Fludarabine-induced apoptosis of B chronic lymphocytic leukemia cells includes early cleavage of p27kip1 by caspases.
B-cell chronic lymphocytic leukemia (B-CLL) is characterized by the accumulation of growth arrested clonal B lymphocytes that undergo apoptosis when treated with fludarabine. To further explore the mechanism for the cell cycle arrest, we examined the expression and activity of cyclin-dependent kinases and inhibitors in primary B-CLL cells. We observed high levels of p27kip1, cyclin D2, cyclin E, cdk2, and cdk4 expression in freshly isolated B-CLL cells. Despite high levels of cyclins and cdks, little cdk2 or cdk4 activity was observed with p27kip1 in complex with cyclinD2/cdk4 and cyclin E/cdk2. Remarkably, when B-CLL cells were treated in vitro with fludarabine, p27kip1 underwent caspase-specific degradation accompanied by an increase in cdk4 activity. We conclude that the G0/G1 arrest of B-CLL cells may protect against apoptosis and that the decrease in p27kip1 expression by caspase cleavage may be a key step in chemotherapy-induced apoptosis in B-CLL.
Sanhes
L
L
Hematology Department, INSERM 9912-EA1517, APHP, Hotel-Dieu, 1 place du parvis Notre-Dame, 75004 Paris, France.
Tang
R
R
Delmer
A
A
DeCaprio
J A
JA
Ajchenbaum-Cymbalista
F
F
D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D042846:CDC2-CDC28 Kinases; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000378:metabolism*; D056742:Cyclin D2; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D020287:In Situ Nick-End Labeling; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000201:enzymology / Q000473:pathology*; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D013347:Subcellular Fractions; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D014740:Vidarabine / Q000031:analogs & derivatives* / Q000494:pharmacology*
D000970:Antineoplastic Agents; C080336:CCND2 protein, human; D061945:Caspase Inhibitors; D018797:Cell Cycle Proteins; D056742:Cyclin D2; D019927:Cyclin E; D016213:Cyclins; D004791:Enzyme Inhibitors; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495900:CDK4 protein, human; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases; D020169:Caspases; D014740:Vidarabine; C024352:fludarabine