title: Involvement of hydrogen peroxide in topoisomerase inhibitor beta-lapachone-induced apoptosis and differentiation in human leukemia cells.
abstract: Beta-Lapachone a novel topoisomerase inhibitor, has been found to induce apoptosis in various human cancer cells. In this study we report that a dramatic elevation of hydrogen peroxide (H2O2) in human leukemia HL-60 cells following 1 microM beta-lapachone treatment and that this increase was effectively inhibited by treatment with antioxidant N-acetyl-L-cysteine (NAC), ascorbic acid, alpha-tocopherol. NAC strongly prevented beta-lapachone-induced apoptotic characteristics such as DNA fragmentation and apoptotic morphology. However, treatment of HL-60 cells with another topoisomerase inhibitor camptothecin (CPT) did not induce H2O2 production as compared to untreated cells. NAC also failed to block CPT-induced apoptosis. Correlated with these findings, we found that cancer cell lines K562, MCF-7, and SW620, contained high level of intracellular glutathione (GSH), were not elevated in H2O2 and were resistant to apoptosis after treatment with beta-lapachone. In contrast, cancer cell lines such as, HL-60, U937, and Molt-4 which have lower level of GSH, were readily increased of H2O2 and were sensitive to this drug. Furthermore, ectopic overexpression of Bcl-2 in HL-60 cells also attenuated beta-lapachone-induced H2O2 and conferred resistance to beta-lapachone-induced cell death. Beta-Lapachone at the concentration as low as 0.25 microM effectively induced HL-60 cells to undergo monocytic differentiation, as evidenced by CD14 antigenicity and alpha-naphthyl acetate esterase activity. Again, the beta-lapachone-induced monocytic differentiation was suppressed by NAC. These results suggest that intracellular H2O2 generation plays a crucial role in beta-lapachone-induced cell death and differentiation.
authors.affiliation: Institute of Anatomy, School of Life Sciences, National Yang-Ming University, Taiwan.
authors.forename: Y P
authors.initials: YP
authors.lastname: Chau
authors.forename: S G
authors.initials: SG
authors.lastname: Shiah
authors.forename: M J
authors.initials: MJ
authors.lastname: Don
authors.forename: M L
authors.initials: ML
authors.lastname: Kuo
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis; D001205:Ascorbic Acid / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D053938:DNA Fragmentation; D004351:Drug Resistance; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D015473:Leukemia, Promyelocytic, Acute / Q000473:pathology*; D009000:Monocytes; D009285:Naphthoquinones / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology; D059004:Topoisomerase I Inhibitors; D014407:Tumor Cells, Cultured; D014810:Vitamin E / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D004791:Enzyme Inhibitors; D009285:Naphthoquinones; D019253:Proto-Oncogene Proteins c-bcl-2; D059004:Topoisomerase I Inhibitors; D014810:Vitamin E; C014638:beta-lapachone; D006861:Hydrogen Peroxide; D005978:Glutathione; D001205:Ascorbic Acid; D000111:Acetylcysteine