Department of Gastroenterology, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai Institute of Digestive Disease, Shanghai, China.
J Dig Dis. 2010 Dec;11(6):343-51. doi: 10.1111/j.1751-2980.2010.00459.x.
To analyze the expression and aberrant methylation of X-ray repair cross-complementing gene 1 (XRCC1) in gastric carcinogenesis, and identify the molecular mechanism of gastric carcinogenesis.
The method based on methyl binding domain protein (MBD) immuno-precipitation and promoter microarray was employed to screen the gastric cancer-related methylation-sensitive gene. An immunohistochemistry assay was applied to detect the protein expression of XRCC1 in the multistep progression of gastric carcinogenesis. The mRNA expression of XRCC1 was determined by real-time PCR in tumor tissues and their corresponding non-tumorous tissues. The methylation status and Arg194Trp and Arg399Gln polymorphisms of XRCC1 in gastric cancer and gastritis tissues were analyzed by methylation-specific PCR, bisulfite genomic sequencing and direct DNA sequencing, respectively.
Promoter microarray screening and identification suggested that XRCC1 was a methylation-sensitive gene. Immunochemistry results showed that XRCC1 protein expression gradually decreased with progression of gastric mucosal lesions (P < 0.05). The positive rate of XRCC1 in patients with well/moderately differentiated gastric cancer was significantly higher than patients with poorly differentiated gastric cancer (P < 0.05). The mRNA expression of XRCC1 in gastric cancer tissues was significantly lower than that in the non-tumorous tissues (P < 0.05). Meanwhile, XRCC1 methylation in gastric cancer tissues was more frequent than that in the gastritis tissues (P < 0.05), and the downregulation of XRCC1 expression was relevant to methylation (P < 0.05).
The expression of XRCC1 is downregulated in gastric carcinogenesis, and promoter hypermethylation may be one of the mechanisms contributing to its downregulation.
分析 X 射线修复交叉互补基因 1（XRCC1）在胃癌发生过程中的表达和异常甲基化，鉴定胃癌发生的分子机制。
采用甲基结合域蛋白（MBD）免疫沉淀和启动子微阵列方法筛选与胃癌相关的甲基化敏感基因。应用免疫组织化学方法检测 XRCC1 蛋白在胃癌发生多步过程中的表达。实时定量 PCR 检测肿瘤组织及其相应非肿瘤组织中 XRCC1 的 mRNA 表达。采用甲基化特异性 PCR、亚硫酸氢盐基因组测序和直接 DNA 测序分别分析 XRCC1 基因在胃癌和胃炎组织中的甲基化状态以及 Arg194Trp 和 Arg399Gln 多态性。
启动子微阵列筛选和鉴定提示 XRCC1 是一个甲基化敏感基因。免疫组织化学结果显示，随着胃黏膜病变的进展，XRCC1 蛋白表达逐渐降低（P < 0.05）。XRCC1 在高分化和中分化胃癌患者中的阳性率显著高于低分化胃癌患者（P < 0.05）。胃癌组织中 XRCC1 的 mRNA 表达明显低于非肿瘤组织（P < 0.05）。同时，胃癌组织中 XRCC1 甲基化较胃炎组织更为频繁（P < 0.05），且 XRCC1 表达下调与甲基化相关（P < 0.05）。
XRCC1 在胃癌发生过程中表达下调，启动子异常甲基化可能是其下调的机制之一。
