Characterization of adriamycin-induced G2 arrest and its abrogation by caffeine in FL-amnion cells with or without p53.
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.
Minemoto
Y
Y
Department of Life Science, Graduate School of Natural Science and Technology, Kanazawa University, Japan.
Gannon
J
J
Masutani
M
M
Nakagama
H
H
Sasagawa
T
T
Inoue
M
M
Masamune
Y
Y
Yamashita
K
K
D000650:Amnion / Q000187:drug effects* / Q000378:metabolism; D017209:Apoptosis; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002110:Caffeine / Q000494:pharmacology*; D019926:Cyclin B / Q000378:metabolism; D056744:Cyclin B1; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism / Q000502:physiology*; D003513:Cycloheximide / Q000494:pharmacology; D004249:DNA Damage; D004317:Doxorubicin / Q000494:pharmacology*; D004789:Enzyme Activation; D016195:G2 Phase; D006801:Humans; D009856:Oncogene Proteins, Viral / Q000235:genetics; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012097:Repressor Proteins; D016196:S Phase; D015398:Signal Transduction / Q000187:drug effects*; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism / Q000502:physiology*
C534699:CCNB1 protein, human; C493956:CDKN1A protein, human; D019926:Cyclin B; D056744:Cyclin B1; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; C068651:E6 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D010726:Phosphodiesterase Inhibitors; D011500:Protein Synthesis Inhibitors; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; D002110:Caffeine; D004317:Doxorubicin; D003513:Cycloheximide; D016203:CDC2 Protein Kinase