人类肝细胞癌中异常的 CpG 岛甲基化和 Oct-6 mRNA 表达下调。

Aberrant CpG island hypermethylation and down-regulation of Oct-6 mRNA expression in human hepatocellular carcinoma.

机构信息

School of Biotechnology, Southern Medical University, Guangzhou, 510515, People's Republic of China.

出版信息

Dig Dis Sci. 2011 Oct;56(10):3072-7. doi: 10.1007/s10620-011-1686-y. Epub 2011 Mar 30.

DOI:10.1007/s10620-011-1686-y

PMID:21448695

Abstract

BACKGROUND

Aberrant CpG island hypermethylation is a major epigenetic mechanism that can inactivate the transcription of cancer-related genes.

PURPOSE

This study aimed to investigate whether Oct-6 transcription was regulated by CpG island methylation in hepatocellular carcinoma (HCC).

METHODS

Quantitative real-time PCR and the MassARRAY platform (Sequenom) were employed in 38 HCC tissues samples and four cell lines.

RESULTS

The levels of Oct-6 mRNA were decreased by more than twofold in 31 of 38 tumor tissues compared to that of adjacent non-cancerous tissues. Among the 31 tumor tissues with lower levels of Oct-6 mRNA, 17 tumor tissues also had higher methylation levels in Oct-6 CpG island. Based on these results, we hypothesized that CpG island hypermethylation may down-regulate Oct-6 mRNA expression in HCC. To confirm this hypothesis, we also analyzed the changes in Oct-6 mRNA expression and CpG island methylation in four HCC cell lines (Huh7, Bel-7402, HepG2 and SMMC-7721) after treatment with 0.1, 0.5 and 2.5 μM 5-Aza-2-deoxycytidine (5-Aza-CdR), a demethylating agent. The results demonstrated that the CpG island methylation levels decreased and Oct-6 mRNA levels increased in a dose-dependent manner in both Huh7 and Bel7402 cells, but there were only slight changes in HepG2 cell. Interestingly, there were no significant alterations of Oct-6 mRNA levels observed in SMMC7721 cell; although lower levels of CpG island methylation were detected after treatment with 5-Aza-CdR.

CONCLUSIONS

Our study shows that CpG island hypermethylation contributes to down-regulation of Oct-6 mRNA expression in HCC.

摘要

背景

异常的 CpG 岛甲基化是一种主要的表观遗传机制，可使癌相关基因的转录失活。

目的

本研究旨在探讨 Oct-6 转录是否受肝细胞癌 (HCC) 中 CpG 岛甲基化的调控。

方法

采用定量实时 PCR 和 MassARRAY 平台（Sequenom）检测 38 例 HCC 组织样本和 4 种细胞系。

结果

与相邻非癌组织相比，38 例肿瘤组织中有 31 例 Oct-6 mRNA 水平降低了两倍以上。在 31 例 Oct-6 mRNA 水平较低的肿瘤组织中，17 例肿瘤组织中 Oct-6 CpG 岛的甲基化水平也较高。基于这些结果，我们假设 CpG 岛甲基化可能下调 HCC 中的 Oct-6 mRNA 表达。为了验证这一假设，我们还分析了四种 HCC 细胞系（Huh7、Bel-7402、HepG2 和 SMMC-7721）在 0.1、0.5 和 2.5μM 5-氮杂-2-脱氧胞苷（5-Aza-CdR），一种去甲基化剂处理后 Oct-6 mRNA 表达和 CpG 岛甲基化的变化。结果表明，在 Huh7 和 Bel7402 细胞中，CpG 岛甲基化水平呈剂量依赖性降低，Oct-6 mRNA 水平升高，但 HepG2 细胞仅有轻微变化。有趣的是，在 SMMC7721 细胞中，未观察到 Oct-6 mRNA 水平的显著变化；尽管在 5-Aza-CdR 处理后检测到较低水平的 CpG 岛甲基化。