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Methods for accurate and reproducible studies of pharmacological effects of selenium in cancer
Arun Kumar Selvam1, Tímea Szekerczés1, Sofia Björnstedt1
1Division of Pathology, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden.
Abstract:
Selenium compounds have pronounced effects on cell growth and proliferation. Nutritional levels induce selenoproteins. However, the antineoplastic effects of supra-nutritional selenium levels are not mediated by selenoproteins. The most studied compound, selenite, was shown in a clinical trial to possess extraordinary pharmacological properties. The uptake of selenite as for GS-Se-SG and selenocystine is dependent on the extracellular reducing environment maintained by the Xc- cystine transporter (xc- antiporter) ensuring a high level of extracellular cysteine. The expression of the xc- antiporter is vital for selenium cytotoxicity and any xenobiotic or media constituents modulating the expression of this antiporter will greatly affect the cellular response. Cytotoxicity determinations are often difficult to interpret and repeat due to differences in culture conditions. In the current chapter, factors influencing the cellular response, e.g., media composition, cell culturing conditions, assays for key enzymes of importance for selenium metabolism and effects, along with selenium mediated modulation of microRNA expression and immune responses are treated.
Insights
Supra-nutritional selenium levels, particularly selenite, exhibit anti-cancer effects independent of selenoproteins. Cellular response to selenium is critically influenced by the Xc- cystine transporter and culture conditions.
Area of Science:
- Biochemistry
- Cell Biology
- Pharmacology
Background:
- Selenium compounds impact cell growth; nutritional levels activate selenoproteins.
- Supra-nutritional selenium levels display anti-cancer effects not mediated by selenoproteins.
- Selenite demonstrates significant pharmacological properties in clinical trials.
Purpose of the Study:
- To explore the mechanisms of selenium's anti-cancer effects.
- To investigate the role of the Xc- cystine transporter in selenium uptake and cytotoxicity.
- To identify factors influencing cellular responses to selenium, including culture conditions and microRNA modulation.
Main Methods:
- Analysis of selenium compound uptake via the Xc- cystine transporter.
- Examination of factors affecting cellular response, including media composition and culturing conditions.
- Assays for key selenium metabolism enzymes and assessment of microRNA expression and immune responses.
Main Results:
- Selenite and other selenium compounds uptake depend on the extracellular reducing environment maintained by the Xc- cystine transporter.
- Xc- antiporter expression is crucial for selenium-induced cytotoxicity.
- Variability in cytotoxicity assays is linked to differences in culture conditions.
Conclusions:
- The Xc- cystine transporter is a key determinant of selenium cytotoxicity.
- Optimizing culture conditions and understanding transporter modulation are vital for reproducible selenium research.
- Further investigation into selenium's effects on microRNA and immune responses is warranted.
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