BACKGROUND: To compare efficacy and toxicity of the human cytomegalovirus-immediate-early (CMV) promoter and the Rous-sarcoma-virus (RSV) promoter to express thymidine kinase (tk) for adenovirus-mediated suicide gene therapy of experimental bladder cancer in vivo and in vitro. MATERIALS AND METHODS: In vitro: 3 human (5637, RT-4 and TCC-SUP) and one murine (MBT-2) bladder cancer cell line were exposed to ADV/RSV-tk or ADV/CMV-tk vectors and cell survival was determined. In vivo: Subcutaneous tumors were established and adenovirus vectors were injected 10 days later. RESULTS: In vitro: ADV/CMV-tk was up to 4 times more potent in terms of cell killing than ADV/RSV-tk. In vivo: ADV/CMV-tk had a three-fold higher antitumor potency per viral particle as compared to ADV/RSV-tk. Higher doses of ADV/CMV-tk caused treatment-associated hepatotoxicity. CONCLUSIONS: Our results confirm the efficacy of adenovirus-mediated tk suicide gene therapy in the treatment of experimental bladder cancer. Dose-related toxicity was greater with the use of ADV/CMV-tk, but lower doses achieved the same efficacy as ADV/RSV-tk.
