Selenomethionine (Semet) is the major seleno-compound in cereal grains and enriched yeast whereas Se-methylselenocysteine (SeMCYS) is the major seleno-compound in Se-accumulator plants and some plants of economic importance such as garlic and broccoli exposed to excess Se. Animals can metabolize both Semet and SeMCYS. Epidemiological studies have indicated an inverse relationship between Se intake and the incidence of certain cancers. Blood or plasma levels of Se are usually lower in patients with cancer than those without this disorder, but inconsistent results have been found with toenail-Se values and the incidence of cancer. There have been eight trials with human subjects conducted on the influence of Se on cancer incidence or biomarkers, and except for one, all have shown a positive benefit of Se on cancer reduction or biomarkers of this disorder. This is consistent with about 100 small-animal studies where Se has been shown to reduce the incidence of tumours in most of these trials. Se-enriched yeast is the major form of Se used in trials with human subjects. In the mammary-tumour model, SeMCYS has been shown to be the most effective seleno-compound identified so far in reduction of tumours. Several mechanisms have been proposed on the mechanism whereby Se reduces tumours. Even though SeMCYS was shown to be the most effective seleno-compound in the reduction of mammary tumours, it may not be the most effective seleno-compound for reduction of colon tumours.
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Affiliation(s)
- P D Whanger
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331, USA.
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2
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Raich PC, Lü J, Thompson HJ, Combs GF. Selenium in cancer prevention: clinical issues and implications. Cancer Invest 2001; 19:540-53. [PMID: 11458820 DOI: 10.1081/cnv-100103851] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- P C Raich
- Center for Behavioral and Community Studies, AMC Cancer Research Center, 1600 Pierce Street, Denver, CO 80214, USA.
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3
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Abstract
The nutritional functions of selenium (Se) are recognized as being due to a number of Se-containing proteins. It is not clear, however, whether any of these function in the anti-tumorigenic effects of Se most of which have been demonstrated for Se exposures greater than those required for selenoprotein expression. Indeed, other anti-tumorigenic mechanisms have been demonstrated for certain Se-metabolites. The Nutritional Prevention of Cancer Trial found supplemental Se (200 microg/day, as Se-enriched yeast) to be associated with significant reductions in cancer risks in subjects with pre-treatment plasma Se concentrations below ca. 120 ng/ml (1.5 nmoles/ml), which level would appear to require food-Se intakes of ca. 1.5 microg/kg body weight/day. However, the putative anti-carcinogenic Se-metabolite(s) should be more relevant than total plasma Se as a supplementation target for cancer prevention. These may be components of the non-protein-bound fraction of Se in plasma, which constitutes 2-4% of total plasma Se.
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Affiliation(s)
- G F Combs
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA.
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4
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Combs GF. Chemopreventive mechanisms of selenium. MEDIZINISCHE KLINIK (MUNICH, GERMANY : 1983) 1999; 94 Suppl 3:18-24. [PMID: 10554523 DOI: 10.1007/bf03042185] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The element selenium (Se) was recognized only 40 years ago as being essential in the nutrition of animals and humans. It is recognized as being an essential component of a number of enzymes in which it is present as the amino acid selenocysteine (SeCys). Selenium compounds have also been found to inhibit tumorigenesis in a variety of animal models and recent studies indicate that supplemental Se in human diets may reduce cancer risk. Anti-tumorigenic activities have been associated with Se intakes that are more than sufficient to correct nutritionally deficient status; that is, Se appears to be anti-tumorigenic at intakes that are substantially greater than those associated with maximal expression of the known SeCys-containing enzymes. Therefore, while some cancer protection may involve one or more Se-enzymes, it is probable that anti-tumorigenic functions of Se are discharged by certain Se-metabolites produced in significant amounts at relatively high Se intakes. Thus, Se supplementation of individuals with relatively low or frankly deficient natural intakes of the element can be expected to support enhanced anti-oxidant protection due to increased expression of the Se-dependent glutathione peroxidases and thioredoxin reductase. Higher levels of Se-supplementation can be expected to affect other functions related to tumorigenesis: carcinogen metabolism, immune function, cell cycle regulation and apoptosis. Thus, according to this 2-stage model of the roles of Se in cancer prevention, even individuals with nutritionally adequate Se intakes may benefit from Se-supplementation.
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Affiliation(s)
- G F Combs
- Cornell University, Ithaca, NY, USA.
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5
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Abstract
The element selenium (Se) was recognized only 40 years ago as being essential in the nutrition of animals and humans. It is recognized as being an essential component of a number of enzymes, in which it is present as the amino acid selenocysteine. Se compounds have also been found to inhibit tumorigenesis in a variety of animal models, and recent studies indicate that supplemental Se in human diets may reduce cancer risk. The antitumorigenic activities have been associated with Se intakes that correct nutritionally deficient status in animals, as well as higher intakes that are substantially greater than those associated with maximal expression of the selenocysteine-containing enzymes. Therefore, it is proposed that while some cancer protection, particularly that involving antioxidant protection, involves selenoenzymes, specific Se metabolites, which are produced in significant amounts at relatively high Se intakes, also discharge antitumorigenic functions. According to this two-stage model of the roles of Se in cancer prevention, individuals with nutritionally adequate Se intakes may benefit from Se supplementation. Evidence for chemoprevention by Se and for the apparent mechanisms underlying these effects is reviewed to the end of facilitating the development of the potential of Se compounds as cancer chemopreventive agents.
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Affiliation(s)
- G F Combs
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
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6
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Abstract
Previous studies have demonstrated that melphalan-resistant human ovarian tumor cells exhibit a higher degree of sensitivity to the cytotoxic effects of selenite in vitro than comparable drug-sensitive cells (P.B. Caffrey, G.D. Frenkel, Selenite cytotoxicity in drug resistant and non-resistant human ovarian tumor cells, Cancer Res. 52 (1992) 4812-4816; P.B. Caffrey, G.D. Frenkel, The development of drug resistance by tumor cells in vitro is accompanied by the development of sensitivity to selenite, Cancer Lett. 81 (1994) 59-65). We have now examined the sensitivity of drug-resistant tumors to selenite in vivo. A2780 human ovarian tumor cells, or their melphalan-resistant derivative (A2780ME) cells were injected subcutaneously into nude mice and the resulting tumors were found to be melphalan-sensitive and -resistant, respectively, in vivo. Treatment with selenite (2 mg/kg Se s.c.), which had no overt toxic effect on the animals, resulted in a significant decrease in the rate of growth of the melphalan-resistant tumors, but not on the rate of growth of the drug-sensitive tumors. Thus, melphalan-resistant ovarian tumors are also more sensitive to selenite treatment in vivo.
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Affiliation(s)
- P B Caffrey
- Department of Biological Sciences, Rutgers University, Newark, NJ 07102, USA
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7
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Tentori L, Prete SP, Pepponi R. Effects of diheptyldiselenide (DDS) on human tumor cell lines and on peripheral blood mononuclear cells. J Chemother 1993; 5:325-33. [PMID: 8106907 DOI: 10.1080/1120009x.1993.11741078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
In vitro effects of graded concentrations of diheptyldiselenide (DDS) on human tumor cell proliferation, and on the proliferative responses and immunological functions of peripheral blood mononuclear cells (MNC) were investigated. The agent significantly decreased tumor cell proliferation in a dose and time dependent manner. Proliferative responses of MNC to phytohemagglutinin (PHA) and interleukin-2 (IL-2) were also significantly depressed when MNCs were exposed to DDS (250 microM for 18 h) led to a significant increase in NK activity only in MNC samples showing very limited baseline NK function. On the other hand, generation of LAK cells was significantly inhibited by DDS. However, when the agent was added to the effector and target cell mixture during the 4 h 51Cr release cytotoxicity assay, no influence was found on NK and LAK-mediated target cell lysis. These studies show that high concentrations of DDS inhibit tumor cell proliferation and could also impair certain proliferative-dependent immune functions, without directly affecting cell-mediated cytolytic activity of effector cells.
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Affiliation(s)
- L Tentori
- Department of Experimental Medicine and Biochemical Sciences, University of Rome Tor Vergata, Italy
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8
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Caffrey PB, Frenkel GD. Selenite-induced inhibition of colony formation by buthionine sulfoximine-sensitive and resistant cell lines. Biol Trace Elem Res 1992; 35:129-36. [PMID: 1280979 DOI: 10.1007/bf02783725] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
We previously demonstrated that treatment of HeLa cells with buthionine sulfoximine (BSO), which decreases the level of cellular glutathione, resulted in a decrease in the potency of selenite in inhibiting cell colony formation. We have now examined the effect of selenite on normal human lung fibroblast (CCL-210) cells, which resemble HeLa cells in their sensitivity to BSO, and on human lung adenocarcinoma (A549) cells, which are relatively insensitive to BSO. We have found that BSO treatment caused an approximately fourfold decrease in selenite potency in the CCL-210 cells, but had no significant effect on its potency in A549 cells. These results support the hypothesis that for selenite to exert its cytotoxic effect, it must undergo the reaction with an SH compound to form the selenotrisulfide. As a result of the lower sensitivity of the tumor cells to BSO, it was possible to achieve a large differential sensitivity to the cytotoxic effect of selenite.
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Affiliation(s)
- P B Caffrey
- Department of Biological Sciences, Rutgers University, Newark, NJ
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9
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Yan L, Yee JA, Boylan LM, Spallholz JE. Effect of selenium compounds and thiols on human mammary tumor cells. Biol Trace Elem Res 1991; 30:145-62. [PMID: 1723886 DOI: 10.1007/bf02990350] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The effect on cell viability and growth rate of sodium selenite, selenocystine, sodium selenate, and selenomethionine at selenium concentrations of 6.25 and 12.5 uM was studied in vitro on cells of the human mammary tumor cell line HTB123/DU4475. Selenite and selenocystine affected both cell viability and growth rate of the tumor cells at these selenium concentrations. Selenite and selenocystine decreased intracellular glutathione concentrations, but did not affect tumor cell glutathione peroxidase activity. After six days of exposure to either selenate or selenomethionine, the viability of tumor cells remained stable, but cell growth, as measured by numbers of cells, was retarded. Neither selenate nor selenomethionine produced changes in concentrations of intracellular glutathione. The toxic effect of selenite on tumor cells was enhanced by addition of 0.25 mM glutathione to the growth medium. Preincubation of the tumor cells with 62.5 uM buthionine sulfoximine decreased cellular glutathione to 15% of controls at 24 h and enhanced the toxicity of selenite toward the tumor cells. Glutathione, 2-mercaptoethanol, and L-cysteine were all toxic to the tumor cells in a dose-dependent manner.
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Affiliation(s)
- L Yan
- Center for Food and Nutrition, Texas Tech University, Lubbock 79409
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10
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Frenkel GD, Falvey D, MacVicar C. Products of the reaction of selenite with intracellular sulfhydryl compounds. Biol Trace Elem Res 1991; 30:9-18. [PMID: 1718373 DOI: 10.1007/bf02990338] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The usual first step in the intracellular metabolism of exogenous selenite is its chemical reaction with glutathione to form selenodiglutathione (1). We have investigated whether selenite also reacts intracellularly with other SH compounds. HeLa cells were exposed to [75Se]selenite and lysed with SDS. Cellular proteins and nucleic acids were precipitated with trichloroacetic acid, and the acid-soluble fraction was analyzed by ion-exchange thin-layer chromatography (ion-exchange TLC) and autoradiography. In control cells, the major [75Se]-containing species detected can be identified by its mobility as selenodiglutathione. Two other species were detected, which can be identified as selenodimercaptoethylamine and the mixed selenotrisulfide of mercaptoethylamine and glutathione. In contrast, in cells that were depleted of glutathione (by treatment with buthionine sulfoximine), very little, if any, selenodiglutathione was detected. However, new [75Se]-containing species were detected, which can be identified as selenodicysteine and the mixed selenotrisulfide of cysteine and glutathione. The same species were detected when [75Se]selenite was added to the acid-soluble fraction of a cell extract (as opposed to living cells), confirming that these compounds can be formed by nonenzymatic reactions.
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Affiliation(s)
- G D Frenkel
- Department of Biological Sciences, Rutgers University, Newark, NJ 07102
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11
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Kuchan MJ, Milner JA. Influence of supplemental glutathione on selenite-mediated growth inhibition of canine mammary cells. Cancer Lett 1991; 57:181-6. [PMID: 2025890 DOI: 10.1016/0304-3835(91)90213-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Present studies show the in vitro addition of glutathione (GSH) can significantly alter selenite induced growth inhibition of mammary tumor cell line 13 (CMT-13). Preincubation with 100 microM GSH for 24 h partially prevented the growth inhibition caused by 12.6 microM selenite. Pre-incubation with 100 microM GSH for 48 h completely prevented the growth inhibition caused by 12.6 microM selenite. In marked contrast, simultaneous addition of GSH and selenite dramatically increased the severity of selenite-mediated growth inhibition and resulted in cell death. Exposure to selenite (12.6 microM) increased intracellular GSH throughout the 3 day incubation period. Addition of GSH to the medium also led to an approximate 25% increase in intracellular GSH that persisted for 72 h. Cellular retention of selenium following selenite supplementation was decreased up to 70% by GSH preincubation yet increased markedly (greater than or equal to 240%) by the simultaneous addition of GSH and selenite. The rate of selenite uptake was not consistently altered by GSH pretreatment. However, the simultaneous addition of GSH and selenite resulted in a dramatically increased rate of selenium uptake. These data indicate that extracellular GSH can alter the toxicity of supplemental selenite. The protective effect of GSH pre-incubation against selenite toxicity appears to relate to altered selenium retention.
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Affiliation(s)
- M J Kuchan
- Department of Food Science, University of Illinois, Urbana 61801
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12
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Frenkel GD, Falvey D. Involvement of cellular sulfhydryl compounds in the inhibition of RNA synthesis by selenite. Biochem Pharmacol 1989; 38:2849-52. [PMID: 2476131 DOI: 10.1016/0006-2952(89)90440-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Selenite has been shown previously to inhibit cellular RNA synthesis. Based upon our previous observation that selenite inhibits purified RNA polymerase only in the presence of a sulfhydryl compound (Frenkel et al., Mol Pharmacol 31: 112-116, 1987), we hypothesized that the inhibition of cellular RNA synthesis by selenite involves endogenous sulfhydryl compounds. We found that depletion of cells of endogenous sulfhydryl compounds, by exposure to diethylmaleate (DEM), virtually eliminated the inhibitory effect of a 1-hr exposure of cells to selenite. This inhibition was restored to normal or higher levels when the selenite was reacted with glutathione or cysteamine prior to addition to the DEM-treated cells. RNA synthesis in DEM-treated cells was inhibited after a 4-hr exposure to higher concentrations of selenite. In contrast to the effect of DEM, specific depletion of the cells of glutathione, by exposure to buthionine sulfoximine, had no effect on the inhibition of RNA synthesis by selenite. These results demonstrate the involvement of endogenous cellular sulfhydryl compounds in the inhibition of RNA synthesis by selenite, but indicate that glutathione, in particular, is not involved in this inhibition.
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Affiliation(s)
- G D Frenkel
- Department of Biological Sciences, Rutgers University, Newark, NJ 07102
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13
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Parnham MJ, Graf E. Seleno-organic compounds and the therapy of hydroperoxide-linked pathological conditions. Biochem Pharmacol 1987; 36:3095-102. [PMID: 3311047 DOI: 10.1016/0006-2952(87)90617-4] [Citation(s) in RCA: 144] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- M J Parnham
- A. Nattermann Research Laboratories, Cologne, Federal Republic of Germany
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14
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Petrie HT, Klassen LW, Tempero MA, Kay HD. In vitro regulation of human lymphocyte proliferation by selenium. Biol Trace Elem Res 1986; 11:129-46. [PMID: 24254509 DOI: 10.1007/bf02795530] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/1986] [Accepted: 09/09/1986] [Indexed: 10/21/2022]
Abstract
A chemoprotective role for dietary selenium in malignancy has been well documented in numerous epidemiological and experimental studies. The precise mechanisms of this relationship are not understood, but may be related to observations that selenium can inhibit the proliferation of various normal and neoplastic cells, both in vivo and in vitro. In this study, we present evidence that selenium at physiologic concentrations can effectively inhibit the overall proliferation of human lymphocyte populations in response to various immune stimuli in vitro, including mixed lymphocyte response and response to soluble antigen (tetanus toxoid). This inhibition was reversible, indicating that selenium was not toxic to the lymphocytes at these concentrations. Preliminary data from our laboratory indicate that the antiproliferative effects of selenium may be specific for certain lymphocyte subsets. Similar modulation of immune responses in vivo could enhance various humoral and cellular immune mechanisms. Together with published evidence that selenium can inhibit tumor cell proliferation, these data may help to explain the decreased incidence of cancer associated with elevated selenium intake.
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Affiliation(s)
- H T Petrie
- Experimental Immunology Laboratory, Section of Rheumatology and Immunology, Department of Internal Medicine, Omaha Veterans Administration Medical Center, 68105, Omaha, Nebraska, USA
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15
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Milner JA. Inhibition of chemical carcinogenesis and tumorigenesis by selenium. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1986; 206:449-63. [PMID: 3109218 DOI: 10.1007/978-1-4613-1835-4_32] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Selenium is effective in inhibiting the incidence and total number of tumors resulting from treatment with various chemical carcinogens. This inhibition occurs both at the initiation and promotion phases of chemical carcinogenesis. At least part of the inhibition of the initiation stage is associated with changes in the metabolism of the parent carcinogen. Studies with 7,12-dimethylbenz(a)anthracene suggest that selenium specifically blocks the enzyme(s) responsible for the formation of anti-dihydrodiol epoxide adducts to DNA. Selenium is also effective in reducing the in vitro and in vivo growth of numerous neoplastic cells. However, differences in the sensitivity to selenium are evident in the various tumor cell lines that have been examined. Continuous selenium intake appears to be necessary to maximal inhibition in both models of carcinogenesis. Evidence suggests that selenodiglutathione or some other intermediate in selenium metabolism is responsible for the anticarcinogenic and antitumorigenic properties of this trace element. The mechanism by which selenium produces these effects is unknown, but it may relate to alterations in either RNA transcription or translation. These and other data strongly suggest that selenium is a naturally occurring anticarcinogenic and antitumorigenic agent.
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Perchellet JP, Perchellet EM, Orten DK, Schneider BA. Inhibition of the effects of 12-O-tetradecanoylphorbol-13-acetate on mouse epidermal glutathione peroxidase and ornithine decarboxylase activities by glutathione level-raising agents and selenium-containing compounds. Cancer Lett 1985; 26:283-93. [PMID: 3995502 DOI: 10.1016/0304-3835(85)90052-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The present study was undertaken to determine the effect of 12-O-tetradecanoylphorbol-13-acetate (TPA), a potent tumor promoter known to inhibit superoxide dismutase (SOD) (superoxide: superoxide oxidoreductase, EC 1.15.1.1) and catalase (CAT) (H2O2: H2O2 oxidoreductase, EC 1.11.1.6) activities, on mouse epidermal glutathione (GSH) peroxidase (glutathione: H2O2 oxidoreductase, EC 1.11.1.9) activity in vivo and in vitro. TPA led to a rapid and transient increase in GSH peroxidase specific activity within 30 min followed by a decrease from 1 to 12 h. Incubation of isolated epidermal cells with GSH level-raising agents and/or selenium-containing compounds increased remarkably basal GSH peroxidase activity, and thus, abolished totally the prolonged inhibitory effects of TPA on this enzyme. The inhibitory effects of 0.2 mM cysteine (Cys) or 0.5 mM GSH and 2.5 microM Na2 SeO3 or 50 microM selenocystamine on TPA-decreased GSH peroxidase activity were additive, in relation with their additive inhibitory effects on TPA-induced ornithine decarboxylase (ODC) (L-ornithine carboxylase, EC 4.1.1.17) activity. These data support the hypothesis that the stimulators of the GSH-dependent antioxidant protective system of the epidermal cells may inhibit the oxidative challenge linked to skin tumor promotion by TPA.
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18
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Aquino TM, Porta EA, Sablan HM, Dorado RD. Effects of selenium supplementation on hepatocarcinogenesis in rats. Nutr Cancer 1985; 7:25-36. [PMID: 4070005 DOI: 10.1080/01635588509513836] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Four groups of weanling male Wistar rats (Groups A-D) received diethylnitrosamine (DEN, 40 ppm) in their drinking water for four weeks; after a recovery period of two weeks, they received (for the rest of the experiment) phenobarbital (PB, 500 ppm) added to a Torula yeast-based diet containing 0.17 ppm of selenium. Dietary selenium (2 ppm), as sodium selenite, was given to Group B one week before and during DEN treatment, to Group C one week before and during PB treatment, and to Group D during the entire experiment. Groups A and E received the unsupplemented diet, whereas Group E was not treated with DEN or PB. Pair-feeding conditions were used to minimize possible influences of differences in food intake and growth. Rats were killed at the 19th and 24th weeks after the experiment began. No significant differences were found in food and fluid intakes or in growth rates among the groups. Livers in Group E were histologically normal, whereas preneoplastic and neoplastic lesions were found in all other groups. In rats killed at the 19th and 24th weeks, the numerical and the volumetric densities of preneoplastic lesions did not differ significantly between all the groups. Similarly, the incidence of hepatocellular carcinomas only detected at 24 weeks was not significantly different between the groups. These results indicated that in this particular model of hepatocarcinogenesis, the dietary supplementation of 2 ppm of selenium did not modify the development of preneoplasia and carcinomas.
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20
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Friedman M. Sulfhydryl groups and food safety. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1984; 177:31-63. [PMID: 6437164 DOI: 10.1007/978-1-4684-4790-3_2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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21
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Hilf R, Leakey PB, Sollott SJ, Gibson SL. Photodynamic inactivation of R3230AC mammary carcinoma in vitro with hematoporphyrin derivative: effects of dose, time, and serum on uptake and phototoxicity. Photochem Photobiol 1983; 37:633-42. [PMID: 6225134 DOI: 10.1111/j.1751-1097.1983.tb04532.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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22
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Vernie LN, De Vries M, Karreman L, Topp RJ, Bont WS. Inhibition of amino acid incorporation in a cell-free system and inhibition of protein synthesis in cultured cells by reaction products of selenite and thiols. BIOCHIMICA ET BIOPHYSICA ACTA 1983; 739:1-7. [PMID: 6403034 DOI: 10.1016/0167-4781(83)90037-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Reaction products of selenite with thiols were tested for an inhibitory effect on amino acid incorporation in a cell-free system derived from rat liver and on protein synthesis in intact P815 and L1210 cells. In the cell-free system maximum inhibition, up to 96%, was reached at about 10 microM selenium. In intact cells inhibitory effect varied depending on which reaction product or cell line was used. Maximum inhibition was obtained after 30 min of incubation with selenium concentrations ranging from 0.25 microM to over 7 microM. Selenite itself also inhibited protein synthesis of L1210 cells, but only after 90 min of incubation and starting at selenium concentrations of 2 microM. Inhibition of protein synthesis in intact cells was followed by cell death. Pre-incubation of the reaction products of a monothiol (2-propanethiol) and of a vicinal dithiol (2,3-dimercapto-1-propanol) in culture medium showed a rapid decrease of the inhibitory capability of the product from the monothiol, but not of the product from the dithiol. The results indicate that selenite and a thiol react to form products which have differential toxic effects to cells in vitro.
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Ankerst J, Sjögren HO. Effect of selenium on the induction of breast fibroadenomas by adenovirus type 9 and 1,2-dimethylhydrazine-induced bowel carcinogenesis in rats. Int J Cancer 1982; 29:707-10. [PMID: 7107071 DOI: 10.1002/ijc.2910290618] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Selenium in its organic and inorganic forms has been shown to inhibit the development of chemically induced, spontaneous and transplanted tumors. The present investigation was performed to study the effect of selenium (4 micrograms per ml of drinking water) on tumorigenesis of adenovirus-type-9-induced breast fibroadenomas and on 1,2-dimethylhydrazine-induced bowel carcinogenesis in WF rats. It was found that identical treatment with Se under identical conditions and with no obvious toxic effects on the rats (1) resulted in inhibition of DMH-induced large-bowel carcinogenesis; (2) facilitated induction of small-bowel cancer by the same carcinogen in the same animals, and (3) greatly facilitated induction of breast fibroadenoma by adenovirus type 9 in the same strain of rats. The effect of Se treatment on DMH-induced large-bowel carcinogenesis confirms previous findings and proves that the opposite effect on fibroadenoma development is not due to differences in e.g. effective dose, animal strains or condition of the animals. It is not yet clear through which mechanisms Se exerts these effects.
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