title: The radiosensitizing agent 7-hydroxystaurosporine (UCN-01) inhibits the DNA damage checkpoint kinase hChk1.
abstract: The investigational anticancer agent 7-hydroxystaurosporine (UCN-01) abrogates the G2 checkpoint in tumor cells and sensitizes them to the lethal effects of genotoxic anticancer agents. On the basis of the role of the Cdc25C phosphatase in maintenance of this damage-inducible checkpoint, we hypothesized that UCN-01 inhibits a component of the signal transduction pathway that modulates Cdc25C phosphorylation. Of the three kinases known to phosphorylate Cdc25C on Ser216, both checkpoint kinase 1 (hChk1) and Cdc25C-associated protein kinase 1 (cTAK1) were potently inhibited by UCN-01 with IC50s of 11 and 27 nM, respectively. Treatment of K562 erythroblastoid leukemia cells with similar drug concentrations resulted in decreased levels of Ser216 phosphorylation of Cdc25C and complete disruption of the y-radiation-induced G2 checkpoint. In contrast to hChk1, the hChk2 kinase was 100-fold more resistant to inhibition by UCN-01 (IC50, 1040 nM). These results suggest that disruption of the DNA damage-induced G2 checkpoint by UCN-01 is mediated through the inhibition of the Cdc25C kinases, hChk1 and cTAK1, and that hChk2 activity is not sufficient to enforce the G2 checkpoint in cells treated with a pharmacological inhibitor of hChk1.
authors.affiliation: Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: E C
authors.initials: EC
authors.lastname: Busby
authors.forename: D F
authors.initials: DF
authors.lastname: Leistritz
authors.forename: R T
authors.initials: RT
authors.lastname: Abraham
authors.forename: L M
authors.initials: LM
authors.lastname: Karnitz
authors.forename: J N
authors.initials: JN
authors.lastname: Sarkaria
mesh_terms: D000470:Alkaloids / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000378:metabolism*; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2; D004249:DNA Damage / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D016195:G2 Phase / Q000187:drug effects* / Q000528:radiation effects; D006801:Humans; D020128:Inhibitory Concentration 50; D020014:K562 Cells; D008954:Models, Biological; D010766:Phosphorylation / Q000187:drug effects; D010768:Phosphoserine / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D019311:Staurosporine / Q000031:analogs & derivatives; D020687:cdc25 Phosphatases / Q000378:metabolism*
chemical_list: D000470:Alkaloids; D000970:Antineoplastic Agents; D018797:Cell Cycle Proteins; D047428:Protein Kinase Inhibitors; D011838:Radiation-Sensitizing Agents; D010768:Phosphoserine; C054852:7-hydroxystaurosporine; D011494:Protein Kinases; C111833:MARK3 protein, human; D064447:Checkpoint Kinase 2; C000605867:CHEK1 protein, human; C578634:CHEK2 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases; C517009:CDC25C protein, human; D020687:cdc25 Phosphatases; D019311:Staurosporine