Anticancer drugs induce caspase-8/FLICE activation and apoptosis in the absence of CD95 receptor/ligand interaction.
Proteases of the caspase family are the critical executioners of apoptosis. Their activation has been mainly studied upon triggering of death receptors, such as CD95 (Fas/APO-1) and tumor necrosis factor-R1, which recruit caspase-8/FLICE as the most proximal effector to the receptor complex. Because apoptosis induced by anticancer drugs has been proposed to involve CD95/CD95 ligand interaction, we investigated the mechanism of caspase activation by daunorubicin, doxorubicin, etoposide, and mitomycin C. In Jurkat leukemic T cells, all drugs induced apoptosis and the cleavage of procaspase-8 to its active p18 subunit. However, cells resistant to CD95 were equally susceptible to anticancer drugs and activated caspase-8 with a similar kinetic and dose response as CD95-sensitive cells. The broad caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone prevented apoptosis and caspase-8 activation in response to CD95 and drug treatment, whereas a neutralizing CD95 decoy as well as a dominant-negative FADD construct selectively abrogated CD95, but not drug-induced effects. A potent activation of caspase-8 was also induced by cycloheximide, indicating that it was independent of protein synthesis. Our data, therefore, show that (1) anticancer drug-induced apoptosis does not require de novo synthesis of death ligands or CD95 interaction, and (2) that caspase-8 can be activated in the absence of a death receptor signaling.
Wesselborg
S
S
Department of Internal Medicine I, Eberhard-Karls-University, Tübingen, Germany.
Engels
I H
IH
Rossmann
E
E
Los
M
M
Schulze-Osthoff
K
K
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000235:genetics / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003630:Daunorubicin / Q000494:pharmacology; D004317:Doxorubicin / Q000494:pharmacology; D004789:Enzyme Activation; D005047:Etoposide / Q000494:pharmacology; D053222:Fas Ligand Protein; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D008562:Membrane Glycoproteins / Q000187:drug effects / Q000502:physiology*; D016685:Mitomycin / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013601:T-Lymphocytes; D014162:Transfection; D014407:Tumor Cells, Cultured; D019014:fas Receptor / Q000187:drug effects / Q000235:genetics / Q000502:physiology*
D000590:Amino Acid Chloromethyl Ketones; D000970:Antineoplastic Agents; D015853:Cysteine Proteinase Inhibitors; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019014:fas Receptor; D016685:Mitomycin; D005047:Etoposide; D004317:Doxorubicin; D003513:Cycloheximide; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D003630:Daunorubicin