Disruption of Rb/E2F pathway results in increased cyclooxygenase-2 expression and activity in prostate epithelial cells
Disruption of Rb/E2F pathway results in increased cyclooxygenase-2 expression and activity in prostate epithelial cells
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DOI：
10.1158/0008-5472.can-04-3129
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发表时间：
2005-05-01
期刊：
影响因子：
11.2
通讯作者：
Day, ML
中科院分区：
文献类型：
--
作者：
Davis, JN;McCabe, MT;Day, ML
视网膜母细胞瘤肿瘤抑制基因（RB）的丢失在许多人类癌症中很常见，包括前列腺癌。我们以前报道过，工程删除RB在前列腺上皮细胞的结果在持续的细胞生长在无血清培养基中，一种倾向，发展增生和发育不良的前列腺组织重组移植物，和激素致癌致敏。检查RB损失在这个系统中的分子后果，我们表明，环氧合酶-2（考克斯-2）是显着上调后，KB删除前列腺组织重组。为了研究RB缺失对考克斯-2调节的影响，我们产生了通过组织重组拯救的野生型（PrE）和Rb-/-（Rb-/-PrE）前列腺上皮细胞系。我们发现在Rb-/-PrE细胞系中考克斯-2 mRNA和蛋白表达升高，前列腺素合成增加。我们还发现Rb的缺失导致E2 F活性失调，E2 F靶基因表达增加，E2 F1的外源性表达导致考克斯-2 mRNA和蛋白水平升高。考克斯-2启动子研究表明E2 F1转录激活考克斯-2，这依赖于E2 F1的反式激活和DNA结合结构域。进一步的分析显示，E2 F1靶基因c-myb在Rb-/-PrE细胞和E2 F1过表达细胞中升高，而c-myb的异位过表达激活前列腺上皮细胞中的考克斯-2启动子。此外，共转染E2 F1和显性阴性c-myb抑制E2 F1激活的考克斯-2启动子。综上所述，这些结果表明E2 F1通过c-myb癌基因调节考克斯-2表达的转录级联激活。这项研究报告了一个新的发现，描述了Rb/E2 F复合物的失调导致增加考克斯-2的表达和活性。
The loss of the retinoblastoma tumor suppressor gene (RB) is common in many human cancers, including prostate. We previously reported that engineered deletion of RB in prostate epithelial cells results in sustained cell growth in serum-free media, a predisposition to develop hyperplasia and dysplasia in prostate tissue recombinant grafts, and sensitization to hormonal carcinogenesis. Examining the molecular consequence of RB loss in this system, we show that cyclooxygenase-2 (COX-2) is significantly up-regulated following KB deletion in prostate tissue recombinants. To study the effect of RB deletion on COX-2 regulation, we generated wild-type (PrE) and Rb-/- (Rb-/-PrE) prostate epithelial cell lines rescued by tissue recombination. We show elevated COX-2 mRNA and protein expression in Rb-/-PrE cell lines with increased prostaglandin synthesis. We also find that loss of Rb leads to deregulated E2F activity, with increased expression of E2F target genes, and that exogenous expression of E2F1 results in elevated COX-2 mRNA and protein levels. COX-2 promoter studies reveal that E2F1 transcriptionally activates COX-2, which is dependent on the transactivation and DNA-binding domains of E2F1. Further analysis revealed that the E2F1 target gene, c-myb, is elevated in Rb-/-PrE cells and E2F1-overexpressing cells, whereas ectopic overexpression of c-myb activates the COX-2 promoter in prostate epithelial cells. Additionally, cotransfection with E2F1 and a dominant-negative c-myb inhibited E2F1 activation of the COX-2 promoter. Taken together, these results suggest activation of a transcriptional cascade by which E2F1 regulates COX-2 expression through the c-myb oncogene. This study reports a novel finding describing that deregulation of the Rb/E2F complex results in increased COX-2 expression and activity.