title: Activation of the Fas pathway independently of Fas ligand during apoptosis induced by camptothecin in p53 mutant human colon carcinoma cells.
abstract: The present study explored the role of the cell surface receptor Fas (CD95/APO-1) in apoptosis induced by camptothecin (CPT) in the HT29 colon carcinoma cell line. CPT-induced apoptosis was associated with high molecular weight DNA fragmentation as measured by filter elution. This fragmentation was inhibited by the caspase inhibitor, z-VAD-fmk and by cycloheximide, which also prevented proteolytic activation of caspase-3 and poly(ADP-ribose)polymerase cleavage. Under such conditions, Fas, Fas ligand, Bax, and p21 expression were increased and Fas recruited the FADD adaptor. Fas expression increase was blocked by cycloheximide but not by z-VAD-fmk, consistent with caspase activation downstream from Fas. Treatment of HT29 cells with FasL or with the CH-11 agonistic anti-Fas antibody potentiated the apoptotic response of cells treated with CPT. The anti-Fas blocking antibody ZB4 and the Fas-ligand inhibitor failed to protect HT29 cells from CPT-induced apoptosis. Such a protection was obtained by transient expression of constructs encoding a dominant-negative mutant of FADD, FADD in an antisense orientation and E8 or MC159 viral proteins that inhibit Fas-induced apoptosis at the level of FADD and procaspase-8, respectively. Together, these data show that topoisomerase I-mediated DNA damage-induced apoptosis involves activation of the Fas pathway without detectable Fas-ligand requirement in CPT-treated cells.
authors: Laboratory of Molecular Pharmacology, Division of Basic Science, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, 20892, USA.
authors: R G
authors: RG
authors: Shao
authors: C X
authors: CX
authors: Cao
authors: W
authors: W
authors: Nieves-Neira
authors: M T
authors: MT
authors: Dimanche-Boitrel
authors: E
authors: E
authors: Solary
authors: Y
authors: Y
authors: Pommier
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002166:Camptothecin / Q000494:pharmacology*; D002352:Carrier Proteins / Q000502:physiology; D003110:Colonic Neoplasms / Q000473:pathology*; D003513:Cycloheximide / Q000494:pharmacology; D053938:DNA Fragmentation / Q000187:drug effects; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D016158:Genes, p53; D019073:HT29 Cells; D006801:Humans; D008562:Membrane Glycoproteins / Q000502:physiology*; D009154:Mutation; D019014:fas Receptor / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000590:Amino Acid Chloromethyl Ketones; D000972:Antineoplastic Agents, Phytogenic; D002352:Carrier Proteins; C505533:FADD protein, human; C505661:FASLG protein, human; D053222:Fas Ligand Protein; D053200:Fas-Associated Death Domain Protein; D008562:Membrane Glycoproteins; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019014:fas Receptor; D003513:Cycloheximide; D002166:Camptothecin