A) Adenovirus wild type 5 (Ad5tg) and the respective mutants with the E1B19K (AdΔ19K), the E1ACR2 (AdΔCR2) or both gene-regions deleted (AdΔΔ) were generated. All mutants had intact E3-region. B) Cell-killing efficacy determined as EC50 values in PC3, DU145, 22Rv1 and LNCaP prostate, PT45 and Suit2 pancreatic, and H460 lung carcinoma cell lines with Ad5tg, AdΔ19K, AdΔCR2 and AdΔΔ viruses. The decreases in EC50 values are presented as percentages of the EC50 for wild type Ad5tg, averages ±SEM, n ≥ 3, * p < 0.05.