Suicide Gene Therapy for Bladder Cancer Using a Recombinant Adenovirus Expressing Escherichia Coli Cytosine Deaminase

Abstract

Purpose: The poor prognosis of advanced bladder cancer requires the investigation of novel treatment modalities. In this study, we investigated the suicide gene therapy for bladder cancer, using the adenovirus-mediated expression of Escherichia coli cytosine deaminase(CD) in conjunction with the prodrug 5-fluorocytosine(5-FC). Materials and Methods: A replication-deficient recombinant adenovirus, which contains the Rous sarcoma virus(RSV) promoter driving the expression of CD,(Ad-RSV-CD) was constructed. In vitro cell-killing assay, using Ad-RSV-CD(20 MOI) plus 5-FC(500mug), was performed in bladder cancer cell lines, HT-1376, UM-UC-3 and NBT-II. The CD enzymatic activity was measured in the Ad-RSV-CD(20 MOI) infected cells, and the concentrations of 5-fluorouracil(5-FU) yielding an IC50 were calculated for those cells. Results: 5-FU dose response curve showed that IC50 of NBT-II was 0.8mug, HT-1376 1.0mug and UM-UC-3 5.1mug at day 6. The CD enzymatic activities of the Ad-RSV-CD infected UM-UC-3, HT-1376 and NBT-II cells were 5696, 4655, 1766 pmole/1x106 cells, respectively. Whereas the administration of 5-FC(500mug) or Ad-RSV-CD(20 MOI) alone demonstrated no cytotoxicity to cells, Ad-RSV-CD/5-FC exhibited a significant cytotoxic effect in the cells, especially the UM-UC-3 and HT-1376. Conclusions: Ad-RSV-CD/5-FC suicide gene therapy is effective for bladder cancer cells in cell cultures, suggesting this approach may have potential as a strategy for the treatment of bladder cancer.