Tong W, Pollard J W
Departments of Developmental and Molecular Biology and Obstetrics and Gynecology and Women's Health, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Mol Cell Biol. 1999 Mar;19(3):2251-64. doi: 10.1128/MCB.19.3.2251.
The response of the uterine epithelium to female sex steroid hormones provides an excellent model to study cell proliferation in vivo since both stimulation and inhibition of cell proliferation can be studied. Thus, when administered to ovariectomized adult mice 17beta-estradiol (E2) stimulates a synchronized wave of DNA synthesis and cell division in the epithelial cells, while pretreatment with progesterone (P4) completely inhibits this E2-induced cell proliferation. Using a simple method to isolate the uterine epithelium with high purity, we have shown that E2 treatment induces a relocalization of cyclin D1 and, to a lesser extent, cdk4 from the cytoplasm into the nucleus and results in the orderly activation of cyclin E- and cyclin A-cdk2 kinases and hyperphosphorylation of pRb and p107. P4 pretreatment did not alter overall levels of cyclin D1, cdk4, or cdk6 nor their associated kinase activities but instead inhibited the E2-induced nuclear localization of cyclin D1 to below the control level and, to a lesser extent, nuclear cdk4 levels, with a consequent inhibition of pRb and p107 phosphorylation. In addition, it abrogated E2-induced cyclin E-cdk2 activation by dephosphorylation of cdk2, followed by inhibition of cyclin A expression and consequently of cyclin A-cdk2 kinase activity and further inhibition of phosphorylation of pRb and p107. P4 is used therapeutically to oppose the effect of E2 during hormone replacement therapy and in the treatment of uterine adenocarcinoma. This study showing a novel mechanism of cell cycle inhibition by P4 may provide the basis for the development of new antiestrogens.
子宫上皮对雌性甾体激素的反应为研究体内细胞增殖提供了一个绝佳的模型，因为在此既能研究细胞增殖的刺激过程，也能研究其抑制过程。因此，给去卵巢成年小鼠注射17β-雌二醇（E2）会刺激上皮细胞中DNA合成和细胞分裂的同步波，而用孕酮（P4）预处理则会完全抑制这种E2诱导的细胞增殖。通过一种简单的方法来高纯度分离子宫上皮，我们发现E2处理会诱导细胞周期蛋白D1以及在较小程度上细胞周期蛋白依赖性激酶4（cdk4）从细胞质重新定位到细胞核，并导致细胞周期蛋白E和细胞周期蛋白A-cdk2激酶的有序激活以及视网膜母细胞瘤蛋白（pRb）和p107的过度磷酸化。P4预处理不会改变细胞周期蛋白D1、cdk4或细胞周期蛋白依赖性激酶6（cdk6）的总体水平及其相关激酶活性，而是抑制E2诱导的细胞周期蛋白D1核定位至对照水平以下，并在较小程度上抑制核cdk4水平，从而抑制pRb和p107的磷酸化。此外，它通过使cdk2去磷酸化消除E2诱导的细胞周期蛋白E-cdk2激活，随后抑制细胞周期蛋白A的表达，进而抑制细胞周期蛋白A-cdk2激酶活性，并进一步抑制pRb和p107的磷酸化。在激素替代疗法以及子宫腺癌的治疗中，P4被用于对抗E2的作用。这项显示P4抑制细胞周期新机制的研究可能为开发新型抗雌激素药物提供基础。
