OBJECTIVETo investigate the effect of stable knockdown of DNA methyltransferase 3b (DNMT3b) on the proliferation and apoptosis of bladder cancer cells.

METHODSLentivirus expressing DNMT3b siRNA or the negative control siRNA was infected in human bladder cancer BIU-87 cells. MTT assay and flow cytometry were used to detect cell proliferation and apoptosis, respectively. The inhibitory effect of DNMT3b knockdown on xenograft tumors in nude mice was observed. Real-time PCR and Western blotting were carried out to investigate the expression level of cell apoptosis related genes. Methylation specific PCR was used to examine the methylation in the promoter region of the cell apoptosis related genes.

RESULTSThe results of real-time PCR and Western blotting showed that DNMT3b mRNA and protein level were stably knocked down in BIU-87 cells. Stable DNMT3b knockdown suppressed BIU-87 cell growth and the tumor formation ability of the cells in nude mice. DNMT3b knockdown promoted the apoptosis of BIU-87 cells, increased the mRNA and protein expression of the cell growth and apoptosis related genes including DAPK, Bax and RASSF1A, and significantly decreased the methylation of these genes.

CONCLUSIONStable DNMT3b knockdown can affect the methylation of the cell growth and apoptosis related genes to regulate their expression, which might be a possible mechanism for suppressed cell growth and enhanced apoptosis of BIU-87 cells.