Inhibition of cell proliferation by an expressed EN-T endonuclease. A series of U2OS and HFL-1 cells were planted in 12 well plates (3 × 105 per well). We added recombinant adenovirus to 1 ml medium at low concentrations of 4.4 × 105 pfu/ml (a), (c) or 8.8 × 105 pfu/ml (b), (d). Cell growth curves for U2OS (a), (b) and HFL-1 (c), (d) are shown (bar: ± standard deviation, n = 4). Numbers of cells at 3 days after infection are indicated as 1.0. EN-T expressing HFL-1 cell cultures died by day 17.