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

Figure 6

TOPO I catalytic activity is inhibited by β-ELE. (a) The effect of β-ELE (β-Elemene) on the relaxation of TOPO I-mediated, negative supercoiled pBR322 DNA. As shown in (a), lane 1 is negative supercoiled pBR322 DNA (supercoiled DNA, S); lane 2 is relaxed DNA that is the product of supercoiled DNA reacted with the enzyme (relaxed DNA, R); and lanes 3 and 4 are positive control groups. HCPT (a typical inhibitor of TOPO I) had no inhibitory effect on the DNA relaxation activity of TOPO I at the concentration of 5 μg/mL, whereas it completely inhibited the relaxation of pBR322 DNA mediated by TOPO I at a concentration of 1 μg/μL. Lane 5 shows the effect of 1 μg/μL HCPT combined with 40 μg/mL β-ELE on the relaxation of TOPO I-mediated negative supercoiled pBR322 DNA. As shown in (a), the combination inhibited the relaxation activity of TOPO I. Lanes 6 to 11 show the effects of different concentrations of β-ELE (40, 60, 80, and 100 μg/mL) on the relaxation of negative supercoiled pBR322 DNA mediated by TOPO I. β-ELE has no inhibitory effect on the relaxation activity of TOPO I at concentrations of 10 and 20 μg/mL; however, with increasing drug concentration, β-ELE showed an increasing inhibitory effect on the DNA relaxation activity of TOPO I at concentrations of 40, 60, 80, and 100 μg/mL. The OD of MAX was , , , and . The statistical analysis showed significant differences between the 100 μg/mL and 40 μg/mL treatment groups and the 60 μg/mL and 80 μg/mL treatment groups (). (b) β-ELE (β-Elemene) has no direct effect on pBR322 DNA. As shown in (b), the average OD of the control group was , and those of the β-ELE treatment groups were , , , , and for 20, 40, 60, 80, and 100 μg/mL of β-ELE, respectively. There was no significant difference between the groups ().

(a)

(b)