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Antitumor imidazolyl disulfide IV-2 causes irreversible G(2)/M cell cycle arrest without hyperphosphorylation of
1Department of Pharmacology, University of Pittsburgh, PA 15261-0001, USA.
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 G(1), S, and G(2)/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 G(2)/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 G(2)/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 G(2)/M.
Insights
The redox-active compound IV-2 halts cancer cells in mitosis by inhibiting thioredoxin, a protein involved in cell cycle control. This targeted cell cycle arrest offers a potential strategy for cancer therapy.
Area of Science:
- Cell Biology
- Biochemistry
- Oncology
Background:
- Aberrant redox-regulated proteins, including the oncogenic thioredoxin, contribute to cellular transformation and uncontrolled cell division.
- Thioredoxin plays a crucial role in regulating cell cycle progression through multiple phases (G(1), S, and G(2)/M).
- The disulfide compound 1-methylpropyl-2-imidazolyl disulfide (IV-2) inhibits thioredoxin activity and tumor growth.
Purpose of the Study:
- To investigate the specific effects of the thioredoxin inhibitor IV-2 on cell cycle progression.
- To elucidate the mechanisms by which IV-2 impacts cell cycle regulation, particularly during mitosis.
Main Methods:
- Cell synchronization and treatment with IV-2 in tsFT210 mouse mammary carcinoma and MCF-7 human breast cancer cells.
- Analysis of cell cycle distribution using flow cytometry.
- Assessment of key cell cycle regulatory proteins, including Cdk1, Cdc25, and Bcl-2, through kinase activity and phosphorylation assays.
Main Results:
- IV-2 induced a cell cycle arrest specifically in the G(2)/M phase in asynchronously growing MCF-7 cells.
- This G(2)/M arrest was concentration-dependent and irreversible, correlating with IV-2's growth inhibitory effects.
- IV-2 treatment increased Cdk1 kinase activity and Bcl-2 phosphorylation, without directly inhibiting Cdk1 or Cdc25.
Conclusions:
- The thioredoxin inhibitor IV-2 effectively targets redox-sensitive pathways critical for mitotic progression.
- IV-2's ability to induce a G(2)/M arrest suggests a potential therapeutic application in cancer treatment.
- These findings support a role for thioredoxin in regulating cell cycle progression through the G(2)/M phase.