Prostate apoptosis response protein 4 sensitizes human colon cancer cells to chemotherapeutic 5-FU through mediation of an NF kappaB and microRNA network.
Prostate apoptosis response protein 4 sensitizes human colon cancer cells to chemotherapeutic 5-FU through mediation of an NF kappaB and microRNA network.
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DOI：
10.1186/1476-4598-9-98
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发表时间：
2010-04-30
期刊：
影响因子：
37.3
通讯作者：
Lee NH
中科院分区：
文献类型：
--
作者：
Wang BD;Kline CL;Pastor DM;Olson TL;Frank B;Luu T;Sharma AK;Robertson G;Weirauch MT;Patierno SR;Stuart JM;Irby RB;Lee NH
前列腺细胞凋亡反应蛋白4(PAR-4)的表达或活性降低在许多癌症中已被证实，尽管缺乏关于PAR-4在结肠癌进展过程中表达的报道。有必要结合受PAR-4影响的遗传网络来理解分子事件。与配对的正常结肠相比，来自患者的结肠癌标本中PAR-4mRNA的表达显著降低。因此，我们评估了将PAR-4重新导入HT29结肠癌细胞的功能后果。在5-氟尿嘧啶(5-FU)作用下，PAR-4与核因子κB在胞浆中的相互作用增强，但在胞核中的相互作用增强，并促进细胞的凋亡。当AKT1促进生存信号被抑制时，也获得了类似的结果。转录组谱分析发现，在HT29细胞中，约有700个基因受PAR-4过表达的差异调控。启动子分析表明，几乎所有受PAR-4调控的基因都含有NFκB的顺式结合序列，对患者表达数据的荟萃分析表明，在结肠癌标本中，这些基因中有三分之一以重复的协同调控网络的形式存在。一组涉及细胞程序性死亡、细胞周期调节和有趣的microRNA途径的基因在网络中被过度表达。值得注意的是，PAR-4的过表达降低了一个特定网络基因DROSHA的启动子上的NFκB的占有率，该基因编码一种微小RNA处理酶。由此导致的DROSHA下调与一组microRNAs的表达变化有关。据预测，其中许多microRNAs的靶标是编码具有凋亡相关功能的蛋白质的mRNAs。西方和功能分析被用来验证几个预测。例如，miR-34a上调与bcl2蛋白下调相对应。用miR-34a反义寡核苷酸处理高表达PAR-4的HT29细胞，可有效逆转5-FU诱导的bcl2表达下调和细胞凋亡。相反，在天然HT29细胞中，通过直接下调DROSHA表达来绕过PAR-4的过度表达，增加了miR-34a的表达和5-FU的敏感性。我们的研究结果表明，PAR-4与胞浆中的核因子κB结合，从而导致microRNA途径组分表达的改变，从而启动了结肠癌细胞对凋亡的敏感性。
Diminished expression or activity of prostate apoptosis response protein 4 (Par-4) has been demonstrated in a number of cancers, although reports on Par-4 expression during colon cancer progression are lacking. An understanding of the molecular events in conjunction with the genetic networks affected by Par-4 is warranted. Colon cancer specimens derived from patients have significantly diminished expression of Par-4 mRNA relative to paired normal colon. Hence, the functional consequences of reintroducing Par-4 into HT29 colon cancer cells were assessed. Overexpression augmented the interaction of Par-4 with NFκB in the cytosol but not nucleus, and facilitated apoptosis in the presence of 5-fluorouracil (5-FU). Analogous findings were obtained when AKT1 pro-survival signaling was inhibited. Transcriptome profiling identified ~700 genes differentially regulated by Par-4 overexpression in HT29 cells. Nearly all Par-4-regulated genes were shown by promoter analysis to contain cis-binding sequences for NFκB, and meta-analysis of patient expression data revealed that one-third of these genes exist as a recurrent co-regulated network in colon cancer specimens. Sets of genes involved in programmed cell death, cell cycle regulation and interestingly the microRNA pathway were found overrepresented in the network. Noteworthy, Par-4 overexpression decreased NFκB occupancy at the promoter of one particular network gene DROSHA, encoding a microRNA processing enzyme. The resulting down-regulation of DROSHA was associated with expression changes in a cohort of microRNAs. Many of these microRNAs are predicted to target mRNAs encoding proteins with apoptosis-related functions. Western and functional analyses were employed to validate several predictions. For instance, miR-34a up-regulation corresponded with a down-regulation of BCL2 protein. Treating Par-4-overexpressing HT29 cells with a miR-34a antagomir functionally reversed both BCL2 down-regulation and apoptosis by 5-FU. Conversely, bypassing Par-4 overexpression by direct knockdown of DROSHA expression in native HT29 cells increased miR-34a expression and 5-FU sensitivity. Our findings suggest that the initiation of apoptotic sensitivity in colon cancer cells can be mediated by Par-4 binding to NFκB in the cytoplasm with consequential changes in the expression of microRNA pathway components.
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4.8
作者：
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