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Hydroxyurea-induced cell death as related to cell cycle in mouse and human T-lymphoma cells
S Skog1, B Tribukait, B Wallström
1Department of Medical Radiobiology, Karolinska Institut, Stockholm, Sweden.
Abstract:
The association between DNA precursor synthesis, cell cycle perturbations, and cell death caused by the anticancer drug hydroxyurea was investigated in mouse and human T-lymphoma cells. Hydroxyurea inhibits the enzyme ribonucleotide reductase, leading to decreased deoxyribo nucleoside triphosphate pools and an accumulation of cells in early S-phase of the cell cycle. We wished to clarify the mechanism of cell death caused by hydroxyurea in concentrations that can be obtained therapeutically. At a 60-microM concentration of the drug, giving 25% growth inhibition during 24 h, no increase in the number of dead cells was observed as determined by cell flow calculations and density gradient centrifugation. However, the removal of hydroxyurea led to 10-30% cell loss during the following 12-h period. In parallel, there was an increase in DNA precursor levels and a rapid progression of cells through S- and G2 phases of the cell cycle. The isolated dead cells showed no overrepresentation of any cell cycle phase. The results demonstrate that, although the toxic effects of low concentrations of hydroxyurea are minimal, the drug-induced unbalanced growth state can cause substantial cell death during a posttreatment period.
Insights
Low-dose hydroxyurea, an anticancer drug, minimally impacts cell death during treatment. However, it triggers significant cell death after treatment by causing unbalanced cell growth.
Area of Science:
- Cell Biology
- Pharmacology
- Cancer Research
Background:
- Hydroxyurea is an anticancer drug that inhibits ribonucleotide reductase.
- This inhibition leads to reduced deoxyribonucleoside triphosphate pools and S-phase cell cycle arrest.
Purpose of the Study:
- To investigate the mechanism of cell death induced by therapeutically achievable concentrations of hydroxyurea.
- To clarify the relationship between DNA precursor synthesis, cell cycle, and cell death.
Main Methods:
- Mouse and human T-lymphoma cells were treated with hydroxyurea.
- Cell death was assessed using cell flow calculations and density gradient centrifugation.
- DNA precursor levels and cell cycle progression were monitored post-treatment.
Main Results:
- A 60-microM concentration of hydroxyurea caused 25% growth inhibition with no immediate increase in cell death.
- Removal of hydroxyurea resulted in 10-30% cell loss within 12 hours.
- This cell loss was accompanied by increased DNA precursor levels and rapid cell cycle progression.
Conclusions:
- Low concentrations of hydroxyurea have minimal direct toxicity.
- Hydroxyurea-induced unbalanced growth can lead to significant cell death after drug removal.
- This suggests a delayed mechanism of cell death following hydroxyurea treatment.