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 control tissue. Additionally, Alu was hypomethylated in ccRCC tissue (0.106±0.04) compared with control tissue (0.115±0.03) (P < 0.05). Furthermore, the methylation of the promoter for RASSF1A, a tumor-suppressor gene, moderately increased in renal cell carcinoma tissue. By contrast, RASF1A expression decreased.

  Conclusion  DNMT3B4 overexpression may play an important role in human kidney tumorigenesis via chromosomal instability and the decreased expression of RASSF1A.