| | Effects of selenium supplementation on expression of glutathione peroxidase isoforms in cultured human lung adenocarcinoma cell linesReceived 20 January 2006; received in revised form 16 August 2006; accepted 17 September 2006. Summary Selenium is an essential nutrient, a component of several anti-oxidant enzymes, and a possible factor in cancer risk, including lung cancer. We determined the subtoxic range of selenium concentration (as sodium selenite) required to increase and maintain the expression of anti-oxidant selenoproteins gluthathione peroxidases GPX1 and GPX4 at a constant level in cultures of human lung adenocarcinoma cell lines (H460, H1703 and H1944) and in HPL1D, a non-transformed lung epithelial cell line. Selenium dose-dependently increased GPX1 protein expression 1.8-fold in HPL1D cells and ∼40-fold in H460 and H1944 cancer cells, with maximum effects at 20–40 nM. GPX4 protein was also increased, but more so in HPL1D (five-fold) than in H460 or H1944 cells (two- to three-fold). GPX1 mRNA showed similar patterns but differences of lesser magnitude. GPX1 protein and activity level was not consistently detectable in H1703 cells, with or without Se supplementation; its mRNA was present but very low. GPX4 protein level was also low in H1703 cells, but was markedly increased by selenium supplementation (48-fold). These results confirm a role for selenium in risk of lung cancer and the independent regulation of GPX1 and GPX4. Characterization of individual tumors with regard to GPX1 and GPX4 levels and regulation might be useful for interpretation of clinical studies on effects of selenium in lung cancer risk. 1. Introduction  Anti-oxidant molecules and enzymes may have an important influence on the formation and development of lung cancers [1]. Among the key anti-oxidant enzymes are the glutathione peroxidases (GPX), which detoxify peroxides. The main GPXs in lung are GPX1, a cytosolic enzyme with activity toward hydrogen peroxide and soluble organic peroxides, and GPX4, which may localize in the mitochondria as well as the cytosol and has broad substrate specificity, including lipid peroxides in cell membranes [2]. GPX4 may also influence intracellular signaling by inhibition of lipooxygenases and cyclooxygenases that generate arachidonic acid metabolites involved in cell proliferation and apoptosis [3]. The role of GPX1 in carcinogenesis still remains unclear. GPX1 knockout mice have been shown normal phenotype until challenged with oxidative stress [4]. In selenium-deficient animals [5] a drastic and sustained decrease in GPX1 activity did not lead to pathologies [5]. These outcomes suggest that the enzyme contributes to anti-oxidant defense particularly in pathological conditions. However, a GPX1 genetic polymorphism has been linked recently to risk of lung cancer [6]. GPXs are selenium (Se) containing, Se-dependent enzymes, and may be part of the apparent protective effect of dietary Se with regard to cancers of lung and other tissues [7], [8], [9], [10]. A recent meta-analysis confirmed increased lung cancer risk associated with the lowest level of Se intake [11]. There is currently ongoing a clinical trial of Se chemoprevention potential in patients with stage I non-small cell lung cancer (http://cancer.gov/clinicaltrials/ECOG-5597). Organoselenium compounds have been shown to suppress carcinogen-induced lung cancer in mice in many studies (reviewed in [12]), by a complexity of mechanisms that may include upregulation of GPX1 in lung [13]. Available Se affects levels of GPX enzymes through several mechanisms. It is incorporated into the protein as selenocysteine (Sec). Sec is encoded by UGA, which is normally a transcription termination codon. Ribosomal reading of UGA to incorporate Sec requires a number of special factors, in eukaryotes including the unique tRNA(ser)Sec and mRNA with a specific sequence in the 3′untranslated region termed selenocysteine insertion sequence (SECIS) (reviewed in [14]). Synthesis of the GPX protein may be directly limited by lack of Se to make Sec, and also by Se-related mRNA instability. There is a hierarchy in this mRNA instability property among selenoproteins, determined by the sequence of the 3′ untranslated region, with GPX1 having the most unstable form, whereas GPX4 mRNA is more stable [15], [16], [17]. The instability of the mRNAs is a function in part of nonsense-mediated decay in the absence of Sec, although the involvement of SECIS binding proteins has not been excluded [15], [18], [19]. Se apparently does not influence the rate of transcription of GPX genes [20]. Plasma or serum concentration is considered a useful indicator of Se status and intake. There are, however, no well-accepted normal Se level requirements because of differences from country to country and variation in availability of different forms of Se. More recently, the activity/expression of selenoproteins including GPXs and selenoprotein P has been shown to be a very useful marker for Se status and requirements (reviewed in [21]). We have been investigating anti-oxidant parameters in human lung adenocarcinoma cell lines, including levels of GPX1 and GPX4. The synthesis of these proteins is expected to be influenced by the amount of Se in the culture medium. Only limited information has been published regarding the Se requirements and sensitivities of normal and neoplastic lung cells in culture and the optimal Se level needed for GPX protein expression in lung cancer cells. Most cell culture media do not include added Se, and even with the addition of serum do not contain Se at the levels found in the plasma of normal, adequately nourished adults, about 45–200μg/L, depending on the regional variations [22], [23]. Experts in this area typically supplement cell culture media with 30–250nM sodium selenite, with 1000nM sometimes leading to toxicity [24], [25]. Sodium selenite at 5750nM suppressed the mitotic index of human lung adenocarcinoma cells; embryonic lung cells were less sensitive [26]. In the human lung adenocarcinoma cell line A-427, 250nM sodium selenite led to a four-fold increase in GPX activity and a 1.8-fold increase in GPX1 mRNA level [27]. High concentrations of methylseleninic acid (2500–10,000nM) inhibited the growth of H522 (lung adenocarcinoma) and H530 (lung squamous cell carcinoma) cell lines [28]. In rat primary tracheal epithelial cells, sodium selenite at concentrations of 60–6000nM stimulated growth, whereas inhibition was seen at 20,000nM. Interestingly, 60–600nM concentrations suppressed spontaneous transformation of these cells [29]. In experiments reported here, we have investigated Se effects on GPX1 and GPX4 expression in lung adenocarcinoma cell lines, H1703, H460 and H1944, which, in a preliminary screen of a panel of lung cancer cell lines, were found to have significantly lower levels of GPX1 protein and activity compared to a non-transformed HPL1D cell line derived from peripheral human lung epithelium. We sought to define optimal levels of Se, as a subtoxic concentration of sodium selenite, which sustainably increases the level of GPX proteins, so that regulation and effects of these proteins could be studied independently of their reliance on Se availability. 2. Materials and methods 2.1. Cell culture and media Human lung cancer cell lines were obtained from the American Type Culture Collection and are described by their NCI numbers in this study: H1703, H1944 and H460 [30]. The non-transformed cell line HPL1D from human lung peripheral epithelium was obtained from Dr. T. Takahashi [31]. The cells were cultured in RPMI 1640 medium (Biosource Int., Rockville, MD) supplemented with 10% fetal calf serum (Gemini Bio-Products, Woodland, CA), glutamine and streptomycin/penicillin at 7% CO2. Total Se concentration in serum and media was assayed by a fluorometric method, using 2,3-diaminonaphthalene as a complexing agent [32], in the Oscar E. Olson Biochemistry Laboratories, Analytical Services Laboratory at South Dakota State University. Then we supplemented culture media with 0–500nM sodium selenite (Na2SeO3) (Sigma–Aldrich, St. Louis, MO) and the cells were cultured at least for 7 days in the Se-containing media prior to experiments. 2.2. Immunoblotting Assays were carried out on proliferating, 75–80% confluent cells. Cell lysates were collected by scraping in 25mM HEPES lysis buffer, pH 7.2, containing 1% Nonidet, 0.25% sodium deoxycholate, 150mM NaCl, 10mM MgCl2, 10% glycerol, 2.5mM EDTA, 0.28TIU/ml aprotinin, 10mM NaF, 2mM phenymethylsulfonyl fluoride (PMSF) and 2mM NaVO3. Protein concentration was determined by BCA Protein Assay Kit (Pierce Biotechnology, Inc., Rockford, IL) using bovine serum albumin (BSA) as a standard. Proteins (50μg or 20μg lysate protein for GPX1 or GPX4, respectively) were subjected to electrophoresis on 10% NuPage Bis–Tris gels (Invitrogen, Carlsbad, CA). Then they were transferred to Hybond ECL nitrocellulose (Amersham Biosciences, Piscataway, NJ) at 30V for 1.5h. After blocking with 5% milk in Tris-buffered saline (TBS) containing 0.1% Tween-20, the blots were incubated with 1:500 dilution of mouse monoclonal anti-GPX1 (Medical & Biological Laboratories CO., LTD., Naka-ku, Nagoya, Japan), or 1:2000 dilution of polyclonal rabbit anti-GPX4 (LabFrontier, Seoul, Korea), then with anti-mouse or anti-rabbit secondary IgG, 1:1000, conjugated with horseradish peroxidase (Amersham). We determined that mouse monoclonal anti-human GPX1 did not cross-react with human recombinant GPX4 protein (LabFrontier, Seoul, Korea) and anti-GPX4 did not react with any other human GPXs (LabFrontier, personal communication). The blots were developed using a chemiluminescence ECL™ Western Blotting Detection Kit (Amersham), exposed to X-ray film, scanned and quantified using UN-SCAN-IT software (Silk Scientific, Inc., Orem, UT). β-Actin, detected with a rabbit antibody (Abcam, Cambridge, MA), was used as loading control. 2.3. GPX1 activity Cell pellets were washed in cold PBS, resuspended in 15mM HEPES, pH 7.4, supplemented with 0.3M mannitol, 0.1% BSA, 3mM MgCl2, 0.28TIU/ml aprotinin, 10mM NaF, 2mM PMSF, and 2mM NaVO3, and homogenized in a glass potter homogenizator. Cell homogenates were centrifuged at 10,000×g for 10min and the supernatants were collected and centrifuged again at 105,000×g for 60min. GPX1 enzymatic activity was measured in the supernatants by the method of Paglia and Valentine [33] with t-butylhydroperoxide as a substrate. One unit of activity is defined as the amount of enzyme that oxidized 1μmol NADPH per minute. 2.4. Isolation of RNA Total RNA was isolated and purified using Versagene RNA Purification Kit (Gentra Systems, Minneapolis, MN) and DNA-free set (Ambion, Inc., Austin, TX) according to the manufacturers’ instructions. Purity and yield was determined spectrophotometrically and RNA integrity was determined by 18S/28S rRNA analysis using agarose gel electrophoresis and ethidium bromide staining. 2.5. cDNA synthesis and quantitative real-time PCR The purified RNA (200ng) was reverse-transcribed in 20-μl mixture using an Omniscript RT kit (Qiagen, Valencia, CA) and oligo dT primer (Invitrogen, Carlsbad, CA). Real-time PCR was performed in duplicate on a PTC-200 thermal cycler with Chromo 4 fluorescence detector (MJ Research, Inc., Waltham, MA). Primer sequences were as follows: GPX4 forward primer: 5′-CCGAAGTAAACTACACTCAGCTCGTC-3′ and reverse primer: 5′-TCTTTGATCTCTTCGTTACTCCCTG-3′ [34, modified]; GPX1 forward primer: 5′-CGCTTCCAGACCATTGACATC-3′ and reverse primer: 5′-CGAGGTGGTATTTTCTGTAAGATCA-3′ [35]. Samples were amplified in 20-μl aliquots containing diluted cDNA, 0.5μM forward and reverse primers and 1× QuantiTect SYBR Green PCR Master Mix (Qiagen, Valencia, CA). Reaction conditions were: 40 cycles of 94°C for 15s, 62°C for 30s and 72°C for 30s following a 15min 95°C initial denaturation step. A melting curve or electrophoresis was run on PCR products to verify primer specificity and purity of products. The ratio of GPX mRNA level to β-actin internal control was used for statistical comparison among cell lines. Determination of cycle number at threshold (Ct value) was performed using Opticon Monitor Version 2.03.5 software (MJ Research, Inc., Waltham, MA). 2.6. Statistical analysis Statistical comparisons included pair-wise tests (t-tests or non-parametric analyses as appropriate), and determination of significant correlations with dose by linear regression analysis, using GraphPad InStat Version 3.00, GraphPad Software, San Diego, CA. 3. Results 3.2. Effect of Se supplementation on GPX1 and GPX4 protein expression The results of these experiments, shown as average increases in protein and activity relative to unsupplemented cells, confirm that supplementation of lung epithelial cell culture media with Se is necessary for maximum expression of GPX1 and GPX4 (Fig. 1, Fig. 2). For GPX1 in the adenocarcinoma cell lines H460 and H1944, the relative effect of added Se was greater than for the non-transformed HPL1D cells, due in part to the apparently higher expression of GPX1 in HPL1D cells without Se supplementation. In HPL1D cells, the addition of sodium selenite led to a significant 1.8-fold increase in GPX1 protein, with a plateau reached at 20nM (Fig. 1A). Much more marked effects were seen for H460 (Fig. 1B) and H1944 (Fig. 1C) cells, with maximum increases of about 40-fold. Greatest effects occurred at 20–40nM for both these cell lines. The Western blot results of GPX1 protein expression were supported by activity assay performed by the NADPH-coupled assay procedure with t-butylhydroperoxide as a substrate (Fig. 1). Se supplementation led to increases in GPX1 activity comparable to the increases in protein level (Fig. 1). With regard to GPX4 protein, Se addition to HPL1D cells led to a significant dose-dependent increase, up to a maximum of five-fold at 100nM (Fig. 2A). In H460 cells (Fig. 2B) and H1944 cells (Fig. 2C) there were significant 1.7- to 2.7-fold increases, also at a maximum at 100–250nM sodium selenite. Relative effects of Se on GPX4 protein expression in HPL1D, H460 and H1944 cells were compared by averaging all values for GPX4 percent increases for HPL1D at 50–250nM (4.75±11.0) and comparing with H460 at 100–500nM (2.36±1.9, P=0.085) and with H1944 at 100–500nM (1.60±1.0, P=0.035). Thus, it appeared likely that Se had a relatively greater effect on GPX4 in HPL1D cells than in H460 and H1944. The most striking results were observed in H1703 cells. In the absence of Se, both GPX1 and GPX4 protein and activity had low to undetectable expression and GPX1 protein and activity remained consistently undetectable in H1703 cells under the conditions used, at Se concentrations up to 250nM (data not shown). However, H1703 cells showed a marked increase in GPX4 in response to Se, with apparent dose–response up to 30nM; there was a 48-fold increase at 100nM. 3.3. Effect of selenium supplementation on GPX1 and GPX4 mRNA GPX1 and GPX4 mRNA levels were determined by real-time PCR. In Se-supplemented HPL1D cells, there was a small increase in GPX1 mRNA expression, which reached a maximum at 10nM Se, whereas in H1944 and H460 cells an increase of about four-fold was seen at 100nM Se (Fig. 3A). Basal GPX1 mRNA was about three-fold higher in HPL1D cells compared with H1944 and H460 cells (Fig. 3B). Thus, the GPX1 mRNA expression patterns were similar to the protein expression patterns (Fig. 1), but the absolute magnitudes of the differences were lower. GPX1 mRNA was low, but detectable, in H1703 cells, and showed a possible increase with Se supplementation up to 30nM, and a reduction at higher concentrations (Fig. 3B). This low level of GPX1 mRNA in H1703 cells corresponded to very low protein expression. GPX4 mRNA showed an increase with Se supplementation in all four cell lines (Fig. 3C). In this case, both the pattern and the magnitude of the increases were similar to what was observed for the protein (Fig. 2). 4. Discussion The results of this study confirm that supplementation of lung epithelial cell culture media with Se is necessary for maximum expression of GPX1 and GPX4. The stimulatory effects of Se on GPX1 expression were optimal at 10–30nM sodium selenite, depending on the cell type. Moreover, maximum effects of 100nM on GPX4 were clear. These results are consistent with most reports for various cell types, as referenced in Section 1. On balance, supplementation with 50–100nM sodium selenite would seem to be a good practice for culture of these types of cells. In addition, the cell- and GPX isoform-specific responses to Se supplementation are of interest. The most striking instance was observed in H1703 cells. Without added Se, both GPX1 and GPX4 had low to undetectable protein expression. Addition of Se resulted in marked upregulation of GPX4 protein, while GPX1 remained undetectable. Allelic loss of GPX1 is known to be associated with lung cancer [36]. However, GPX1 mRNA was detectable in this line, albeit at extremely low levels (Fig. 3B), indicating the presence of at least one GPX1 allele. The very low level of mRNA presumably accounts for lack of GPX1 protein in this cell line, and could reflect lesions in transcription and/or mRNA stability. The cancer of origin for this cell line was a stage I adenocarcinoma in a Caucasian male heavy smoker, characterized by mutation and loss of heterozygosity of the p53 gene. GPX1 is known to have a p53 responsive gene promoter [37], [38]; it is likely that the lack of normal p53 accounts for the low levels of GPX1 mRNA in H1703 cells. The non-transformed HPL1D cells presented higher basal GPX1 protein and mRNA than did the H460 and H1944 adenocarcinoma cell lines, where the effects of Se supplementation were correspondingly greater. Reduced GPX1 in lung cancers, compared with normal surrounding tissues, has been reported in some [39] though not all [40], [41] studies. It could be of interest to know whether these differences, when they occur, relate to differential availability or uptake of Se. In one study where increased glutathione peroxidase was measured in neoplastic compared with normal human lung tissues, this was associated with higher Se levels [41]. It is of interest that a proline/leucine polymorphism in GPX1 was associated with lung cancer risk in Caucasians [42]; and this polymorphism correlated with lower responsiveness of enzyme activity to Se supplementation in mammary cells [43]. GPX1 protein and mRNA levels showed similar patterns in the comparisons among cell lines and different Se concentrations, but effects of Se were quantitatively smaller for mRNA level compared with protein. This result is consistent with Se affecting GPX protein through at least two mechanisms, level of Sec regulating translation, and mRNA stability. A similar differential was observed in livers of rats fed Se deficient versus Se adequate diets: GPX1 mRNA was decreased 6- to 8-fold, while GPX1 protein was 30- to 40-fold lower [17]. Results obtained with GPX4 were distinct from those with GPX1. GPX4 basal levels were higher in the H460 and H1944 cancer lines, compared with HPL1D cells, and the stimulatory effects of Se were correspondingly weaker. Se supplementation had relative less effect on GPX4 compared with GPX1, as was also observed in rat liver [17]. This is consistent with higher stability of GPX4 mRNA, compared with that of GPX1 mRNA [15], [16]. The effects of Se on GPX4 protein and mRNA were similar in magnitude, suggesting that mRNA stability may have been rate-limiting for this isoform. In H1703 cells, basal GPX4 protein and mRNA levels were very low, which may again reflect lack of a normal p53. However, in contrast to GPX1 in these cells, supplementation with Se caused a marked upregulation in GPX4 protein, along with a more modest increase in GPX4 mRNA. Thus, this cell line retains the ability to respond to Se by upregulating GPX4 mRNA and especially protein expression, in spite of absence of normal p53. Separate regulatory systems for different GPX isoforms have been reported previously in various cells and tissues [15], [17], [44]. The details of GPX4 regulation in H1703 should be further investigated. In sum, our data clearly confirm that full expression of GPX1 and GPX4 in human lung epithelial cells and lung adenocarcinoma cells requires the presence of about 100nM Se in the culture media. In view of the importance of these enzymes as anti-oxidants and signaling regulators, and the putative importance of reactive oxygen species in lung cancer, our findings are consistent with increased lung cancer risk when Se is deficient. In the lung cancer cells, the impact of Se supplementation varied, depending on the GPX isoform and the nature of the cell line. In two cancer lines Se deficiency markedly reduced GPX1 levels but had lesser impact on GPX4. In a third line, GPX1 had minimal expression regardless of Se concentration, but GPX4 was highly responsive to Se supplementation. Therefore, interpretation of ongoing clinical trials of the effects of Se on lung cancer might be aided by determination of the levels of specific GPXs and of their regulatory contexts (for example, p53 gene mutations) for each of the cancers involved. Acknowledgments This research was supported by the Intramural Research Program of the NIH, NCI, Center for Cancer Research. We gratefully acknowledge expert advice from Dr. Dolph Hatfield, Laboratory of Cancer Prevention, NCI and Dr. Alan Diamond, University of Illinois at Chicago; and selenium analyses by Nancy Thiex at South Dakota State University. References [1]. [1]Maciag A, Anderson LM. Reactive oxygen species and lung tumorigenesis by mutant K-ras: a working hypothesis. Exp Lung Res. 2005;31:83–104. MEDLINE |
CrossRef
[2]. [2]Gromer S, Eubel JK, Lee BL, Jacob J. Human selenoproteins at a glance. Cell Mol Life Sci. 2005;62:2414–2437.
CrossRef
[3]. [3]Imai H, Nakagawa Y. Biological significance of phospholipid hydroperoxide glutathione peroxidase (PHGPx, GPx4) in mammalian cells. Free Radic Biol Med. 2003;34:145–169. MEDLINE |
CrossRef
[4]. [4]de Haan JB, Bladier C, Griffiths P, Kelner M, O'Shea RD, Cheung NS, et al. Mice with a homozygous null mutation for the most abundant glutathione peroxidase, Gpx1, show increased susceptibility to the oxidative stress-inducing agents paraquat and hydrogen peroxide. J Biol Chem. 1998;273:22528–22536. MEDLINE |
CrossRef
[5]. [5]Sunde RA, Thompson BM, Palm MD, Weiss SL, Thompson KM, Evenson JK. Selenium regulation of selenium-dependent glutathione peroxidases in animals and transfected CHO cells. Biomed Environ Sci. 1997;10:346–355. MEDLINE [6]. [6]Lee CH, Lee KY, Choe KH, Hong YC, Noh SI, Eom SY, et al. Effects of oxidative DNA damage and genetic polymorphism of the glutathione peroxidase 1 (GPX1) and 8-oxoguanine glycosylase 1 (hOGG1) on lungcancer. J Prev Med Public Health. 2006;39:130–134. [7]. [7]Clark LC, Combs GF, Turnbull BW, Slate EH, Chalker DK, Chow J, et al. Effects of selenium supplementation for cancer prevention in patients with carcinoma of the skin. A randomized controlled trial. The nutritional prevention of cancer study group. JAMA. 1996;276:1957–1963. MEDLINE [8]. [8]Reid ME, Duffield-Lillico AJ, Garland L, Turnbull BW, Clark LC, Marshall JR. Selenium supplementation and lung cancer incidence: an update of the nutritional prevention of cancer trial. Cancer Epidemiol Biomarkers Prev. 2002;11:1285–1291. MEDLINE [9]. [9]Lu J, Jiang C. Selenium and cancer chemoprevention: hypotheses integrating the actions of selenoproteins and selenium metabolites in epithelial and non-epithelial target cells. Antioxid Redox Signal. 2005;7:1715–1727. MEDLINE |
CrossRef
[10]. [10]Rayman MP. Selenium in cancer prevention: a review of the evidence and mechanism of action. Proc Nutr Soc. 2005;64:527–542. MEDLINE [11]. [11]Zhuo H, Smith AH, Steinmaus C. Selenium and lung cancer: a quantitative analysis of heterogeneity in the current epidemiological literature. Cancer Epidemiol Biomarkers Prev. 2004;13:771–778. MEDLINE [12]. [12]Li L, Xie Y, El-Sayed WM, Szakacs JG, Franklin MR, Roberts JC. Chemopreventive activity of selenocysteine prodrugs against tobacco-derived nitrosamine (NNK) induced lung tumors in the A/J mouse. J Biochem Mol Toxicol. 2005;19:396–405. MEDLINE |
CrossRef
[13]. [13]Prokopczyk B, Rosa JG, Desai D, Amin S, Sohn OS, Fiala ES, et al. Chemoprevention of lung tumorigenesis induced by a mixture of benzo(a)pyrene and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone by the organoselenium compound 1,4-phenylenebis(methylene)-selenocyanate. Cancer Lett. 2000;161:35–46. Abstract | Full Text |
Full-Text PDF (142 KB)
|
CrossRef
[14]. [14]Hoffmann PR, Berry MJ. Selenoprotein synthesis: a unique translational mechanism used by a diverse family of proteins. Thyroid. 2005;15:769–775. MEDLINE |
CrossRef
[15]. [15]Muller C, Wingler K, Brigelius-Flohe R. 3′UTRs of glutathione peroxidases differentially affect selenium-dependent mRNA stability and selenocysteine incorporation efficiency. Biol Chem. 2003;384:11–18. MEDLINE |
CrossRef
[16]. [16]Brigelius-Flohe R. Tissue-specific functions of individual glutathione peroxidases. Free Radic Biol Med. 1999;27:951–965. MEDLINE |
CrossRef
[17]. [17]Weiss Sachdev S, Sunde RA. Selenium regulation of transcript abundance and translational efficiency of glutathione peroxidase-1 and -4 in rat liver. Biochem J. 2001;357(Pt 3):851–858. MEDLINE |
CrossRef
[18]. [18]Weiss SL, Sunde RA. Cis-acting elements are required for selenium regulation of glutathione peroxidase-1 mRNA levels. RNA. 1998;4:816–827. MEDLINE |
CrossRef
[19]. [19]Moriarty PM, Reddy CC, Maquat LE. Selenium deficiency reduces the abundance of mRNA for Se-dependent glutathione peroxidase 1 by a UGA-dependent mechanism likely to be nonsense codon-mediated decay of cytoplasmic mRNA. Mol Cell Biol. 1998;18:2932–2939. MEDLINE [20]. [20]Christensen MJ, Burgener KW. Dietary selenium stabilizes glutathione peroxidase mRNA in rat liver. J Nutr. 1992;122:1620–1626. MEDLINE [21]. [21]Thomson CD. Assessment of requirements for selenium and adequacy of selenium status: a review. Eur J Clin Nutr. 2004;58:391–402. MEDLINE |
CrossRef
[22]. [22]Duffield-Lillico AJ, Reid ME, Turnbull BW, Combs GF, Slate EH, Fischbach LA, et al. Baseline characteristics and the effect of selenium supplementation on cancer incidence in a randomized clinical trial: a summary report of the Nutritional Prevention of Cancer Trial. Cancer Epidemiol Biomarkers Prev. 2002;11:630–639. MEDLINE [23]. [23]Lyons GH, Judson GJ, Stangoulis JCR, Palmer LT, Jones JA, Graham RD. Trends in selenium status of South Australians. Med J Aust. 2004;180:383–386. [24]. [24]Abul-Hassan KS, Lehnert BE, Guant L, Walmsley R. Abnormal DNA repair in selenium-treated human cells. Mutat Res. 2004;565:45–51. MEDLINE [25]. [25]Ebert R, Ulmer M, Zeck S, Meissner-Weigl J, Schneider D, Stopper H, et al. Selenium supplementation restores the antioxidative capacity and prevents cell damage in bone marrow stromal cells in vitro. Stem Cells. 2006;24:1226–1235. MEDLINE |
CrossRef
[26]. [26]Ao P, Yu SY, Zhao M, Sun J. Different effects of selenium on proliferation of human lung adenocarcinoma cells and human embryonic lung diploid cells in vitro. Zhonghua Zhong Liu Za Zhi. 1987;9:408–411. MEDLINE [27]. [27]Schonberg SA, Rudra PK, Noding R, Skorpen F, Bjerve KS, Krokan HE. Evidence that changes in Se-glutathione peroxidase levels affect the sensitivity of human tumor cell lines to n-3 fatty acids. Carcinogenesis. 1997;18:1897–1904. MEDLINE |
CrossRef
[28]. [28]Swede H, Dong Y, Reid M, Marshall J, Ip C. Cell cycle arrest biomarkers in human lung cancer cells after treatment with selenium in culture. Cancer Epidemiol Biomarkers Prev. 2003;12:1248–1252. MEDLINE [29]. [29]Zhu S, Gray TE, Nettesheim P. The effect of sodium selenite on cell proliferation and transformation of primary rat tracheal epithelial cells. Carcinogenesis. 1992;13:1725–1729. MEDLINE [30]. [30]Phelps RM, Johnson BE, Ihde DC, Gazdar AF, Carbone DP, McClintock RI, et al. NCI-Navy Medical Oncology Branch cell line data base. J Cell Biochem Suppl. 1996;24:32–91. MEDLINE [31]. [31]Masuda A, Kondo M, Saito T, Yatabe Y, Kobayashi T, Okamoto M, et al. Establishment of human peripheral lung epithelial cell lines (HPL1) retaining differentiated characteristics and responsiveness to epidermal growth factor, hepatocyte growth factor, and transforming growth factor beta. Cancer Res. 1997;57:4898–4904. MEDLINE [32]. [32]Palmer IS, Thiex N. Determination of selenium in feeds and premixes: collaborative study. J AOAC Int. 1997;80:469–480. MEDLINE [33]. [33]Paglia DE, Valentine WN. Studies on the quantitative and qualitative characterization of erythrocyte glutathione peroxidase. J Lab Clin Med. 1967;70:158–169. MEDLINE [34]. [34]Kim YJ, Chai YG, Ryu JC. Selenoprotein W as molecular target of methylmercury in human neuronal cells is down-regulated by GSH depletion. Biochem Biophys Res Commun. 2005;330:1095–1102.
CrossRef
[35]. [35]Yang P, Bamlet WR, Ebbert JO, Taylor WR, de Andrade M. Glutathione pathway genes and lung cancer risk in young and old populations. Carcinogenesis. 2004;25:1935–1944. MEDLINE |
CrossRef
[36]. [36]Hardie LJ, Briggs JA, Davidson LA, Allan JM, King RF, Williams GL, et al. The effect of hOGG1 and glutathione peroxidase I genotypes and 3p chromosomal loss on 8-hydroxydeoxyguanosine levels in lung cancer. Carcinogenesis. 2000;21:167–172. MEDLINE |
CrossRef
[37]. [37]Hussain SP, Amstad P, He P, Robles A, Lupold S, Kaneko I, et al. p53-Induced up-regulation of MnSOD and GPx but not catalase increases oxidative stress and apoptosis. Cancer Res. 2004;64:2350–2356. MEDLINE |
CrossRef
[38]. [38]Tan M, Li S, Swaroop M, Guan K, Oberley LW, Sun Y. Transcriptional activation of the human glutathione peroxidase promoter by p53. J Biol Chem. 1999;274:12061–12066. MEDLINE |
CrossRef
[39]. [39]Jaruga P, Zastawny TH, Skokowski J, Dizdaroglu M, Olinski R. Oxidative DNA base damage and antioxidant enzyme activities in human lung cancer. FEBS Lett. 1994;341:59–64. MEDLINE |
CrossRef
[40]. [40]Zachara BA, Marchaluk-Wisniewska E, Maciag A, Peplinski J, Skokowski J, Lambrecht W. Decreased selenium concentration and glutathione peroxidase activity in blood and increase of these parameters in malignant tissue of lung cancer patients. Lung. 1997;175:321–332. MEDLINE |
CrossRef
[41]. [41]Di Ilio C, Del Boccio G, Casaccia R, Aceto A, Di Giacomo F, Federici G. Selenium level and glutathione-dependent enzyme activities in normal and neoplastic human lung tissues. Carcinogenesis. 1987;8:281–284. MEDLINE [42]. [42]Ratnasinghe D, Tangrea JA, Andersen MR, Barrett MJ, Virtamo J, Taylor PR, et al. Glutathione peroxidase codon 198 polymorphism variant increases lung cancer risk. Cancer Res. 2000;60:6381–6383. MEDLINE [43]. [43]Hu YJ, Diamond AM. Role of glutathione peroxidase 1 in breast cancer: loss of heterozygosity and allelic differences in the response to selenium. Cancer Res. 2003;63:3347–3351. MEDLINE [44]. [44]Lei XG, Evenson JK, Thompson KM, Sunde RA. Glutathione peroxidase and phospholipid hydroperoxide glutathione peroxidase are differentially regulated in rats by dietary selenium. J Nutr. 1995;125:1438–1446. MEDLINE Laboratory of Comparative Carcinogenesis, National Cancer Institute at Frederick, Building 538, Ft. Detrick, Frederick, MD 21702, USA  Corresponding author. Tel.: +1 301 846 1246; fax: +1 301 846 5946.
PII: S0169-5002(06)00486-7 doi:10.1016/j.lungcan.2006.09.007 © 2006 Elsevier Ireland Ltd. All rights reserved. | |
|
FULL TEXT00486-7/journalimage?img=PIIS0169500206004867.gr1.lrg.gif&fig=fig1&kwhquery=&issn=0169-5002&ishighres=false&allhighres=false&free=yes','journalimage');)
00486-7/journalimage?img=PIIS0169500206004867.gr2.lrg.gif&fig=fig2&kwhquery=&issn=0169-5002&ishighres=false&allhighres=false&free=yes','journalimage');)
00486-7/journalimage?img=PIIS0169500206004867.gr3.lrg.gif&fig=fig3&kwhquery=&issn=0169-5002&ishighres=false&allhighres=false&free=yes','journalimage');)