Typical figures analyzing Annexin-V-FITC binding and propidium iodide (PI) staining for MCF-7 and MDA-MB-231 cells treated with gemcitabine, nsPEFs and combinations. Experiments were carried out as described in Methods and shown with GEM alone (0.38 µM), nsPEF alone at indicated electric fields and GEM after treatment with nsPEFs. Panel A shows an experiment with MCF-7 cells and panel B show an experiment with MDA-MB-231 cells. Cell populations are shown in quadrants with Annexin-V-FITC levels indicated on the X-axis and PI staining indicated on the Y-axis. Cells with Annexin-V-FITC labeling only are considered apoptotic (lower right quadrant) and cells with Annexin-V-FITC and PI labeling are considered necrotic (upper right quadrant). Synergism quotients are shown for each cell death type in the respective quadrants. A typical experiment is shown for each cell line.