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Characterization of adriamycin-induced G2 arrest and its abrogation by caffeine in FL-amnion cells with or without
Y Minemoto1, J Gannon, M Masutani
1Department of Life Science, Graduate School of Natural Science and Technology, Kanazawa University, Japan.
Abstract:
We investigated the effect of Adriamycin on FL-amnion (FL) cells. After treatment with the drug, the cells arrested at G2, but we did not detect an increase in the p21 levels. We established a p53-deficient derivative of these cells, in which G2 arrest also occurred after treatment with Adriamycin, suggesting that the arrest we observed in these cells is independent of the p53 pathway. Low doses of Adriamycin (100-200 ng/ml) induced G2 arrest, while late S-phase arrest was observed at high doses (500-1000 ng/ml) in both FL and p53-deficient FL cells. Accumulation of cyclin B1 was detected only in cells arrested at G2, and not in those arrested at S phase, suggesting that the S-phase checkpoint functioned efficiently even in p53-deficient FL cells. In both cell lines, caffeine-induced activation of CDC2 kinase was detected only in cells arrested at G2 and CDC2 kinase-activated cells died exhibiting features of apoptosis. CDC2 kinase activation was inhibited by cycloheximide. Furthermore, cycloheximide inhibited activation of CDK2:cyclin A, which normally precedes CDC2 kinase activation in caffeine-treated cells. These results suggest that p53 and p21 do not have special roles in the S- and G2-phase checkpoints and that CDK2:cyclin A could be the target of the G2-phase DNA damage checkpoint.
Insights
Adriamycin induces cell cycle arrest at G2 or S phase in FL cells, independent of p53. This Adriamycin-induced G2 arrest involves CDC2 kinase activation and apoptosis, suggesting CDK2:cyclin A as a potential G2 checkpoint target.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- Adriamycin is a chemotherapy drug that induces DNA damage.
- Cell cycle checkpoints are crucial for maintaining genomic stability.
- The roles of p53 and p21 in DNA damage response are well-established.
Purpose of the Study:
- To investigate the effects of Adriamycin on FL-amnion (FL) cells.
- To determine the involvement of the p53 pathway in Adriamycin-induced cell cycle arrest.
- To elucidate the molecular mechanisms underlying G2 and S-phase checkpoints.
Main Methods:
- Treatment of FL cells and p53-deficient FL cells with varying doses of Adriamycin.
- Cell cycle analysis to detect G2 and S-phase arrest.
- Western blotting to detect p21 and cyclin B1 levels.
- Caffeine and cycloheximide treatments to study kinase activation and apoptosis.
Main Results:
- Adriamycin induced G2 arrest at low doses and S-phase arrest at high doses in both cell types.
- G2 arrest occurred independently of the p53 pathway and p21 levels.
- Cyclin B1 accumulated in G2-arrested cells, while S-phase arrest showed efficient checkpoint function.
- Caffeine-induced CDC2 kinase activation and apoptosis were observed in G2-arrested cells, inhibited by cycloheximide.
- Cycloheximide also inhibited CDK2:cyclin A activation, suggesting its role in the G2 checkpoint.
Conclusions:
- p53 and p21 are not essential for S- and G2-phase checkpoints in response to Adriamycin.
- CDK2:cyclin A may be a key target of the G2-phase DNA damage checkpoint.
- Adriamycin's effects on cell cycle progression are dose-dependent and can occur through p53-independent pathways.