In vitro oncolytic potency and selectivity of Ad5/3-9HIF-Δ24-VEGFR-1-Ig. Renal cancer cells (a and b), fibroblast (c) and HUVEC (d) were infected with indicated viruses at different concentrations for 1 h. Medium was changed and cells were incubated for 8–11 days before cell viability was measured. Ad5/3-9HIF-Δ24-VEGFR-1-Ig was as potent as the unarmed Ad5/3-9HIF-Δ24-E3 in kidney tumor cells. Both the new viruses were more potent than wild-type adenovirus. On fibroblasts, both new viruses were more selective than the highly potent Ad5/3-Δ24. HUVECs were analyzed because they need VEGF for survival and, therefore, are sensitive to VEGFR-1-Ig. Demonstrating the rigorous control of transgene expression in Ad5/3-9HIF-Δ24-VEGFR-1-Ig, minimal toxicity was seen. Bars, standard error.