Fig. 4

Effect of cetuximab and trastuzumab on the cell death of tumor cells expressing EGFR and/or HER-2. Target tumor cells were stained with annexin V/propidium iodide (PI) to analyze apoptosis of cells after culture of the cells in complete medium containing 10 μg/ml of cetuximab or 10 μg/ml of trastuzumab for 96 h. Control groups were treated with media alone or 10 μg/ml of human IgG isotype control antibody. a Representative flow cytometry data of annexin V/PI staining of cells from four independent experiments, each tested in triplicate. b The frequency of cell death 96 h after culture. The population of cells that was negative for both annexin V and PI was defined as living cells. Annexin V⁺/PI⁻ cells were classified as early apoptotic cells, and double-positive cells were classified as late apoptotic cells. Annexin V⁻/PI⁺ cells were classified as dead cells. The data are representative of four independent experiments, each tested in triplicate. *p < 0.05