Role of Chk1 and Chk2 in Ara‐C‐induced differentiation of human leukemia K562 cells

• Published in: Genes to cells : devoted to molecular & cellular mechanisms 2005-02, Vol.10 (2), p.97-106
• Main Authors: Takagaki, Kazuchika, Katsuma, Susumu, Kaminishi, Yoshinori, Horio, Tatsuya, Tanaka, Teruo, Ohgi, Tadaaki, Yano, Junichi
• Format: Article
• Language: English
• Subjects: Antimetabolites, Antineoplastic - pharmacology; Ataxia Telangiectasia Mutated Proteins; Caffeine - pharmacology; Carbazoles - pharmacology; cdc25 Phosphatases - metabolism; Cell Cycle Proteins - antagonists & inhibitors; Cell Cycle Proteins - metabolism; Cell Differentiation; Checkpoint Kinase 1; Checkpoint Kinase 2; Cytarabine - pharmacology; DNA-Binding Proteins - antagonists & inhibitors; DNA-Binding Proteins - metabolism; Erythrocytes - cytology; Humans; Indoles - pharmacology; Intracellular Signaling Peptides and Proteins - pharmacology; K562 Cells; Phosphorylation; Proteasome Endopeptidase Complex - metabolism; Protein Kinases - genetics; Protein Kinases - metabolism; Protein-Serine-Threonine Kinases - antagonists & inhibitors; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - metabolism; RNA, Small Interfering - genetics; Tumor Suppressor Proteins - antagonists & inhibitors; Tumor Suppressor Proteins - metabolism
• ISSN: 1356-9597; 1365-2443
• DOI: 10.1111/j.1365-2443.2005.00821.x

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 Gö6976, 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.