The antitumor agent imexon activates antioxidant gene expression: evidence for an oxidative stress response.
OBJECTIVE
The aim of this study was to identify biomarkers that may be predictive for the clinical activity of the redox-active antitumor agent imexon.


METHODS
cDNA microarray and quantitative real-time PCR were used to identify global changes in gene expression in peripheral blood mononuclear cells (PBMC) collected from patients treated with imexon during a phase I trial. Electrophoretic mobility shift assays and Western blot analysis were done using the RPMI8226 myeloma cell line grown in vitro and PBMCs treated ex vivo to investigate the molecular mechanism responsible for these gene changes.


RESULTS
Both cDNA microarray and quantitative real-time PCR showed the up-regulation of many antioxidant genes, including thioredoxin reductase-1, glutaredoxin-2, and peroxiredoxin-3 in PBMCs collected from patients treated with imexon. Studies in PBMCs treated ex vivo and RPMI8226 myeloma cells showed that imexon increased binding to the activator protein-1 consensus sequence measured by electrophoretic mobility shift assay. Supershift analysis showed that the majority of the activator protein-1 DNA binding activity was c-Jun, with minor contribution of Jun-D. Nuclear translocation of the nuclear factor (erythroid-derived 1)-like 2 transcription factor and its binding to the antioxidant response element was also increased after imexon treatment, which correlated with an increase in the message levels for nuclear factor (erythroid-derived 1)-like 2/antioxidant response element-regulated antioxidant genes.


CONCLUSIONS
Together, these results show that a predominant biological effect of imexon is a change in redox state that can be detected in surrogate normal tissues as increased redox-sensitive transcription factor binding and increased antioxidant gene expression.
Baker
Amanda F
AF
University of Arizona Cancer Center, Tucson, Arizona 85724, USA. abaker@azcc.arizona.edu
Landowski
Terry
T
Dorr
Robert
R
Tate
Wendy R
WR
Gard
Jaime M C
JM
Tavenner
Breonna E
BE
Dragovich
Tomislov
T
Coon
Amy
A
Powis
Garth
G
D000975:Antioxidants / Q000378:metabolism*; D014408:Biomarkers, Tumor; D045744:Cell Line, Tumor; D002986:Clinical Trials as Topic; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D006588:Hexanones / Q000494:pharmacology*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000378:metabolism
D000975:Antioxidants; D014408:Biomarkers, Tumor; D018076:DNA, Complementary; D006588:Hexanones; D014157:Transcription Factors; C014919:4-imino-1,3-diazabicyclo(3.1.0)hexan-2-one