| 1. |
- Los, Marek Jan, et al.
(author)
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Cross-resistance of CD95- and drug-induced apoptosis as a consequence of deficient activation of caspases (ICE/Ced-3 proteases)
- 1997
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In: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 90:8, s. 3118-3129
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Journal article (peer-reviewed)abstract
- The cytotoxic effect of anticancer drugs has been shown to involve induction of apoptosis. We report here that tumor cells resistant to CD95 (APO-1/Fas) -mediated apoptosis were cross-resistant to apoptosis-induced by anticancer drugs. Apoptosis induced in tumor cells by cytarabine, doxorubicin, and methotrexate required the activation of ICE/Ced-3 proteases (caspases), similarly to the CD95 system, After drug treatment, a strong increase of caspase activity was found that preceded cell death, Drug-induced activation of caspases was also found in ex vivo-derived T-cell leukemia cells. Resistance to cell death was conferred by a peptide caspase inhibitor and CrmA, a poxvirus-derived serpin, The peptide inhibitor was effective even if added several hours after drug treatment, indicating a direct involvement of caspases in the execution and not in the trigger phase of drug action. Drug-induced apoptosis was also strongly inhibited by antisense approaches targeting caspase-1 and -3, indicating that several members of this protease family were involved. CD95-resistant cell lines that failed to activate caspases upon CD95 triggering were cross-resistant to drug-mediated apoptosis, Our data strongly support the concept that sensitivity for drug-induced cell death depends on intact apoptosis pathways leading to activation of caspases. The identification of defects in caspase activation may provide molecular targets to overcome drug resistance in tumor cells. (C) 1997 by The American Society of Hematology.
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| 2. |
- Wesselborg, Sebastian, et al.
(author)
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Anticancer drugs induce caspase-8/FLICE activation and apoptosis in the absence of CD95 receptor/ligand interaction
- 1999
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In: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 93:9, s. 3053-3063
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Journal article (peer-reviewed)abstract
- 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. (C) 1999 by The American Society of Hematology.
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