Hypermethylation of metallothionein-3 CpG island in gastric carcinoma
Hypermethylation of metallothionein-3 CpG island in gastric carcinoma
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DOI：
10.1093/carcin/24.1.25
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发表时间：
2003-01-01
期刊：
影响因子：
4.7
通讯作者：
Powel, SM
中科院分区：
文献类型：
--
作者：
Deng, DJ;El-Rifai, W;Powel, SM
胃癌组织中金属硫蛋白(MT)-3的表达常明显降低。MT-3下调的分子机制尚不清楚。通过核苷酸测序和变性高效液相色谱（DHPLC）分析，研究了CpG岛甲基化对MT-3转录沉默的影响。我们发现正常脑组织和表达MT-3 mRNA的异种移植GC在该基因的内含子中具有未甲基化的CpG岛区域。另一方面，胃癌细胞系AGS和MKN445、异种移植的胃癌细胞系以及未表达MT-3 mRNA的具有代表性的原发性胃癌细胞系均表现出MT-3内含子CpG岛的高甲基化。5-氮杂胞苷处理胃癌细胞系后，胃癌细胞中有新的mt - 3mrna表达。定量DHPLC测定法被开发来确定MT-3基因这一特定区域的甲基化状态。用DHPLC对58例原发性胃癌及其相应的正常胃上皮组织和34例正常胃粘膜进行初步鉴定的甲基化异常区域MT-3甲基化分析。我们对甲基化MT-3产物的DHPLC分析表明，原发性胃癌的平均甲基化百分比为每个肿瘤6.3%，而正常胃组织的甲基化百分比为2.4% （P < 0.05）。免疫组化染色显示，MT-3在所有8例p53阳性的GCs中未甲基化，在13例p53阴性的GCs中有8例出现高甲基化（P = 0.007）。综上所述，MT-3内含子中的CpG岛在许多胃癌中异常高甲基化，可能是胃癌发生过程中MT-3下调的原因。
The expression of metallothionein (MT)-3 is often markedly reduced in gastric carcinoma (GC). The molecular mechanism of this MT-3 downregulation is unknown. Transcriptional silencing of MT-3 by methylation of CpG island was investigated by nucleotide sequencing and denaturing high performance liquid chromatography (DHPLC) analyses. We found that normal brain tissue and a xenografted GC that expressed MT-3 mRNA had unmethylated regions of the CpG island in intronl of this gene. On the other hand, gastric cancer cell lines AGS and MKN445, a xenografted GC, and a representative primary gastric cancer that had no expression of MT-3 mRNA demonstrated hypermethylation of the MT-3 intronl CpG island. Treatment of the gastric cancer cell lines with 5-azacytidine resulted in new expression of MT-3 mRNA in these cells. A quantifying DHPLC assay was developed to determine the methylation status of this specific region of the MT-3 gene.Fifty-eight primary GC and their corresponding normal gastric epithelial tissues, and 34 normal gastric mucosa were analyzed for MT-3 methylation by DHPLC in the region of methylation abnormalities initially identified. Our DHPLC analyses of the methylated MT-3 product demonstrated that the primary gastric cancers have an average methylation percentage of 6.3% per tumor compared with 2.4% in normal gastric tissues (P < 0.05). The MT-3 was not methylated in all of eight P53-positive GCs and hypermethylated in eight of 13 P53-negative cases by immunohistochemistry staining (P = 0.007). In conclusion, the CpG island in the MT-3 intronl are abnormally hypermethylated in many gastric carcinomas and may account for the downregulation of MT-3 in gastric carcinogenesis.