Targeting the replication checkpoint using SCH 900776, a potent and functionally selective CHK1 inhibitor identified via high content screening

Checkpoint kinase 1 (CHK1) is an essential serine/threonine kinase that responds to DNA damage and stalled DNA replication. CHK1 is essential for maintenance of replication fork viability during exposure to DNA antimetabolites. In human tumor cell lines, ablation of CHK1 function during antimetaboli...

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Bibliographic Details
Published in:	Molecular cancer therapeutics Vol. 10; no. 4; pp. 591 - 602
Main Authors:	Guzi, Timothy J, Paruch, Kamil, Dwyer, Michael P, Labroli, Marc, Shanahan, Frances, Davis, Nicole, Taricani, Lorena, Wiswell, Derek, Seghezzi, Wolfgang, Penaflor, Ervin, Bhagwat, Bhagyashree, Wang, Wei, Gu, Danling, Hsieh, Yunsheng, Lee, Suining, Liu, Ming, Parry, David
Format:	Journal Article
Language:	English
Published:	United States 01-04-2011
Subjects:	Animals Antimetabolites, Antineoplastic - administration & dosage Antimetabolites, Antineoplastic - pharmacology Antineoplastic Combined Chemotherapy Protocols - therapeutic use Apoptosis - drug effects Bridged Bicyclo Compounds, Heterocyclic - administration & dosage Bridged Bicyclo Compounds, Heterocyclic - pharmacology Cell Line, Tumor Checkpoint Kinase 1 Checkpoint Kinase 2 Cyclin-Dependent Kinases - genetics Cyclin-Dependent Kinases - metabolism Deoxycytidine - analogs & derivatives Deoxycytidine - pharmacology DNA Breaks, Double-Stranded - drug effects DNA Replication - drug effects Drug Screening Assays, Antitumor - methods Histones - metabolism Humans Immunoblotting Mice Mice, Nude Molecular Structure Protein Kinase Inhibitors - administration & dosage Protein Kinase Inhibitors - chemistry Protein Kinase Inhibitors - pharmacology Protein Kinases - genetics Protein Kinases - metabolism Protein-Serine-Threonine Kinases - genetics Protein-Serine-Threonine Kinases - metabolism Pyrazoles - administration & dosage Pyrazoles - chemistry Pyrazoles - pharmacology Pyridinium Compounds - administration & dosage Pyridinium Compounds - pharmacology Pyrimidines - administration & dosage Pyrimidines - chemistry Pyrimidines - pharmacology RNA Interference Tumor Burden - drug effects Xenograft Model Antitumor Assays
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Summary:	Checkpoint kinase 1 (CHK1) is an essential serine/threonine kinase that responds to DNA damage and stalled DNA replication. CHK1 is essential for maintenance of replication fork viability during exposure to DNA antimetabolites. In human tumor cell lines, ablation of CHK1 function during antimetabolite exposure led to accumulation of double-strand DNA breaks and cell death. Here, we extend these observations and confirm ablation of CHK2 does not contribute to these phenotypes and may diminish them. Furthermore, concomitant suppression of cyclin-dependent kinase (CDK) activity is sufficient to completely antagonize the desired CHK1 ablation phenotypes. These mechanism-based observations prompted the development of a high-content, cell-based screen for γ-H2AX induction, a surrogate marker for double-strand DNA breaks. This mechanism-based functional approach was used to optimize small molecule inhibitors of CHK1. Specifically, the assay was used to mechanistically define the optimal in-cell profile with compounds exhibiting varying degrees of CHK1, CHK2, and CDK selectivity. Using this approach, SCH 900776 was identified as a highly potent and functionally optimal CHK1 inhibitor with minimal intrinsic antagonistic properties. SCH 900776 exposure phenocopies short interfering RNA-mediated CHK1 ablation and interacts synergistically with DNA antimetabolite agents in vitro and in vivo to selectively induce dsDNA breaks and cell death in tumor cell backgrounds.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	1535-7163 1538-8514
DOI:	10.1158/1535-7163.mct-10-0928