Our aim was to evaluate the feasibility and efficacy of tumor necrosis factor-alpha gene therapy in preventing bladder tumor recurrence using an orthotopic model of bladder cancer. We transiently transfected a murine bladder cancer cell line MB49 with pBud-TNF-alpha using a transfection system consisting of the cationic liposome N-(1-(2,3-dioleoyloxyl)propyl)-N,N,N-trimethylammoniummethyl sulfate (DOTAP) plus methyl-beta-cyclodextrin solubilized cholesterol (MBC). MB49 cells produced 893.7+/-24.0 pg/ml of TNF-alpha 2 days after transfection. Cell growth was inhibited, apoptosis was induced and MHC class I, B7.1 and Fas expression on the MB49 cells were increased. In vivo, an orthotopic murine bladder cancer model was established by intravesical instillation of bladder cancer cells after transurethral cauterization of the mouse bladder mucosa. TNF-alpha gene transfer was initiated 2 days after the tumor inoculation, when the tumor burden was small, and given twice per week for 3 weeks. RT-PCR showed TNF-alpha mRNA was observed to increase after the first instillation and then return to basal level 1 month after the sixth instillation. Histology revealed that TNF-alpha gene transfer decreases the bladder tumor incidence from 75% for the control group to 25% for the treated group. Increased level of T lymphocytes and NK cells was found in the TNF-alpha transfected bladders. In situ cytokine gene transfer provides significant protection against tumor growth. This approach may be useful to reduce the incidence of a subsequent tumor after endoscopic resection when used for prophylaxis.

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