Document Detail

UCN-01: a potent abrogator of G2 checkpoint function in cancer cells with disrupted p53.
MedLine Citation:
PMID:  8667426     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Arrest of the cell cycle in G2 phase following DNA damage helps protect cell viability by allowing time for DNA repair before entry into mitosis (M phase). Abrogation of G2 arrest sensitizes cells to the effects of DNA-damaging agents. UCN-01 (7-hydroxystaurosporine), a protein kinase C inhibitor that may block G2 checkpoint regulation, has been reported to enhance the cytotoxicity of mitomycin C, a known DNA-damaging agent.
PURPOSE: We studied the effect of UCN-01 on G2 checkpoint control in human lymphoma CA46 cells, whose sensitivity to various DNA-damaging agents and G2 response to DNA damage have been characterized. We also assessed the ability of UCN-01 to enhance the cytotoxicity of gamma irradiation in CA46 cells and human colon carcinoma HT-29 cells, both of which are mutant for p53 function. The influence of p53 function on UCN-01-mediated abrogation of the G2 checkpoint and enhancement of DNA-damaging agent cytotoxicity was studied in transfected human breast carcinoma MCF-7 cells that either expressed or did not express the human papillomavirus type-16 E6 protein. MCF-7 cells have normal p53 function, and the E6 protein binds p53 protein and promotes its destruction.
METHODS: The effect of UCN-01 on cell cycle arrest induced by gamma irradiation was studied in CA46 cells and in transfected MCF-7 cells by use of flow cytometry. A histone H1 phosphorylation assay was employed to measure cyclin B1/Cdc2 kinase activity in extracts derived from irradiated and nonirradiated CA46 cells that had been either treated or not treated with UCN-01; the phosphorylation status of Cdc2 kinase protein in the same extracts was determined by use of western blotting. The effect of UCN-01 on the cytotoxicity of gamma irradiation in CA46 and HT-29 cells was determined by use of MTT (thiazolyl blue) and clonogenic (colony-forming) assays, respectively; a clonogenic assay was also used to measure the effect of UCN-01 on the cytotoxicity of cisplatin in transfected and nontransfected MCF-7 cells.
RESULTS: G2 arrest induced in CA46 cells by gamma irradiation was minibited by treatment with UCN-01 in a dose-dependent manner; arrest in G2 was completely abrogated by exposure to 300 nM UCN-01. Biochemical markers indicative of the G2/M transition, including the activation of cyclin B1/Cdc2 kinase and the suppression of Cdc2 threonine-14 and tyrosine-15 phosphorylation, were detected in irradiated cells treated with UCN-01. UCN-01 enhanced the cytotoxicity of gamma irradiation in CA46 and HT-29 cells. MCF-7 cells with functional p53 protein were more resistant to G2 checkpoint abrogation by UCN-01 than MCF-7 cells with disrupted p53 function. UCN-01 markedly enhanced the cell-killing activity of cisplatin in MCF-7 cells defective for p53 function.
CONCLUSIONS AND IMPLICATIONS: UCN-01 is a potent abrogator of G2 checkpoint control in cancer cells with disrupted p53 function. UCN-01 might be capable of enhancing the effectiveness of DNA-damaging agents in the treatment of tumors with cells lacking normal p53 function.
Q Wang; S Fan; A Eastman; P J Worland; E A Sausville; P M O'Connor
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of the National Cancer Institute     Volume:  88     ISSN:  0027-8874     ISO Abbreviation:  J. Natl. Cancer Inst.     Publication Date:  1996 Jul 
Date Detail:
Created Date:  1996-08-07     Completed Date:  1996-08-07     Revised Date:  2013-05-24    
Medline Journal Info:
Nlm Unique ID:  7503089     Medline TA:  J Natl Cancer Inst     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  956-65     Citation Subset:  IM    
Laboratory of Biological Chemistry, Division of Basic Science, National Cancer Institute, Bethesda, MD, USA.
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MeSH Terms
Alkaloids / pharmacology*
Antineoplastic Agents / pharmacology*
Burkitt Lymphoma / drug therapy
CDC2 Protein Kinase / drug effects,  radiation effects
Cell Division / drug effects*,  genetics,  radiation effects
Cell Survival / drug effects,  radiation effects
Cisplatin / pharmacology
Colonic Neoplasms / drug therapy
Cyclin B*
Cyclin B1
Cyclins / drug effects,  radiation effects
Drug Synergism
Flow Cytometry
G2 Phase / drug effects*,  radiation effects
Gamma Rays
Genes, p53 / genetics*
Mitotic Index
Precipitin Tests
Radiation Dosage
Staurosporine / analogs & derivatives
Tumor Cells, Cultured
Reg. No./Substance:
0/Alkaloids; 0/Antineoplastic Agents; 0/CCNB1 protein, human; 0/Cyclin B; 0/Cyclin B1; 0/Cyclins; 15663-27-1/Cisplatin; 62996-74-1/Staurosporine; 7BU5H4V94A/7-hydroxystaurosporine; EC Protein Kinase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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