Figure 1.

Synergistic cytotoxic effects of vaccinia (VVDD) and VSVΔ51 combination treatment on various cancer cell lines. (a) HT29, 786-O or SKOV-3 were left untreated or treated with VVDD-eGFP [0.1 multiplicity of infection (MOI)] for 2 hours, or with VSVΔ51DsRed (0.0001 MOI HT29, SKOV-3; 0.1 for 786-O) for 45 minutes, or in combination, VVDD for 2 hours and 4 hours later with VSVΔ51 during 45 minutes. Enhanced green fluorescent protein (eGFP) (VV) and DsRed (VSV) fluorescence were detected 48 hours after VSVΔ51 infection. One of three independent experiments. (b) 72 hours after VSVΔ51 infection, viral oncolytic effect was assessed by a crystal violet assay. One of three independent experiments. (c) VSV titers were determined 48 hours after infection. Mean ± SEM from three independent experiments. (d) Isobologram analysis: 786-O cells were treated with serial dilutions of VVDD followed by VSV. Cytotoxicity was assessed using alamar blue reagent after 72 hours. Combination indexes (CIs) were calculated using Calcusyn software according to the method of Chou and Talalay. Plots represent the algebraic estimate of the CI in function of the fraction of cells affected (F_a). Error bars: mean ± SEM. One of two independent experiments in quadruplicate.