title: Hsp90-inhibitor geldanamycin abrogates G2 arrest in p53-negative leukemia cell lines through the depletion of Chk1.
abstract: Checkpoint protein Chk1 has been identified as an Hsp90 client. Treatment with 100 nM geldanamycin (GM) for 24 h markedly reduced the Chk1 amount in Jurkat and ML-1 leukemia cell lines. Because Chk1 plays a central role in G2 checkpoint, we added GM to G2-arrested Jurkat and HL-60 cells pretreated with 50 nM doxorubicin for 24 h. GM slowly released both cell lines from doxorubicin-induced G2 arrest into G1 phase. GM also abrogated ICRF-193-induced decatenation G2 checkpoint in Jurkat and HL-60 cells. Western blot analysis showed that addition of GM attenuates doxorubicin- and ICRF-193-induced Chk1 phosphorylation at Ser345. GM, however, failed to abrogate G2 arrest in p53-positive ML-1 cells maybe due to the p21 induction. GM released HeLa cells from doxorubicin-induced G2 arrest but trapped them at M phase. Flow cytometric analysis showed that addition of GM converted doxorubicin-induced necrosis into apoptosis in Jurkat cells. Colony assay indicated that although GM has a weak cytotoxic effect as a single agent, it dramatically intensifies the cytotoxicity of doxorubicin and ICRF-193 in Jurkat and HL-60 cells. These results suggest that abrogation of G2 checkpoint by GM may play a central role in sensitizing p53-negative tumor cells to DNA-damaging and decatenation-inhibiting agents.
authors: Division of Hematology, Department of Internal Medicine, Juntendo University School of Medicine, Tokyo, Japan. ksugimot@med.juntendo.ac.jp
authors: K
authors: K
authors: Sugimoto
authors: M
authors: M
authors: Sasaki
authors: Y
authors: Y
authors: Isobe
authors: M
authors: M
authors: Tsutsui
authors: H
authors: H
authors: Suto
authors: J
authors: J
authors: Ando
authors: K
authors: K
authors: Tamayose
authors: M
authors: M
authors: Ando
authors: K
authors: K
authors: Oshimi
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D016227:Benzoquinones / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D000071877:Checkpoint Kinase 1; D004249:DNA Damage / Q000187:drug effects / Q000502:physiology; D054659:Diketopiperazines; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D016195:G2 Phase / Q000187:drug effects*; D016158:Genes, p53; D018922:HL-60 Cells; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D047029:Lactams, Macrocyclic / Q000494:pharmacology*; D007938:Leukemia / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D010879:Piperazines / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism*
chemical_list: D000903:Antibiotics, Antineoplastic; D016227:Benzoquinones; D054659:Diketopiperazines; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D010879:Piperazines; C070899:4,4'-(1,2-dimethyl-1,2-ethanediyl)bis-2,6-piperazinedione; D004317:Doxorubicin; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C001277:geldanamycin