Long-term 17alpha-ethinyl estradiol treatment decreases cyclin E and cdk2 expression, reduces cdk2 kinase activity and inhibits S phase entry in regenerating rat liver.
Long-term 17alpha-ethinyl estradiol treatment decreases cyclin E and cdk2 expression, reduces cdk2 kinase activity and inhibits S phase entry in regenerating rat liver.
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发表时间：
2005
影响因子：
25.7
通讯作者：
Lena Koroxenidou;L. Ohlson;I. Porsch Hällström
中科院分区：
文献类型：
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作者：
Lena Koroxenidou;L. Ohlson;I. Porsch Hällström
背景/目的合成雌激素17 α-乙炔雌二醇（EE）是一种有效的大鼠肝脏肿瘤促进剂，在短期治疗期间刺激生长，但在长期治疗时抑制肝细胞增殖。为了确定EE的有丝分裂抑制作用的分子靶点，在EE处理的雌性Wistar大鼠的第一个细胞周期中分析了调节G（1）和S进程的蛋白质的表达。方法长期（60天）EE治疗。增殖细胞核抗原（PCNA）的免疫组织化学染色，以检测S期细胞和有丝分裂的定量。Western blot检测蛋白表达。Cdk 2激酶测定以检查组蛋白H1磷酸化。结果EE使S期细胞数和有丝分裂数减少约70%。细胞周期蛋白D1和D3不受影响，而cdk 4中度降低。细胞周期蛋白E和cdk 2明显降低，同时cdk 2激酶活性显著降低。EE还降低了细胞周期蛋白A并增加了p53和p21的G1水平。结论EE可导致细胞周期阻滞于S期前。Cdk 2激酶活性的降低可能与细胞周期阻滞有关，而Cdk 2激酶活性对G1/S转换至关重要。此外，EE治疗导致p53激活和cdk抑制剂p21的上调，这可能有助于G1期阻滞。
BACKGROUND/AIMS The synthetic estrogen 17alpha-ethinyl estradiol (EE), a potent tumor promoter in rat liver, stimulates growth during short-term treatment but inhibits hepatocyte proliferation upon prolonged treatment. To identify the molecular targets of the mitoinhibitory effect of EE, the expression of proteins regulating G(1)- and S-progression were analyzed during the first cell cycle in EE-treated female Wistar rats. METHODS Long-term (60 days) EE treatment. Immunohistochemical staining for proliferation cell nuclear antigen (PCNA) to detect cells in S phase and quantification of mitosis. Western blot to monitor protein expression. Cdk2 kinase assay to examine histone H1 phosphorylation. RESULTS EE reduced the number of cells in S phase and mitosis by about 70%. Cyclin D1 and D3 were unaffected, while cdk4 was moderately decreased. Cyclin E and cdk2 were markedly decreased with concomitant marked reduction of cdk2 kinase activity. EE also decreased cyclin A and increased G1 levels of p53 and p21. CONCLUSIONS EE causes a cell cycle block before S-phase. The reduction of the cdk2 kinase activity, essential for G1/S-transition, might be involved in the cell cycle block. Also, EE treatment results in p53 activation and upregulation of the cdk inhibitor p21 that might contribute to the G1 arrest.