Abstract: Objective To investigate the effect of stable knockdown of DNA methyltransferase 3b (DNMT3b) on the proliferation
and apoptosis of bladder cancer cells. Methods Lentivirus 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.
Results The 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. Conclusion Stable 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.