The role of EZH2 and DNA methylation in the silencing of the tumour suppressor RUNX3 in colorectal cancer.
The role of EZH2 and DNA methylation in the silencing of the tumour suppressor RUNX3 in colorectal cancer.
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DOI：
10.1093/carcin/bgq147
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发表时间：
2010-09
期刊：
影响因子：
4.7
通讯作者：
Hardwick JC
中科院分区：
文献类型：
--
作者：
Kodach LL;Jacobs RJ;Heijmans J;van Noesel CJ;Langers AM;Verspaget HW;Hommes DW;Offerhaus GJ;van den Brink GR;Hardwick JC
在胃癌中，已经提出了一种新的肿瘤抑制因子丢失的表观遗传机制，其中组蛋白甲基转移酶增强子zeste同源物2（EZH2）负责RUNX3表达的丢失。这与多种癌症类型中EZH2上调与不良预后相关一致。我们研究了EZH2是否影响结直肠癌（CRC）中RUNX3的表达，以及这是否独立于甲基化。我们使用72个人CRC和8个CRC细胞系测定了EZH2和RUNX3的蛋白质和信使RNA（mRNA）水平，并使用甲基化特异性聚合酶链反应评估了RUNX3甲基化。我们使用染色质免疫沉淀评估了有效RNA干扰介导的EZH2敲低对RUNX3水平、细胞活力和RUNX3启动子的H3K27三甲基化的影响。尽管在CRC样本中EZH2水平较高，RUNX3水平较低，但在配对样本中EZH2和RUNX3之间没有发现负相关性，这与组蛋白甲基化在CRC中沉默RUNX3中的主要作用相反。相反，同一肿瘤中RUNX3 mRNA的下调与RUNX3 DNA甲基化相关（P < 0.05）。在细胞系中，EZH2的敲除去除了RUNX3的抑制性染色质标记，但没有导致RUNX3的重新表达。然而，在去除去甲基化剂后，它阻止了RUNX3的重新沉默。总之，DNA甲基化是CRC中RUNX3转录沉默的主要原因，但EZH2和组蛋白甲基化是去除去甲基化剂后其甲基化依赖性重新沉默所必需的。这些结果将预测EZH2和组蛋白甲基化的抑制剂将增强去甲基化剂在癌症治疗中的作用。
In gastric cancer, a new epigenetic mechanism of tumour suppressor loss has been suggested where the histone methyltransferase enhancer of zeste homolog 2 (EZH2) is responsible for loss of expression of RUNX3. This is consistent with EZH2 upregulation in multiple cancer types being associated with poor prognosis. We investigated whether EZH2 influences the expression of RUNX3 in colorectal cancer (CRC) and whether this is independent of methylation. We determined protein and messenger RNA (mRNA) levels of EZH2 and RUNX3 and assessed RUNX3 methylation with methylation-specific polymerase chain reaction using 72 human CRCs and 8 CRC cell lines. We assessed the effect of efficient RNA interference-mediated knockdown of EZH2 on RUNX3 levels, cell viability and H3K27 trimethylation of the RUNX3 promoter using chromatin immunoprecipitation. Despite higher levels of EZH2 and lower levels of RUNX3 in CRC specimens in general, no inverse correlation between EZH2 and RUNX3 in paired samples was found arguing against a major role for histone methylation in silencing RUNX3 in CRC. Conversely, downregulation of RUNX3 mRNA in the same tumours was associated with RUNX3 DNA methylation (P < 0.05). In cell lines, knockdown of EZH2 removed the repressive chromatin marks from RUNX3 but did not result in RUNX3 re-expression. However, it prevented the re-silencing of RUNX3 after the removal of demethylating agents. In conclusion, DNA methylation is primarily responsible for the transcriptional silencing of RUNX3 in CRC, but EZH2 and histone methylation are necessary for its methylation-dependent re-silencing after the removal of demethylating agents. These results would predict that inhibitors of EZH2 and histone methylation would enhance the effects of demethylating agents in cancer therapy.
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影响因子：
64.8
作者：
Varambally, S;Dhanasekaran, SM;Chinnaiyan, AM
通讯作者：
Chinnaiyan, AM
影响因子：
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Lee, TI;Jenner, RG;Young, RA
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Young, RA
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Viré, E;Brenner, C;Fuks, F
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Fuks, F
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Li, QL;Ito, K;Ito, Y
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Ito, Y
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Goel, A;Arnold, CN;Boland, CR
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Boland, CR