Tobacco smoke induces polycomb-mediated repression of Dickkopf-1 in lung cancer cells.
Tobacco smoke induces polycomb-mediated repression of Dickkopf-1 in lung cancer cells.
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DOI：
10.1158/0008-5472.can-08-2807
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发表时间：
2009-04-15
期刊：
影响因子：
11.2
通讯作者：
Schrump DS
中科院分区：
文献类型：
--
作者：
Hussain M;Rao M;Humphries AE;Hong JA;Liu F;Yang M;Caragacianu D;Schrump DS
关于吸烟促进肺癌发生和发展的表观遗传机制的信息有限。为了研究这个问题，在临床相关暴露条件下，在含有或不含有烟草烟雾冷凝物（TSC）的正常培养基中培养A549和Calu-6肺癌细胞。TSC暴露10天显著增加肺癌细胞在裸鼠体内的致瘤性。微阵列和定量逆转录-PCR（RT-PCR）实验表明，这种现象与Dickkopf-1（Dkk-1）的表达减少相吻合。Western blot、染色质免疫沉淀、甲基化特异性PCR和焦磷酸测序实验表明，尽管长时间接触TSC，Dkk-1的抑制与H4K16Ac减少、H3K27me3增加以及SirT1、EZH2、SUZ12和Bmi1的募集一致，而Dkk-1启动子内没有DNA超甲基化。从培养基中去除TSC导致启动子相关多梳阻遏复合物的丢失和Dkk-1的重新表达。siRNA介导的EZH2和SirT1的敲低部分消除了TSC介导的Dkk-1表达抑制。Western blot和定量RT-PCR阵列实验表明，TSC暴露以及敲低Dkk-1激活Wnt信号转导，并显着上调肺癌细胞中的Wnt5a。Dkk-1的敲除再现了TSC暴露在C alu-6细胞中的显著促肿瘤发生作用。尽管体外TSC暴露后Dkk-1抑制的短暂性质，但Dkk-1在源自TSC t-处理的C alu-6细胞的肿瘤异种移植物中保持沉默。总的来说，这些数据提供了证据，表明香烟烟雾直接参与polycomb机制，以激活与癌症干细胞维持有关的信号网络。
Limited information is available about epigenetic mechanisms by which cigarette smoke enhances the initiation and progression of lung cancer. To examine this issue, A549 and Calu-6 lung cancer cells were cultured in normal media with or without tobacco smoke condensate (TSC) under clinically relevant exposure conditions. Ten-day TSC exposure dramatically increased the tumorigenicity of lung cancer cells in nude mice. Microarray and quantitative reverse transcription-PCR (RT-PCR) experiments revealed that this phenomenon coincided with diminished expression of Dickkopf-1 (Dkk-1). Western blot, chromatin immunoprecipitation, methylation-specific PCR, and pyrosequencing experiments showed that repression of Dkk-1 coincided with decreased H4K16Ac, increased H3K27me3, and recruitment of SirT1, EZH2, SUZ12, and Bmi1 without DNA hypermethylation within the Dkk-1 promoter despite prolonged TSCexposures. Removal of TSCfrom culture media resulted in loss of promoter-associated polycomb repressor complexes and reexpression of Dkk-1. siRNA-mediated knockdown of EZH2 and SirT1 partially abrogated TSC-mediated inhibition of Dkk-1 expression. Western blot and quantitative RT-PCR array experiments showed that TSC exposure as well as knockdown of Dkk-1 activated Wnt signaling and significantly up-regulated Wnt5a in lung cancer cells. Knockdown of Dkk-1 recapitulated the dramatic protumorigenic effects of TSC exposure in C alu-6 cells. Despite the transient nature of Dkk-1 repression following TSCexposure in vitro, Dkk-1 remained silenced in tumor xenografts derived from TSC t-reated C alu-6 cells. Collectively, these data provide evidence that cigarette smoke directly engages polycomb machinery to activate a signaling network implicated in maintenance of cancer stem cells.