Figure 4.

Functionality and efficacy of FCU1 expressed by deVV5. (a) Conversion of 5-fluorocytosine (5-FC) to 5-fluorouracil (5-FU) and release of 5-FU in the cell culture supernatant. HCT 116 cells were infected with the indicated vector at a MOI of 10^–5 and then incubated with 0.1 mM 5-FC from day 2 to day 5 post infection. The relative concentration of 5-FC and 5-FU in the culture supernatant was measured by HPLC. The results are expressed as the percentage of 5-FU released relative to the total amount of 5-FC + 5-FU. Each data point represents the mean of triplicate determinations ± SD. (b) In vitro sensitivities of infected human tumor cells to 5-FC. HCT 116 human tumor cells were mock-infected or infected with deVV5 and deVV5-fcu1 at a MOI of 10^–5. After 48 h, cells were treated by increasing concentrations of 5-FC. Cell survival was determined 3 days later as described in Materials and Methods section. Cell viability results are expressed as the percentage of viable cells in the presence and absence of the prodrug. Values are represented as mean ± SD of triplicate determinations.