title: Role of Chk1 and Chk2 in Ara-C-induced differentiation of human leukemia K562 cells.
abstract: Human chronic myelogenous leukemia K562 cells are relatively resistant to the anti-metabolite cytosine arabinoside (Ara-C) and, when treated with Ara-C, they differentiate into erythrocytes without undergoing apoptosis. In this study we investigated the mechanism by which Ara-C induces K562 cells to differentiate. We first observed that Ara-C-induced differentiation of these cells is completely inhibited by the radiosensitizing agent caffeine, an inhibitor of ATM and ATR protein kinases. We next found that Ara-C activates Chk1 and Chk2 in the cells, and that the activation of Chk1, but not of Chk2, was almost completely inhibited by caffeine. Proteasome-mediated degradation of Cdc25A and phosphorylation of Cdc25C were induced by Ara-C treatment, presumably due to the activation of Chk2 and Chk1, respectively. To directly observe the effects of checkpoint kinase activation in Ara-C-induced differentiation, we suppressed Chk1 or Chk2 with the Chk1-specific inhibitor Go6976, by generating cell lines stably over-expressing dominant-negative forms of Chk2, or by siRNA-mediated knock-down of the Chk1 or the Chk2 gene. The results suggest that Ara-C-induced erythroid differentiation of K562 cells depends on both Chk1 and Chk2 pathways.
authors.affiliation: Research Laboratories, Nippon Shinyaku Co. Ltd, 3-14-1 Sakura, Tsukuba, Ibaraki 305-0003, Japan. k.takagaki@nippon-shinyaku.co.jp
authors.forename: Kazuchika
authors.initials: K
authors.lastname: Takagaki
authors.forename: Susumu
authors.initials: S
authors.lastname: Katsuma
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kaminishi
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Horio
authors.forename: Teruo
authors.initials: T
authors.lastname: Tanaka
authors.forename: Tadaaki
authors.initials: T
authors.lastname: Ohgi
authors.forename: Junichi
authors.initials: J
authors.lastname: Yano
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D064007:Ataxia Telangiectasia Mutated Proteins; D002110:Caffeine / Q000494:pharmacology; D002227:Carbazoles / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002454:Cell Differentiation; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D003561:Cytarabine / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D004912:Erythrocytes / Q000166:cytology; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000494:pharmacology; D020014:K562 Cells; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D020687:cdc25 Phosphatases / Q000378:metabolism
chemical_list: D000964:Antimetabolites, Antineoplastic; D002227:Carbazoles; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; C015482:protein kinase modulator; D003561:Cytarabine; C081021:Go 6976; D002110:Caffeine; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; C578634:CHEK2 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases; C517004:CDC25A protein, human; C517009:CDC25C protein, human; D020687:cdc25 Phosphatases; D046988:Proteasome Endopeptidase Complex