Selenium and prostate cancer prevention: insights from the selenium and vitamin E cancer prevention trial (SELECT)

Exiguobacterium sp. as a bioinoculant for plant-growth promotion and Selenium biofortification strategies in horticultural plants

Plant growth-promoting rhizobacteria (PGPR) have a positive effect on plant development and being a promising way to enhance crop productivity and as substitution of chemical fertilizers. Selenium (Se) is an important trace element and its intake is usually lower than the daily minimum amount required for humans; hence, there is a demand on the design of Se biofortification strategies. Here, the genetic traits known to be associated with Plant-Growth Promotion (PGP) and Se biotransformation of Exiguobacterium sp. S17 were evaluated through genome analysis. Its growth-promoting capacity was tested through plant-growth promotion assays in laboratory and field conditions, using Brassica juncea (indian mustard), Beta vulgaris (chard), and Lactuca sativa (lettuce). Additionally, the Se biotransformation ability of Exiguobacterium sp. S17 was evaluated and the obtained selenized bacteria were tested in mustard plants. The sequenced bacteria genome revealed the presence of multiple genes involved in important functions regarding soil and plant colonization, PGP and Se biotransformation. Moreover, it was demonstrated that Exiguobacterium sp. S17 enhanced plant growth and could be useful to produce Se accumulation and biofortification in accumulator plants such as mustard. Thereby, Exiguobacterium sp. S17 might be used for developing new, sustainable, and environmentally friendly agro-technological strategies.

Effect of Copper and Selenium Supplementation on the Level of Elements in Rats' Femurs under Neoplastic Conditions

A study was conducted to determine the effect of long-term supplementation with selenium and copper, administered at twice the level used in the standard diet of rats, on the content of selected elements in the femoral bones of healthy rats and rats with implanted LNCaP cancer cells. After an adaptation period, the animals were randomly divided into two experimental groups. The rats in the experimental group were implanted with prostate cancer cells. The rats in the control group were kept in the same conditions as those in the experimental group and fed the same diet, but without implanted cancer cells. The cancer cells (LNCaP) were intraperitoneally implanted in the amount of 1 × 106 (in PBS 0.4 mL) at the age of 90 days. The content of elements in the samples was determined by a quadrupole mass spectrometer with inductively coupled plasma ionization (ICP-MS). In the femoral bones of rats with implanted LNCaP cells, in the case of the standard diet and the copper-enriched diet, there was a marked decreasing trend in the content of the analysed elements relative to the control rats. This may indicate slow osteolysis taking place in the bone tissue. Contrasting results were obtained for the diet enriched with selenium; there was no significant reduction in the level of these elements, and there was even an increase in the concentrations of Fe and K in the bones of rats with implanted LNCaP cells. Particularly, numerous changes in the mineral composition of the bones were generated by enriching the diet with copper. The elements that most often underwent changes (losses) in the bones were cobalt, iron, manganese and molybdenum. The changes observed, most likely induced by the implantation of LNCaP cells, may indicate a disturbance of mineral homeostasis.

Vitamin E: Where Are We Now in Vascular Diseases?

Vitamin E is one of the most popular fat-soluble vitamins in pathological research and has been under scrutiny since the 1980s as a vital dietary component of food. The antioxidant effect of vitamin E has been widely studied due to its benefits in the prevention of various cardiovascular diseases. In recent years, alternative effects of vitamin E, in terms of anti-inflammatory pathways and gene regulation, have also been of interest to researchers. This review examines the role of dietary vitamin E (α-tocopherol) as an antioxidant and bioactive molecule in promoting vascular health. While the antioxidant effect of vitamin E is well established, knowledge about its capacity as a promising regulatory molecule in the control of the vascular system is limited. The aim of this review is to discuss some of these mechanisms and summarize their role in the prevention of cardiovascular diseases (CVD). Here, we also briefly discuss foods rich in vitamin E, and deliberate some potential toxicological effects of excessive supplemental vitamin E in the body.

The Impact of ZIP8 Disease-Associated Variants G38R, C113S, G204C, and S335T on Selenium and Cadmium Accumulations: The First Characterization

The metal cation symporter ZIP8 (SLC39A8) is a transmembrane protein that imports the essential micronutrients iron, manganese, and zinc, as well as heavy toxic metal cadmium (Cd). It has been recently suggested that selenium (Se), another essential micronutrient that has long been known for its role in human health and cancer risk, may also be transported by the ZIP8 protein. Several mutations in the ZIP8 gene are associated with the aberrant ion homeostasis of cells and can lead to human diseases. However, the intricate relationships between ZIP8 mutations, cellular Se homeostasis, and human diseases (including cancers and illnesses associated with Cd exposure) have not been explored. To further verify if ZIP8 is involved in cellular Se transportation, we first knockout (KO) the endogenous expression of ZIP8 in the HeLa cells using the CRISPR/Cas9 system. The elimination of ZIP8 expression was examined by PCR, DNA sequencing, immunoblot, and immunofluorescence analyses. Inductively coupled plasma mass spectrometry indicated that reduced uptake of Se, along with other micronutrients and Cd, was observed in the ZIP8-KO cells. In contrast, when ZIP8 was overexpressed, increased Se uptake could be detected in the ZIP8-overexpressing cells. Additionally, we found that ZIP8 with disease-associated single-point mutations G38R, G204C, and S335T, but not C113S, showed reduced Se transport ability. We then evaluated the potential of Se on Cd cytotoxicity prevention and therapy of cancers. Results indicated that Se could suppress Cd-induced cytotoxicity via decreasing the intracellular Cd transported by ZIP8, and Se exhibited excellent anticancer activity against not all but only selected cancer cell lines, under restricted experimental conditions. Moreover, clinical-based bioinformatic analyses revealed that up-regulated ZIP8 gene expression was common across multiple cancer types, and selenoproteins that were significantly co-expressed with ZIP8 in these cancers had been identified. Taken together, this study concludes that ZIP8 is an important protein in modulating cellular Se levels and provides insights into the roles of ZIP8 and Se in disease prevention and therapy.

Selenomethionine alleviated Ochratoxin A induced pyroptosis and renal fibrotic factors expressions in MDCK cells

Ochratoxin A (OTA) is universally known to induce nephrotoxicity via inducing oxidative stress and apoptosis, inhibiting protein synthesis and activating autophagy. Our previous studies have proved that OTA induces nephrotoxicity in vitro and in vivo by adjusting the NOD-like receptor protein 3 (NLRP3) inflammasome activation and caspase-1-dependent pyroptosis. Based on these findings, we further investigated the protective role of selenomethionine (SeMet) on OTA-caused nephrotoxicity using the Madin-Darby canine kidney (MDCK) epithelial cells as an in vitro model, proposing to offer a new way for remedying OTA-induced nephrotoxicity by nutritional manipulation. We measured the cell vitality, lactate dehydrogenase (LDH) activity and the expression of renal fibrotic genes, NLRP3 inflammasome and pyroptosis related genes. MTT and LDH results indicated that SeMet supplementation significantly mitigated 2.0 μg/ml OTA-induced cytotoxicity in MDCK cells (p < 0.05). Meanwhile, SeMet alleviated OTA induced increase of reactive oxygen species in MDCK cells. Then, the expressions of α-SMA, Vimentin, and TGF-β were detected both in mRNA and protein levels. The results indicated 8 μM SeMet supplementation could significantly downregulate the expression of OTA-induced renal fibrosis-related genes (p < 0.05). In addition, the upregulation of OTA-induced NLRP3 inflammasome and pyroptosis downstream genes was also significantly inhibited by 8 μM of SeMet (p < 0.05). In summary, SeMet could alleviate OTA-induced renal fibrotic genes expression and reduce NLRP3-caspase-1-dependent pyroptosis. Therefore, SeMet supplementation may become an effective approach for preserving animals from renal injury exposed to OTA.

Characterization of Selenium Compounds for Anti-ferroptotic Activity in Neuronal Cells and After Cerebral Ischemia-Reperfusion Injury

The emergence of ferroptosis as a cell death pathway associated with brain disorders including stroke and neurodegenerative diseases emphasizes the need to develop therapeutics able to target the brain and to protect neurons from ferroptotic death. Selenium plays an essential role in reducing lipid peroxidation generated during ferroptosis through its incorporation into the catalytic site of glutathione peroxidase 4. Here, we compared the anti-ferroptotic activity of several organic and inorganic selenium compounds: methylselenocysteine, selenocystine, selenomethionine, selenocystamine, ebselen, sodium selenite, and sodium selenate. All were effective against erastin- and RSL3-induced ferroptosis in vitro. We characterized the ability of the selenium compounds to release selenium and boost glutathione peroxidase expression and activity. Based on our results, we selected organic selenium compounds of similar characteristics and investigated their effectiveness in protecting against neuronal death in vivo using the cerebral ischemia-reperfusion injury mouse model. We found that pretreatment with methylselenocysteine or selenocystamine provided protection from ischemia-reperfusion neuronal damage in vivo. These data support the use of ferroptosis inhibitors for treatment and select selenium compounds for prevention of neuronal damage in ischemic stroke and other diseases of the brain where ferroptosis is implicated.

Selenium Deficiency Due to Diet, Pregnancy, Severe Illness, or COVID-19-A Preventable Trigger for Autoimmune Disease

The trace element selenium (Se) is an essential part of the human diet; moreover, increased health risks have been observed with Se deficiency. A sufficiently high Se status is a prerequisite for adequate immune response, and preventable endemic diseases are known from areas with Se deficiency. Biomarkers of Se status decline strongly in pregnancy, severe illness, or COVID-19, reaching critically low concentrations. Notably, these conditions are associated with an increased risk for autoimmune disease (AID). Positive effects on the immune system are observed with Se supplementation in pregnancy, autoimmune thyroid disease, and recovery from severe illness. However, some studies reported null results; the database is small, and randomized trials are sparse. The current need for research on the link between AID and Se deficiency is particularly obvious for rheumatoid arthritis and type 1 diabetes mellitus. Despite these gaps in knowledge, it seems timely to realize that severe Se deficiency may trigger AID in susceptible subjects. Improved dietary choices or supplemental Se are efficient ways to avoid severe Se deficiency, thereby decreasing AID risk and improving disease course. A personalized approach is needed in clinics and during therapy, while population-wide measures should be considered for areas with habitual low Se intake. Finland has been adding Se to its food chain for more than 35 years-a wise and commendable decision, according to today's knowledge. It is unfortunate that the health risks of Se deficiency are often neglected, while possible side effects of Se supplementation are exaggerated, leading to disregard for this safe and promising preventive and adjuvant treatment options. This is especially true in the follow-up situations of pregnancy, severe illness, or COVID-19, where massive Se deficiencies have developed and are associated with AID risk, long-lasting health impairments, and slow recovery.

The Potential Protective Effect of Orange Peel and Selenium against 17β-Estradiol- Induced Chronic Non-Bacterial Prostatitis in Rats

BACKGROUND

Prostate Cancer (PCa) is defined as a major health problem faced by the male population.

AIM

We aimed to investigate the protective effects of Orange Peel Extract (OPE) and/or Selenium (Se) on chronic non-bacterial prostatitis in a rat model.

METHODS

Fifty-six adult male Wistar albino rats were castrated; after 5 days, they were divided randomly into eight groups (n= 7). The control group received saline treatment; while 17β-estradiol (E2) (0.25mg/kg) was injected subcutaneously in rats from Groups V, VI, VII, and VIII to induce chronic non-bacterial prostatitis. They were then treated with OPE (400mg/kg body weight; Groups II, IV, VI, and VIII) and/or sodium selenite (0.5mg/kg body weight; Groups III, IV, VII, and VIII) for 30 days. Interleukin-2 (IL2) and Prostate Cancer Antigen 3 (PCA3) mRNA expressions were determined using qPCR; Prostate-Specific Antigen (PSA) protein expression was determined immunohistochemically. Prostate tissue histology was examined by hematoxylin and eosin staining, and the levels of oxidative stress markers and antioxidant enzymes were measured.

RESULTS

E2 administration significantly increased IL2 and PCA3 mRNA expressions, and PSA protein expression. It also increased the prostate wet weight and body weight, and lipid peroxidation, nitric oxide, TNF-α, and IL-1β levels, decreased the glutathione and antioxidant enzyme levels and caused distinct histological alterations in the prostate gland. OPE and/or Se markedly improved all the studied parameters due to their antioxidant properties and anti-inflammatory effects.

CONCLUSION

OPE and Se showed protective effects against 17β-estradiol-induced chronic non-bacterial prostatitis. These results suggest that protection of chronic non-bacterial prostatitis by OPE+Se combination involves anti-oxidation and anti-inflammation. Moreover, their synergistic mechanism was mostly achieved via the regulation of oxidative stress and inflammation processes.

Food Sources of Selenium and Its Relationship with Chronic Diseases

Selenium (Se) is an essential micronutrient for mammals, and its deficiency seriously threatens human health. A series of biofortification strategies have been developed to produce Se-enriched foods for combating Se deficiency. Although there have been some inconsistent results, extensive evidence has suggested that Se supplementation is beneficial for preventing and treating several chronic diseases. Understanding the association between Se and chronic diseases is essential for guiding clinical practice, developing effective public health policies, and ultimately counteracting health issues associated with Se deficiency. The current review will discuss the food sources of Se, biofortification strategies, metabolism and biological activities, clinical disorders and dietary reference intakes, as well as the relationship between Se and health outcomes, especially cardiovascular disease, diabetes, chronic inflammation, cancer, and fertility. Additionally, some concepts were proposed, there is a non-linear U-shaped dose-responsive relationship between Se status and health effects: subjects with a low baseline Se status can benefit from Se supplementation, while Se supplementation in populations with an adequate or high status may potentially increase the risk of some diseases. In addition, at supra-nutritional levels, methylated Se compounds exerted more promising cancer chemo-preventive efficacy in preclinical trials.

Selenium as a Bioactive Micronutrient in the Human Diet and Its Cancer Chemopreventive Activity

This review answers the question of why selenium is such an important trace element in the human diet. Daily dietary intake of selenium and its content in various food products is discussed in this paper, as well as the effects of its deficiency and excess in the body. Moreover, the biological activity of selenium, which it performs mainly through selenoproteins, is discussed. These specific proteins are responsible for thyroid hormone management, fertility, the aging process, and immunity, but their key role is to maintain a redox balance in cells. Furthermore, taking into account world news and the current SARS-CoV-2 virus pandemic, the impact of selenium on the course of COVID-19 is also discussed. Another worldwide problem is the number of new cancer cases and cancer-related mortality. Thus, the last part of the article discusses the impact of selenium on cancer risk based on clinical trials (including NPC and SELECT), systematic reviews, and meta-analyses. Additionally, this review discusses the possible mechanisms of selenium action that prevent cancer development.

Toxicology and pharmacology of synthetic organoselenium compounds: an update

Here, we addressed the pharmacology and toxicology of synthetic organoselenium compounds and some naturally occurring organoselenium amino acids. The use of selenium as a tool in organic synthesis and as a pharmacological agent goes back to the middle of the nineteenth and the beginning of the twentieth centuries. The rediscovery of ebselen and its investigation in clinical trials have motivated the search for new organoselenium molecules with pharmacological properties. Although ebselen and diselenides have some overlapping pharmacological properties, their molecular targets are not identical. However, they have similar anti-inflammatory and antioxidant activities, possibly, via activation of transcription factors, regulating the expression of antioxidant genes. In short, our knowledge about the pharmacological properties of simple organoselenium compounds is still elusive. However, contrary to our early expectations that they could imitate selenoproteins, organoselenium compounds seem to have non-specific modulatory activation of antioxidant pathways and specific inhibitory effects in some thiol-containing proteins. The thiol-oxidizing properties of organoselenium compounds are considered the molecular basis of their chronic toxicity; however, the acute use of organoselenium compounds as inhibitors of specific thiol-containing enzymes can be of therapeutic significance. In summary, the outcomes of the clinical trials of ebselen as a mimetic of lithium or as an inhibitor of SARS-CoV-2 proteases will be important to the field of organoselenium synthesis. The development of computational techniques that could predict rational modifications in the structure of organoselenium compounds to increase their specificity is required to construct a library of thiol-modifying agents with selectivity toward specific target proteins.

Selenomethionine (Se-Met) Induces the Cystine/Glutamate Exchanger SLC7A11 in Cultured Human Retinal Pigment Epithelial (RPE) Cells: Implications for Antioxidant Therapy in Aging Retina

Oxidative damage has been identified as a major causative factor in degenerative diseases of the retina; retinal pigment epithelial (RPE) cells are at high risk. Hence, identifying novel strategies for increasing the antioxidant capacity of RPE cells, the purpose of this study, is important. Specifically, we evaluated the influence of selenium in the form of selenomethionine (Se-Met) in cultured RPE cells on system xc- expression and functional activity and on cellular levels of glutathione, a major cellular antioxidant. ARPE-19 and mouse RPE cells were cultured with and without selenomethionine (Se-Met), the principal form of selenium in the diet. Promoter activity assay, uptake assay, RT-PCR, northern and western blots, and immunofluorescence were used to analyze the expression of xc-, Nrf2, and its target genes. Se-Met activated Nrf2 and induced the expression and function of xc- in RPE. Other target genes of Nrf2 were also induced. System xc- consists of two subunits, and Se-Met induced the subunit responsible for transport activity (SLC7A11). Selenocysteine also induced xc- but with less potency. The effect of Se-met on xc- was associated with an increase in maximal velocity and an increase in substrate affinity. Se-Met increased the cellular levels of glutathione in the control, an oxidatively stressed RPE. The Se-Met effect was selective; under identical conditions, taurine transport was not affected and Na+-coupled glutamate transport was inhibited. This study demonstrates that Se-Met enhances the antioxidant capacity of RPE by inducing the transporter xc- with a consequent increase in glutathione.

Dietary Factors and Supplements Influencing Prostate Specific-Antigen (PSA) Concentrations in Men with Prostate Cancer and Increased Cancer Risk: An Evidence Analysis Review Based on Randomized Controlled Trials

The quest for dietary patterns and supplements efficient in down-regulating prostate-specific antigen (PSA) concentrations among men with prostate cancer (PCa) or increased PCa risk has been long. Several antioxidants, including lycopene, selenium, curcumin, coenzyme Q10, phytoestrogens (including isoflavones and flavonoids), green tea catechins, cernitin, vitamins (C, E, D) and multivitamins, medicinal mushrooms (Ganoderma lucidum), fruit extracts (saw palmetto, cranberries, pomegranate), walnuts and fatty acids, as well as combined supplementations of all, have been examined in randomized controlled trials (RCTs) in humans, on the primary, secondary, and tertiary PCa prevention level. Despite the plethora of trials and the variety of examined interventions, the evidence supporting the efficacy of most dietary factors appears inadequate to recommend their use.

Inflammation factors and element supplementation in cancer

The aim of the study was to evaluate the effect of dietary supplementation with chosen minerals (Zn, Se, Fe) on expression of selected cytokines (IL-1, IL-6, TNFα) in spleen of rats and on their concentrations in rat serum under inflammatory and pathological conditions obtained by implantation of prostate cancer cells (LnCaP). Serum levels of metabolites of arachidonic, eicosapentaenoic and linoleic acids (hydroxyeicosatetraenoic, hydroxyeicosapentaenoic and hydroxyoctadecadienoic acids, respectively), as compounds involved in inflammation and cancer development, were also investigated. Male rats were randomised into dietary groups supplemented with Zn, Se or Fe. Prostate cancer cells were implanted to some rats in each group. The study demonstrated that minerals supplemented with the diet may exert various effects on an organism. Selenium, zinc and iron influence pro-inflammatory cytokine expression, what leads to stimulation of inflammation. They also affect synthesis of arachidonic and linoleic acid metabolites that exert pro-inflammatory action and enable cancer development and metastasis.

The Effect of Zinc, Selenium, and Their Combined Supplementation on Androgen Receptor Protein Expression in the Prostate Lobes and Serum Steroid Hormone Concentrations of Wistar Rats

BACKGROUND

Zinc (Zn) and selenium (Se) play a well-documented role in cancer prevention (e.g., for prostate cancer), and their combined supplementation is often given as a recommended prophylactic agent. The aim of the study was to determine the influence of Zn and/or Se supplementation on the androgen receptor (AR) in the prostate lobes and the serum selected hormone concentrations; a hitherto unresearched topic.

METHODS

Male rats (n = 84) were administered with Zn and/or Se intragastrically for up to 90 days. The effects of administration on the tested parameters were checked after 30 and 90 days of administration and additionally, 90 days after the end of 90 day administration.

RESULTS

Zn alone leads to an increase in serum testosterone concentrations, while the protein expression of AR in both parts of the prostate increases. Combined administration of Zn and Se eliminates the effect of Zn, which may suggest that these two elements act antagonistically. Se supplementation alone results in the same level of AR protein expression in administration and 90 days after administration periods.

CONCLUSION

This paper presents the first report of the influence of Zn and/or Se supplementation on the protein expression of AR in the prostate. Our findings seem to indicate that simultaneous supplementation of both elements may be ineffective.

Emerging Anticancer Potentials of Selenium on Osteosarcoma

Selenium is a trace element essential to humans and forms complexes with proteins, which exert physiological functions in the body. In vitro studies suggested that selenium possesses anticancer effects and may be effective against osteosarcoma. This review aims to summarise current evidence on the anticancer activity of inorganic and organic selenium on osteosarcoma. Cellular studies revealed that inorganic and organic selenium shows cytotoxicity, anti-proliferative and pro-apoptotic effects on various osteosarcoma cell lines. These actions may be mediated by oxidative stress induced by selenium compounds, leading to the activation of p53, proapoptotic proteins and caspases. Inorganic selenium is selective towards cancer cells, but can cause non-selective cell death at a high dose. This condition challenges the controlled release of selenium from biomaterials. Selenium treatment in animals inoculated with osteosarcoma reduced the tumour size, but did not eliminate the incidence of osteosarcoma. Only one study investigated the relationship between selenium and osteosarcoma in humans, but the results were inconclusive. In summary, although selenium may exert anticancer properties on osteosarcoma in experimental model systems, its effects in humans require further investigation.

Selenium and Sex Steroid Hormones in a U.S. Nationally Representative Sample of Men: A Role for the Link between Selenium and Estradiol in Prostate Carcinogenesis?

BACKGROUND

Given the recent findings from pooled studies about a potential inverse association between selenium levels and prostate cancer risk, this cross-sectional study aimed to investigate the association between serum selenium and serum concentrations of sex steroid hormones including estradiol in a nationally representative sample of U.S. men to investigate one mechanism by which selenium may influence prostate cancer risk.

METHODS

The study included 1,420 men ages 20 years or older who participated in the Third National Health and Nutrition Examination Survey between 1988 and 1994. We calculated age/race-ethnicity-adjusted and multivariable-adjusted geometric mean serum concentrations of total and estimated free testosterone and estradiol, androstanediol glucuronide, and sex hormone binding globulin, and compared them across quartiles of serum selenium.

RESULTS

Adjusting for age, race/ethnicity, smoking status, serum cotinine, household income, physical activity, alcohol consumption, and percent body fat, mean total estradiol [e.g., Q1, 38.00 pg/mL (95% confidence interval (CI), 36.03-40.08) vs. Q4, 35.29 pg/mL (95% CI, 33.53-37.14); P _trend = 0.050] and free estradiol [e.g., Q1, 0.96 pg/mL (95% CI, 0.92-1.01) vs. Q4, 0.90 (95% CI, 0.85-0.95); P _trend = 0.065] concentrations decreased over quartiles of selenium. Stratification by smoking and alcohol consumption, showed that the latter observation was stronger for never smokers (P _interaction = 0.073) and those with limited alcohol intake (P _interaction = 0.017). No associations were observed for the other sex steroid hormones studied.

CONCLUSIONS

Our findings suggests that a possible mechanism by which selenium may be protective for prostate cancer is related to estrogen.

IMPACT

Further studies of longitudinal measurements of serum and toenail selenium in relation to serum measurements of sex steroid hormones are needed.

Selenium, selenoprotein P, and Alzheimer's disease: is there a link?

The essential trace element, selenium (Se), is crucial to the brain but it may be potentially neurotoxic, depending on dosage and speciation; Se has been discussed for decades in relation to Alzheimer's disease (AD). Selenoprotein P (SELENOP) is a secreted heparin-binding glycoprotein which serves as the main Se transport protein in mammals. In vivo studies showed that this protein might have additional functions such as a contribution to redox regulation. The current review focuses on recent research on the possible role of SELENOP in AD pathology, based on model and human studies. The review also briefly summarizes results of epidemiological studies on Se supplementation in relation to brain diseases, including PREADViSE, EVA, and AIBL. Although mainly positive effects of Se are assessed in this review, possible detrimental effects of Se supplementation or exposure, including potential neurotoxicity, are also mentioned. In relation to AD, various roles of SELENOP are discussed, i.e. as the means of Se delivery to neurons, as an antioxidant, in cytoskeleton assembly, in interaction with redox-active metals (copper, iron, and mercury) and with misfolded proteins (amyloid-beta and hyperphosphorylated tau-protein).

Impact of adherence to cancer-specific prevention recommendations on subsequent risk of cancer in participants in Alberta's Tomorrow Project

Objective

The World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR) publish recommendations for cancer prevention. The present study aimed to estimate the association between adherence to these cancer-specific prevention recommendations and subsequent development of cancer in a prospective cohort.

Design

A composite adherence score was constructed based on questionnaire data to reflect overall adherence to WCRF/AICR lifestyle-related recommendations on body fatness, physical activity, diet and alcoholic drinks. Multivariable Cox proportional hazard regression models were used to assess the association (hazard ratio; 95 % CI) between the adherence score and risk of developing cancer.

Setting

Alberta’s Tomorrow Project, a prospective cohort study.

Participants

Men and women (n 25 100, mean age at enrolment 50·5 years) recruited between 2001 and 2009 with no previous cancer diagnosis were included in analyses.

Results

Cancer cases (n 2066) were identified during a mean follow-up of 11·7 years. Participants who were most adherent to the selected WCRF/AICR recommendations (composite score: 4–6) were 13 % (0·87; 0·78, 0·98) less likely to develop cancer compared with those who were least adherent (composite score: 0–2). Each additional recommendation met corresponded to a 5 % (0·95; 0·91, 0·99) reduction in risk of developing cancer. When stratified by sex, the associations remained significant for women, but not for men.

Conclusions

Adherence to lifestyle-related cancer prevention recommendations was associated with reduced risk of developing cancer over the follow-up term in this Canadian cohort.

Causal Inference in Cancer Epidemiology: What Is the Role of Mendelian Randomization?

Observational epidemiologic studies are prone to confounding, measurement error, and reverse causation, undermining robust causal inference. Mendelian randomization (MR) uses genetic variants to proxy modifiable exposures to generate more reliable estimates of the causal effects of these exposures on diseases and their outcomes. MR has seen widespread adoption within cardio-metabolic epidemiology, but also holds much promise for identifying possible interventions for cancer prevention and treatment. However, some methodologic challenges in the implementation of MR are particularly pertinent when applying this method to cancer etiology and prognosis, including reverse causation arising from disease latency and selection bias in studies of cancer progression. These issues must be carefully considered to ensure appropriate design, analysis, and interpretation of such studies. In this review, we provide an overview of the key principles and assumptions of MR, focusing on applications of this method to the study of cancer etiology and prognosis. We summarize recent studies in the cancer literature that have adopted a MR framework to highlight strengths of this approach compared with conventional epidemiological studies. Finally, limitations of MR and recent methodologic developments to address them are discussed, along with the translational opportunities they present to inform public health and clinical interventions in cancer. Cancer Epidemiol Biomarkers Prev; 27(9); 995-1010. ©2018 AACR.

Selenium fortification of infant formulas: does selenium form matter?

Selenium is a trace element essential for the health and development of the growing infant. It is a necessary component of proteins and enzymes required for a variety of functions, including antioxidant defense, modulation of the inflammatory response, and production of thyroid hormones. In breast-fed infants, selenium stores depend on the selenium content of the mother's diet. In formula-fed infants, selenium levels are correlated to the residual selenium stores accumulated in utero and the level and type of selenium fortification used in the formula. Today, the United States Food and Drug Administration (FDA) recommends that infant formulas contain selenium at levels between 2.0 and 7.0 μg per 100 kcal. While the US FDA does not recommend a particular selenium form for fortification, evidence indicates that organically bound selenium forms (e.g., selenomethionine and selenium-enriched yeast) are better absorbed and retained than inorganic forms (e.g., selenite and selenate). Preliminary data from studies in adults do suggest that fortification with standardized selenium-enriched yeast may offer benefits compared to fortification with other organically bound selenium forms. However, because most studies evaluating the impact of selenium fortification of infant formula have assessed inorganic selenium supplements, additional research into the bioavailability and outcomes associated with the use of selenium-enriched yeast in infants is needed.

Methylseleninic acid induces NAD(P)H:quinone oxidoreductase-1 expression through activation of NF-E2-related factor 2 in Chang liver cells

Selenium has been reported to induce the expression of some cytoprotective enzymes, which may account for its chemoprotective and chemopreventive effects. However, it remains largely unresolved whether these effects are exerted by selenium itself or mediated by its metabolite(s). In the present study, methylseleninic acid (MSeA), a monomethylated selenium, induced the expression of NAD(P)H:quinone oxidoreductase-1 (NQO-1) in human Chang liver cells. Expression of NQO-1 and other antioxidant/stress response genes is primarily regulated by the transcription factor NF-E2-related factor2 (Nrf2). Exposure of human Chang liver cells to MSeA (3 μM) increased nuclear translocation of Nrf2 and binding to antioxidant response elements. Silencing Nrf2 markedly reduced the MSeA-induced NQO-1 expression. In comparison with embryonic fibroblasts from Nrf2 wild-type mice, those from Nrf2 knockout mice failed to induce NQO-1 expression when treated with MSeA. Moreover, MSeA treatment enhanced ubiquitination of Keap1, but repressed Nrf2 ubiquitination. Pretreatment of cells with dithiothreitol abrogated the MSeA-induced NQO-1 expression, suggesting that MSeA causes Keap1 thiol modification. MSeA-induced NQO-1 upregulation was attenuated in cells harbouring the mutant Keap1 in which the cysteine 151 residue was replaced by serine. Oral administration of MSeA (1 mg/kg) by gavage to mice induced hepatic NQO-1 expression. Similar to MSeA, methylselenol generated from selenomethionine by methioninase activity induced NQO-1 expression. In conclusion, MSeA, the immediate precursor of methylselenol, upregulates the expression of NQO-1 via the Keap1-Nrf2 signaling. The above findings suggest that biological activities of selenium are dependent on the nature of the metabolites as well as the type of ingested selenium formulations.

Selenium in Poultry Nutrition: from Sodium Selenite to Organic Selenium Sources

Selenium (Se) is an essential element in poultry nutrition and its bio-efficacy depends on its chemical form. A growing body of research proves that organic forms of Se, mainly selenomethionine (SeMet), in poultry diets have a range of important advantages over traditional sodium selenite. In fact, the organic Se concept considers SeMet as a storage form of Se in the chicken body. As chickens are not able to synthesize SeMet, its provision through diet is a key strategy to fight commercially relevant stresses. Indeed, in stress conditions, when increased selenoprotein expression requires additional Se, while its provision via feed usually decreases due to a reduction in feed consumption, Se reserves in the body (mainly in the muscles) could help maintain an effective antioxidant defense and prevent detrimental consequences of stresses. The poultry industry is looking for the most effective sources of organic Se for commercial use. In this review, advantages and disadvantages of main organic Se sources for poultry (Se-yeast, SeMet, and OH-SeMet) are analyzed, and future directions for the development of new Se sources are identified.

Association between selenium and lycopene supplementation and incidence of prostate cancer: Results from the post-hoc analysis of the procomb trial

BACKGROUND

Many potential chemopreventive agents have been used in PCa prevention, including selenium (Se) and lycopene (Ly). However, their role has been matter of debate over the years, due to potential of promotion of PCa.

PURPOSE

In this study we aimed at evaluating the incidence risk of prostate cancer (PCa) in a cohort of patients treated with Se and Ly.

METHODS

The Procomb trial design has been previously published (ISRCTN78639965). From April 2012 to April 2014 209 patients were followed and underwent prostate biopsy when PSA ≥4 ng/ml and/or suspicion of PCa. The all cohort was composed by patients treated with Se and Ly (Group A = 134 patients) and control (Group B = 75 patients).

RESULTS

During the follow-up time of 2 years, a total of 24 patients (11.5%) underwent prostate biopsy, of which 9 (4.3%) where diagnosed with PCa and 15 (7.2%) where diagnosed with benign prostatic hyperplasia. We did not observe statistical differences in terms of mean changes of PSA between the two groups (p-value for trend = 0.33). The relative risk (RR) for PCa was 1.07 and 0.89 in group A and B, respectively (p = 0.95). At the multivariate Cox regression analysis supplementation with Se and Ly was not associated with greater risk of PCa (hazard ratio: 1.38; p = 0.67).

CONCLUSION

In this analysis we did not show evidences supporting a detrimental role of Selenium and Lycopene supplementation in increasing PCa after 2 years of therapy, nor supporting a protective role.

Crab Shell Extract Induces Prostate Cancer Cell Line (LNcap) Apoptosis and Decreases Nitric Oxide Secretion

OBJECTIVE

Prostate cancer is the second most common cancer worldwide. Chemotherapeutic agents have been shown to have adverse side-effects, and natural compounds have been recommended for cancer treatment, nowadays. Crab shell has been shown to have cancer preventative and suppressive effects in vivo and in vitro. The aim of present study was to investigate the effect of crab shell extract on prostate cancer cell line (LNcap) in vitro.

MATERIALS AND METHODS

In this in vitro experimental study, LNcap cells were treated with different concentrations (0, 100, 200, 400, 800 and 1000 µg/ml) of crab shell hydroalcoholic extract in three different culture periods (24, 48 and 72 hours). LNcap viability was evaluated by trypan blue staining and MTT assay. Cell apoptosis and nitric oxide (NO) secretion were determined by TUNEL and Griess assays, respectively. Data were analyzed by one-way ANOVA test and P<0.05 was considered significant.

RESULTS

LNcap viability was decreased dose- and time-dependently. Thus 400, 800, and 1000 µg/ml doses showed significant differences compared to control group (P<0.001). Dose-dependent increase in the apoptotic index was also observed in 800 and 1000 µg/ ml concentrations (P<0.001). Nitric oxide secretion of LNcap cell was decreased time- and dose-dependently, while it was significant for 1000 µg/ml (P<0.05).

CONCLUSION

Crab shell extract showed anti-prostate cancer effect, by inducing cell apop- tosis and decreasing NO production.

Concepts in diagnosis and therapy for male reproductive impairment

An accurate medical history and directed physical examination are essential in diagnosis of male infertility. We review the hormonal assessments and specific genetic analyses that are useful additional tests, and detail other evidence-based examinations that are available to help guide therapeutic strategies. By contrast with female infertility treatments-especially hormonal manipulations to stimulate or enhance oocyte production-spermatogenesis and sperm quality abnormalities are much more difficult to affect positively. In general, a healthy lifestyle can improve sperm quality. A few men have conditions in which evidence-based therapies can increase their chances for natural conception. In this second of two papers in The Lancet Diabetes and Endocrinology Series on male reproductive impairment, we examine the agreements and controversies that surround several of these conditions. When we are not able to cure, correct, or mitigate the cause of conditions such as severe oligozoospermia, non-remedial ductal obstruction, and absence of sperm fertilising ability, assisted reproductive technologies, such as in-vitro fertilisation (IVF) with intracytoplasmic sperm injection (ICSI), can be used as an adjunctive measure to allow for biological paternity. Not considered possible just two decades ago, azoospermia due to testicular failure, including 47,XXY (Klinefelter syndrome), is now treatable in approximately 50% of cases when combining surgical harvesting of testicular sperm and ICSI. Although genetic fatherhood is now possible for many men previously considered sterile, it is crucial to discover and abrogate causes as best possible, provide reliable and evidenced-based therapy, consider seriously the health and wellness of any offspring conceived, and always view infertility as a possible symptom of a more general or constitutional disease.

Evidenced-based clinical practice guideline for prostate cancer (summary: Japanese Urological Association, 2016 edition)

These guidelines cover a wide range of topics from prostate cancer epidemiology to palliative care. Questions arising in daily clinical practice have been extracted and formulated as clinical questions. In the 4 years since the previous edition, there have been major changes - for example, robot-assisted prostatectomy has rapidly come into widespread use, and new hormones and anticancer drugs have been developed for castration-resistant prostate cancer. In response to these developments, the number of fields included in this guideline was increased from 11 in the 2012 edition to 16, and the number of clinical questions was increased from 63 to 70. The number of papers identified in searches of the existing literature increased from 4662 in the first edition, published in 2006, to 10 490 in the 2012 edition. The number of references has reached 29 448 just during this review period, indicating the exponential increase in research on the topic of prostate cancer. Clinical answers have been prepared based on the latest evidence. Recommendation grades for the clinical answers were determined by radiologists, pathologists, and other specialists in addition to urologists in order to reflect the recent advances and diversity of prostate cancer treatment. Here, we present a short English version of the original guideline, and overview its key clinical issues.

Alberta's Tomorrow Project: adherence to cancer prevention recommendations pertaining to diet, physical activity and body size

Objective

To explore cross-sectional adherence to cancer prevention recommendations by adults enrolled in a prospective cohort in Alberta, Canada.

Design

Questionnaire data were used to construct a composite cancer prevention adherence score for each participant, based on selected personal recommendations published by the World Cancer Research Fund/American Institute for Cancer Research (2007). Data were self-reported on health and lifestyle, past-year physical activity and past-year FFQ. The scores accounted for physical activity, dietary supplement use, body size, and intakes of alcohol, fruit, vegetables and red meat. Tobacco exposure was also included. Scores ranged from 0 (least adherent) to 7 (most adherent).

Setting

Alberta’s Tomorrow Project; a research platform based on a prospective cohort.

Subjects

Adult men and women (n 24 988) aged 35–69 years recruited by random digit dialling and enrolled in Alberta’s Tomorrow Project between 2001 and 2009.

Results

Of the cohort, 14 % achieved adherence scores ≥5 and 60 % had scores ≤3. Overall adherence scores were higher in women (mean (sd): 3·4 (1·1)) than in men (3·0 (1·2)). The extent of overall adherence was also associated with level of education, employment status, annual household income, personal history of chronic disease, family history of chronic disease and age.

Conclusions

Reported adherence to selected personal recommendations for cancer prevention was low in this cohort of adults. In the short to medium term, these results suggest that more work is required to identify behaviours to target with cancer prevention strategies at a population level. Future work will explore the associations between adherence scores and cancer risk in this cohort.

The effects of selenium supplementation on biomarkers of inflammation and oxidative stress in patients with diabetic nephropathy: a randomised, double-blind, placebo-controlled trial

This study was carried out to assess the effects of Se supplementation on biomarkers of inflammation and oxidative stress in patients with diabetic nephropathy (DN). This randomised, double-blind, placebo-controlled clinical trial was conducted among sixty patients with DN. Patients were randomly divided into two groups to take either 200 µg/d Se supplements as Se yeast (n 30) or placebo (n 30) for 12 weeks. In unadjusted analyses, compared with the placebo, Se supplementation led to a significant reduction in high-sensitivity C-reactive protein (hs-CRP) (-1069·2 (sd 1752·2) v. -135·3 (sd 1258·9) ng/ml, P=0·02), matrix metalloproteinase-2 (MMP-2) (-612·3 (sd 679·6) v. +76·0 (sd 309·1) ng/ml, P<0·001) and plasma malondialdehyde (MDA) concentrations (-0·1 (sd 0·7) v. +0·4 (sd 0·9) µmol/l, P=0·01). In addition, a significant increase in plasma total antioxidant capacity (TAC) (+174·9 (sd 203·9) v. +15·8 (sd 382·2) mmol/l, P=0·04) was observed following supplementation with Se compared with the placebo. Subjects who received Se supplements experienced a borderline statistically significant decrease in serum protein carbonyl (PCO) levels (P=0·06) compared with the placebo. When we adjusted the analysis for baseline values of biochemical parameters, age and BMI, serum hs-CRP (P=0·14) and MDA levels (P=0·16) became non-significant, whereas plasma nitric oxide (NO) (P=0·04) and glutathione (GSH) (P<0·001) became statistically significant, and other findings did not change. Supplementation with Se had no significant effect on NO, transforming growth factor β (TGF-β), advanced glycation end products (AGE), PCO and GSH compared with the placebo. Overall, our study demonstrated that Se supplementation among DN patients had favourable effects on serum MMP-2, plasma NO, TAC and GSH, but did not affect hs-CRP, TGF-β, AGE, PCO and MDA.

The rise, the fall and the renaissance of vitamin E

This review deals with the expectations of vitamin E ability of preventing or curing, as a potent antioxidant, alleged oxidative stress based ailments including cardiovascular disease, cancer, neurodegenerative diseases, cataracts, macular degeneration and more. The results obtained with clinical intervention studies have highly restricted the range of effectiveness of this vitamin. At the same time, new non-antioxidant mechanisms have been proposed. The new functions of vitamin E have been shown to affect cell signal transduction and gene expression, both in vitro and in vivo. Phosphorylation of vitamin E, which takes place in vivo, results in a molecule provided with functions that are in part stronger and in part different from those of the non-phosphorylate compound. The in vivo documented functions of vitamin E preventing the vitamin E deficiency ataxia (AVED), slowing down the progression of non-alcoholic steato-hepatitis (NASH), decreasing inflammation and potentiating the immune response are apparently based on these new molecular mechanisms. It should be stressed however that vitamin E, when present at higher concentrations in the body, should exert antioxidant properties to the extent that its chromanol ring is unprotected or un-esterified.

Selenium Alleviates Aflatoxin B₁-Induced Immune Toxicity through Improving Glutathione Peroxidase 1 and Selenoprotein S Expression in Primary Porcine Splenocytes

Selenium (Se) is generally known as an essential micronutrient and antioxidant for humans and animals. Aflatoxin B1 (AFB1) is a frequent contaminant of food and feed, causing immune toxicity and hepatotoxicity. Little has been done about the mechanisms of how Se protects against AFB1-induced immune toxicity. The aim of this present study is to investigate the protective effects of Se against AFB1 and the underlying mechanisms. The primary splenocytes isolated from healthy pigs were stimulated by anti-pig-CD3 monoclonal antibodies and treated by various concentrations of different Se forms and AFB1. The results showed that Se supplementation alleviated the immune toxicity of AFB1 in a dose-dependent manner, as demonstrated by increasing T-cell proliferation and interleukin-2 production. Addition of buthionine sulfoximine abrogated the protective effects of SeMet against AFB1. SeMet enhanced mRNA and protein expression of glutathione peroxidase 1 (GPx1), selenoprotein S (SelS), and thioredoxin reductase 1 without and with AFB1 treatments. Furthermore, knockdown of GPx1 and SelS by GPx1-specific siRNA and SelS-specific siRNA diminished the protective effects of SeMet against AFB1-induced immune toxicity. It is concluded that SeMet diminishes AFB1-induced immune toxicity through increasing antioxidant ability and improving GPx1 and SelS expression in splenocytes. This study suggests that organic selenium may become a promising supplementation to protect humans and animals against the decline in immunity caused by AFB1.

Genotoxic effects of two-generational selenium deficiency in mouse somatic and testicular cells

Many studies have investigated genotoxic effects of high Se diets but very few have addressed the genotoxicity of Se deprivation and its consequences in germ cells and none in somatic cells. To address these data gaps, C57BL/6 male mice were subjected to Se deprivation starting in the parental generation, i.e. before conception. Mice were given a diet of either low (0.01mg Se/kg diet) or normal (0.23mg Se/kg diet) Se content. Ogg1-deficient (Ogg1 (-/-) ) mice were used as a sensitive model towards oxidative stress due to their reduced capacity to repair oxidised purines. Ogg1 (-/-) mice also mimic the repair characteristics of human post-meiotic male germ cells which have a reduced ability to repair such lesions. The genotoxicity of Se deficiency was addressed by measuring DNA lesions with the alkaline single cell gel electrophoresis (+ Fpg to detect oxidised DNA lesions) in somatic cells (nucleated blood cells and lung cells) and male germ cells (testicular cells). Total Se concentration in liver and GPx activity in plasma and testicular cells were measured. Gene mutation was evaluated by an erythrocyte-based Pig-a assay. We found that Se deprivation of F1 from their conception and until early adulthood led to the induction of DNA lesions in testicular and lung cells expressed as significantly increased levels of DNA lesions, irrespective of the mouse genotype. In blood cells, Se levels did not appear to affect DNA lesions or mutant cell frequencies. The results suggest that the testis was the most sensitive tissue. Thus, genotoxicity induced by the low Se diet in the spermatozoal genome has potential implications for the offspring.

Genome-wide association study of selenium concentrations

Selenium (Se) is an essential trace element in human nutrition, but its role in certain health conditions, particularly among Se sufficient populations, is controversial. A genome-wide association study (GWAS) of blood Se concentrations previously identified a locus at 5q14 near BHMT. We performed a GW meta-analysis of toenail Se concentrations, which reflect a longer duration of exposure than blood Se concentrations, including 4162 European descendants from four US cohorts. Toenail Se was measured using neutron activation analysis. We identified a GW-significant locus at 5q14 (P < 1 × 10(-16)), the same locus identified in the published GWAS of blood Se based on independent cohorts. The lead single-nucleotide polymorphism (SNP) explained ∼1% of the variance in toenail Se concentrations. Using GW-summary statistics from both toenail and blood Se, we observed statistical evidence of polygenic overlap (P < 0.001) and meta-analysis of results from studies of either trait (n = 9639) yielded a second GW-significant locus at 21q22.3, harboring CBS (P < 4 × 10(-8)). Proteins encoded by genes at 5q14 and 21q22.3 function in homocysteine (Hcy) metabolism, and index SNPs for each have previously been associated with betaine and Hcy levels in GWAS. Our findings show evidence of a genetic link between Se and Hcy pathways, both involved in cardiometabolic disease.

Prostate cancer and the influence of dietary factors and supplements: a systematic review

Background

Prostate cancer is the second most common cause of cancer worldwide after lung cancer. There is increasing evidence that diet and lifestyle plays a crucial role in prostate cancer biology and tumourigenesis. Prostate cancer itself represents a good model of cancer in which to look for chemopreventive agents due to the high disease prevalence, slowly progressive nature, and long latency period. Dietary agents have gained considerable attention, often receiving much publicity in the media.

Aim

To review the key evidence available for potential chemopreventive nutrients.

Methods

The methodology for this review involved a PubMed search from 1990 to 2013 using the key-words “diet and prostate cancer”, “nutrition and prostate cancer”, “dietary factors and prostate cancer”, “prostate cancer epidemiology”, “prostate cancer prevention”, “prostate cancer progression”.

Results

Red meat, dietary fat and milk intake should be minimised as they appear to increase the risk of prostate cancer. Fruit and vegetables and polyphenols may be preventive in prostate cancer, but further studies are needed to draw more solid conclusions and to clarify their role in patients with an established diagnosis of prostate cancer. Selenium and vitamin supplements cannot be advocated for the prevention of prostate cancer and indeed higher doses may be associated with a worse prognosis. There is no specific evidence regarding benefits of probiotics or prebiotics in prostate cancer.

Conclusions

From the wealth of evidence available, many recommendations can be made although more randomised control trials are required. These need to be carefully designed due to the many confounding factors and heterogeneity of the population.

Nutrition and the brain: what advice should we give?

The knowledge base of nutrition and the brain is steadily expanding. Much of the research is aimed at ways to protect the brain from damage. In adults, the major causes of brain damage are aging and dementia. The most prominent dementia, and the condition that grabs the most public attention, is Alzheimer's disease. The assumption in the field is that possibly some change in nutrition could protect the brain and prevent, delay, or minimize Alzheimer's disease damage. Presented here is a framework for understanding the implications of this research. There is a gap between publishing research results and change in public nutrition behavior. Several influencing elements intervene. These include regulatory agencies and all the organizations and people who advise the public, all with their own perspectives. In considering what advice to give, advisors may consider effectiveness, research model, persuasiveness, and risks, among other factors. Advice about nutrition and Alzheimer's disease today requires several caveats.

Selenoprotein gene variants, toenail selenium levels, and risk for advanced prostate cancer

Lower selenium levels have been associated with increased risk of prostate cancer (PCa), and genetic variation in the selenoprotein genes selenoprotein P (SEPP1) and glutathione peroxidase 1 (GPX1) is thought to modify this relationship. We investigated whether the association between toenail selenium levels and advanced PCa risk in the prospective Netherlands Cohort Study is modified by common genetic variation in SEPP1 and GPX1. Toenail clippings were used to determine selenium levels and to isolate DNA for genotyping. This case-cohort study, which included 817 case subjects with advanced PCa and 1048 subcohort members, was analyzed with Cox regression models. All statistical tests were two-sided. Three genetic variants were associated with advanced (stage III/IV or IV) PCa risk: SEPP1 rs7579 (lower risk; P trend = .01), GPX1 rs17650792 (higher risk; P trend = .03), and GPX1 rs1800668 (lower risk; P trend = .005). Toenail selenium levels were inversely associated with advanced PCa risk, independently of common genetic variation in SEPP1 and GPX1.

Increasing dietary selenium elevates reducing capacity and ERK activation associated with accelerated progression of select mesothelioma tumors

To study the effect of the micronutrient selenium on malignant mesothelioma (MM) progression, we cultured four different MM cell lines in media containing increasing amounts of sodium selenite (30, 50, and 80 nmol/L). Increasing selenium levels increased density-dependent proliferation and mobility for CRH5 and EKKH5 but not AB12 and AK7. Comparing these cell lines revealed that extracellular regulated kinase (ERK) phosphorylation was sensitive to a selenium increase in CRH5 and EKKH5 but not AB12 and AK7 cells. Stable expression of a dominant-negative mutant ERK eliminated the effects of increasing selenium. Because ERK is redox sensitive, we compared the MM cell lines in terms of glutathione levels and the capacity to reduce exogenous hydrogen peroxide. Increasing selenium levels led to higher glutathione and reducing capacity in CRH5 and EKKH5 but not AB12 and AK7. The reducing agent N-acetylcysteine eliminated the effects of selenium on ERK activation, proliferation, and mobility. Mice fed diets containing increasing levels of selenium (0.08, 0.25, and 1.0 ppm) showed increased tumor progression for CRH5 but not AB12, MM cells, and in vivo N-acetylcysteine treatment eliminated these effects. These data suggest that the effects of dietary selenium on MM tumor progression depend on the arising cancer cells' redox metabolism, and the tumors able to convert increased selenium into a stronger reducing capacity actually benefit from increased selenium intake.