DNA甲基转移酶3B4过表达与肾透明细胞癌的关系

  目的  探究DNA甲基转移酶（DNA methyltransferase，DNMT）在肾透明细胞癌（clear cell renal cell carcinoma，ccRCC）发生发展中的机制。  方法  收集2012年1月至12月15例内蒙古科技大学包头医学院第一附属医院术前均未结予放化疗并行肾癌根治术患者的组织标本，均经病理证实为ccRCC。应用实时定量PCR、蛋白印迹、联合亚硫酸氢钠限制酶分析法和甲基化特异PCR等方法检测ccRCC组织中DNMT的mRNA表达，及ccRCC组织中整体甲基化（global methylation）水平和抑癌基因RASSF1A甲基化和表达水平。  结果  ccRCC组织中DNMT3B4的mRNA表达增加，同时其蛋白含量也相应增加。ccRCC患者癌组织中DNA重复序列Alu的甲基化水平0.106±0.04较癌旁组织中0.115±0.03低，差异具有统计学意义（P < 0.05）。而肿瘤抑制基因RASSF1A启动子区域发生高甲基化，其mRNA和蛋白的表达均降低。  结论  DNMT3B4基因过表达可能与染色体不稳定以及RASSF1A基因低表达有关，在ccRCC的发生发展中可能扮演着重要的角色。 

Relationship between the overexpression of DNA methyltransferase 3B4 and clear cell renal cell carcinoma

Objective:To determine the molecular role of DNA methyltransferase (DNMT) in kidney tumorigenesis. Methods:Tissue samples consisted of 15 cancer tissues and 15 matched adjacent tissues from clear cell renal cell carcinoma (ccRCC) patients who had undergone nephrectomy in 2012 at the First Affiliated Hospital of Baotou Medical College, Science and Technology University of Inner Mongolia were collected. Real-time PCR, Western blot, combined bisulfite restriction analysis (COBRA) and methylation specific PCR were used in this study. Real-time PCR was used to examine the mRNA expression levels of DNMT. The global methylation level, DNA methylation level, and the expression of the antioncogene RASSF1A in ccRCC tissues were concurrently detected. Results:Both mRNA and protein levels of DNMT3B4, a splice variant of DNMT3B, were elevated in renal cell carcinoma tissue compared with those in con-troll tissue. Additionally, Alu was hypomethylated in ccRCC tissue (0.106±0.04) compared with control tissue (0.115±0.03) (P<0.05). Fur-thermore, the methylation of the promoter for RASSF1A, a tumor-suppressor gene, moderately increased in renal cell carcinoma tis-sue. By contrast, RASF1A expression decreased. Conclusion:DNMT3B4 overexpression may play an important role in human kidney tu-morigenesis via chromosomal instability and the decreased expression of RASSF1A.