title: Involvement of Cdc25A phosphatase in Hep3B hepatoma cell growth inhibition induced by novel K vitamin analogs.
abstract: We previously found that K vitamin analogues caused cell growth inhibition in Hep3B hepatoma cells in vitro, which was associated with their inhibitory effects on protein tyrosine-phosphatases. In this study, we show that Cdc25A, a protein phosphatase, was inactivated by novel arylating K vitamin analogues. The inactivation of Cdc25A correlated with their effects on cell growth inhibition. Cyclin-dependent kinase (Cdk) 4, an important regulator for G(1) progression, was found to be tyrosine-phosphorylated by the arylating analogues, and this phosphorylation was correlated with the inhibitory effects of the analogues on Cdc25A activity. Furthermore, Cdk4 dephosphorylation experiments showed that Compound (Cpd) 5, a prototype arylating analogue, inhibited Cdc25A-mediated Cdk4 dephosphorylation, whereas Cpd 26, a nonarylating vitamin K analogue, had no effect on this event. We also examined Cdk4 kinase activity using retinoblastoma protein as a substrate and found that Cpd 5 inhibited retinoblastoma protein phosphorylation in a concentration-dependent manner, indicating that Cdk4 activity was inhibited by Cpd 5 treatment. Moreover, the thiol-antioxidants glutathione and N-acetyl-L-cysteine antagonized the Cpd 5-induced Cdk4 tyrosine phosphorylation, whereas the nonthiol-antioxidants catalase and superoxide dismutase did not. These results suggest that Hep3B cell growth inhibition by these K vitamin analogues may be related in part to inactivation of Cdc25A activity and support the hypothesis that Cdc25A is an attractive target for drugs designed to inhibit cancer cell growth.
authors.affiliation: Department of Surgery, Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: E C
authors.initials: EC
authors.lastname: Southwick
authors.forename: M
authors.initials: M
authors.lastname: Wang
authors.forename: S
authors.initials: S
authors.lastname: Kar
authors.forename: K S
authors.initials: KS
authors.lastname: Rosi
authors.forename: C S
authors.initials: CS
authors.lastname: Wilcox
authors.forename: J S
authors.initials: JS
authors.lastname: Lazo
authors.forename: B I
authors.initials: BI
authors.lastname: Carr
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology; D002374:Catalase / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004347:Drug Interactions; D004789:Enzyme Activation / Q000187:drug effects; D005978:Glutathione / Q000494:pharmacology; D006131:Growth Inhibitors / Q000494:pharmacology*; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D014812:Vitamin K / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D020687:cdc25 Phosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D006131:Growth Inhibitors; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; D013438:Sulfhydryl Compounds; D014812:Vitamin K; D002374:Catalase; C495900:CDK4 protein, human; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; C517004:CDC25A protein, human; D020687:cdc25 Phosphatases; D005978:Glutathione; D000111:Acetylcysteine