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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.
RESUMO
Background and purpose:DNMT3B has nearly 40 known splice variants expressed in a tissue-and disease-speciifc manner, but the roles of these splice variants in the cell are still unclear. The aim of this study was to investigate the effects of overexpression of DNA methyltransferase 3B4 (DNMT3B4) gene on proliferation of human embryo kidney 293A cells. Methods:293A cells were transfected with plasmid pCMV-DNMT3B4 or pCMV-2B and then treated with G418 to get the stable cell line. The stable cell lines were determined for proliferation level by MTT method, and for cell cycle distribution by lfow cytometry. The expression of p21 was detected by real-time PCR and Western blot. The methylation status of p21 gene promoter was detected by methylation-speciifc PCR (MS-PCR). Results:The absorbance value in DNMT3B4-1 and DNMT3B4-2 clone were (58.92±3.47)%and (68.82±5.64)%as compared to 293A-vector cells using MTT method. DNMT3B4 overexpression signiifcantly decreased cell proliferation (P<0.05). S phase fraction of 293A-vector cells was (40.44±0.91)%. While in DNMT3B4-1 and DNMT3B4-2 clone cells, the S phase fraction was (35.88±2.00)%and (37.00±1.79)%respectively. Overexpression of DNMT3B4 could significantly decrease S phase fraction (P<0.05). The expression of p21 in DNMT3B4 overexpressed cells was increased, but the methylation status of p21 gene promoter was unchanged.Conclusion:Overexpression of DNMT3B4 can inhibit 293A cell proliferation and can facilitate p21 expression.