No synergism on cell death. (A) Bcl2 expression. A549 or H2009 cells were transfected with 20 nM precursors and harvested 42 h post-transfection. Western blot analysis was performed using a monoclonal antibody against Bcl2. Protein levels were normalized to α-tubulin and presented relative to the level obtained for the control. (B) Time-course of propidium iodide (PI)-positive A549 and H2009 cells by flow cytometry. Cells were transfected with concentrations of precursors as indicated in the legend to Fig. 4B (n = 3). Cells were gated as shown in Additional file 1A. (C) Cleaved caspase-3-positive cells. H2009 cells were analysed for the presence of cleaved caspase 3 by flow cytometry 72 h post-transfection (n = 3). Values are relative to the level obtained for the control transfected with precursor control. As a positive control, cells were treated with UV.