胆管癌p53-bax线粒体凋亡通路的甲基化研究

目的探讨胆管癌p53-bax线粒体凋亡通路中多个基因的甲基化状态及其在胆管癌发生过程中的意义。方法采用甲基化特异性聚合酶链反应（MSP），对胆管癌组织和癌旁组织中的p14^ARF、DAPK和TMS1／ASC基因启动子的甲基化状态进行检测，并对胆管癌组织中p53基因外显子5～8进行DNA序列分析。结果36例胆管癌组织标本中，有24例（66．7％）至少存在1个抑癌基因的甲基化，其中p14^ARF、DAPK和TMS1／ASC基因甲基化的比率分别为25．0％、30．6％和36．1％；癌旁组织中，有5例（13．9％）存在抑癌基因的甲基化，其中TMS1／ASC3例（8．3％），DAPK2例（5．6％）。36例胆管癌组织标本巾，有22例（61．1％）存在p53基因的突变。p53突变伴1个以上抑癌基因甲基化者共14例，占38．9％，其发生率与胆管癌的病理类型、分化程度和浸润深度有关（P〈0．05）。结论p53-bax线粒体凋亡通路中，DNA甲基化是胆管癌中常见的分子事件。癌旁组织中，DAPK和TMS1／ASC基因的甲基化率虽然较低，但可能有早期诊断意义。p53突变伴抑癌基因的甲基化与胆管癌的病理生物学行为有关，并趋向于较高的恶性程度。

The study on DNA methylation of p53-bax mitochondrial apoptosis pathway in cholangiocarcinoma

Objective To investigate the clinical significance of gene methylation of p53-bax mitochondrial apoptosis pathway in the carcinogenesis of cholangiocarcinoma. Methods Promoter hypermethylation of DAPK, P14ARF and ASC genes were detected by methylation-specific PCR. Exon 5-8 of p53 gene were examined by automatic sequencing. Results It was found that 66.7% of 36 cholangiocarcinoma patients had methylation of at least one tumor suppressor gene. The rate of tumor suppressor gene methylation in these cholangiocarcinomas was 25.0% in P14FRF, 30.6% in DAPK and 36.1% in TMS1/ASC. The methylation rate of tumor suppressor gene in tissues adjacent to the cancer tissue was 13.9% including 5.6% in DAPK and 8.3% in TMS1/ASC. p53 gene mutation was detected in 22 of 36 patients(61.1%). Fourteen patients (38.9%)was found to have p53 gene mutation associated with the methylation of tumor suppressor gene. The rate of p53 gene mutation and methylation of tumor suppressor gene were statistically and significantly correlated with the features of tumor biology including differentiation and invasion (P< 0.05). Conclusion DNA methylation of p53-bax mitchondrial apoptosis pathway may be a frequent molecular event in the carcinogenesis of cholangiocarcinoma. Although the methylation rate of ASC, DAPK genes is relatively low, it may be helpful for early diagnosis, p53 gene mutation associated with the methylation of tumor suppressor genes may be correlated with tumor malignant biologic features.