The morphology of the nuclei for apoptotic changes of cells treated with 200 μM of EGCG for 24 h was observed by DAPI staining (4′,6-diamidino-2-phenylindole, 50 μg/ml), using an inverting fluorescence microscope with Axio camera (Zeiss, Germany). TUNEL staining was conducted to observe the cells undergoing apoptosis. The cells were treated with 200 μM EGCG for 24 h and then apoptotic cells were stained by the TUNEL method using an in situ apoptosis detection kit. The cells were fixed in 4% paraformaldehyde, washed twice with phosphate buffered saline (PBS), and permeabilized in 0.5% Triton X-100 for 5 min on ice. TUNEL staining was conducted with fluorescein-dUTP (Roche Applied Science, Germany) in the presence of terminal deoxynucleotidyl transferase for 1 h at 37 °C. Following labeling, the cells were washed with PBS twice and then directly observed under a fluorescence microscope. Samples were visualized using an LSM5 PASCAL confocal laser-scanning microscope (Zeiss, Germany). The percentage of apoptotic cells was scored by counting at least 200 cells within the treatment group.