Abstract
Activation of checkpoint kinase 1 (Chk1) is essential in chemoresistance of hepatocarcinoma (HCC) to 5-fluorouracil (5-FU) and other antimetabolite family of drugs. In this study, we demonstrated that PHA-767491, a dual inhibitor of two cell cycle checkpoint kinases, cell division cycle kinase 7 (Cdc7) and cyclin-dependent kinase 9 (Cdk9), has synergistic antitumor effect with 5-FU to suppress human HCC cells both in vitro and in vivo. Compared with the sole use of each agent, PHA-767491 in combination with 5-FU exhibited much stronger cytotoxicity and induced significant apoptosis manifested by remarkably increased caspase 3 activation and poly(ADP-Ribose) polymerase fragmentation in HCC cells. PHA-767491 directly counteracted the 5-FU-induced phosphorylation of Chk1, a substrate of Cdc7; and decreased the expression of the anti-apoptotic protein myeloid leukemia cell 1, a downstream target of Cdk9. In tumor tissues sectioned from nude mice HCC xenografts, administration of PHA-767491 also decreased Chk1 phosphorylation and increased in situ cell apoptosis. Our study suggests that PHA- 767491 could enhance the efficacy of 5-FU by inhibiting Chk1 phosphorylation and down-regulating Mcl1 expression through inhibition of Cdc7 and Cdk9, thus combinational administration of PHA-767491 with 5-FU could be potentially beneficial to patients with advanced and resistant HCC.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Antineoplastic Combined Chemotherapy Protocols / pharmacology*
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Carcinoma, Hepatocellular / drug therapy*
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Carcinoma, Hepatocellular / metabolism
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Cell Cycle Proteins / antagonists & inhibitors*
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Cell Cycle Proteins / metabolism
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Cell Line, Tumor / drug effects
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Checkpoint Kinase 1
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Cyclin-Dependent Kinase 9 / antagonists & inhibitors*
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Cyclin-Dependent Kinase 9 / metabolism
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Female
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Fluorouracil / administration & dosage
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Humans
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Liver Neoplasms / drug therapy*
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Liver Neoplasms / metabolism
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Mice, Inbred BALB C
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Mice, Nude
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Molecular Targeted Therapy / methods
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Myeloid Cell Leukemia Sequence 1 Protein / genetics
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Myeloid Cell Leukemia Sequence 1 Protein / metabolism
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Phosphorylation / drug effects
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Piperidones / administration & dosage
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Piperidones / pharmacology*
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Protein Kinase Inhibitors / pharmacology
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Protein Kinases / metabolism
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Protein Serine-Threonine Kinases / antagonists & inhibitors*
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Protein Serine-Threonine Kinases / metabolism
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Pyrroles / administration & dosage
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Pyrroles / pharmacology*
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Xenograft Model Antitumor Assays
Substances
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Cell Cycle Proteins
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MCL1 protein, human
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Myeloid Cell Leukemia Sequence 1 Protein
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PHA 767491
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Piperidones
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Protein Kinase Inhibitors
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Pyrroles
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Protein Kinases
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CDC7 protein, human
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CHEK1 protein, human
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Checkpoint Kinase 1
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Chek1 protein, mouse
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Protein Serine-Threonine Kinases
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CDK9 protein, human
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Cyclin-Dependent Kinase 9
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Fluorouracil