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- Fulda, S., et al.
(författare)
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Betulinic acid triggers CD95 (APO-1/Fas)- and p53-independent apoptosis via activation of caspases in neuroectodermal tumors
- 1997
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Ingår i: Cancer Research. - : American Association for Cancer Research. - 0008-5472 .- 1538-7445. ; 57:21, s. 4956-4964
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Tidskriftsartikel (refereegranskat)abstract
- Betulinic acid CBA), a melanoma-specific cytotoxic agent, induced apoptosis in neuroectodermal tumors, such as neuroblastoma, medulloblastoma, and Ewing's sarcoma, representing the most common solid tumors of childhood. BA triggered an apoptosis pathway different from the one previously identified for standard chemotherapeutic drugs. BA-induced apoptosis was independent of CD95-ligand/receptor interaction and accumulation of wild-type p53 protein, but it critically depended on activation of caspases (interleukin 1 beta-converting enzyme/Ced-3-like proteases), FLICE/MACH (caspase-8), considered to be an upstream protease in the caspase cascade, and the downstream caspase CPP32/YAMA/Apopain (caspase-3) were activated, resulting in cleavage of the prototype substrate of caspases PARP. The broad-spectrum peptide inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone, which blocked cleavage of FLICE and PARP, also completely abrogated BA-triggered apoptosis. Cleavage of caspases was preceded by disturbance of mitochondrial membrane potential and by generation of reactive oxygen species. Overexpression of Bcl-2 and Bcl-x(L) conferred resistance to BA at the level of mitochondrial dysfunction, protease activation, and nuclear fragmentation. This suggested that mitochondrial alterations were involved in BA-induced activation of caspases. Furthermore, pax and Bcl-x(s), two death-promoting proteins of the Bcl-2 family, were up-regulated following BA treatment. Most importantly, neuroblastoma cells resistant to CD95- and doxorubicin-mediated apoptosis were sensitive to treatment with BA, suggesting that BA may bypass some forms of drug resistance. Because BA exhibited significant antitumor activity on patients' derived neuroblastoma cells ex vivo, BA may be a promising new agent for the treatment of neuroectodermal tumors in vivo.
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- Fulda, S., et al.
(författare)
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Chemosensitivity of solid tumor cells in vitro is related to activation of the CD95 system
- 1998
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Ingår i: International Journal of Cancer. - 0020-7136 .- 1097-0215. ; 76:1, s. 105-114
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Tidskriftsartikel (refereegranskat)abstract
- We have identified the CD95 system as a key mediator of chemotherapy-induced apoptosis in leukemia and neuroblastoma cells. Here, we report that sensitivity of various solid tumor cell lines for drug-induced cell death corresponds to activation of the CD95 system, Upon drug treatment, strong induction of CD95 ligand (CD95-L) and caspase activity were found in chemosensitive tumor cells (Hodgkin, Ewing's sarcoma, colon carcinoma and small cell lung carcinoma) but not in tumor cells which responded poorly to drug treatment (breast carcinoma and renal cell carcinoma). Blockade of CD95 using F(ab')(2) anti-CD95 antibody fragments markedly reduced drug-induced apoptosis, suggesting that drug-triggered apoptosis depended on CD95-L/receptor interaction. Moreover, drug treatment induced CD95 expression, thereby increasing sensitivity for CD95-induced apoptosis, Drug-induced apoptosis critically depended on activation of caspases (ICE/Ced-3-like proteases) since the broad-spectrum inhibitor of caspases zVAD-fmk strongly reduced drug-mediated apoptosis, The prototype substrate of caspases, poly(ADP-ribose) polymerase, was cleaved upon drug treatment, suggesting that CD95-L triggered autocrine/paracrine death via activation of caspases, Our data suggest that chemosensitivity of solid tumor cells depends on intact apoptosis pathways involving activation of the CD95 system and processing of caspases. Our findings may have important implications for new treatment approaches to increase sensitivity and to overcome resistance of solid tumors. (C) 1998 Wiley-Liss, Inc.
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- Los, Marek Jan, et al.
(författare)
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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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Ingår i: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 90:8, s. 3118-3129
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Tidskriftsartikel (refereegranskat)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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