Selenium metabolism in cancer cells: The combined application of XAS and XFM techniques to the problem of selenium speciation in biological systems
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2013-05-21
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Nutrients
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MDPI
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Biochemistry and Molecular Biology
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Journal Article
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Weekley, C. M., Aitken, J. B., Finney, L., Vogt, S., Witting, P. K. & Harris, H. H. (2013). Selenium metabolism in cancer cells: The combined application of XAS and XFM techniques to the problem of selenium speciation in biological systems. Nutrients, 5 (5), pp.1734-1756. https://doi.org/10.3390/nu5051734.
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Abstract
Determining the speciation of selenium in vivo is crucial to understanding the biological activity of this essential element, which is a popular dietary supplement due to its anti-cancer properties. Hyphenated techniques that combine separation and detection methods are traditionally and effectively used in selenium speciation analysis, but require extensive sample preparation that may affect speciation. Synchrotron-based X-ray absorption and fluorescence techniques offer an alternative approach to selenium speciation analysis that requires minimal sample preparation. We present a brief summary of some key HPLC-ICP-MS and ESI-MS/MS studies of the speciation of selenium in cells and rat tissues. We review the results of a top-down approach to selenium speciation in human lung cancer cells that aims to link the speciation and distribution of selenium to its biological activity using a combination of X-ray absorption spectroscopy (XAS) and X-ray fluorescence microscopy (XFM). The results of this approach highlight the distinct fates of selenomethionine, methylselenocysteine and selenite in terms of their speciation and distribution within cells: organic selenium metabolites were widely distributed throughout the cells, whereas inorganic selenium metabolites were compartmentalized and associated with copper. New data from the XFM mapping of electrophoretically-separated cell lysates show the distribution of selenium in the proteins of selenomethionine-treated cells. Future applications of this top-down approach are discussed.