title: A cell-active inhibitor of mitogen-activated protein kinase phosphatases restores paclitaxel-induced apoptosis in dexamethasone-protected cancer cells.
abstract: Mitogen-activated protein kinase phosphatase (MKP)-1 is a dual-specificity phosphatase that negatively regulates the activity of mitogen-activated kinases and that is overexpressed in human tumors. Contemporary studies suggest that induction of MKP-1 during chemotherapy may limit the efficacy of clinically used antineoplastic agents. Thus, MKP-1 is a rational target to enhance anticancer drug activity, but suitable small-molecule inhibitors of MKP-1 are currently unavailable. Here, we have used a high-content, multiparameter fluorescence-based chemical complementation assay for MKP activity in intact mammalian cells to evaluate the cellular MKP-1 and MKP-3 inhibitory activities of four previously described, quinone-based, dual-specificity phosphatase inhibitors, that is, NSC 672121, NSC 95397, DA-3003-1 (NSC 663284), and JUN-1111. All compounds induced formation of reactive oxygen species in mammalian cells, but only one (NSC 95397) inhibited cellular MKP-1 and MKP-3 with an IC(50) of 13 mumol/L. Chemical induction of MKP-1 by dexamethasone protected cells from paclitaxel-induced apoptosis but had no effect on NSC 95397. NSC 95397 phenocopied the effects of MKP-1 small inhibitory RNA by reversing the cytoprotective effects of dexamethasone in paclitaxel-treated cells. Isobologram analysis revealed synergism between paclitaxel and NSC 95397 only in the presence of dexamethasone. The data show the power of a well-defined cellular assay for identifying cell-active inhibitors of MKPs and support the hypothesis that small-molecule inhibitors of MKP-1 may be useful as antineoplastic agents under conditions of high MKP-1 expression.
authors.affiliation: Department of Pharmacology, University of Pittsburgh, Pittsburgh, PA 15260, USA.
authors.forename: Andreas
authors.initials: A
authors.lastname: Vogt
authors.forename: Peter R
authors.initials: PR
authors.lastname: McDonald
authors.forename: Aletheia
authors.initials: A
authors.lastname: Tamewitz
authors.forename: Rachel P
authors.initials: RP
authors.lastname: Sikorski
authors.forename: Peter
authors.initials: P
authors.lastname: Wipf
authors.forename: John J
authors.initials: JJ
authors.lastname: Skoko
authors.forename: John S
authors.initials: JS
authors.lastname: Lazo
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols; D001943:Breast Neoplasms / Q000188:drug therapy / Q000473:pathology; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection / Q000187:drug effects; D003907:Dexamethasone / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D004353:Drug Evaluation, Preclinical; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004357:Drug Synergism; D054638:Dual Specificity Phosphatase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D054642:Dual Specificity Phosphatase 6 / Q000037:antagonists & inhibitors / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D054639:Mitogen-Activated Protein Kinase Phosphatases / Q000037:antagonists & inhibitors*; D008954:Models, Biological; D009285:Naphthoquinones / Q000008:administration & dosage / Q000494:pharmacology*; D017239:Paclitaxel / Q000008:administration & dosage / Q000494:pharmacology*; D011809:Quinones / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: C451261:2,3-bis(2-hydroxyethylsulfanyl)-(1,4)naphthoquinone; D009285:Naphthoquinones; D011809:Quinones; D017382:Reactive Oxygen Species; D003907:Dexamethasone; D054639:Mitogen-Activated Protein Kinase Phosphatases; C517019:DUSP1 protein, human; C517035:DUSP6 protein, human; D054638:Dual Specificity Phosphatase 1; D054642:Dual Specificity Phosphatase 6; D017239:Paclitaxel