title: Imatinib induces H2AX phosphorylation and apoptosis in chronic myelogenous leukemia cells in vitro via caspase-3/Mst1 pathway.
abstract: OBJECTIVE
  Histone H2AX is a novel tumor suppressor and its phosphorylation at the C terminus (Ser139 and Tyr142) is required for tumor cell apoptosis. The aim of the present study was to elucidate the mechanisms underlying imatinib-induced C-terminal phosphorylation of H2AX in chronic myelogenous leukemia cells in vitro.
  
  
  METHODS
  BCR-ABL-positive K562 cells were used. Microscopy, Western blotting and flow cytometry were used to study the signaling pathways that regulate imatinib-induced H2AX phosphorylation and the apoptotic mechanisms.
  
  
  RESULTS
  Treatment of K562 cells with imatinib (1-8 μmol/L) induced phosphorylation of H2AX at Ser139 and Tyr142 in time- and dose-dependent manners. In contrast, imatinib at the same concentrations did not affect H2AX acetylation at Lys 5, and the acetylated H2AX maintained a higher level in the cells. Meanwhile, imatinib (1-8 μmol/L) activated caspase-3 and its downstream mammalian STE20-like kinase 1 (Mst1), and induced apoptosis of K562 cells. The caspase-3 inhibitor Z-VAD (40 μmol/L) reduced imatinib-induced H2AX phosphorylation at Ser139 and Tyr142 and blocked imatinib-induced apoptosis of K562 cells. Imatinib (4 μmol/L) induced expression of Williams-Beuren syndrome transcription factor (WSTF), but not wild-type p53-induced phosphatase 1 (Wip1) in K562 cells.
  
  
  CONCLUSIONS
  The caspase-3/Mst1 pathway is required for H2AX C-terminal phosphorylation at Ser139 and Tyr142 and subsequent apoptosis in Bcr-Abl-positive K562 cells induced by imatinib.
authors.affiliation: Aviation Medicine Research Lab, General Hospital of Air Force, Beijing, China.
authors.forename: Yan-jun
authors.initials: YJ
authors.lastname: Zhang
authors.forename: Cheng-rong
authors.initials: CR
authors.lastname: Lu
authors.forename: Yan
authors.initials: Y
authors.lastname: Cao
authors.forename: Yuan
authors.initials: Y
authors.lastname: Luo
authors.forename: Rong-feng
authors.initials: RF
authors.lastname: Bao
authors.forename: Shu
authors.initials: S
authors.lastname: Yan
authors.forename: Mei
authors.initials: M
authors.lastname: Xue
authors.forename: Feng
authors.initials: F
authors.lastname: Zhu
authors.forename: Zhe
authors.initials: Z
authors.lastname: Wang
authors.forename: Lian-ning
authors.initials: LN
authors.lastname: Duan
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides; D053148:Caspase 3 / Q000378:metabolism*; D045744:Cell Line, Tumor; D017228:Hepatocyte Growth Factor / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D006801:Humans; D000068877:Imatinib Mesylate; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D001549:Benzamides; C468783:H2AX protein, human; D006657:Histones; D010879:Piperazines; D011518:Proto-Oncogene Proteins; D011743:Pyrimidines; C082332:macrophage stimulating protein; D017228:Hepatocyte Growth Factor; D000068877:Imatinib Mesylate; D053148:Caspase 3