RT Journal Article
SR Electronic
T1 Potent Activity of Indolequinones against Human Pancreatic Cancer: Identification of Thioredoxin Reductase as a Potential Target
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 163
OP 172
DO 10.1124/mol.109.055855
VO 76
IS 1
A1 Chao Yan
A1 Biehuoy Shieh
A1 Philip Reigan
A1 Zhiyong Zhang
A1 Marie A. Colucci
A1 Aurélie Chilloux
A1 Jeffery J. Newsome
A1 David Siegel
A1 Dan Chan
A1 Christopher J. Moody
A1 David Ross
YR 2009
UL http://molpharm.aspetjournals.org/content/76/1/163.abstract
AB The indolequinone ES936 {5-methoxy-1,2-dimethyl-3-[(4-nitrophenoxy)methyl]indole-4,7-dione} was previously developed in our lab as an antitumor agent against pancreatic cancer. The objective of this study was to identify indolequinones with improved potency against pancreatic cancer and to define their mechanisms of action. Pancreatic cancer cell lines PANC-1, MIA PaCa-2, and BxPC-3 were used in in vitro assays [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) and clonogenic assays]; indolequinones displayed potent cytotoxicity against all three cell lines, and two specific classes of indolequinone were particularly potent agents. These indolequinones induced caspase-dependent apoptosis but no redox cycling or oxidative stress in MIA PaCa-2 and BxPC-3 cells. Selected indolequinones were also screened against the NCI-60 cell line panel and were found to be particularly effective against colon, renal, and melanoma cancer cells. A potential target of these indolequinones was identified as thioredoxin reductase. Indolequinones were found to be potent inhibitors of thioredoxin reductase activity both in pancreatic cancer cells and in cell-free systems. The mechanism of action of the indolequinones was shown to involve metabolic reduction, loss of a leaving group to generate a reactive electrophile resulting in alkylation of the selenocysteine residue in the active site of thioredoxin reductase. In vivo efficacy of the indolequinones was also tested in the MIA PaCa-2 pancreatic tumor xenograft in nude mice, and lead indolequinones demonstrated high efficacy and low toxicity. Inhibition of thioredoxin reductase represents a potential novel target in pancreatic cancer and may provide a biomarker of effect of lead indolequinones in this type of cancer.