Figure 2. Synergistic cell killing with a replication-defective virus expressing the small AdE1A12S protein, in combination with cytotoxic drugs.

A) Isobolograms generated from EC₅₀ values for combinations of the AdE1A12S mutant with mitoxantrone (Mit) or docetaxel (Doc) at four constant ratios (0.5. 2.5, 12.5 and 62.5 ppc/nM drug) in PC-3 and DU145 cells. The straight lines represent the theoretical values for additive effects and points below the line synergistic cell killing, one representative study (n = 3–4). B) Characterization of replication of the AdE1A12S, AdE1A1102, AdE1A1108 and AdE1A1104 mutants in PC-3, DU145 and 22Rv1 cells. Levels of viral replication determined by the limiting dilution assay (TCID₅₀) for replicating and replication-defective mutants with identical E1A-deletions except for the additional deletion of the CR3-domain in E1A12S. Cells were infected with each mutant at 100 ppc and harvested 72 h later, averages ±SD, n≥3. The non-replicating AdGFP mutant was used as a control in all assays, *p<0.001 for the replicating compared to the corresponding replication-defective mutant (t-test). C) qPCR analysis of cells infected as described for the replication assays and harvested 24, 48 and 72 h later. Total copy number at each time point was normalised to the copy numbers detected 3 h after infection in 10 ng of total DNA, averages ± SEM, n = 2–3. D) Viral replication in normal human primary bronchial epithelial cells (NHBE) determined by TCID₅₀ for Ad5wt, dl1102 and dl1104 mutants infected at 100 ppc, n = 3, *p<0.005.