Chemical Speciation Influences Comparative Activity of Selenium-Enriched Garlic and Yeast in Mammary Cancer Prevention

Ip, Clement; Birringer, Marc; Block, Eric; Kotrebai, Mihály; Tyson, Julian F.; Uden, Peter C.; Lisk, Donald J.

doi:10.1021/jf000932m

Cited by 85 publications

(121 citation statements)

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“…However, follow-up analysis showed that only the patients with low baseline selenium levels benefited from increased dietary selenium (17). Selenium supplementation did not prevent the recurrence of skin cancer, and a more recent follow-up has shown that squamous cell carcinoma and total nonmelanoma skin cancer incidence increased in this patient population (18), highlighting the potential danger of toxicity resulting from selenium supplementation (19,20). Selenium only acts as an antioxidant when used as selenocysteine in a specific group of oxidoreductases (21).…”

Section: Semet Incorporation Into Proteins In a Cys3⌬ Null Strain By mentioning

confidence: 93%

Genome-wide screen of Saccharomyces cerevisiae null allele strains identifies genes involved in selenomethionine resistance

Bockhorn¹,

Balar²,

He³

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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Selenomethionine (SeMet) is a potentially toxic amino acid, and yet it is a valuable tool in the preparation of labeled proteins for multiwavelength anomalous dispersion or single-wavelength anomalous dispersion phasing in X-ray crystallography. The mechanism by which high levels of SeMet exhibits its toxic effects in eukaryotic cells is not fully understood. Attempts to use Saccharomyces cerevisiae for the preparation of fully substituted SeMet proteins for X-ray crystallography have been limited. A screen of the viable S. cerevisiae haploid null allele strain collection for resistance to SeMet was performed. Deletion of the CYS3 gene encoding cystathionine gamma-lyase resulted in the highest resistance to SeMet. In addition, deletion of SSN2 resulted in both increased resistance to SeMet as well as reduced levels of Cys3p. A methionine auxotrophic strain lacking CYS3 was able to grow in media with SeMet as the only source of Met, achieving essentially 100% occupancy in total proteins. The CYS3 deletion strain provides advantages for an easy and cost-effective method to prepare SeMet-substituted protein in yeast and perhaps other eukaryotic systems.CYS3 ͉ SSN2

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Section: Semet Incorporation Into Proteins In a Cys3⌬ Null Strain By mentioning

confidence: 93%

Genome-wide screen of Saccharomyces cerevisiae null allele strains identifies genes involved in selenomethionine resistance

Bockhorn¹,

Balar²,

He³

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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“…The in vivo production of small-molecular-weight Se metabolites such as CH 3 SeH that have potent anti-cancer properties has been inferred from work carried out by a number of research groups (Ip, 1998;Jiang et al 1999;Ip et al 2000Ip et al , 2002Davis & Finley, 2003;Spallholz et al 2004;Whanger, 2004). The metabolism of dietary forms of Se is shown in Fig.…”

Section: Methyl Selenol and Its Precursorsmentioning

confidence: 99%

Selenium in cancer prevention: a review of the evidence and mechanism of action

2005

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Se is an unusual trace element in having its own codon in mRNA that specifies its insertion into selenoproteins as selenocysteine (SeCys), by means of a mechanism requiring a large SeCysinsertion complex. This exacting insertion machinery for selenoprotein production has implications for the Se requirements for cancer prevention. If Se may protect against cancer, an adequate intake of Se is desirable. However, the level of intake in Europe and some parts of the world is not adequate for full expression of protective selenoproteins. The evidence for Se as a cancer preventive agent includes that from geographic, animal, prospective and intervention studies. Newly-published prospective studies on oesophageal, gastric-cardia and lung cancer have reinforced previous evidence, which is particularly strong for prostate cancer. Interventions with Se have shown benefit in reducing the risk of cancer incidence and mortality in all cancers combined, and specifically in liver, prostate, colo-rectal and lung cancers. The effect seems to be strongest in those individuals with the lowest Se status. As the level of Se that appears to be required for optimal effect is higher than that previously understood to be required to maximise the activity of selenoenzymes, the question has been raised as to whether selenoproteins are involved in the anti-cancer process. However, recent evidence showing an association between Se, reduction of DNA damage and oxidative stress together with data showing an effect of selenoprotein genotype on cancer risk implies that selenoproteins are indeed implicated. The likelihood of simultaneous and consecutive effects at different cancer stages still allows an important role for anti-cancer Se metabolites such as methyl selenol formed from g-glutamyl-selenomethyl-SeCys and selenomethyl-SeCys, components identified in certain plants and Se-enriched yeast that have anti-cancer effects. There is some evidence that Se may affect not only cancer risk but also progression and metastasis. Current primary and secondary prevention trials of Se are underway in the USA, including the Selenium and Vitamin E Cancer Prevention Trial (SELECT) relating to prostate cancer, although a large European trial is still desirable given the likelihood of a stronger effect in populations of lower Se status.

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“…It has also been demonstrated that certain Se-containing compounds (e.g., MeSeCys, GGMeSeCys, and SeMet) are effective chemoprotective agents, reducing the incidence of breast, liver, prostate, and colorectal cancers in model systems (Ip and Ganther, 1992;Vadgama et al, 2000;Whanger, 2002Whanger, , 2004. Plant foods are important sources of dietary Se, and low dietary intake of Se may increase the risk of cardiovascular disease, muscle disorders, and cancer (Salonen et al, 1982;Ip et al, 2000;Rajpathak et al, 2005). Globally, about 0.5-1.0 billion people suffer from inadequate intake of Se (Combs, 2001).…”

Section: Introductionmentioning

confidence: 99%

Physiological characteristics of selenite uptake by maize roots in response to different pH levels

Zhang

Shi

et al. 2010

Z. Pflanzenernähr. Bodenk.

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In selenite solutions, H 2 SeO 3 , HSeO À 3 , and SeO 2À 3 are in equilibrium in proportions that vary with solution pH. The physiological characteristics of selenite uptake were studied with excised roots of maize (Zea mays L.) seedlings at pH 3.0, 5.0, and 8.0. The results showed that 0.10 mM 2,4-dinitrophenol (DNP), 1.0 mM sodium fluoride (NaF), and a temperature of 4°C inhibited selenite uptake by maize roots by 16%, 20%, and 23% at pH 3.0, by up to 80%, 79%, and 78% at pH 5.0, and by 5%, 9%, and 16% at pH 8.0. Hence, selenite may enter roots at pH 5.0 in an energy-dependent manner, in contrast to pH 3.0 and 8.0. The uptake kinetics for selenite were determined for excised roots of maize, and the curves were linear at pH 3.0 and 8.0, but saturated at pH 5.0, showing that carrier-mediated uptake of selenite occurred at pH 5.0, but not at pH 3.0 or 8.0. Further studies showed that HgCl 2 and AgNO 3 inhibited selenite uptake separately by 81% and 76% at pH 3.0 and indicated that selenite was absorbed by maize roots through aquaporins at pH 3.0. At pH 8.0, anion-channel inhibitors only inhibited a small fraction of selenite uptake, indicating that the major absorption pathway of SeO 2À 3 species into roots was not absorbed passively through anion channels, but might involve other processes. According to these results, it is proposed that selenite uptake occurs via different mechanisms depending on its species in solution in response to pH levels.

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Chemical Speciation Influences Comparative Activity of Selenium-Enriched Garlic and Yeast in Mammary Cancer Prevention

Cited by 85 publications

References 0 publications

Genome-wide screen of Saccharomyces cerevisiae null allele strains identifies genes involved in selenomethionine resistance

Genome-wide screen of Saccharomyces cerevisiae null allele strains identifies genes involved in selenomethionine resistance

Selenium in cancer prevention: a review of the evidence and mechanism of action

Physiological characteristics of selenite uptake by maize roots in response to different pH levels

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