title: Mechanistic studies of cancer cell mitochondria- and NQO1-mediated redox activation of beta-lapachone, a potentially novel anticancer agent.
abstract: Beta-lapachone (beta-Lp) derived from the Lapacho tree is a potentially novel anticancer agent currently under clinical trials. Previous studies suggested that redox activation of beta-Lp catalyzed by
  quinone oxidoreductase 1 (NQO1) accounted for its killing of cancer cells. However, the exact mechanisms of this effect remain largely unknown. Using chemiluminescence and electron paramagnetic resonance (EPR) spin-trapping techniques, this study for the first time demonstrated the real-time formation of ROS in the redox activation of beta-lapachone from cancer cells mediated by mitochondria and NQO1 in melanoma B16-F10 and hepatocellular carcinoma HepG2 cancer cells. ES936, a highly selective NQO1 inhibitor, and rotenone, a selective inhibitor of mitochondrial electron transport chain (METC) complex I were found to significantly block beta-Lp meditated redox activation in B16-F10 cells. In HepG2 cells ES936 inhibited beta-Lp-mediated oxygen radical formation by ~80% while rotenone exerted no significant effect. These results revealed the differential contribution of METC and NQO1 to beta-lapachone-induced ROS formation and cancer cell killing. In melanoma B16-F10 cells that do not express high NQO1 activity, both NOQ1 and METC play a critical role in beta-Lp redox activation. In contrast, in hepatocellular carcinoma HepG2 cells expressing extremely high NQO1 activity, redox activation of beta-Lp is primarily mediated by NQO1 (METC plays a minor role). These findings will contribute to our understanding of how cancer cells are selectively killed by beta-lapachone and increase our ability to devise strategies to enhance the anticancer efficacy of this potentially novel drug while minimizing its possible adverse effects on normal cells.
authors.affiliation: Virginia Tech CRC, Blacksburg, VA, USA.
authors.forename: Jason Z
authors.initials: JZ
authors.lastname: Li
authors.affiliation: Shenzhen Center for Disease Control and Prevention, Shenzhen 518055, China.
authors.forename: Yuebin
authors.initials: Y
authors.lastname: Ke
authors.affiliation: Virginia Tech CRC, Blacksburg, VA, USA.
authors.forename: Hara P
authors.initials: HP
authors.lastname: Misra
authors.affiliation: Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Trush
authors.affiliation: Campbell University School of Osteopathic Medicine, Buies Creek, NC, USA; Virginia Tech-Wake Forest University SBES, Blacksburg, VA, USA; Department of Biology, University of North Carolina at Greensboro, NC, USA.
authors.forename: Y Robert
authors.initials: YR
authors.lastname: Li
authors.affiliation: Campbell University School of Osteopathic Medicine, Buies Creek, NC, USA. Electronic address: zhu@campbell.edu.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhu
authors.affiliation: Department of Biology, University of North Carolina at Greensboro, NC, USA. Electronic address: z_jia@uncg.edu.
authors.forename: Zhenquan
authors.initials: Z
authors.lastname: Jia
mesh_terms: D065767:Activation, Metabolic / Q000187:drug effects; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D045744:Cell Line, Tumor; D042967:Electron Transport Complex I / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D045563:Indolequinones / Q000494:pharmacology; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009285:Naphthoquinones / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009369:Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D011355:Prodrugs / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D018894:Reverse Transcriptase Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D012402:Rotenone / Q000494:pharmacology
chemical_list: C444919:5-methoxy-1,2-dimethyl-3-((4-nitrophenoxy)methyl)indole-4,7-dione; D000972:Antineoplastic Agents, Phytogenic; D004791:Enzyme Inhibitors; D045563:Indolequinones; D009285:Naphthoquinones; D009363:Neoplasm Proteins; D011355:Prodrugs; D017382:Reactive Oxygen Species; D018894:Reverse Transcriptase Inhibitors; D012402:Rotenone; C014638:beta-lapachone; D016660:NAD(P)H Dehydrogenase (Quinone); D042967:Electron Transport Complex I
keywords: Beta-lapachone; Cancer cells; EPR; Mitochondrial electron transport chain; NQO1; ROS