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

Abstract

Objective. To investigate the effects ofβ-Elemene (β-ELE) on the proliferation, apoptosis, and topoisomerase I (TOPO I) and topoisomerase IIα(TOPO IIα) expression and activity of human hepatocarcinoma HepG-2 cells.Methods. After treatment withβ-ELE, morphological alterations of HepG-2 cells were observed under an inverted microscope. Cell proliferation was assessed using an MTT assay, cell cycles were analyzed using flow cytometry, and apoptosis was detected by Annexin V/PI staining. The expression of TOPO I and TOPO IIαwas analyzed by Western blot techniques, and their activity was measured using the TOPO I-mediated, supercoiled pBR322 DNA relaxation and TOPO IIα-mediated Kinetoplast DNA (kDNA) decatenation assays, respectively. Supercoiled pBR322 and kDNA were also used to determine the direct effect ofβ-ELE on DNA breaks.Results.β-ELE significantly inhibited HepG-2 cell proliferation in a dose- and time-dependent manner.β-ELE also induced tumor cell arrest at S phase, induced cell apoptosis, and downregulated the protein expression of TOPO I and TOPO IIαin a dose-dependent manner.β-ELE also inhibited TOPO I- and TOPO IIα-mediated DNA relaxation but did not directly induce DNA breakage at any concentration.Conclusion.β-ELE could inhibit the proliferation of HepG-2 cells and interfere with the expression and activity of TOPO I and TOPO IIα.