Microsatellite instability in inflammatory bowel disease-associated neoplastic lesions is associated with hypermethylation and diminished expression of the DNA mismatch repair gene, hMLH1.
Microsatellite instability in inflammatory bowel disease-associated neoplastic lesions is associated with hypermethylation and diminished expression of the DNA mismatch repair gene, hMLH1.
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发表时间：
2000-09
期刊：
影响因子：
11.2
通讯作者：
A. Fleisher;M. Esteller;N. Harpaz;A. Leytin;A. Rashid;Yan Xu;Jingliang Liang;O. Stine;Jing Yin-Jing
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作者：
A. Fleisher;M. Esteller;N. Harpaz;A. Leytin;A. Rashid;Yan Xu;Jingliang Liang;O. Stine;Jing Yin-Jing
12 - 15%的散发性结直肠癌显示出DNA错配修复缺陷（MMR），表现为微卫星不稳定性（MSI）。在这组癌症中，MMR基因hMLH 1的启动子超甲基化与MSI密切相关，并且被认为是MSI的原因。炎症性肠病（IBD）中出现的结直肠肿瘤性病变的一个子集也以MSI为特征。我们希望确定hMLH 1超甲基化是否与IBD肿瘤中hMLH 1蛋白表达减少和MSI相关。我们研究了148例IBD肿瘤患者，定义为溃疡性结肠炎或克罗恩病患者中发生的癌或异型增生。采用多重荧光PCR扩增D2 S123、BAT-25、BAT-26、D5 S346和D17 S250基因座，对所有病例进行MSI评估。如果病变在两个或多个位点表现出不稳定性，则将其表征为高频MSI（MSI-H），如果仅在一个位点不稳定，则将其表征为低频MSI（MSI-L），或者如果在任何位点均未显示不稳定性，则将其表征为MS稳定（MSS）。进行甲基化特异性PCR以确定hMLH 1启动子区域的甲基化状态。hMLH 1蛋白表达也通过免疫组织化学进行了评价。148例IBD中出现的肿瘤中有13例（9%）为MSI-H，包括11例癌和2例异型增生病变。另外16个病变（11%）为MSI-L，包括11个癌和5个发育不良病变。其余118例肿瘤（80%）为MSS。6/13例（46%）MSI-H、1/16例（6%）MSI-L和4/27例（15%）MSS病变显示hMLH 1高甲基化（P = 0.013）。肿瘤细胞核相对于周围正常细胞核的hMLH 1蛋白表达减少，在四个（100%）高甲基化病变中进行了免疫组化检测。在IBD肿瘤中，hMLH 1启动子高甲基化经常发生在MSI的背景下，特别是MSI-H。此外，hMLH 1高甲基化和MSI与IBD肿瘤中hMLH 1蛋白表达减少密切相关。这些发现表明，hMLH 1超甲基化导致缺陷的DNA MMR在至少一个子集的IBD肿瘤。
Twelve to 15% of sporadic colorectal cancers display defective DNA mismatch repair (MMR), manifested as microsatellite instability (MSI). In this group of cancers, promoter hypermethylation of the MMR gene hMLH1 is strongly associated with, and believed to be the cause of, MSI. A subset of colorectal neoplastic lesions arising in inflammatory bowel disease (IBD) is also characterized by MSI. We wished to determine whether hMLH1 hypermethylation was associated with diminished hMLH1 protein expression and MSI in IBD neoplasms. We studied 148 patients with IBD neoplasms, defined as carcinoma or dysplasia occurring in patients with ulcerative colitis or Crohn's disease. MSI was evaluated using multiplex fluorescent PCR to amplify loci D2S123, BAT-25, BAT-26, D5S346, and D17S250 in all cases. Lesions were characterized as high-frequency MSI (MSI-H) if they manifested instability at two or more loci, low-frequency MSI (MSI-L) if unstable at only one locus, or MS-stable (MSS) if showing no instability at any loci. Methylation-specific PCR was performed to determine the methylation status of the hMLH1 promoter region. hMLH1 protein expression was also evaluated by immunohistochemistry. Thirteen (9%) of 148 neoplasms arising in IBD were MSI-H, comprising 11 carcinomas and 2 dysplastic lesions. Sixteen additional lesions (11%) were MSI-L, comprising 11 carcinomas and 5 dysplastic lesions. The remaining 118 neoplasms (80%) were MSS. Six (46%) of 13 MSI-H, 1 (6%) of 16 MSI-L, and 4 (15%) of 27 MSS lesions showed hMLH1 hypermethylation (P = 0.013). Diminished hMLH1 protein expression in neoplastic cell nuclei relative to surrounding normal cell nuclei was demonstrated immunohistochemically in four of four (100%) hypermethylated lesions tested. In IBD neoplasia, hMLH1 promoter hypermethylation occurs frequently in the setting of MSI, particularly MSI-H. Furthermore, hMLH1 hypermethylation and MSI are strongly associated with diminished hMLH1 protein expression in IBD neoplasms. These findings suggest that hMLH1 hypermethylation causes defective DNA MMR in at least a subset of IBD neoplasms.