Estrogen regulates activity of cyclin-dependent kinases and retinoblastoma protein phosphorylation in breast cancer cells
Estrogen regulates activity of cyclin-dependent kinases and retinoblastoma protein phosphorylation in breast cancer cells
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DOI：
10.1210/me.10.5.488
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发表时间：
1996-05-01
影响因子：
--
通讯作者：
Wimalasena, J
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文献类型：
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作者：
Foster, JS;Wimalasena, J
细胞周期蛋白依赖性激酶（Cdk）在哺乳动物细胞中起调节G（1）-到S-期转变的作用。我们研究了雌二醇和甾体抗雌激素ICI 182，780对诱导雌激素敏感的MCF-7乳腺癌细胞中Cdk活性和随之发生的视网膜母细胞瘤蛋白（Rb）磷酸化的影响。用生理浓度的雌二醇处理生长停滞的MCF-7细胞导致Cdk 2相关和细胞周期蛋白E依赖性激酶活性的时间依赖性增加，这伴随着Rb的过度磷酸化和S期进入。雌二醇对Cdk 2活性和DNA合成的诱导具有剂量依赖性，并可被ICI 182，780联合给药抑制。Cdk 2活性的激发需要长时间（>8小时）的雌二醇暴露。在MCF-7细胞中，细胞周期蛋白E和A的水平在经历G（1）-到S-转运时没有变化;然而，雌二醇增加了细胞周期蛋白D-1蛋白的合成和稳态水平。Cdk 4相关的Rb激酶活性在MCF-7细胞雌二醇暴露后6 h明显，并被抗雌激素抑制。Cdk 2和Cdk 4蛋白水平没有改变雌激素治疗，但是，更快的迁移，磷酸化的Cdk 2形式增加雌二醇处理的MCF-7细胞12小时后释放生长停滞。与p27（kip-1）相关的Cdk抑制活性在用雌二醇处理后从生长停滞的MCF-7细胞中消除，但在用雌二醇和ICI 182，780共处理的细胞中没有消除。这些发现表明，雌二醇通过直接影响Cdk活化、Rb磷酸化和诱导Cdk抑制剂的消除来调节MCF-7细胞的G（1）进程。
Cyclin-dependent kinases (Cdk) act to regulate G(1)- to S-phase transition in mammalian cells. We have studied the effects of estradiol and the steroidal antiestrogen ICI 182,780 on induction of Cdk activity and the consequent phosphorylation of retinoblastoma protein (Rb) in estrogen-responsive MCF-7 breast cancer cells. Treatment of growth-arrested MCF-7 cells with physiological concentrations of estradiol led to a time-dependent increase in Cdk2-associated and cyclin E-dependent kinase activity, which was accompanied by hyperphosphorylation of Rb and S-phase entry. Induction of both Cdk2 activity and DNA synthesis by estradiol was dose dependent and was inhibited by coadministration of ICI 182,780. Elicitation of Cdk2 activity was found to require prolonged (>8 h) estradiol exposure. Levels of cyclins E and A were unchanged in MCF-7 cells undergoing G(1)- to S-transit; however, synthesis and steady state levels of cyclin D-1 protein were increased by estradiol. Cdk4-associated Rb kinase activity was evident in MCF-7 cells by 6 h after estradiol exposure and was inhibited by antiestrogen. Cdk2 and Cdk4 protein levels were not altered by estrogen treatment; however, faster migrating, phosphorylated Cdk2 forms increased in estradiol-treated MCF-7 cells by 12 h after release from growth arrest. Cdk-inhibitory activities, associated with p27(kip-1), were eliminated from growth-arrested MCF-7 cells after treatment with estradiol but were not eliminated from cells cotreated with estradiol and ICI 182,780. These findings suggest that estradiol regulates G(1) progression in MCF-7 cells through direct effects upon Cdk activation, Rb phosphorylation, and by inducing elimination of Cdk inhibitors.