PMID: 15375486Sep 18, 2004Paper

Inhibition of mammary gland tumors by short-term treatment of estradiol-3-benzoate associated with down-regulation of estrogen receptor ERalpha and ERbeta

Oncology Reports
Jin Seok KangKi-Hwa Yang

Abstract

Epidemiological evidence indicates that estrogens are one of the risk factors of breast cancer. However, there have been reports that pre-pubertal estrogen exposure is related to reduced breast cancer risk. These discrepancies made us investigate the time-point and duration of estrogen exposure. Our studies focus on the effect of estradiol-3-benzoate (EB) on the mammary gland that was exposed to carcinogens. Ninety-six female Sprague-Dawley rats were randomly divided into 6 groups. Animals at 7 weeks of age were injected with 7,12-dimethylbenz[a]anthracene (DMBA) in groups 1, 2 and 3 or N-methyl-N-nitrosourea (MNU) in groups 4, 5 and 6. One week later, the animals were subjected to sustained treatment with 0 micro g (groups 1 and 4), 30 micro g (groups 2 and 5) or 300 micro g (groups 3 and 6) of EB containing pellets for 4 weeks. All animals were sacrificed at 5 weeks or 21 weeks after carcinogen treatment, for the examination of mammary gland differentiation or mammary gland tumors, respectively. At 21 weeks after carcinogen treatment, the incidence of mammary tumors in group 2 was significantly decreased (P<0.05). EB treatment decreased the multiplicity of DMBA- or MNU-induced mammary gland tumors. At 5 weeks after carcinogen...Continue Reading

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