title: Radiosensitization by Chir-124, a selective CHK1 inhibitor: effects of p53 and cell cycle checkpoints.
abstract: Checkpoint kinase-1 (CHK1) is a key regulator of the DNA damage-elicited G(2)-M checkpoints. The aim of the present study was to investigate the effects of a selective CHK1 inhibitor, Chir124, on cell survival and cell cycle progression following ionizing radiation (IR). Treatment with Chir-124 resulted in reduced clonogenic survival and abrogated the IR-induced G(2)-M arrest in a panel of isogenic HCT116 cell lines after IR. This radiosensitizing effect was relatively similar between p53(-/-) and p53-sufficient wild type (WT) HCT116 cells. However, the number of mitotic cells (as measured by assessing the phosphorylation of mitotic proteins) increased dramatically in p53(-/-) HCT116 cells after concomitant Chir-124 exposure, compared to IR alone, while no such effect was observed in p53-sufficient WT HCT116 cells. In p53(-/-) cells, Chir-124 treatment induced a marked accumulation of polyploid cells that were characterized by micronucleation or multinucleation. p21(-/-) HCT116 cells displayed a similar pattern of response as p53(-/-) cells. Chir-124 was able to radiosensitize HCT116 cells that lack checkpoint kinase-2 (CHK2) or that were deficient for the spindle checkpoint protein Mad2. Finally, Chir-124 could radiosensitize tetraploid cell lines, which were relatively resistant against DNA damaging agents. Altogether these results suggest that Chir-124-mediated radiosensitization is profoundly influenced by the p53 and cell cycle checkpoint system.
authors.affiliation: UPRES EA27-10 Laboratoire Radiosensibilité des Tumeurs et Tissus Sains, University Paris-Sud XI Kremlin-Bicêtre and Institut Gustave-Roussy, 39 rue Camille-Desmoulins,Villejuif, France.
authors.forename: Yungan
authors.initials: Y
authors.lastname: Tao
authors.forename: Céline
authors.initials: C
authors.lastname: Leteur
authors.forename: Ceyao
authors.initials: C
authors.lastname: Yang
authors.forename: Ping
authors.initials: P
authors.lastname: Zhang
authors.forename: Maria
authors.initials: M
authors.lastname: Castedo
authors.forename: Alain
authors.initials: A
authors.lastname: Pierré
authors.forename: Roy M
authors.initials: RM
authors.lastname: Golsteyn
authors.forename: Jean
authors.initials: J
authors.lastname: Bourhis
authors.forename: Guido
authors.initials: G
authors.lastname: Kroemer
authors.forename: Eric
authors.initials: E
authors.lastname: Deutsch
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism; D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects* / Q000528:radiation effects; D018797:Cell Cycle Proteins / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D000071877:Checkpoint Kinase 1; D004249:DNA Damage; D004789:Enzyme Activation / Q000187:drug effects / Q000528:radiation effects; D005434:Flow Cytometry; D016195:G2 Phase / Q000187:drug effects / Q000528:radiation effects; D045325:HCT116 Cells; D006801:Humans; D007150:Immunohistochemistry; D064246:Mad2 Proteins; D051379:Mice; D008940:Mitotic Index; D011123:Polyploidy; D011494:Protein Kinases / Q000378:metabolism*; D011804:Quinolines / Q000494:pharmacology; D011812:Quinuclidines / Q000494:pharmacology; D011839:Radiation, Ionizing; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D012097:Repressor Proteins / Q000378:metabolism; D008941:Spindle Apparatus / Q000187:drug effects / Q000528:radiation effects; D014410:Tumor Stem Cell Assay; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
chemical_list: D048948:14-3-3 Proteins; C518919:CHIR-124; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; D011804:Quinolines; D011812:Quinuclidines; D011838:Radiation-Sensitizing Agents; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C000605869:Chek1 protein, mouse