title: The synergic effect of vincristine and vorinostat in leukemia in vitro and in vivo.
abstract: BACKGROUND
  Combination therapy is a key strategy for minimizing drug resistance, a common problem in cancer therapy. The microtubule-depolymerizing agent vincristine is widely used in the treatment of acute leukemia. In order to decrease toxicity and chemoresistance of vincristine, this study will investigate the effects of combination vincristine and vorinostat (suberoylanilide hydroxamic acid (SAHA)), a pan-histone deacetylase inhibitor, on human acute T cell lymphoblastic leukemia cells.
  
  
  METHODS
  Cell viability experiments were determined by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay, and cell cycle distributions as well as mitochondria membrane potential were analyzed by flow cytometry. In vitro tubulin polymerization assay was used to test tubulin assembly, and immunofluorescence analysis was performed to detect microtubule distribution and morphology. In vivo effect of the combination was evaluated by a MOLT-4 xenograft model. Statistical analysis was assessed by Bonferroni's t test.
  
  
  RESULTS
  Cell viability showed that the combination of vincristine and SAHA exhibited greater cytotoxicity with an IC50 value of 0.88 nM, compared to each drug alone, 3.3 and 840 nM. This combination synergically induced G2/M arrest, followed by an increase in cell number at the sub-G1 phase and caspase activation. Moreover, the results of vincristine combined with an HDAC6 inhibitor (tubastatin A), which acetylated α-tubulin, were consistent with the effects of vincristine/SAHA co-treatment, thus suggesting that SAHA may alter microtubule dynamics through HDAC6 inhibition.
  
  
  CONCLUSIONS
  These findings indicate that the combination of vincristine and SAHA on T cell leukemic cells resulted in a change in microtubule dynamics contributing to M phase arrest followed by induction of the apoptotic pathway. These data suggest that the combination effect of vincristine/SAHA could have an important preclinical basis for future clinical trial testing.
authors.affiliation: Pharmacological Institute, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, Sec. 1, Taipei, Taiwan.
authors.forename: Min-Wu
authors.initials: MW
authors.lastname: Chao
authors.affiliation: Center for Translational Medicine, Taipei Medical University, No. 250, Wu-hsing Street, Taipei, 11031, Taiwan.
authors.forename: Mei-Jung
authors.initials: MJ
authors.lastname: Lai
authors.affiliation: School of Pharmacy, College of Pharmacy, Taipei Medical University, No. 250, Wu-hsing Street, Taipei, 11031, Taiwan.
authors.forename: Jing-Ping
authors.initials: JP
authors.lastname: Liou
authors.affiliation: Pharmacological Institute, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, Sec. 1, Taipei, Taiwan.
authors.forename: Ya-Ling
authors.initials: YL
authors.lastname: Chang
authors.affiliation: The Ph.D. Program for Cancer Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University, No. 250, Wu-hsing St., Taipei, 11031, Taiwan.
authors.forename: Jing-Chi
authors.initials: JC
authors.lastname: Wang
authors.affiliation: The Ph.D. Program for Cancer Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University, No. 250, Wu-hsing St., Taipei, 11031, Taiwan. slpan@tmu.edu.tw.
authors.forename: Shiow-Lin
authors.initials: SL
authors.lastname: Pan
authors.affiliation: Pharmacological Institute, College of Medicine, National Taiwan University, No. 1, Jen-Ai Road, Sec. 1, Taipei, Taiwan. cmteng@ntu.edu.tw.
authors.forename: Che-Ming
authors.initials: CM
authors.lastname: Teng
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000008:administration & dosage / Q000627:therapeutic use*; D045744:Cell Line, Tumor; D002470:Cell Survival; D004357:Drug Synergism; D006801:Humans; D006877:Hydroxamic Acids / Q000008:administration & dosage / Q000627:therapeutic use*; D007938:Leukemia / Q000188:drug therapy*; D014750:Vincristine / Q000008:administration & dosage / Q000627:therapeutic use*; D000077337:Vorinostat
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D006877:Hydroxamic Acids; D000077337:Vorinostat; D014750:Vincristine