Inhibition of mitogen-activated protein kinase and phosphatidylinositol 3-kinase activity in MCF-7 cells prevents estrogen-induced mitogenesis.
Inhibition of mitogen-activated protein kinase and phosphatidylinositol 3-kinase activity in MCF-7 cells prevents estrogen-induced mitogenesis.
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发表时间：
2000-02
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通讯作者：
E. Lobenhofer;G. Huper;J. Iglehart;J. Marks
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作者：
E. Lobenhofer;G. Huper;J. Iglehart;J. Marks
雌激素通过与高水平的雌激素受体相互作用，促进MCF-7人乳腺癌细胞系的DNA合成。雌激素作用的主要方式被认为是通过转录激活包含雌激素反应元件的基因，包括即刻早期基因c-myc和fos。最近的报道表明，雌激素通过雌激素受体发挥作用，能够诱导丝裂原活化蛋白激酶(MAPK)胞浆信号级联反应。在这项研究中，使用了MAPK和磷脂酰肌醇3-激酶活性的特异性小分子抑制剂来确定这些级联反应对雌激素介导的有丝分裂的影响。磷脂酰肌醇3-激酶抑制剂LY294002和Wortmannin以及MAPK-1抑制剂PD098059和U0126可减少17β-雌二醇处理后进入DNA合成的细胞比例。这些化合物不抑制myc和fos的表达。然而，这些药物确实阻止了细胞周期蛋白D1和过度磷酸化的视网膜母细胞瘤蛋白的积累，表明这种阻断发生在细胞周期的这个时间点或之前。虽然这些化合物有效地阻止了雌激素介导的有丝分裂，但下游的细胞外信号调节激酶1、细胞外信号调节激酶2和蛋白激酶B不能被雌激素处理的基础水平激活。这些研究表明，雌激素通过诱导即刻早期基因的转录来启动有丝分裂，但细胞质信号通路在控制细胞周期中的后续事件中发挥着重要作用。
Estrogen acts to promote DNA synthesis in the MCF-7 human breast cancer cell line via its interaction with high levels of estrogen receptor. The primary mode of estrogen action has been considered to be through transcriptional activation of genes containing estrogen response elements, including the immediate early genes c-myc and fos. Recent reports have indicated that estrogen, acting through the estrogen receptor, is capable of inducing the mitogen-activated protein kinase (MAPK) cytoplasmic signaling cascade. In this study, specific small molecule inhibitors of MAPK and phosphatidylinositol 3-kinase activity were used to determine the influence of these cascades on estrogen-mediated mitogenesis. Phosphatidylinositol 3-kinase inhibitors, LY294002 and wortmannin, as well as inhibitors of MAPK kinase-1, PD098059 and U0126, decreased the fraction of cells entering DNA synthesis after treatment with 17beta-estradiol. These compounds did not inhibit expression of myc or fos. However, the drugs did prevent the accumulation of cyclin D1 and hyperphosphorylated retinoblastoma protein, indicating that the block occurred at, or prior to, this point in the cell cycle. Although these compounds were effective in preventing estrogen-mediated mitogenesis, the downstream kinases extracellular signal-regulated kinase 1, extracellular signal-regulated kinase 2, and protein kinase B were not activated over basal levels by estrogen treatment. These studies suggest that estrogen initiates mitogenesis by inducing the transcription of immediate early genes, but cytoplasmic signaling pathways play an important role in the control of subsequent events in the cell cycle.