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目的:探讨atrogin-1基因在贲门腺癌(gastric cardia adenocarcinoma,GCA)中的异常甲基化及表达,并分析其临床意义。方法:选用河北医科大学第四医院2004—2008年间的贲门腺癌患者手术标本共139例,分别应用亚硫酸氢盐转换-甲基化特异性PCR(bisulfite conversion-methylation specific polymerase chain reaction,BS-MSP)、RT-PCR和免疫组织化学法检测贲门腺癌组织及相应癌旁(距癌灶边缘3~5 cm)组织中atrogin-1基因的甲基化、mRNA和蛋白表达情况,应用免疫组织化学法检测相应组织中Smad4蛋白的表达。结果:贲门腺癌组织中atrogin-1基因启动子区的甲基化率[44.6%(62/139)]显著高于癌旁组织[3.6%(5/139)](χ2=63.891,P=0.001),且atrogin-1基因的甲基化与TNM分期及肿瘤的组织学分化程度密切相关(χ2=6.144,P<0.05)。贲门腺癌组织中atrogin-1基因的mRNA和蛋白表达水平显著低于癌旁组织[(0.482 5±0.175 4)vs(0.896 9±0.290 1),t=10.62,P=0.01;34.5%vs 82.0%,χ2=4.441,P=0.001],且与其启动子区的甲基化状态之间有明显的相关性(r=-0.256,P=0.001)。贲门腺癌组织中Smad4蛋白表达的阳性率显著低于癌旁组织(46.0%vs95.7%;χ2=2.945,P=0.001),且与atrogin-1蛋白表达之间呈明显的正相关(r=0.604,P=0.001)。结论:Atrogin-1基因启动子区高甲基化导致的基因沉默可能是贲门癌组织中此基因表达降低的机制之一。
Objective: To investigate the abnormal methylation and expression of atrogin-1 gene in gastric cardia adenocarcinoma (GCA) and analyze its clinical significance. METHODS: A total of 139 surgical specimens of patients with cardiac adenocarcinoma from 2004 to 2008 in the Fourth Hospital of Hebei Medical University were selected for their application. Bisulfite conversion-methylation specific polymerase chain reaction (BS- MSP), methylation, mRNA and protein expression of atrogin-1 gene in gastric cardia adenocarcinoma tissues and its corresponding adjacent tissues (3 ~ 5 cm away from the edge of the lesion) were detected by RT-PCR and immunohistochemistry. Immunohistochemistry The expression of Smad4 protein in the corresponding tissues was detected by chemical method. Results: The methylation rate of atrogin-1 gene promoter region in gastric cardia adenocarcinoma (44.6%, 62/139) was significantly higher than that in paracancerous tissues (3.6%, 5/139) (χ2 = 63.891, P = 0.001). Methylation of atrogin-1 gene was closely related to TNM staging and tumor histological differentiation (χ2 = 6.144, P <0.05). The mRNA and protein expression of atrogin-1 in gastric cardia adenocarcinoma was significantly lower than that in paracancer tissues [(0.482 5 ± 0.175 4) vs (0.896 9 ± 0.290 1), t = 10.62, P = 0.01; 34.5% vs 82.0 %, χ2 = 4.441, P = 0.001], and there was a significant correlation between methylation status of its promoter region (r = -0.256, P = 0.001). The positive rate of Smad4 expression in gastric cardia adenocarcinoma was significantly lower than that in paracancerous tissues (46.0% vs95.7%; χ2 = 2.945, P = 0.001), and positively correlated with atrogin-1 protein expression = 0.604, P = 0.001). CONCLUSION: Gene silencing induced by hypermethylation of Atrogin-1 promoter region may be one of the mechanisms of decreased gene expression in cardia cancer.