Extensive but Hemiallelic Methylation of the hMLH1 Promoter Region in Early-Onset Sporadic Colon Cancers With Microsatellite Instability
Extensive but Hemiallelic Methylation of the hMLH1 Promoter Region in Early-Onset Sporadic Colon Cancers With Microsatellite Instability
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DOI：
10.1016/s1542-3565(03)00314-8
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发表时间：
2004-02-01
影响因子：
12.6
通讯作者：
Nagai, Hideo
中科院分区：
文献类型：
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作者：
Miyakura, Yasuyuki;Sugano, Kokichi;Nagai, Hideo
背景和目标：在微卫星不稳定性（MSI）阳性的散发性结直肠癌中经常观察到hMLH 1启动子区域的甲基化。我们研究了29例遗传性非息肉病性结直肠癌（HNPCCs），28例非典型HNPCCs，30例早发性结直肠癌或多原发癌的发展散发病例的87个指标患者的外周血淋巴细胞中的hMLH 1启动子甲基化。研究方法：通过亚硫酸氢钠聚合酶链反应/单链构象多态性分析或甲基化特异性聚合酶链反应分析hMLH 1启动子区域的甲基化。MSI，hMLH 1基因座的等位基因状态，和hMLH 1蛋白表达的损失进行了检查的情况下，肿瘤组织可用。结果如下：30例散发性早发性结肠癌患者中有4例外周血淋巴细胞hMLH 1启动子甲基化，其中2例发生多原发癌（1例结肠癌和1例子宫内膜癌）。在HNPCC或非典型HNPCC组或健康对照受试者的分析中未检测到这种甲基化。MSI均为阳性，在所有受检病例（3/3）的癌组织（结肠癌和子宫内膜癌）和正常组织（结肠、胃粘膜、子宫内膜和骨髓）中均检测到广泛的甲基化。在2例信息性病例中，hMLH 1启动子的多态性位点分析显示甲基化为半等位基因。在1例病例中，未甲基化等位基因在结肠癌中丢失，但在异时性子宫内膜癌中未丢失。结论：hMLH 1启动子区的组成性半等位基因甲基化与散发性早发MSI阳性结肠癌的发生相关。
Background & Aims: Methylation of the hMLH1 promoter region is frequently observed in microsatellite instability (MSI)-positive sporadic colorectal carcinomas. We studied hMLH1 promoter methylation in peripheral blood lymphocytes of 87 index patients representing 29 cases of hereditary nonpolyposis colorectal cancers (HNPCCs), 28 cases of atypical HNPCCs, and 30 sporadic cases of the development of early-onset colorectal carcinomas or multiple primary cancers. Methods: Methylation of the hMLH1 promoter region was analyzed by Na-bisulfite polymerase chain reaction/single-strand conformation polymorphism analysis or methylation-specific polymerase chain reaction. MSI, allelic status of the hMLH1 locus, and loss of hMLH1 protein expression were examined in cases for which tumor tissues were available. Results: Extensive methylation of the hMLH1 promoter was detected in peripheral blood lymphocytes of 4 of 30 patients with sporadic early-onset colon cancer, among whom multiple primary cancers (1 colon and 1 endometrial cancer) developed in 2 cases. This methylation was not detected in analyses of HNPCC or atypical HNPCC groups or healthy control subjects. MSI was positive, and extensive methylation was detected in both cancers (colon and endometrial cancer) and normal tissues (colon, gastric mucosa, endometrium, and bone marrow) in all of the examined cases (3 of 3). Analysis of a polymorphic site in the hMLH1 promoter in 2 informative cases showed that methylation was hemiallelic. In 1 case, the unmethylated allele was lost in the colon cancer but not in the metachronous endometrial cancer. Conclusions: Constitutive, hemiallelic methylation of the hMLH1 promoter region was shown to be associated with carcinogenesis in sporadic, early-onset MSI-positive colon cancers.