Selenium Compounds as Novel Potential Anticancer Agents

The high number of new cancer incidences and the associated mortality continue to be alarming, leading to the search for new therapies that would be more effective and less burdensome for patients. As there is evidence that Se compounds can have chemopreventive activity, studies have begun to establish whether these compounds can also affect already existing cancers. This review aims to discuss the different classes of Se-containing compounds, both organic and inorganic, natural and synthetic, and the mechanisms and molecular targets of their anticancer activity. The chemical classes discussed in this paper include inorganic (selenite, selenate) and organic compounds, such as diselenides, selenides, selenoesters, methylseleninic acid, 1,2-benzisoselenazole-3[2H]-one and selenophene-based derivatives, as well as selenoamino acids and Selol.

Dynamics of selenium uptake and metabolism of organic selenium species in the leaves and seeds of Brassica napus L.

The essential micronutrient selenium (Se) is retained better in animal and human tissues in its organic forms while nonprotein selenoamino acids, such as selenomethylselenocysteine (SeMetSeCys), are considered as functional organic Se species. We studied the ability of oilseed rape Brassica napus to metabolize inorganic selenate/selenite (SeVI/SeIV) into various organic Se species, including SeMetSeCys. At 14 d after the inorganic Se application, 33% of the Se had accumulated as selenomethionine (SeMet) and 60% as SeVI, whereas no SeMetSeCys was detected. SeMet was the main organic Se species (53−94%) in seeds. Brassica napus selenocysteine methyltransferase (SMT) protein sequence revealed a substitution typical of nonaccumulators explaining the low SeMetSeCys accumulation. Brassica napus absorbs rapidly inorganic Se and converts it into organic Se forms, mainly SeMet, that are suitable for augmenting animal feed and thereby supplementing the human food chain in Se-deficient countries. In contrast, Se biofortification did not result in accumulation of the more valuable SeMetSeCys.

Biotransformation of organic selenium compounds in budding yeast,Saccharomyces cerevisiae

Organic selenium metabolites of plants and animals such as selenoamino acids and selenosugars are metabolized to selenomethionine in yeast.

Recent advances in the mechanism of selenoamino acids toxicity in eukaryotic cells

Selenium is an essential trace element due to its incorporation into selenoproteins with important biological functions. However, at high doses it is toxic. Selenium toxicity is generally attributed to the induction of oxidative stress. However, it has become apparent that the mode of action of seleno-compounds varies, depending on its chemical form and speciation. Recent studies in various eukaryotic systems, in particular the model organism Saccharomyces cerevisiae, provide new insights on the cytotoxic mechanisms of selenomethionine and selenocysteine. This review first summarizes current knowledge on reactive oxygen species (ROS)-induced genotoxicity of inorganic selenium species. Then, we discuss recent advances on our understanding of the molecular mechanisms of selenocysteine and selenomethionine cytotoxicity. We present evidences indicating that both oxidative stress and ROS-independent mechanisms contribute to selenoamino acids cytotoxicity. These latter mechanisms include disruption of protein homeostasis by selenocysteine misincorporation in proteins and/or reaction of selenols with protein thiols.

Comparison of the metabolism of inorganic and organic selenium species between two selenium accumulator plants, garlic and Indian mustard

Selenomethionine (SeMet) can be metabolized into other selenoamino acids such as Se-methylselenocysteine and selenohomolanthionine in selenium-accumulator plants.