β-Elemene Inhibits Cell Proliferation by Regulating the Expression and Activity of Topoisomerases I and IIα in Human Hepatocarcinoma HepG-2 Cells

Figure 7

TOPO IIα catalytic activity inhibited by β-ELE. (a) The effect of β-ELE (β-Elemene) on the decatenation of TOPO IIα-mediated kDNA. As shown in (a), lane 1 is kDNA and served as a control group; lane 2 is the free DNA minicircles that were produced by the decatenation of TOPO IIα, in this case, without β-ELE. Lanes 3 and 4 are the positive control groups. VP16 (a typical inhibitor of TOPO IIα) at a concentration of 5 μg/mL had no inhibitory effect on the DNA decatenation activity of TOPO IIα, whereas DNA minicircles disappeared at a concentration of 1 μg/μL, which suggests that VP16 inhibits the catalytic activity of TOPO IIα. Lane 5 shows the effect of 1 μg/μL VP16 with 40 μg/mL β-ELE on the decatenation of TOPO IIα-mediated kDNA. As shown in the figure, the activity of TOPO IIα was inhibited. Lanes 6 to 11 show the effects of different concentrations (40, 60, 80, and 100 μg/mL) of β-ELE on the decatenation of TOPO IIα-mediated kDNA. (b) β-ELE (β-Elemene) has no direct effect on kDNA. As shown in (b), DNA minicircles, which form after DNA double-strand breakage, did not appear in the figure, suggesting that β-ELE has no direct effect on DNA.

(a)

(b)