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Stage specificity of selenium-mediated inhibition of mouse mammary tumorigenesis
1Department of Cell Biology (DM), Baylor College of Medicine, 77030, Houston, Texas.
Abstract:
The experiments reported herein examined the inhibitory role of selenium in chemical carcinogen-induced mouse mammary tumorigenesis. The results from four different experiments are presented herein and are summarized briefly. First, the results demonstrated that relatively low doses of dietary selenium (0.5-2.0 ppm) inhibited 7,12-dimethylbenzanthracene (DBMA)-induced mouse mammary tumorigenesis. At 2 ppm Se, the mammary tumor incidence was reduced from 56 to 15%. Second, the results suggested that the later stages of mammary tumorigenesis (preneoplastic to neoplastic transformation and tumor growth) are not as sensitive to selenium-mediated inhibition as the early stages, i.e., the induction and/or expression of mammary preneoplastic lesions. Finally, the results demonstrated that selenium markedly inhibited mammary tumorigenesis (from 42 to 8%) even when the mice were exposed to selenium only after the carcinogen treatments had been concluded. The results from these experiments are discussed from the viewpoint that selenium-mediated inhibition is a result of a direct block of DNA synthesis.
Insights
Selenium supplementation significantly inhibits chemical carcinogen-induced mouse mammary tumors. Even late-stage selenium exposure effectively reduces tumor incidence by blocking DNA synthesis.
Area of Science:
- Biochemistry
- Oncology
- Nutritional Science
Background:
- Chemical carcinogens like 7,12-dimethylbenzanthracene (DBMA) are known to induce mouse mammary tumorigenesis.
- Selenium is a trace element with potential chemopreventive properties.
- Understanding the role of selenium in inhibiting mammary tumor development is crucial for cancer prevention strategies.
Purpose of the Study:
- To investigate the inhibitory effect of selenium on 7,12-dimethylbenzanthracene (DBMA)-induced mouse mammary tumorigenesis.
- To determine the optimal stage for selenium intervention during mammary tumorigenesis.
- To elucidate the mechanism underlying selenium's anti-tumorigenic effects.
Main Methods:
- Four experiments were conducted using mice exposed to DBMA.
- Varying doses of dietary selenium (0.5-2.0 ppm) were administered.
- Selenium exposure timing was manipulated, including post-carcinogen treatment administration.
- Mammary tumor incidence and progression were monitored.
Main Results:
- Low doses of dietary selenium (0.5-2.0 ppm) significantly inhibited DBMA-induced mammary tumorigenesis.
- At 2 ppm selenium, mammary tumor incidence decreased from 56% to 15%.
- Selenium was more effective in inhibiting early stages of tumorigenesis (lesion induction/expression) than later stages (transformation/growth).
- Selenium administration after carcinogen treatment concluded still markedly inhibited tumorigenesis (from 42% to 8%).
Conclusions:
- Selenium exhibits a potent inhibitory effect on chemical carcinogen-induced mouse mammary tumorigenesis.
- Selenium's efficacy is linked to its action during the early stages of tumor development.
- Selenium's anti-tumorigenic mechanism is proposed to involve a direct inhibition of DNA synthesis.
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