Abstract: Objective: To investigate the expression of the Smac gene in bladder cancer cells after transfection of apcDNA3.1 vector containing the Smac gene controlled by the UpIb promoter and to observe its effect on bladder cancer cell growth. Methods: Human bladder cancer-derived BIU-87 cells were inoculated into male Balb/c-nu/nu mice subcu-taneously to establish a nude mouse model with bladder cancer. When the injected cells formed a mass that reached a di-ameter of 0.5 cm, a mixture of liposome and pcDNA3-UpIb promoter-Smac was injected into the tumor in vivo once everyother day for 5 days. On days 2 through 4 we induced apoptosis of cancer cells with daily injections of Mitomycin C intothe tumor. There were 3 groups in the study: group 1 was treated with the mixture of liposome and pcDNA3.1-UpIb pro-moter-Smac, group 2 was treated with Mitomycin C, and group 3 was not given any treatment. The expression of SmacmRNA was measured by RT-PCR. The expression of Smac protein was detected by immunohistochemistry. Apoptosis of cancer cells was observed by H&E staining, DNA ladder analysis and TUNEL-Fluorescence. Results: The nude mousemodel for bladder cancer was successfully established. After intratumoral injection of the liposome and pcDNA3.1-UpIbpromoter-Smac mixture, the expression of Smac in the tumors increased 2.1-fold. Apoptosis of the bladder cancer cellswas observed in the group treated with the vector combined with Mitomycin C and in the group treated with only Mito-mycin C. The apoptosis ratio was 49.8% in the combination group and 23.5% in the mitomycin C alone group. Conclu-sion: Direct injection of the pcDNA3.1-UpIb promoter-Smac construct into human bladder cancer in nude mice cancause a detectable increase in the expression of the Smac gene in the tumors. This increase subsequently promotes apop-tosis which was increased further with the injection of Mitomycin C. Our research lays the foundation for the clinical ap-plication of pcDNA3.1-UpIb promoter-Smac combined with apoptosis-inducing reagents such as Mitomycin C.