Involvement of CED-3/ICE proteases in the apoptosis of B-chronic lymphocytic leukemia cells.
B-chronic lymphocytic leukemia (B-CLL) is characterized by the accumulation of long-lived B lymphocytes that express high levels of Bcl-2. We examined the involvement of CED-3/ICE-like proteases in the apoptosis of B-CLL cells. One of the substrates of these proteases is poly(ADP [adenosine 5'-diphosphate]-ribose) polymerase (PARP). The effect of different factors that induce the apoptosis of B-CLL cells on the proteolytic cleavage of PARP has been studied. Treatment of B-CLL cells with different concentrations of dexamethasone (1 to 1,000 micromol/L) induced in a dose-dependent manner the cleavage of PARP. Dexamethasone induced PARP cleavage after 12 hours of incubation, which was almost complete at 48 hours. PARP cleavage during apoptosis of B-CLL cells was studied in cells from eight patients and a correlation was found between cell viability and the degree of PARP cleavage. Incubation in vitro of B-CLL cells with fludarabine for 48 hours induced PARP cleavage in all the cases studied. Protein kinase C (PKC) activation with 100 nmol/L TPA (12-O-tetradecanoylphorbol 13-acetate) or incubation with interleukin-4 (10 ng/mL) prevented either dexamethasone- or fludarabine-induced proteolysis of PARP. Incubation of B-CLL cells with the CED-3/ICE-like protease inhibitor Z-VAD.fmk inhibited spontaneous and dexamethasone-induced PARP cleavage and DNA fragmentation in a dose-dependent manner. Furthermore, Z-VAD.fmk prevented the cytotoxic effect of dexamethasone. These results indicate that CED-3/ICE-like proteases play an important role in the apoptosis of B-CLL cells.
Bellosillo
B
B
Departament de Ciències Fisiologiques Humanes i de la Nutrició, Universitat de Barcelona, Spain.
Dalmau
M
M
Colomer
D
D
Gil
J
J
D000368:Aged; D017209:Apoptosis; D029742:Caenorhabditis elegans Proteins; D020170:Caspase 1; D020169:Caspases; D002470:Cell Survival / Q000187:drug effects; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D053938:DNA Fragmentation; D003907:Dexamethasone / Q000494:pharmacology; D005260:Female; D006801:Humans; D007700:Kinetics; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000201:enzymology / Q000473:pathology / Q000503:physiopathology*; D008214:Lymphocytes / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured
D029742:Caenorhabditis elegans Proteins; D003907:Dexamethasone; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases; D003546:Cysteine Endopeptidases; C089223:ced-3 protein, C elegans; D020170:Caspase 1