中文摘要：

目的 探讨DNA甲基转移酶（DNMTs）在肝癌中的表达及其临床意义.方法 收集2007年7月至2008年4月中山大学附属第一医院行根治性切除的50例肝癌患者的肝癌组织、癌旁组织、肝硬化组织和慢性肝炎组织.采用RT-PCR和免疫组织化学方法检测肝癌组织及癌旁组织中DNMT1、DNMT3a、DNMT3b mRNA与蛋白表达水平,采用配对t检验和Mann-Whitney U检验比较肝癌组织与癌旁组织,肝硬化组织与慢性肝炎组织DNMTs mRNA表达的差异,x2检验和Fisher确切概率法分析肝癌组织DNMTs蛋白表达与临床病理因素的相关性,Kaplan-Meier法分析患者无瘤生存时间,不同患者无瘤生存时间的比较采用Log-rank检验.结果 肝癌组织中DNMT1、DNMT3a、DNMT3b mRNA的表达水平分别为癌旁组织的2.57、2.29和4.86倍（t=3.94,2.72,4.06,P＜0.05）.肝癌组织中DNMT1、DNMT3a、DNMT3b mRNA的表达分别是肝硬化组织和慢性肝炎组织的2.38、2.14、4.66倍和6.12、4.58、12.99倍.DNMT1、DNMT3a、DNMT3b mRNA在肝癌组织的表达显著高于其在肝硬化组织和慢性肝炎组织中的表达（U=587.5、730.0、562.5,65.5、64.5、71.0,P＜0.05）.DNMT1蛋白表达与肿瘤大小、数目、有无血管侵犯、TNM分期有关（x2=5.24,4.08,4.08,14.13,P＜0.05）;DNMT3a蛋白表达与肿瘤大小、数目、TNM分期有关（x2=4.08,5.95,4.08,P＜0.05）.DNMT1和DNMT3a低表达者平均肿瘤复发时间分别为9.4个月和8.7个月,显著长于高表达者的5.0个月和3.2个月,两者比较,差异有统计学意义（x2=3.89,9.91,P＜0.05）.结论 DNMTs在肝癌发生、发展中起重要作用;DNMT1与DNMT3a高表达与肿瘤切除术后复发密切相关,可望成为肝癌预后的重要预测因子.

英文摘要：

Objective To investigate the expression of DNA methyltransferases （DNMTs） in liver cancer and its clinical significance. Methods The specimens of liver cancer tissues, adjacent tissues, cirrhotic tissues and chronic hepatitis tissues were collected from 50 patients who received radical resection at the First Affiliated Hospital of Sun Yat-Sen University from July 2007 to April 2008. The mRNA and protein expressions of DNMT1,DNMT3a and DNMT3b in liver cancer tissues, adjacent tissues, cirrhotic tissues and chronic hepatitis tissues were detected by real-time quantitative PCR and immunohistochemical staining. The mRNA expression of DNMTs in the liver cancer tissues was compared with those in the adjacent tissues, cirrhotic tissues and chronic hepatitis tissues by using t test and Mann-Whitney U test. The correlation between the protein expression of DNMTs in the liver cancer tissue and the clinicopathological features was analyzed by chi-square test or Fisher exact test, and the tumor-free survival time was analyzed by using Kaplan-Meier method and the difference in tumor-free survival rate between different patients was analyzed by Log-rank test. Results The mRNA expressions of DNMT1, DNMT3a and DNMT3b in the liver cancer tissue were 2.57, 2.29 and 4.86 times higher than those in the adjacent tissues （t = 3.94, 2. 72, 4. 06, P ＜ 0.05 ）. The mRNA expressions of DNMT1, DNMT3a and DNMT3b were 2.38,2.14 and 4.66 times higher than those in the cirrhotic tissues, and 6.12, 4.58 and 12.99 times higher than those in the chronic hepatitis tissues. The mRNA expressions of DNMT1, DNMT3a and DNMT3b in the liver cancer tissue were significantly higher than those in the cirrhotic tissues and chronic hepatitis tissues （ U = 587.5,730. 0,562.5; 65.5, 64.5, 71.0, P ＜ 0.05）. The protein expression of DNMT1 was correlated with the size, number,TNM stages and vascular invasion of tumors （ x2 = 4.08, 5.95, 4.08, P ＜ 0.05 ）. The protein expression of DNMT3a was correlated with the size, number and TNM stages of tu