Epigenetic modification of TLR4 promotes activation of NF-κB by regulating methyl-CpG-binding domain protein 2 and Sp1 in gastric cancer.
Epigenetic modification of TLR4 promotes activation of NF-κB by regulating methyl-CpG-binding domain protein 2 and Sp1 in gastric cancer.
复制标题
DOI：
10.18632/oncotarget.6549
复制
发表时间：
2016-01-26
期刊：
影响因子：
--
通讯作者：
Lee HG
中科院分区：
文献类型：
--
作者：
Kim TW;Lee SJ;Oh BM;Lee H;Uhm TG;Min JK;Park YJ;Yoon SR;Kim BY;Kim JW;Choe YK;Lee HG
Toll样受体4（TLR 4）在促进各种癌症的免疫反应中很重要。近年来，TLR 4在胃癌中呈阶段依赖性高表达，但其表达调控机制尚不清楚，本研究探讨了胃癌细胞中TLR 4基因转录调控与沉默之间的关系，即启动子甲基化和组蛋白修饰对TLR 4表达的调控机制。进行染色质免疫沉淀以筛选与TLR 4甲基化相关的因子，例如TLR 4启动子上的MeCP 2、HDAC 1和Sp1。此外，DNA甲基转移酶抑制剂5-氮杂脱氧胞苷（5-aza-dC）诱导TLR 4启动子的去甲基化，并增加H3 K4三甲基化和Sp1结合，以重新激活沉默的TLR 4。与此相反，尽管TLR 4的沉默激活了H3 K9三甲基化和MeCP 2复合物，但TLR 4激动剂和5-aza-dC联合处理上调了H3 K4三甲基化，并激活了转录因子Sp1和NF-κB。这项研究表明，MeCP 2/HDAC 1阻遏复合物的募集通过表观遗传修饰TLR 4启动子上的DNA和组蛋白增加TLR 4的低水平表达，但Sp1通过低甲基化和NF-κB信号转导激活TLR 4在胃癌细胞中的高表达。
Toll-like receptor 4 (TLR4) is important in promoting the immune response in various cancers. Recently, TLR4 is highly expressed in a stage-dependent manner in gastric cancer, but the regulatory mechanism of TLR4 expression has been not elucidated it. Here, we investigated the mechanism underlying regulation of TLR4 expression through promoter methylation and histone modification between transcriptional regulation and silencing of the TLR4 gene in gastric cancer cells. Chromatin immunoprecipitation was carried out to screen for factors related to TLR4 methylation such as MeCP2, HDAC1, and Sp1 on the TLR4 promoter. Moreover, DNA methyltransferase inhibitor 5-aza-deoxycytidine (5-aza-dC) induced demethylation of the TLR4 promoter and increased H3K4 trimethylation and Sp1 binding to reactivate silenced TLR4. In contrast, although the silence of TLR4 activated H3K9 trimethylation and MeCP2 complex, combined treatment with TLR4 agonist and 5-aza-dC upregulated H3K4 trimethylation and activated with transcription factors as Sp1 and NF-κB. This study demonstrates that recruitment of the MeCP2/HDAC1 repressor complex increases the low levels of TLR4 expression through epigenetic modification of DNA and histones on the TLR4 promoter, but Sp1 activates TLR4 high expression by hypomethylation and NF-κB signaling in gastric cancer cells.