Epigenetic Silencing of MicroRNA miR-107 Regulates Cyclin-Dependent Kinase 6 Expression in Pancreatic Cancer
Epigenetic Silencing of MicroRNA miR-107 Regulates Cyclin-Dependent Kinase 6 Expression in Pancreatic Cancer
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DOI：
10.1159/000186051
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发表时间：
2009-01-01
期刊：
影响因子：
3.6
通讯作者：
Maitra, Anirban
中科院分区：
文献类型：
--
作者：
Lee, Kwang-Hyuck;Lotterman, Craig;Maitra, Anirban
microRNAs （miRNAs）的异常表达已经成为癌症的一个重要标志。然而，调节mirna本身的假定机制仅部分为人所知。众所周知，人类癌症中的许多肿瘤抑制基因会因染色质改变而沉默，包括启动子甲基化和组蛋白去乙酰化。我们假设mirna在胰腺癌中经历了类似的表观遗传失活。用去甲基化剂5-aza-2'-脱氧胞苷（5-Aza-dC）或组蛋白去乙酰化酶抑制剂trichostatin A，以及两者的组合处理两种人胰腺癌细胞系miapaca -2和panc -1。使用定制的微阵列平台评估对照和处理细胞系中mirna的表达。暴露于两种染色质修饰剂后，每种细胞系中有14种mirna上调两倍或更高，其中包括5种MiaPACA-2和PANC-1共有的mirna （miR-107、miR-103、miR-29a、miR-29b和miR-320）。Northern blot检测证实了miR-107在处理过的癌细胞系中的差异过表达。用于评估miR-107主要转录物5'启动子区域CpG岛甲基化状态的甲基化特异性PCR分析显示，暴露于5- aza - dc后甲基化完全丧失。在MiaPACA-2和PANC-1细胞中，miR-107的强制表达下调了体外生长，这与推测的miR-107靶点周期蛋白依赖性激酶6的抑制有关，从而为胰腺癌中该miRNA的表观遗传失活提供了功能基础。版权所有(C) 2009 S. Karger AG，巴塞尔和IAP
Aberrant expression of microRNAs (miRNAs) has emerged as an important hallmark of cancer. However, the putative mechanisms regulating miRNAs per se are only partially known. It is well established that many tumor suppressor genes in human cancers are silenced by chromatin alterations, including promoter methylation and histone deacetylation. We postulated that miRNAs undergo similar epigenetic inactivation in pancreatic cancer. Two human pancreatic cancer cell lines-MiaPACA-2 and PANC-1-were treated with the demethylating agent, 5-aza-2'-deoxycytidine (5-Aza-dC) or the histone deacetylase inhibitor, trichostatin A, as well as the combination of the two. Expression of miRNAs in control and treated cell lines was assessed using a custom microarray platform. Fourteen miRNAs were upregulated two-fold or greater in each of the cell lines following exposure to both chromatin-modifying agents, including 5 that were in common (miR-107, miR-103, miR-29a, miR-29b, and miR-320) to both MiaPACA-2 and PANC-1. The differential overexpression of miR-107 in the treated cancer cell lines was confirmed by Northern blot assays. Methylation-specific PCR assays for assessment of CpG island methylation status in the 5' promoter region of the miR-107 primary transcript demonstrated complete loss of methylation upon exposure to 5-Aza-dC. Enforced expression of miR-107 in MiaPACA-2 and PANC-1 cells downregulated in vitro growth, and this was associated with repression of the putative miR-107 target, cyclin-dependent kinase 6, thereby providing a functional basis for the epigenetic inactivation of this miRNA in pancreatic cancer. Copyright (C) 2009 S. Karger AG, Basel and IAP