Selenium: epidemiology and basic science

Unbalance of Se and nutritional status in male infertility

Objective:

To evaluate the selenium status and oxidative stress in male infertility cases selected from a private human reproduction center in the state of Ceará, Brazil.

Methods:

The present study had a cross-sectional quantitative approach, carried out between January and October 2013 at a Human Reproduction Center. The studied population was composed of 49 male individuals seen at the clinic, aged between 18 and 60 years. Blood samples were collected to measure serum selenium concentrations, erythrocyte activity and glutathione peroxidase. After medical diagnosis, the participants were divided into fertile and infertile groups. Blood samples were collected for establishing Se concentrations in plasma and erythrocytes, and measurements of the enzymatic activity of glutathione peroxidase in the erythrocytes.

Result:

it resulted in 53.1% of fertile men and 46.9% of infertile men. The average age of the fertile group was 34.1 years and the infertile group was 37.3 years. Regarding the assessment of nutritional status, the scatter diagram of the infertility group showed a higher body mass index and waist circumference, showing that this group has a higher risk of global and abdominal obesity compared to the fertile group (p<0.0001, respectively). There were similarities between the groups regarding caloric intake, macronutrient and selenium intake.

Conclusion:

We can conclude that the serum values of selenium, in excess and in deficiency, can be harmful to male fertility.

Ameliorative effects of nano-selenium against NiSO4-induced apoptosis in rat testes

Nickel (Ni) is a common environmental pollutant, which has toxic effects on reproductive system. Nowadays, nano-selenium (Nano-Se) has aroused great attention due to its unique antioxidant effect, excellent biological activities and low toxicity. The aim of this study was to explore the protective effects of Nano-Se on NiSO₄-induced testicular injury and apoptosis in rat testes. Nickel sulfate (NiSO₄) (5 mg/kg b.w.) was administered intraperitoneally and Nano-Se (0.5, 1, and 2 mg Se/kg b.w., respectively) was given by oral gavage in male Sprague-Dawley rats. Histological changes in the testes were determined by H&E staining. The terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay and immunohistochemistry were performed to evaluate the apoptosis in testes. Expression levels of mitochondrial apoptosis-related genes and proteins were analyzed by RT-qPCR and Western blot. The results showed that Nano-Se improved lesions of testicular tissue induced by NiSO₄. Nano-Se significantly alleviated NiSO₄-induced apoptosis in rat testes, as well as significantly downregulated the Bak, cytochrome c, caspase-9 and caspase-3 and upregulated Bcl-2 expression levels, all of which were involved in mitochondria-mediated apoptosis. Altogether, we concluded that Nano-Se may potentially exert protective effects on NiSO₄-induced testicular injury and attenuate apoptosis, at least partly, via regulating mitochondrial apoptosis pathways in rat testes.

Selenium-Binding Protein 1 in Human Health and Disease

Selenium-binding protein 1 (SBP1) is a highly conserved protein that covalently binds selenium. SBP1 may play important roles in several fundamental physiological functions, including protein degradation, intra-Golgi transport, cell differentiation, cellular motility, redox modulation, and the metabolism of sulfur-containing molecules. SBP1 expression is often reduced in many cancer types compared to the corresponding normal tissues and low levels of SBP1 are frequently associated with poor clinical outcome. In this review, the transcriptional regulation of SBP1, the different physiological roles reported for SBP1, as well as the implications of SBP1 function in cancer and other diseases are presented.

Dietary Antioxidants, Circulating Antioxidant Concentrations, Total Antioxidant Capacity, and Risk of All-Cause Mortality: A Systematic Review and Dose-Response Meta-Analysis of Prospective Observational Studies

The associations of various dietary or circulating antioxidants with the risk of all-cause mortality in the general population have not been established yet. A systematic search was performed in PubMed and Scopus, from their inception up to October 2017. Prospective observational studies reporting risk estimates of all-cause mortality in relation to dietary intake and/or circulating concentrations of antioxidants were included. Random-effects meta-analyses were conducted. Forty-one prospective observational studies (total n = 507,251) involving 73,965 cases of all-cause mortality were included. The RRs of all-cause mortality for the highest compared with the lowest category of circulating antioxidant concentrations were as follows: total carotenes, 0.60 (95% CI: 0.46, 0.74); vitamin C, 0.61 (95% CI: 0.53, 0.69); selenium, 0.62 (95% CI: 0.45, 0.79); β-carotene, 0.63 (95% CI: 0.57, 0.70); α-carotene, 0.68 (95% CI: 0.58, 0.78); total carotenoids, 0.68 (95% CI: 0.56, 0.80); lycopene, 0.75 (95% CI: 0.54, 0.97); and α-tocopherol, 0.84 (95% CI: 0.77, 0.91). The RRs for dietary intakes were: total carotenoids, 0.76 (95% CI: 0.66, 0.85); total antioxidant capacity, 0.77 (95% CI: 0.73, 0.81); selenium, 0.79 (95% CI: 0.73, 0.85); α-carotene, 0.79 (95% CI: 0.63, 0.94); β-carotene, 0.82 (95% CI: 0.77, 0.86); vitamin C, 0.88 (95% CI: 0.83, 0.94); and total carotenes, 0.89 (95% CI: 0.81, 0.97). A nonsignificant inverse association was found for dietary zinc, zeaxanthin, lutein, and vitamin E. The nonlinear dose-response meta-analyses demonstrated a linear inverse association in the analyses of dietary β-carotene and total antioxidant capacity, as well as in the analyses of circulating α-carotene, β-carotene, selenium, vitamin C, and total carotenoids. The association appeared to be U-shaped in the analyses of serum lycopene and dietary vitamin C. The present study indicates that adherence to a diet with high antioxidant properties may reduce the risk of all-cause mortality. Our results confirm current recommendations that promote higher intake of antioxidant-rich foods such as fruit and vegetables.

Sodium selenite induces apoptosis and inhibits autophagy in human synovial sarcoma cell line SW982 in vitro

The present study aimed to examine the effects of sodium selenite on the SW982 human synovial sarcoma cell line in relation to cell viability, apoptosis and autophagy. The results indicated that sodium selenite reduced cell viability and induced apoptosis by activating caspase-3 and members of the poly (ADP-ribose) polymerase and Bcl-2 protein families in SW982 cells. Furthermore, autophagy was also suppressed by sodium selenite treatment in SW982 cells, and apoptosis was upregulated in cells co-treated with sodium selenite and the autophagy inhibitor 3-methyladenine. By contrast, apoptosis was downregulated when sodium selenite was combined with rapamycin, an inducer of autophagy. The results indicated that autophagy may protect cells from the cytotoxicity of sodium selenite. The present study results demonstrated that sodium selenite induced apoptosis and inhibited autophagy and autophagy-protected cells from death by antagonizing sodium selenite-induced apoptosis in SW982 cells in vitro.

Selenium-binding protein 1 is down-regulated in malignant melanoma

Selenium-binding protein 1 (SELENBP1) expression is reduced in various epithelial cancer entities compared to corresponding normal tissue and has already been described as a tumor suppressor involved in the regulation of cell proliferation, senescence, migration and apoptosis. We identified SELENBP1 to be down-regulated in cutaneous melanoma, a malignant cancer of pigment-producing melanocytes in the skin, which leads to the assumption that SELENBP1 also functions as tumor suppressor in the skin, as shown by others e.g. for prostate or lung carcinoma.

However, in vitro analyses indicate that SELENBP1 re-expression in human melanoma cell lines has no impact on cell proliferation, migration or tube formation of the tumor cells themselves when compared to control-transfected cells. Interestingly, supernatant taken from melanoma cell lines transfected with a SELENBP1 re-expression plasmid led to suppression of vessel formation of HMEC cells. Furthermore, SELENBP1 re-expression alters the sensitivity of melanoma cells for Vemurafenib treatment.

The data also hint to a functional interaction of SELENBP1 with GPX1 (Glutathione peroxidase 1). Low SELENBP1 mRNA levels correlate inversely with GPX1 expression in melanoma. The re-expression of SELENBP1 combined with down-regulation of GPX1 expression led to reduction of the proliferation of melanoma cells. In summary, SELENBP1 influences the tumor microenvironment and SELENBP1 action is functionally influenced by GPX1.

Se2Mo10V3, a heteropoly compound containing selenium, inhibits tumor growth

Selenium compounds have strong anti-tumor effects and are well-tolerated. We examined the anti-tumor effects of (NH₄)₂H₁₅Se₂^VIMo₁₀V₃O₅₂·2H₂O (Se₂Mo₁₀V₃₎, a heteropoly compound containing selenium. Se₂Mo₁₀V₃ inhibited proliferation in K562 cells with a half-maximal inhibitory concentration of 78.72±2.82 mg/L after 48 h and 24.94±0.88 mg/L after 72 h. Typical apoptotic morphologies were also observed in K562 cells treated with Se₂Mo₁₀V₃, as were increased intracellular levels of Ca²⁺, Mg²⁺, H⁺, and reactive oxygen species, and decreased mitochondrial membrane potential. In addition, Se₂Mo₁₀V₃ treatment triggered cytochrome C release and inhibited IκBα degradation and NF-κB translocation. In vivo experiments revealed that 5 or 10 mg/kg Se₂Mo₁₀V₃ inhibited the growth of sarcoma 180 and hepatoma 22 xenograft tumors. These results indicate that Se₂Mo₁₀V₃ inhibits tumor growth both in vitro and in vivo and induces apoptosis in K562 cells, possibly by inhibiting the NF-κB/IκBα pathway.

pH-Assisted surface functionalization of selenium nanoparticles with curcumin to achieve enhanced cancer chemopreventive activity

A pH-assisted strategy is proposed for synthesizing curcumin-functionalized selenium nanoparticles (SeNPs@Cur), which well combine the advantages of SeNPs with those of Cur in cancer chemoprevention and overcome their limitations in application.

Dietary supplementation of organic selenium could improve performance, antibody response, and yolk oxidative stability in laying hens fed on diets containing oxidized fat

The present study was carried out to investigate the effect of dietary supplementation of organic selenium (Se) on performance, egg quality indices, and yolk oxidative stability in laying hens fed diets with different fat sources. A total of 270 Hy-line W-36 Leghorn hens of 47 weeks of age were randomly distributed into the 5 replicate cages of 9 dietary treatments. Experimental diets consisted of a 3 × 3 factorial arrangement of treatments with three different fat sources (soybean oil, SO; yellow grease, YG; and palm fat powder, PFP) and three different levels of supplemental Se (0, 0.2, and 0.4 mg/kg of diet) as supplied by zinc-L-selenomethionine (ZnSeMet) complex, which fed during a 77-day feeding trial including 7 days for adaptation and 70 days as the main recording period. Results showed that the highest (P < 0.05) egg weights assigned to the hens fed on SO-supplemented diets. Hen-day egg production was affected by both dietary fat source (P < 0.01) and Se level (P < 0.05) throughout the trial period. Regardless of dietary fat source, dietary supplementation of ZnSeMet improved (P < 0.05) egg mass during all trial periods. Moreover, the significant (P < 0.05) fat  source× Se interactions were observed for egg mass, so that dietary supplementation with 0.4 mg/kg Se was more effective in diets supplemented with YG. Although feed intake was not affected by experimental diets during the first 35-day period, dietary inclusion of PFP reduced feed intake during both second 35-day (P < 0.01) and entire trial period (P < 0.05). The best (P < 0.01) feed conversion ratio during the first 35-day period was assigned to the birds fed on SO-diets, followed by those fed YG-diets. Dietary supplementation of ZnSeMet improved (P < 0.05) feed efficiency during the first 35-day period. Supplementation of ZnSeMet into the diets increased yolk index, with more impact in hens fed on YG-diets. The highest concentration of yolk malondialdehyde was observed in YG-fed groups, and ZnSeMet supplementation of diets decreased (P < 0.05) yolk malondialdehyde. The highest (P<0.01) glutathione peroxidase activity was observed for hens fed on diets supplemented by YG, followed by those on SO-diets. Although different fat sources had no effect on antibody titer against Newcastle disease virus, supplemental ZnSeMet improved (P < 0.05) antibody response. The present findings indicate that dietary supplementation of ZnSeMet could improve performance parameters and egg oxidative stability in laying hens, with the highest impact in diets containing oxidized (high peroxide values) fat sources.

Keto, thione, selone, and tellone carotenoids — Changing antioxidants to antireductants

Heterocarotenoids can be considered as xenobiotic compounds as they are foreign to living organisms. Thione carotenoids are heterocarotenoids that are particularly interesting because the presence of sulfur shifted the absorption to longer wavelengths than the corresponding keto carotenoids. This may be important for further applications such as the development of new pigments. Keto carotenoids are well-known antiradical molecules, however, nothing is known about heterocarotenoids acting as free radical scavengers. Thus, the main goal of this investigation is to study the antiradical properties of some heterocarotenoids, such as thione, selone, and tellone carotenoids. For this purpose, the energy differences between singlets and triplets are used to analyze the singlet oxygen quenching mechanism, and the electron transfer mechanism is investigated, taking into account that these may constitute antiradical molecules either donating or accepting electrons (antioxidants or antireductants). To analyze these mechanisms, vertical ionization energy (I), vertical electron affinity (A), and electrodonating (χ−) and electroaccepting (χ+) electronegativities were evaluated by applying density functional theory calculations. The investigated heterocarotenoids are as effective as keto carotenoids in terms of being either electron donors or acceptors, and therefore, they have a similar capacity for scavenging free radicals. Changing the C=O group to C=S, C=Se, or C=Te converts an antioxidant to an antireductant.

Selenium is inversely associated with interleukin-6 in the elderly

BACKGROUND

Selenium is an essential trace element with antioxidant property. Decreased serum selenium concentration with aging had been found in previous report. In this study, we aim to investigate the association between serum selenium and the inflammatory cytokine interleukin-6 in the elderly living in long-term care facilities in Taiwan.

MATERIALS AND METHODS

A total of 336 subjects aged 65 years and older (range of age: 65 - 101 years) were recruited from eight long-term care facilities in 2002-2003. Baseline characteristics, anthropometric indices, and biochemical data were obtained. Selenium deficiency was defined as serum selenium concentration < 80 μg/L. Multiple logistic and linear regression analyses were used to examine the relationships between selenium deficiency and interleukin-6 (divided into quartiles).

RESULTS

The prevalence of selenium deficiency was 35.6% in men and 43.2% in women, respectively. After adjusting for potential confounders using multiple logistic regression analysis, interleukin-6 quartiles were significantly associated with selenium deficiency. Compared to the interleukin-6 quartile I, the adjusted odds ratios of having selenium deficiency for interleukin-6 quartile II, III, IV were 1.00(0.50~2.01), 1.24 (0.62~2.50), and 2.35(1.15~4.83), respectively. The increasing odds ratios for selenium deficiency in higher interleukin-6 quartiles revealed dose-response effects (p < 0.05). Moreover, multiple linear regression analysis showed that serum selenium was significantly inversely associated with interleukin-6 after adjusting for potential confounders.

CONCLUSIONS

Serum selenium was inversely associated with inflammatory cytokine interleukin-6 among elderly living in long-term care facilities in Taiwan. Monitoring serum selenium should be considered in these institutionalized elderly.

Prostatic response to supranutritional selenium supplementation: comparison of the target tissue potency of selenomethionine vs. selenium-yeast on markers of prostatic homeostasis

Prostate cancer is the product of dysregulated homeostasis within the aging prostate. Supplementation with selenium in the form of selenized yeast (Se-yeast) significantly reduced prostate cancer incidence in the Nutritional Prevention of Cancer Trial. Conversely, the Selenium and Vitamin E Cancer Prevention Trial (SELECT) showed no such cancer-protective advantage using selenomethionine (SeMet). The possibility that SeMet and Se-yeast are not equipotent in promoting homeostasis and cancer risk reduction in the aging prostate has not been adequately investigated; no direct comparison has ever been reported in man or animals. Here, we analyzed data on prostatic responses to SeMet or Se-yeast from a controlled feeding trial of 49 elderly beagle dogs-the only non-human species to frequently develop prostate cancer during aging-randomized to one of five groups: control; low-dose SeMet, low-dose Se-yeast (3 μg/kg); high-dose SeMet, high-dose Se-yeast (6 μg/kg). After seven months of supplementation, we found no significant selenium form-dependent differences in toenail or intraprostatic selenium concentration. Next, we determined whether SeMet or Se-yeast acts with different potency on six markers of prostatic homeostasis that likely contribute to prostate cancer risk reduction-intraprostatic dihydrotestosterone (DHT), testosterone (T), DHT:T, and epithelial cell DNA damage, proliferation, and apoptosis. By analyzing dogs supplemented with SeMet or Se-yeast that achieved equivalent intraprostatic selenium concentration after supplementation, we showed no significant differences in potency of either selenium form on any of the six parameters over three different ranges of target tissue selenium concentration. Our findings, which represent the first direct comparison of SeMet and Se-yeast on a suite of readouts in the aging prostate that reflect flux through multiple gene networks, do not further support the notion that the null results of SELECT are attributable to differences in prostatic consequences achievable through daily supplementation with SeMet, rather than Se-yeast.

Effect of selenium on methimazole-induced liver damage and oxidative stress in adult rats and their offspring

This study aimed to investigate the protective effect of selenium (Se) on methimazole (MMI; an antithyroid drug)-induced hepatotoxicity in adult rats and their progeny. Female Wistar rats were randomly divided into four groups of six rats in each group: group I served as controls that received standard diet; group II received MMI in drinking water as 250 mg L−1 and standard diet; group III received both MMI (250 mg L−1, orally) and Se (0.5 mg kg−1 of diet); group IV received Se (0.5 mg kg−1 of diet) as sodium selenite. Treatments were started from the 14th day of pregnancy until day 14 after delivery. Exposure of rats to MMI promoted oxidative stress with an increase in liver malondialdehyde levels, advanced oxidation protein products and protein carbonyl contents and a decrease in the levels of glutathione, nonprotein thiols and vitamin C. A decrease in the activities of liver glutathione peroxidase, superoxide dismutase, catalase and lactate dehydrogenase and in the levels of plasma total protein and albumin was also observed. Plasma transaminase activities and total, direct and indirect bilirubin levels increased. Coadministration of Se through diet improved all biochemical parameters. The histopathological changes confirmed the biochemical results. Therefore, our investigation revealed that Se, a trace element with antioxidant properties, was effective in preventing MMI-induced liver damage.

Serum levels of selenium and smoking habits at age 50 influence long term prostate cancer risk; a 34 year ULSAM follow-up

BACKGROUND

Serum selenium level (s-Se) has been associated with prostate cancer (PrCa) risk. We investigated the relation between s-Se, smoking and non-screening detected PrCa and explored if polymorphisms in two DNA repair genes: OGG1 and MnSOD, influenced any effect of s-Se.

METHODS

ULSAM, a population based Swedish male cohort (n = 2322) investigated at age 50 for s-Se and s-Se influencing factors: serum cholesterol, erythrocyte sedimentation rate and smoking habits. At age 71 a subcohort, (n = 1005) was genotyped for OGG1 and MnSOD polymorphisms.

RESULTS

In a 34-year-follow-up, national registries identified 208 PrCa cases further confirmed in medical records. Participants with s-Se in the upper tertile had a non-significantly lower risk of PrCa. Smokers with s-Se in the two lower tertiles (≤80 μg/L) experienced a higher cumulative incidence of PrCa than smokers in the high selenium tertile (Hazard Ratio 2.39; 95% CI: 1.09-5.25). A high tertile selenium level in combination with non-wt rs125701 of the OGG1 gene in combination with smoking status or rs4880 related variation of MnSOD gene appeared to protect from PrCa.

CONCLUSIONS

S-Se levels and smoking habits influence long-term risk of PrCa. Smoking as a risk factor for PrCa in men with low s-Se is relevant to explore further. Exploratory analyses of variations in OGG1 and MnSOD genes indicate that hypotheses about patterns of exposure to selenium and smoking combined with data on genetic variation in genes involved in DNA repair can be valuable to pursue.

Selenium-vitamin E supplementation in infertile men: effects on semen parameters and pregnancy rate

Objectives

Infertility is an important medical and social problem that has an impact on well-being. A significant development in the last 10 years in the study of human infertility has been the discovery that oxidative sperm DNA damage has a critical role in the etiology of poor semen quality and male infertility. Selenium (Se) is an essential element for normal testicular development, spermatogenesis, and spermatozoa motility and function. The predominant biochemical action of Se in both humans and animals is to serve as an antioxidant via the Se-dependent enzyme glutathione peroxidase and thus protect cellular membranes and organelles from peroxidative damage. We explored the efficacy of Se in combination with vitamin E for improving semen parameters and pregnancy rates in infertile men.

Materials and methods

The study included 690 infertile men with idiopathic asthenoteratospermia who received supplemental daily Se (200 μg) in combination with vitamin E (400 units) for at least 100 days. The mean age of cases was 28.5 years (range 20–45), and the median age was 30 years. These cases had presented with male factor infertility (primary or secondary) for at least 1 year. The longest and shortest duration of infertility was 10 years and 1 year, respectively. The median time of diagnosis of infertility was 1 year with a mean of 2.5 years.

Results

We observed 52.6% (362 cases) total improvement in sperm motility, morphology, or both, and 10.8% (75 cases) spontaneous pregnancy in comparison with no treatment (95% confidence interval: 3.08 to 5.52). No response to treatment occurred in 253 cases (36.6%) after 14 weeks of combination therapy. Mean difference between semen analyses of cases before and after treatment was 4.3% with a standard deviation of 4.29. On the basis of paired t-test results, combination therapy with oral Se and vitamin E was effective for treatment of asthenospermia or asthenoteratospermia or induction of spontaneous pregnancy (P ≤ 0.001).

Conclusions

Supplemental Se and vitamin E may improve semen quality and have beneficial and protective effects, especially on sperm motility. We advocate their use for the treatment of idiopathic male infertility diagnosed with asthenoteratospermia or asthenospermia in semen analysis.

Selenium supplementation ameliorates static magnetic field-induced disorders in antioxidant status in rat tissues

The aim of this study was to investigate the effect of selenium supplementation on the antioxidant enzymatic system (such as GPx, GR and SOD), GSH and selenium level in liver, kidney, muscle and brain of static magnetic field (SMF) exposed rats. Male adult rats were divided into control rats (n=6), SMF-exposed rats (128 mT; 1h/day for 5 days), selenium-treated rats (Na(2)SeO(3), 0.2mg/l, in drinking water for 4 weeks) and co-exposed rats (selenium for 4 weeks and SMF during the last 5 consecutive days). Sub-acute exposure to SMF induces a decrease of selenium levels in kidney, muscle and brain. Our results also revealed a decrease of GPx activities in kidney and muscle. By contrast, SMF exposure increased total GSH levels and total SOD activities in liver, while glutathione reductase activity is unaffected. Selenium supplementation in SMF-exposed rats restored selenium levels in kidney, muscle and brain and elevated the activities of GPx in kidney and muscle to those of control group. In the liver, selenium supplementation failed to bring down the elevated levels of total GSH and SOD activity. Our investigations suggested that sub-acute exposure to SMF altered the antioxidant response by decreasing the level of total selenium in kidney, muscle and brain. Interestingly, selenium supplementation ameliorates antioxidant capacity in rat tissues exposed to SMF.

Novel targets for prostate cancer chemoprevention

Among many endocrine-related cancers, prostate cancer (PCa) is the most frequent male malignancy, and it is the second most common cause of cancer-related death in men in the United States. Therefore, this review focuses on summarizing the knowledge of molecular signaling pathways in PCa because, in order to better design new preventive strategies for the fight against PCa, documentation of the knowledge on the pathogenesis of PCa at the molecular level is very important. Cancer cells are known to have alterations in multiple cellular signaling pathways; indeed, the development and the progression of PCa are known to be caused by the deregulation of several selective signaling pathways such as the androgen receptor, Akt, nuclear factor-kappaB, Wnt, Hedgehog, and Notch. Therefore, strategies targeting these important pathways and their upstream and downstream signaling could be promising for the prevention of PCa progression. In this review, we summarize the current knowledge regarding the alterations in cell signaling pathways during the development and progression of PCa, and document compelling evidence showing that these are the targets of several natural agents against PCa progression and its metastases.

Autophagy inhibition through PI3K/Akt increases apoptosis by sodium selenite in NB4 cells

Selenium possesses the chemotherapeutic feature by inducing apoptosis in cancer cell with trivial side effects on normal cells. However, the mechanism in which is not clearly understood. Emerging evidence indicates the overlaps between the autophagy and the apoptosis. In this study, we have investigated the role of autophagy in selenium-induced apoptosis in NB4 cells. We find that autophagy is suppressed in NB4 cells treated by sodium selenite, as measured by electron microscope, acridine orange staining and western blot. Moreover, selenite combined with autophagy inhibitor contributes to the up-regulation of apoptosis, while the PI3K/Akt signaling pathway is down- regulated. Consistently, when the inhibitor of PI3K was applied, the autophagic level significantly decreased. In summary, sodium selenite increases NB4 cell apoptosis by autophagy inhibition through PI3K/Akt, and the inhibition of autophagy contributes to the up-regulation of apoptosis. [BMB reports 2009; 42(9): 599-604].

Low serum carotenoids are associated with a decline in walking speed in older women

BACKGROUND AND OBJECTIVES

Walking speed is an important measure of physical performance that is predictive of disability and mortality. The relationship of dietary factors to changes in physical performance has not been well characterized in older adults. The aim was to determine whether total serum carotenoid concentrations, a marker for fruit and vegetable intake, and serum selenium are related to changes in walking speed in older women.

SUBJECTS AND METHODS

The relationship between total serum carotenoids and selenium measured at baseline, 12, and 24 months follow-up and walking speed assessed at baseline and every six months for 36 months was examined in 687 moderately to severely disabled women, 65 years or older, living in the community.

RESULTS

Mean total serum carotenoids were associated with mean walking speed over three years of follow-up (P = 0.0003) and rate of change of walking speed (P = 0.007) in multivariate linear regression models adjusting for age, body mass index, and chronic diseases. Mean serum selenium was associated with mean walking speed over three years of follow-up (P = 0.0003) but not with the rate of change of walking speed (P = 0.26).

CONCLUSIONS

These findings suggest that a higher fruit and vegetable intake, as indicated by higher total serum carotenoid concentrations, may be protective against a decline in walking speed in older women.

Expression of selenium-binding protein 1 characterizes intestinal cell maturation and predicts survival for patients with colorectal cancer

To identify candidate genes involved in the development of colorectal cancer, we used cDNA microarrays to analyze gene expression differences between human colorectal tumors and paired adjacent normal mucosa. We identified approximately 3.5-fold significant downregulation of selenium-binding protein 1 (SBP1) in colorectal tumors compared to normal mucosa (p = 0.003). Importantly, stage III colorectal cancer patients with low tumor-SBP1 expression had significantly shorter disease-free and overall survival as compared with those patients with high tumor-SBP1 expression (p = 0.04 and 0.03, respectively). We further characterized the role of SBP1 in colorectal cancer in vivo and in vitro. In normal tissue, SBP1 was maximally expressed in terminally differentiated epithelial cells on the luminal surface of crypts in the large intestine. Consistent with this in vivo localization, SBP1 was upregulated during in vitro colonic cell differentiation along the absorptive (Caco-2) and secretory (HT29 Clones 16E and 19A) cell lineages. Downregulation (approximately 50%) of SBP1 expression by small interfering RNA in colonic cancer cells was associated with reduced expression of another epithelial differentiation marker, carcinoembryonic antigen (CEA), although PCNA and p21(WAF1/cip1 )expression were not altered. These data demonstrate that higher expression of SBP1 is associated with differentiation of the normal colonic epithelia and may be a positive prognostic factor for survival in stage III colorectal carcinoma.

Low plasma selenium concentrations and mortality among older community-dwelling adults: the InCHIANTI Study

AIMS

We examined the relationship between plasma selenium levels at enrollment and all-cause mortality over a 6-year period among participants in the InCHIANTI study.

METHODS

1042 men and women > or =65 years from the InCHIANTI study, a population- based study of older adults living in the Chianti region of Tuscany, a population-based cohort in Tuscany, Italy. Plasma selenium was measured at enrollment (1998-2000), and vital status was ascertained until May 2006.

RESULTS

During follow-up, 237 participants (22.7%) died. At enrollment, mean (SD) plasma selenium concentrations among participants who survived or died were 0.96 (0.14) and 0.87 (0.18) micromol/L (p<0.0001), respectively. The proportion of participants who died, from lowest to highest quartile of selenium, was 41.3, 27.0, 18.1 and 13.5% (p<0.0001 by Mantel-Haenszel chi-square). After adjusting for age, sex, education, and chronic diseases, adults in the lowest quartile of plasma selenium at enrollment had higher mortality compared with those in the highest quartile (Hazard Ratio (HR) 1.60, 95% Confidence Interval (CI) 1.04-2.47, p=0.034).

CONCLUSION

Low plasma selenium may be an independent predictor of mortality among older adults living in the community.

Selenium-Binding Protein 1 expression in ovaries and ovarian tumors in the laying hen, a spontaneous model of human ovarian cancer

OBJECTIVE

Reduced Selenium-Binding Protein 1 (SELENBP1) expression was recently shown in multiple cancers. There is little information on the expression and function of SELENBP1 in cancer progression. In order to develop a better understanding of the role of SELENBP1 in ovarian cancer, our objective was to determine if SELENBP1 is expressed in the normal ovaries and ovarian tumors in the egg-laying hen, a spontaneous model of human ovarian cancer.

METHODS

SPB1 mRNA expression in normal ovary (n=20) and ovarian tumors (n=23) was evaluated by RT-PCR. Relative levels of mRNA were compared by quantitative RT-PCR (qRT-PCR) in selected samples. SELENBP1 protein expression was evaluated by 1D Western blot and immunohistochemistry with a commercial anti-human SELENBP1 antibody.

RESULTS

SELENBP1 mRNA and protein was expressed in 100% of normal and ovarian tumors and qRT-PCR confirmed decreased mRNA expression in 80% of ovarian tumors. SELENBP1 was primarily localized in surface epithelial cells of normal ovaries. In ovaries containing early tumor lesions, SELENBP1 expression was reduced in the surface epithelium near the tumor and was expressed in tumor cells, while more distant regions with normal histology retained SELENBP1 expression in the surface epithelium.

CONCLUSIONS

We have shown for the first time that SELENBP1 is expressed in both normal ovaries and ovarian tumors in the hen and that SELENBP1 expression is altered in the vicinity of the tumor. Furthermore, SELENBP1 expression in normal ovarian surface epithelium and in ovarian tumors parallels that previously reported for ovarian cancer in women.

The bacterial response to the chalcogen metalloids Se and Te

Microbial metabolism of inorganics has been the subject of interest since the 1970s when it was recognized that bacteria are involved in the transformation of metal compounds in the environment. This area of research is generally referred to as bioinorganic chemistry or microbial biogeochemistry. Here, we overview the way the chalcogen metalloids Se and Te interact with bacteria. As a topic of considerable interest for basic and applied research, bacterial processing of tellurium and selenium oxyanions has been reviewed a few times over the past 15 years. Oddly, this is the first time these compounds have been considered together and their similarities and differences highlighted. Another aspect touched on for the first time by this review is the bacterial response in cell-cell or cell-surface aggregates (biofilms) against the metalloid oxyanions. Finally, in this review we have attempted to rationalize the considerable amount of literature available on bacterial resistance to the toxic metalloids tellurite and selenite.

Estrogen receptor activation and estrogen-regulated gene expression are unaffected by methylseleninic acid in LNCaP prostate cancer cells

Prostate cancer is the most frequently diagnosed cancer and a leading cause of cancer deaths in American men. High dietary intake and status of the essential trace element selenium (Se) have been consistently correlated with reduced risk for prostate cancer. One molecular mechanism by which Se may reduce prostate cancer risk is by catalyzing disulfide bond formation or, otherwise, complexing with reactive sulfhydryl groups in transcription factors, thus altering their binding to DNA and regulation of gene expression. Estrogen plays a role in the etiology of prostate cancer. Estrogen receptors contain cysteines in zinc fingers that are susceptible to oxidation and internal disulfide bond formation, which can prevent DNA binding. We hypothesized that Se alteration of estrogen receptor (ER) binding to DNA and estrogen-regulated gene expression may be one mechanism by which it exerts its chemopreventive effects. LNCaP human prostate cancer cells were treated with 0.05 mumol/L (control) or 5.0 mumol/L (high) Se as methylseleninic acid (MSA). Electrophoretic mobility shift assays showed that binding of ER-beta to the estrogen response element was a nonsignificant 14% lower in cells treated with high MSA. Run-on transcription assays showed no significant changes in transcription rates for estrogen-regulated genes, and steady-state mRNA levels for those genes, assayed by reverse transcription-polymerase chair reaction, were likewise unaffected by MSA. These results suggest that the well-documented chemopreventive effects of Se against prostate cancer may be mediated by mechanisms other than inhibition by monomethylated Se compounds of ER-beta activation or estrogen-regulated gene expression.

Early childhood wheezing symptoms in relation to plasma selenium in pregnant mothers and neonates

OBJECTIVE

Reduced dietary selenium intake has been linked to the development of asthma. We have investigated whether childhood wheezing symptoms, and asthma up to the age of 5 years are associated with plasma selenium and erythrocyte glutathione peroxidase (GPx) concentrations in pregnant mothers and neonates.

METHODS

Two thousand pregnant women were recruited and their 1924 singleton children followed up. Plasma selenium and erythrocyte GPx concentrations were measured in maternal blood during early pregnancy (12 weeks gestation) and in neonatal cord blood. Cohort children were followed up at 1, 2 and 5 years using a respiratory symptom questionnaire and at 5 years children were also invited for spirometry and skin-prick test (SPT). Maternal and neonatal plasma selenium and erythrocyte GPx were related to the childhood outcomes of wheezing, and asthma.

RESULTS

At 2 years 1282 children were followed up. At 5 years symptom data were available for 1167 children, 700 children were SPT tested, and forced expiratory volume in 1 s (FEV(1)) was measured in 478. Maternal plasma selenium concentration during early pregnancy was inversely associated with wheezing (odds ratio per 10 microg/kg plasma selenium 0.86, 95% confidence interval 0.76-0.97), and consulting a doctor because of wheeze (0.79, 0.69-0.93) in the second year of life. Cord plasma selenium was also inversely associated with wheezing (0.67, 0.47-0.96), and consulting a doctor because of wheeze (0.62, 0.41-0.93) in the second year of life. By age 5 these associations had disappeared. Maternal and neonatal erythrocyte GPx concentrations were not associated with any childhood outcomes at 2 or 5 years.

CONCLUSION

The selenium status of mothers during early pregnancy, and neonates is associated with early childhood wheezing but not asthma or atopic sensitization, furthermore, this association is absent by the age of 5 years.

Tea beverage in chemoprevention and chemotherapy of prostate cancer

Prostate cancer (PCa) is the most frequently diagnosed malignancy and the second leading cause of cancer-related deaths in American males with similar trends in many western countries. The existing treatment approaches and surgical intervention have not been able to effectively cope with this dreaded disease. For these reasons, it is necessary to intensify our efforts for a better understanding of the disease process and for the development of novel approaches for its prevention and treatment. Based on considerable evidence from in vivo and in vitro data and epidemiological studies, in recent years the beverage tea has gained considerable attention for reducing the risk of several cancers. Much of the cancer preventive effects of tea, especially green tea appear to be mediated by the polyphenols present therein. Geographical evidence suggests that the incidence and occurrence of PCa is lower in populations that consume tea regularly. This evidence suggests that tea polyphenols could be extrapolated to optimize their chemopreventive properties against PCa. PCa represents an excellent candidate disease for chemoprevention because it is typically diagnosed in men over 50 years of age and therefore, even a modest delay in neoplastic development achieved through pharmacological or nutritional intervention could result in a substantial reduction in the incidence of clinically detectable disease. In this review we address the issue of possible use of tea, especially green tea, for the prevention as well as treatment of PCa.

Association of low plasma selenium concentrations with poor muscle strength in older community-dwelling adults: the InCHIANTI Study

BACKGROUND

Although selenium plays an important role in muscle function, the relation between circulating selenium and muscle strength in elderly adults has not been characterized.

OBJECTIVE

The objective was to examine the hypothesis that low plasma selenium is associated with poor muscle strength in older adults.

DESIGN

We measured plasma selenium and hip, grip, and knee strength in a cross-sectional study of 891 men and women aged >or=65 y from the Invecchiare in Chianti (InCHIANTI) Study, a population-based cohort study in Tuscany (Italy). Poor muscle strength was defined as the lowest quartile of hip flexion, grip, and knee extension strength.

RESULTS

Overall, mean (+/-SD) plasma selenium was 0.95 +/- 0.15 mumol/L. After adjustment for age, sex, education, total energy intake, body mass index, and chronic disease, participants in the lowest versus the highest quartile of plasma selenium were at higher risk of poor hip strength [odds ratio (OR): 1.69; 95% CI: 1.02, 2.83; P = 0.04, P for linear trend = 0.04], knee strength (OR: 1.94; 95% CI: 1.18, 3.19; P = 0.009, P for linear trend = 0.01), and grip strength (OR: 1.94; 95% CI: 1.19, 3.16; P = 0.008, P for linear trend = 0.08).

CONCLUSIONS

Low plasma selenium is independently associated with poor skeletal muscle strength in community-dwelling older adults in Tuscany.

The mechanism of methylselenocysteine and docetaxel synergistic activity in prostate cancer cells

The study was designed to evaluate the combination treatment of methylselenocysteine (MSeC) and docetaxel and to delineate the underlying mechanism associated with observed in vitro synergy between MSeC and docetaxel in prostate cancer cells. Cells were treated with different concentrations and schedules (concurrent or sequential) of MSeC and docetaxel alone or in combination. Cell growth/death was assessed with sulforhodamine B assay, trypan blue assay, and time-lapse video. Loewe synergism/antagonism model was used to determine whether the combination effect was additive, synergistic, or antagonistic. Apoptosis and caspase-3 activity were evaluated with cell death ELISA assay and caspase activity assay, respectively. Synergy between MSeC and docetaxel was further assessed in the presence and absence of z-VAD-fmk, a pan-caspase inhibitor. Effect of MSeC and docetaxel alone or in combination on the cellular expression of the antiapoptotic protein survivin was measured with Western blot analyses. Pretreatment with MSeC was crucial to enhance docetaxel antitumor activity. The enhanced antitumor activity of the sequential combination treatment of MSeC and docetaxel (MSeC/docetaxel) was highly synergistic. Apoptosis increased after MSeC/docetaxel, compared with each drug alone or concurrent treatment. Pretreatment with z-VAD-fmk converted the synergy into antagonism, suggesting that the synergy is caspase-dependent apoptosis. The survivin level was down-regulated following MSeC/docetaxel treatment when compared with each drug alone. In conclusion, pretreatment with MSeC was essential to markedly sensitize cells to docetaxel. The synergy between MSeC and docetaxel in C2G prostate cancer cells is associated with increased level of caspase-dependent apoptosis and decreased level of survivin.

Low serum selenium concentrations are associated with poor grip strength among older women living in the community

Aging is associated with a loss of muscle strength, and, in turn, loss of muscle strength has been associated with increased risk of frailty, disability and mortality. The factors that contribute to loss of muscle strength with aging have not been well characterized. Selenium is important in normal muscle function because of its role in selenoenzymes that protect muscle against oxidative damage. We hypothesized that low serum selenium concentrations were associated with poor grip strength. We examined the association between serum selenium and hand grip strength among 676 moderately to severely disabled community-dwelling women in the Women's Health and Aging Study I in Baltimore, Maryland. After adjusting for age, race, body mass index, Mini-Mental Status Examination score, current smoking, hypertension, congestive heart failure and depression, serum selenium was associated with grip strength (P=0.04). This study supports the idea that selenium is important to muscle strength in older women.

Chemoprevention of prostate cancer

Prostate cancer is a common malignancy with multiple potential opportunities for cancer prevention. As the genetic basis of this malignancy is further understood, prevention strategies will be developed for individual patients based on specific risk factors and pathways of carcinogenesis. The PCPT has conclusively proven that prostate cancer prevention is possible. The results of the SELECT should be available within several years. An enormous challenge for the medical community will be the development of an efficient strategy to evaluate the substantial number of dietary, behavioral, and pharmacologic prevention opportunities. Ultimately, the goal of prostate can-cer prevention is to (1) identify men who are destined to develop clinically significant prostate cancer, and (2) provide individualized agents to prevent disease development.

Low Serum Selenium Is Associated with Anemia Among Older Women Living in the Community: the Women's Health and Aging Studies I and II

Anemia is common among older adults, and a substantial proportion of anemia in the older population is of indeterminate cause. Low selenium levels have been associated with anemia in animals, but this relationship has not been well characterized in humans. The objective was to determine whether low serum selenium concentrations are associated with anemia among older women. We conducted a cross-sectional analysis of participants in the Women's Health and Aging Studies, a population-based sample of women living in the community in Baltimore, MD, USA. Of 632 women, aged 70-79 yr, 14.1% of women were anemic (hemoglobin <120 g/L). The prevalence of anemia among women in the lowest to highest quartile of serum selenium was 22.4%, 14.6%, 11.9% and 6.6%, respectively (p < 0.0001). An increase in loge selenium was associated with a reduced risk of anemia (odds ratio per 1 SD increase = 0.63, 95% confidence interval = 0.47-0.84), adjusting for age, education, chronic diseases, iron status, and serum interleukin-6. We conclude that low serum selenium is independently associated with anemia among older women living in the community.

Chemoprevention of prostate cancer

Prostate cancer is an attractive target for chemoprevention because of its ubiquity, treatment-related morbidity, long latency between premalignant lesions and clinically evident cancer, and defined molecular pathogenesis. The Prostate Cancer Prevention Trial has provided the first firm evidence that this cancer can be prevented by a relatively nontoxic oral agent. Additional agents, many of which are antioxidants with antiandrogenic effects, are being tested (or soon will be) in large clinical trials. The current body of evidence is insufficient to make a routine recommendation of any dietary or nutritional supplement for the prevention of prostate cancer.

Dietary Selenium Intake and Genetic Polymorphisms of the GSTP1 and p53 Genes on the Risk of Esophageal Squamous Cell Carcinoma

Few studies have assessed potential effect modifications by polymorphisms of susceptibility genes on the association between selenium intake and esophageal squamous cell carcinoma (ESCC). We studied the joint effects of dietary selenium and the GSTP1 and p53 polymorphisms on ESCC risk in a population-based case-control study with 218 ESCC cases and 415 controls in Taixing City, China. Dietary selenium intake was estimated from a food frequency questionnaire with 97 food items. GSTP1 and p53 polymorphisms were detected by RFLP-PCR assays. Logistic regression analyses were done to estimate odds ratios (OR) and 95% confidence intervals (95% CI). Reduced ESCC risk was observed among individuals in the highest quartile of dietary selenium intake (adjusted OR, 0.31; 95% CI, 0.13-0.70) with a dose-dependent gradient (P(trend) = 0.01). The p53 Pro/Pro genotype was associated with increased risk of ESCC compared with the Arg/Arg genotype (adjusted OR, 2.02; 95% CI, 1.19-3.42). When combined with selenium consumption, an obvious increased risk was observed among individuals with the p53 Pro/Pro or GSTP1 Ile/Ile genotype with adjusted ORs of 3.19 (95% CI, 1.74-5.84) and 1.90 (95% CI, 1.03-3.51), respectively. Among smokers and alcohol drinkers, elevation of ESCC risk was more prominent among p53 Pro/Pro individuals who consumed a low level of dietary selenium (adjusted OR, 3.59; 95% CI, 1.49-8.66 for smokers and 6.19; 95% CI, 1.83-20.9 for drinkers). Our study suggests that the effect of dietary selenium on the risk of ESCC may be modulated by tobacco smoking, alcohol drinking, and p53 Pro/Pro and GSTP1 Ile/Ile genotypes.

Low serum selenium and total carotenoids predict mortality among older women living in the community: the women's health and aging studies

Selenium and the carotenoids play an important role in antioxidant defenses and in the redox regulation involved in inflammation. We tested the hypothesis that low selenium and carotenoids predict mortality in older women living in the community. Women who were enrolled in the Women's Health and Aging Studies I and II in Baltimore, MD (n = 632; 70-79 y old) had serum selenium and carotenoids measured at baseline and were followed for mortality over 60 mo. Median (minimum, maximum) serum selenium and carotenoids were 1.53 (0.73, 2.51) micromol/L and 1.67 (0.13, 9.10) micromol/L; 14.1% of the women died. The 5 major causes of death were heart disease (32.6%), cancer (18.0%), stroke (9.0%), infection (6.7%), and chronic obstructive pulmonary disease (5.6%). Adjusting for age, education, smoking, BMI, poor appetite, and chronic diseases, higher serum selenium [hazard ratio (HR) 0.71, 95% CI 0.56-0.90/1 SD increase in log(e) selenium; P = 0.005] and higher serum total carotenoids (HR 0.77, 95% CI 0.64-0.84/1 SD increase in log(e) total carotenoids; P = 0.009) were associated with a lower risk of mortality. Women living in the community who have higher serum selenium and carotenoids are at a lower risk of death.

Towards a dietary prevention of hereditary breast cancer

Inheritance of a deleterious mutation in BRCA1 or BRCA2 confers a high lifetime risk of developing breast cancer. Variation in penetrance between individuals suggests that factors other than the gene mutation itself may influence the risk of cancer in susceptible women. Several risk factors have been identified which implicate estrogen-induced growth stimulation as a probable contributor to breast cancer pre-disposition. The protein products of both of these genes appear to help preserve genomic integrity via their participation in the DNA damage response and repair pathways. To date, the evidence for a cancer-protective role of dietary nutrients, for the most part those with antioxidant properties, has been based on women without any known genetic pre-disposition and it is important to identify and evaluate dietary factors which may modify the risk of cancer in BRCA carriers. Here we propose that diet modification may modulate the risk of hereditary breast cancer by decreasing DNA damage (possibly linked to estrogen exposure) or by enhancing DNA repair. The prevention of hereditary breast cancer through diet is an attractive complement to current management strategies and deserves exploration.

Identifying and defusing weapons of mass inflammation in carcinogenesis

The continued cancer risks associated with chronic inflammation necessitate the identification of inflammatory molecules and the cancer pathways they affect. Evidence indicates that there are multiple mechanisms linking inflammation to cancer and that there are multiple targets for chemoprevention. Here, we review some of the key factors and the cancer pathways they disturb as a necessary prerequisite to the identification of targets for chemoprevention.

REDOX REGULATION BY INTRINSIC SPECIES AND EXTRINSIC NUTRIENTS IN NORMAL AND CANCER CELLS

Cells in multicellular organisms are exposed to both endogenous oxidative stresses generated metabolically and to oxidative stresses that originate from neighboring cells and from other tissues. To protect themselves from oxidative stress, cells are equipped with reducing buffer systems (glutathione/GSH and thioredoxin/thioredoxin reductase) and have developed several enzymatic mechanisms against oxidants that include catalase, superoxide dismutase, and glutathione peroxidase. Other major extrinsic defenses (from the diet) include ascorbic acid, beta-carotene and other carotenoids, and selenium. Recent evidence indicates that in addition to their antioxidant function, several of these redox species and systems are involved in regulation of biological processes, including cellular signaling, transcription factor activity, and apoptosis in normal and cancer cells. The survival and overall well-being of the cell is dependent upon the balance between the activity and the intracellular levels of these antioxidants as well as their interaction with various regulatory factors, including Ref-1, nuclear factor-kappaB, and activating protein-1.

Histological and ultrastructural changes induced by selenium in early experimental gastric carcinogenesis

AIM: To investigate the effect and significance of selenium in early experimental gastric carcinogenesis.

METHODS: Weaning male Wistar rats were divided randomly into normal control group, experiment control group, low selenium (2 mg/L) group and high selenium (4 mg/L) group. Wistar rat gastric carcinogenesis was induced by N-methyl-N-nitro-N-nitroso guanidine (MNNG) (20 mg/kg) gavage daily for 10 d. Na₂SeO₃ was given by piped drinking 1 wk prior to MNNG gavage. The rats were killed at the 43^rd wk. The surface characteristics of gastric mucosa were observed with naked eyes. Histopathologic changes of rat gastric mucosa were observed by HE staining and AB-PAS methods. The changes of cellular ultrastructure were observed under transmission electron microscope. Statistical analysis was carried out by SPSS.

RESULTS: The incidence rate of gastric mucosa erosion, hemorrhage and intestinal metaplasia was 0, 45.5%, 66.7%, and 92.9%, respectively (92.9% vs 45.5%, P<0.05) in the normal control group, experiment control group, low selenium group, and high selenium group. Leiomyoma formed in the process of inducement of rat gastric carcinoma. Dietary Na₂SeO₃ (2 and 4 mg/L) slightly increased the incidence rate of leiomyoma (0, 23%, 46.6%, and 46.6%). gastric mucosa did not change in the course of rat gastric carcinogenesis. Dietary Na₂SeO₃ by pipe drinking could expand the intracellular secretory canaliculus of parietal cells and increase the number of endocrine cells and lysosomes.

CONCLUSION: Dietary Na₂SeO₃ by pipe drinking aggravates gastric erosion, hemorrhage and promotes intestinal metaplasia of gastric mucosa. The mechanism may be related with the function of parietal cells.

Selenium and vitamin E cancer prevention trial

Preclinical, epidemiological, and phase III data from randomized, placebo-controlled clinical trials suggest that both selenium and vitamin E have potential efficacy in prostate cancer prevention. In vitro evidence suggests that selenium and vitamin E work synergistically to cause cell-cycle arrest, induce caspase-mediated apoptosis, and act as antiandrogens in arresting clonal expansion of nascent tumors. The Selenium and Vitamin E Cancer Prevention Trial (SELECT), sponsored by the National Cancer Institute, is an intergroup Phase III, randomized, double-blind, placebo-controlled, population-based clinical trial designed to test the efficacy of selenium and vitamin E alone and in combination in the prevention of prostate cancer. The study has a 2 x 2 factorial design with a target accrual of 32,400. Eligibility criteria include an age of at least 50 years for African Americans and of at least 55 years for Caucasians; a DRE not suspicious for cancer; a serum PSA no greater than 4 ng/mL; and a normal blood pressure. Randomization will be equally distributed among the four study arms, with intervention consisting of a daily oral dose of study supplement (200 mug l-selenomethionine or 400 mg of racemic alpha-tocopheryl) or matched placebo. Study duration is planned for 12 years, with a 5-year uniform accrual period and a minimum of 7 and maximum of 12 years of intervention. The primary endpoint for SELECT is the clinical incidence of prostate cancer as determined by a recommended routine clinical diagnostic work-up, including yearly DRE and serum PSA level. SELECT is the second large-scale study of chemoprevention for prostate cancer. Enrollment began in 2001, with final results anticipated in 2013.