Abstract
Indolequinones (IQs) were developed as potential antitumor agents against human pancreatic cancer. IQs exhibited potent antitumor activity against the human pancreatic cancer cell line MIA PaCa-2 with growth inhibitory IC50 values in the low nanomolar range. IQs were found to induce time- and concentration-dependent apoptosis and to be potent inhibitors of thioredoxin reductase 1 (TR1) in MIA PaCa-2 cells at concentrations equivalent to those inducing growth-inhibitory effects. The mechanism of inhibition of TR1 by the IQs was studied in detail in cell-free systems using purified enzyme. The C-terminal selenocysteine of TR1 was characterized as the primary adduction site of the IQ-derived reactive iminium using liquid chromatography-tandem mass spectrometry analysis. Inhibition of TR1 by IQs in MIA PaCa-2 cells resulted in a shift of thioredoxin-1 redox state to the oxidized form and activation of the p38/c-Jun NH2-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) signaling pathway. Oxidized thioredoxin is known to activate apoptosis signal-regulating kinase 1, an upstream activator of p38/JNK in the MAPK signaling cascade and this was confirmed in our study providing a potential mechanism for IQ-induced apoptosis. These data describe the redox and signaling events involved in the mechanism of growth inhibition induced by novel inhibitors of TR1 in human pancreatic cancer cells.
Footnotes
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The online version of this article (available at http://molpharm.aspetjournals.org) contains supplemental material.This work was supported by the National Institutes of Health National Cancer Institute [Grant R01-CA114441].
D.S., C.J.M., and D.R. are scientific cofounders and stockholders in QGenta Inc., which holds an option to license molecules described in this article.
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
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ABBREVIATIONS:
- IQ
- indolequinone
- 1
- 2-hydroxymethyl-5-methoxy-1-methyl-3-[(4-nitrophenoxy)methyl]indole-4,7-dione
- 2
- 5-methoxy-1-methyl-3-[(2,4,6-trifluorophenoxy)methyl]indole-4,7-dione
- TR1
- thioredoxin reductase 1
- ASK1
- apoptosis signal-regulating kinase 1
- JNK
- c-Jun NH2-terminal kinase
- MAPK
- mitogen-activated protein kinase
- NQO2
- NRH:quinone oxidoreductase 2
- NRH
- dihydronicotinamide riboside
- SB203580
- 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole
- l-JNKi
- l-form of the JNK-inhibitory peptide
- CMV
- cytomegalovirus
- MTT
- 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide
- DMSO
- dimethyl sulfoxide
- PI
- propidium iodide
- RIPA
- radioimmunoprecipitation assay
- DTNB
- 5,5′-dithio-bis(2-nitrobenzoid acid
- LC-MS/MS
- liquid chromatography-tandem mass spectrometry
- GR
- glutathione reductase
- GPx
- glutathione peroxidase
- PBS
- phosphate-buffered saline
- ROS
- reactive oxygen species
- PX-12
- 2-[(1-methylpropyl)dithio]-1H-imidazole
- NSC131233
- 2,5-bis[(dimethylamino)methyl]cyclopentanone
- AW464
- 4-(benzothiazol-2-yl)-4-hydroxy-2,5-cyclohexadien-1-one
- PX916
- 2-(5-hydroxy-4-oxo-4H-spiro[naphthalene-1,2′-naphtho[1,8-de][1,3]dioxine]-6′-yloxy)-2-oxoethanminium trifluoroacetate
- Sec
- selenocysteine.
- Received September 26, 2011.
- Accepted December 6, 2011.
- Copyright © 2012 The American Society for Pharmacology and Experimental Therapeutics
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