Figure 4

Cell survival studies after prodrug treatment and infection. Cells were infected with a low multiplicity of infection of 0.05 or mock infected and treated with 10 nM prodrug. Non-prodrug-treated cells served as the control. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)-assays on days 3 and 7 post-infection. On day 3 post-infection, no significant difference in cell viability between the different samples was observed. Combined treatment of cells with GLV-1h68 and prodrug induced a significantly higher tumor cell kill 7 days post-infection compared with infection with GLV-1h68 alone. Although prodrug treatment alone as well as rVACV treatment alone had inhibitory effects when compared with untreated cells (significance not shown), only simultaneous treatment of cells with GLV-1h68 and prodrug contributed to strong synergistic effects and the most efficient cell killing (inset, showing survival of prodrug-treated vs corresponding untreated cells). In each chart, average plus standard deviation (n=3) is shown. Asterisk indicates statistical significance (P<0.05). PBS, phosphate-buffered saline.