Abstract
Aberrant function of redox-regulated proteins is a possible cause for cellular transformation and loss of cell cycle control. The small protein thioredoxin has oncogenic properties and controls cell cycle movement through G1, S, and G2/M phases. The redox-active, asymmetrical 1-methylpropyl-2-imidazolyl disulfide (IV-2) has previously been shown to react with and inhibit thioredoxin activity in vitro, the proliferation of human tumor cells in culture, and the growth of tumors in mice. We now examined the effects of IV-2 on cell cycle progression. In synchronized tsFT210 mouse mammary carcinoma cells, IV-2 halted cells in mitosis. In asynchronously growing MCF-7 human breast cancer cells, IV-2 exclusively and irreversibly blocked cells in G2/M at concentrations that correlated with its growth inhibitory activity. Neither the closely related, less redox active 2-hydroxy-1-methylpropyl-2-imidazolyl disulfide (AIV-2), which differs from IV-2 only by an additional hydroxyl group, nor the symmetrical diallyl disulfide caused a G2/M arrest under these conditions. Furthermore, MCF-7 cells treated with IV-2 showed increased Cdk1 kinase activity and a decrease in Cdk1 tyrosine phosphorylation, indicating that IV-2 did not directly inhibit Cdk1 or Cdc25 activities. IV-2 did, however, increase Bcl-2 phosphorylation. These data suggest that the thioredoxin inhibitor IV-2, despite its simple structure, is able to target redox-sensitive processes that are critical for cell cycle progression through mitosis. The results are also consistent with a role of thioredoxin regulating cell cycle progression through G2/M.
Footnotes
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Send reprint requests to: John S. Lazo, University of Pittsburgh, School of Medicine, Department of Pharmacology, Pittsburgh, PA 15261-0001. E-mail: lazo{at}pitt.edu
- Abbreviations:
- IV-2
- 1-methylpropyl 2-imidazolyl disulfide
- DADS
- diallyl disulfide
- AIV-2
- 2-hydroxy-1-methylpropyl 2-imidazolyl disulfide
- PAGE
- polyacrylamide gel electrophoresis
- Received March 20, 2000.
- Accepted May 8, 2000.
- The American Society for Pharmacology and Experimental Therapeutics
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