Regulation of EP4 expression via the Sp-1 transcription factor: Inhibition of expression by anti-cancer agents
Regulation of EP4 expression via the Sp-1 transcription factor: Inhibition of expression by anti-cancer agents
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DOI：
10.1016/j.bbamcr.2008.01.032
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发表时间：
2008-06-01
影响因子：
5.1
通讯作者：
Eling, Thomas E.
中科院分区：
文献类型：
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作者：
Kambe, Atsushi;Iguchi, Genzo;Eling, Thomas E.
对于胶质母细胞瘤，COX-2的表达与生存不良有关。环氧合酶-2的作用是由受体EP2和EP4介导的，而EP2和EP4的调节机制尚不清楚。人胶质母细胞瘤T98G细胞中EP4的表达和活性的激活或抑制与软琼脂上的生长有关。化学预防药物曲格列酮(TGZ)和一些COX抑制剂显著抑制T98G细胞EP4的表达，并呈剂量依赖关系。特异性蛋白1(Sp-1)结合位点位于人EP4启动子的-197~-160区域，对人EP4基因的转录启动起重要作用，并与TGZ抑制EP4有关。Sp-1位点的突变改变了荧光素酶结构的启动子活性和TGZ对启动子的影响。TGZ对EP4表达的抑制作用可被MEK-1/ERK抑制剂PD98059逆转。免疫沉淀-Western印迹分析检测到Sp-1的磷酸化依赖于TGZ诱导的ERKS激活。芯片分析证实，Sp-1的磷酸化降低了其与DNA的结合，从而抑制了Ep4的表达。因此，我们认为EP4的表达受Sp-1的调节，但TGZ诱导的Sp-1的磷酸化抑制了这一表达。这代表了一种新的独特的EP4受体表达调控机制。爱思唯尔出版公司(Elsevier B.V.)
For glioblastomas, COX-2 expression is linked to poor survival. COX-2 effects are mediated by the receptors EP2 and EP4, whose regulation is poorly understood. The expression of EP4, and activation or inhibition of EP4 activity in human glioblastoma T98G cells, was found to correlate with growth on soft agar. Chemoprevention drugs, troglitazone (TGZ) and some COX inhibitors, significantly suppressed EP4 expression in T98G cells in a dose dependant manner. Specificity protein 1 (Sp-1) binding sites, located within region -197 to -160 of the human EP4 promoter, are important for the transcription initiation of the human EP4 gene and are responsible for the EP4 suppression by TGZ. Mutation in the Sp-1 sites altered the promoter activity of luciferase constructs and TGZ effects on the promoter. The inhibitory effect of TGZ on EP4 expression was reversed by PD98059, a MEK-1/Erk inhibitor. Immunoprecipitation-Western blot analysis detected Sp-1 phosphorylation that was dependent on TGZ-induced Erks activation. ChIP assay confirmed that Sp-1 phosphorylation decreases its binding to DNA and as a result, leads to the suppression of EP4 expression. Thus, we propose that the expression of EP4 is regulated by Sp-1, but phosphorylation of Sp-1 induced by TGZ suppresses this expression. This represents a new and unique mechanism for the regulation of the EP4 receptor expression. Published by Elsevier B.V.