胰腺癌组织SPARC基因CpG岛甲基化状态及临床意义

目的 检测胰腺癌SPARC基因CpG岛的甲基化状态及其与临床病理参数的关系.方法 收集17例胰腺癌及相应癌旁组织、6例CP和6例正常胰腺组织以及6例健康成人外周血液标本,抽提DNA,进行亚硫酸氢盐修饰,然后行甲基化特异性PCR,检测SPARC基因第一外显子区CpG岛的甲基化状态,并分析与肿瘤病理参数的关系.结果 健康人外周血白细胞DNA中SPARC基因第一外显子区CpG位点均无甲基化.正常胰腺、CP、胰腺癌及相应癌旁组织SPARC基因第2、3、4、5、6、7 CpG位点的甲基化率分别为61.6%、47.1%、37.5%、24.7%;第1,8、9、10、11、12 CpG位点的甲基化率分别为52.0%、28.7%、16.7%和0.胰腺癌SPARC基因甲基化率与正常胰腺、CP比较均差别非常显著(P＜0.001),与相应癌旁组织比较差别不显著.胰腺癌SPARC基因CpG岛甲基化与患者性别、年龄、危险诱因(如长期吸烟或饮酒、CP)、肿瘤大小、分化程度、TNM分期、淋巴结转移等均无显著差异.结论 胰腺癌SPARC基因第一外显子区CpG岛为高甲基化状态,可能为胰腺癌发生、发展的早期事件.

The characteristic and clinical value of SPARC CpG island methylation in pancreatic adenocarcinoma tissue

Objective To assess the methylation patterns in CpG islands of SPARC genes and its relationship with clinicopathological parameters. Methods Bisulfite treatment of genomie DNA and sequencing analysis was used to study methylation patterns in the CpG islands of SPARC genes in fresh tissues from 6 cases of chronic pancreatitis, 6 normal pancreatic tissues, 17 pancreatic adenocarcinoma and the cancer adjacent tissues, as well as 6 normaI blood samples for normal control, and compared the results with clinicopathological parameters. Results WBC DNA showed no methylation of SPARC gene CpG islands. The methylation rates in CpG islands of SPARC genes in pancreatic adenocarcinoma, the cancer adjacent tissues, chronic pancreatitis and normal pancreatic groups (2, 3, 4, 5, 6, 7 CpG sites) were 61.6%, 47.1%, 37.5%, 24.7%, respectively. The methylation rates in CpG islands (1, 8, 9, 10, 11, 12 sites) were 52.0%, 28.7%, 16.7% and 0. The difference were statistically significant between the pancreatic adenocarcinoma and chronic pancreatitis as well as normal pancreas groups (P＜0.001), and the difference were not statistically significant between the pancreatic adenocarcinoma and the cancer adjacent tissues. CpG hypermethylation were not related to risk factors such as smoking, alcohol, history of CP, the tumor size, differentiation and TNM staging, lymph node metastasis. Conclusions CpG in SPARC gene extron 1 was hypermethylated in pancreatic cancer, and this may be an early event in the development of pancreatic cancer.