Figure 1. Effect of continuous treatment with MMC on cell cycle, apoptosis and EdU incorporation. (A) Exponentially growing A549 cells were left untreated (Control) or were continuously exposed to 0.1–2.0 µg/ml MMC for up to 72 h. A) DNA content frequency histograms; the arrow indicates objects with fractional DNA content (sub-G₁), likely apoptotic cells. (B) Percentage of cells in respective phases of the cell cycle. The S_T and G₂M_T/G₁O represent cells at a higher DNA ploidy. (C) Percent of cells expressing activated (cleaved) caspase-3. (D) Exponentially growing cells untreated (Control) or treated with 0.1–2.0 µg/ml MMC for 24 h were exposed to EdU for 1 h. On these bivariate (DNA content vs EdU incorporation) distributions the cells above the dashed (threshold) line are positive for EdU. The percent of cells with an S-phase DNA content that show evidence of EdU incorporation (above the threshold) is shown in each panel.