Inactivating mutations of the human base excision repair gene NEIL1 in gastric cancer
Inactivating mutations of the human base excision repair gene NEIL1 in gastric cancer
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DOI：
10.1093/carcin/bgh267
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发表时间：
2004-12-01
期刊：
影响因子：
4.7
通讯作者：
Sugimura, H
中科院分区：
文献类型：
--
作者：
Shinmura, K;Tao, H;Sugimura, H
氧化的 DNA 碱基损伤，例如胸腺嘧啶乙二醇 (Tg) 和 8-羟基鸟嘌呤，通常具有毒性和致突变性，并与致癌有关。为了阐明对此类基础病变表现出切除修复活性的 NEIL1 蛋白是否与胃癌发生有关，我们检查了来自日本患者的 71 例原发性胃癌和 4 种胃癌细胞系的 NEIL1 基因突变和遗传多态性。我们还检查了来自中国患者的 20 份血液样本的 NEIL1 基因多态性。鉴定出三种突变（c.82_84delGAG:p.Glu28del、c.936G > A 和 c.1000A > G:p.Arg334Gly）和两种遗传多态性。当比较六种重组NEIL1蛋白对含有Tg:A碱基对的双链寡核苷酸的切除修复活性时，发现在原发病例中发现的p.Glu28del型NEIL1表现出极低的活性水平。此外，在 KATO-III 细胞系中检测到的位于外显子 10 最后一个核苷酸的 c.936G > A 通过体内剪接测定显示与剪接异常相关。免疫荧光分析显示，野生型 NEIL1 蛋白（而非 c.936G > A 突变产生的异常转录物编码的截短蛋白）位于细胞核中，这表明截短蛋白不太可能能够修复核 DNA。表达分析显示，在检查的 13 个原发性胃癌标本中，有 6 个 (46%) 的 NEIL1 mRNA 表达降低。这些结果表明，突变和表达减少引起的 NEIL1 低活性可能与部分胃癌的发病机制有关。
Oxidized DNA base lesions, such as thymine glycol (Tg) and 8-hydroxyguanine, are often toxic and mutagenic and have been implicated in carcinogenesis. To clarify whether NEIL1 protein, which exhibits excision repair activity towards such base lesions, is involved in gastric carcinogenesis, we examined 71 primary gastric cancers from Japanese patients and four gastric cancer cell lines for mutations and genetic polymorphisms of the NEIL1 gene. We also examined 20 blood samples from Chinese patients for NEIL1 genetic polymorphisms. Three mutations (c.82_84delGAG:p.Glu28del, c.936G > A and c.1000A > G:p.Arg334Gly) and two genetic polymorphisms were identified. When the excision repair activity towards double-stranded oligonucleotide containing a Tg:A base pair was compared among six types of recombinant NEIL1 proteins, p.Glu28del-type NEIL1, found in a primary case, was found to exhibit an extremely low activity level. Moreover, c.936G > A, located in the last nucleotide of exon 10 and detected in the KATO-III cell line, was shown to be associated with a splicing abnormality using an in vivo splicing assay. An immunofluorescence analysis showed that the wild-type NEIL1 protein, but not the truncated protein encoded by the abnormal transcript arising from the c.936G > A mutation, was localized in the nucleus, suggesting that the truncated protein is unlikely to be capable of repairing nuclear DNA. An expression analysis revealed that NEIL1 mRNA expression was reduced in six of 13 (46%) primary gastric cancer specimens that were examined. These results suggest that low NEIL1 activities arising from mutations and reduced expression may be involved in the pathogenesis in a subset of gastric cancers.