Cestrum nocturnum Flower Extracts Attenuate Proliferation and Induce Apoptosis in Malignant Cells through Inducing DNA Damage and Inhibiting Topoisomerase II Activity

Figure 4

(a) and (b) DNA damage induced by fractions C4 and C5 in Bel-7404 cells measured by comet assay. Fifty cells were randomly selected per slide and the contents of head and tail DNA in the comet were measured by comet assay software project (CASP). The percentages of DNA in the comet head (headDNA%) and tail (tailDNA%) were considered as parameters of the content of head and tail DNA, respectively. The data in different groups were expressed as the mean ± SD from 3 experiments. Statistical difference between groups was assessed by -test using SPSS 20.0. versus the control group. (c) and (d) Effects of fractions C4 and C5 on topoisomerase II activity. Topoisomerase II activity was measured by plasmid DNA cleavage assay. DNA bands were visualized using UV light and the intensity of linear DNA band in each lane was measured using imageJ software. Lane 1: plasmid PBR322DNA. Lane 2: control, topoisomerase II + plasmid PBR322DNA. Lanes 3, 4, and 5: 40, 20, and 10 μg/mL fraction C4 + plasmid PBR322DNA, respectively. Lanes 6, 7, and 8: 40, 20, and 10 μg/mL fraction C5 + plasmid PBR322DNA, respectively. Lane 9: 100 μM etoposide + plasmid PBR322DNA. The data in different groups were expressed as the mean ± SD from 3 experiments. Statistical difference between groups was assessed by -test using SPSS 20.0. versus the control group.