title: Synergistic growth inhibition in HL-60 cells by the combination of acyclic retinoid and vitamin K2.
abstract: OBJECTIVE
  The aim of this study was to assess the effects of acyclic retinoid (ACR) and vitamin K(2) (VK(2)) in HL-60 cells.
  
  
  METHODS
  We used HL-60 cells, and the Trypan Blue dye exclusion method was used for cell proliferation assays. For detection of apoptosis, the Annexin V-binding capacity of treated cells was examined by flow cytometry. To evaluate the cell cycle, we used a FITC BrdU Flow KIT and flow cytometry. Total extracted and equivalent amounts of protein were examined by Western blotting using specific antibodies.
  
  
  RESULTS
  ACR and VK(2) dose dependently inhibited the proliferation of HL-60 cells. These two agents in combination synergistically inhibited cell growth and induced apoptosis. VK(2) inhibited activation of the Ras/MAPK signaling pathway, and ACR plus VK(2) cooperatively inhibited phosphorylation of RXRα and the growth of HL-60 cells. Moreover, ACR and VK(2) induced increases in G0/G1 phase HL-60 cells, alone and synergistically in combination.
  
  
  CONCLUSIONS
  The synergistic effects of ACR and VK(2) on HL-60 cells may provide a novel strategy for treating leukemia.
authors.affiliation: First Department of Internal Medicine, Gifu University Graduate School of Medicine, 1-1 Yanagido, Gifu, 501-1194, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Kitagawa
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hara
authors.forename: Hisashi
authors.initials: H
authors.lastname: Tsurumi
authors.forename: Soranobu
authors.initials: S
authors.lastname: Ninomiya
authors.forename: Kengo
authors.initials: K
authors.lastname: Ogawa
authors.forename: Seiji
authors.initials: S
authors.lastname: Adachi
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Kanemura
authors.forename: Senji
authors.initials: S
authors.lastname: Kasahara
authors.forename: Masahito
authors.initials: M
authors.lastname: Shimizu
authors.forename: Hisataka
authors.initials: H
authors.lastname: Moriwaki
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D049109:Cell Proliferation / Q000187:drug effects*; D004357:Drug Synergism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000502:physiology; D018922:HL-60 Cells; D006801:Humans; D047490:Retinoid X Receptor alpha / Q000502:physiology; D012176:Retinoids / Q000008:administration & dosage / Q000494:pharmacology*; D024482:Vitamin K 2 / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D047490:Retinoid X Receptor alpha; D012176:Retinoids; D024482:Vitamin K 2; C487689:(2E,4E,6E,10E)-3,7,11,15-tetramethyl-2,4,6,10,14-hexadecapentaenoic acid; D048049:Extracellular Signal-Regulated MAP Kinases