Apoptosis-inducing activity of lycopene in human cancer cells. (A) Human cancer cells incubated with lycopene (3 μM) for 96 h were analyzed by the TUNEL assay. TUNEL-positive cells were measured by fluorescence microscope. (B) Lycopene-treated human cancer cells were then stained with DAPI (4′,6-diamidino-2-phenylindole) for 3 min. Chromatin condensation was observed using fluorescence microscopy. Arrows in the micrographs indicate areas of chromatin condensation. Percentage of cells undergoing apoptosis was determined by counting apoptotic nuclei of DAPI-stained cells. ND, not detected. Values are means ± SD (n = 3). Bars with asterisks are significantly different from controls (p > 0.05). (C) Detection of apoptotic cells (in green) by TUNEL method in human cancer cells. The cells were treated (M-P) or not (I-L) with lycopene for 48 h. Nuclei were counterstained with DAPI (blue) (A-H). Chromatin condensation was observed in treated cells (E-H).