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Dissociation of the genotoxic and growth inhibitory effects of selenium
Abstract:
The effects of forms of selenium compounds that enter the cellular selenium metabolic pathway at different points were investigated in a mouse mammary carcinoma cell line. The goal of these experiments was to determine if the genotoxicity of selenium, defined as its ability to induce DNA single-strand breaks, could be dissociated from activities proposed to account for its cancer inhibitory activity. The results demonstrated that growth inhibition, measured as inhibition of cell proliferation and induction of cell death, was induced by all the forms of selenium evaluated. However, sodium selenite and sodium selenide, which are metabolized predominantly to hydrogen selenide, caused the rapid induction of DNA single-strand breaks as an early event that preceded growth inhibition. Interestingly methylselenocyanate and Se-methylselenocysteine, which are initially metabolized predominantly to methylselenol, induced growth inhibition in the absence of DNA single-strand breakage. Differences in the time course of selenium retention, in the occurrence of membrane damage, and in the induction of morphological changes by selenite versus methylselenocyanate were noted. Collectively, these data indicate that different pathways affecting cell proliferation and cell death are induced depending on whether selenium undergoes metabolism predominantly to hydrogen selenide or to methylselenol.
Insights
Different selenium compounds impact cancer cells uniquely. Some forms cause DNA damage before inhibiting growth, while others inhibit growth without DNA damage, revealing distinct cellular pathways.
Area of Science:
- Biochemistry
- Cell Biology
- Cancer Research
Background:
- Selenium compounds exhibit anticancer properties.
- The mechanisms underlying selenium's genotoxicity and cancer inhibitory activities are not fully understood.
- Cellular selenium metabolism influences its biological effects.
Purpose of the Study:
- To investigate the differential effects of various selenium compounds on cancer cells.
- To determine if selenium's genotoxicity (DNA damage) can be separated from its cancer-inhibitory effects.
- To elucidate the distinct cellular pathways influenced by different selenium metabolites.
Main Methods:
- Utilized a mouse mammary carcinoma cell line.
- Administered various forms of selenium compounds.
- Assessed genotoxicity by measuring DNA single-strand breaks.
- Evaluated cancer inhibitory activity through cell proliferation inhibition and cell death induction.
- Monitored selenium retention, membrane damage, and morphological changes.
Main Results:
- All tested selenium forms induced growth inhibition (cell death/proliferation inhibition).
- Sodium selenite and selenide rapidly induced DNA single-strand breaks prior to growth inhibition.
- Methylselenocyanate and Se-methylselenocysteine induced growth inhibition without significant DNA single-strand breaks.
- Distinct differences were observed in selenium retention, membrane damage, and morphological changes between selenite and methylselenocyanate treatments.
Conclusions:
- Selenium's genotoxicity is dissociable from its cancer-inhibitory activity.
- The metabolic pathway of selenium dictates its cellular effects.
- Metabolism to hydrogen selenide leads to rapid DNA damage, while metabolism to methylselenol primarily causes growth inhibition without DNA damage.