title: The synergistic antitumor activity of arsenic trioxide and vitamin K2 in HL-60 cells involves increased ROS generation and regulation of the ROS-dependent MAPK signaling pathway.
abstract: OBJECTIVE
  The aim of this study was to investigate the synergistic anticancer effects of arsenic trioxide (ATO) and vitamin K2 (VK2) in HL-60 cells, and elucidate the potential mechanisms.
  
  
  METHODS
  HL-60 cells were exposed to ATO and VK2, either alone or in combination. Cell proliferation and apoptosis were assessed. The combination index (CI) method was used to evaluate whether the action of the drug combination was synergistic, additive or antagonistic. Reactive oxygen species (ROS) and the mitogen-activated protein kinase (MAPK) signaling pathway were also studied, to provide insight into potential mechanisms.
  
  
  RESULTS
  The results showed that combining ATO with VK2 significantly inhibited HL-60 cell growth more than either agent alone, indicating a synergistic effect with CI < 1. Annexin V staining demonstrated that the inhibition of cell growth by the drug combination was mediated through an increase in apoptosis; this was supported by examination of caspase-3 and caspase-9 with Western blot assays. Furthermore, induction of ROS, and phosphorylation and activation of the JNK and p38 (but not ERK1/2) pathways, was observed in cells administered the drug combination. Prior treatment with the antioxidant, N-acetylcysteine, partly blocked the apoptosis and expression of caspase-3 induced by the drug combination; apoptosis and expression of caspase-3 were also reversed by inhibitors of JNK or p38.
  
  
  CONCLUSIONS
  These results suggest that ATO and VK2 act synergistically to increase HL-60 cell apoptosis, through ROS generation and regulation of the MAPK signaling pathway.
authors.affiliation: Department of Pediatrics, The Second Affiliated Hospital, Harbin Medical University, Harbin, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Qu
authors.forename: Danan
authors.initials: D
authors.lastname: Tong
authors.forename: Yanqing
authors.initials: Y
authors.lastname: Zhang
authors.forename: Kai
authors.initials: K
authors.lastname: Kang
authors.forename: Yuling
authors.initials: Y
authors.lastname: Zhang
authors.forename: Lan
authors.initials: L
authors.lastname: Chen
authors.forename: Lihong
authors.initials: L
authors.lastname: Ren
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology*; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D007202:Indicators and Reagents; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010087:Oxides / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D024482:Vitamin K 2 / Q000494:pharmacology*
chemical_list: D000970:Antineoplastic Agents; D001152:Arsenicals; D007202:Indicators and Reagents; D010087:Oxides; D017382:Reactive Oxygen Species; D024482:Vitamin K 2; D020928:Mitogen-Activated Protein Kinases; D053148:Caspase 3; D053453:Caspase 9; D000077237:Arsenic Trioxide