title: Phosphorylation of Fas-associated death domain contributes to enhancement of etoposide-induced apoptosis in prostate cancer cells.
abstract: Fas-associated death domain (FADD) plays an important role as an adapter molecule in Fas (CD95/APO-1)-mediated apoptosis and contributes to anticancer drug-induced cytotoxicity. We treated three human prostate cancer cell lines with etoposide, a toposiomerase II inhibitor with activity against various tumors including prostate cancer. We found that the overexpression of FADD sensitizes etoposide-induced apoptosis through a rapid activation of c-Jun NH(2)-terminal kinase (JNK) and, subsequently, of caspase 3. In addition, phosphorylation of FADD at serine 194 coincided with this sensitization. Treatment with the caspase 3 inhibitor, N-acetyl-Asp-Glu-Val-Asp-aldehyde (DEVD-CHO), or overexpression of either mitogen-activated protein kinase kinase (MKK) 7 or Bcl-xL canceled FADD-mediated sensitization to etoposide-induced apoptosis. Moreover, treatment with the caspase 8 inhibitor, benzyloxy-carbonyl-Val-Ala-Asp-fluoromethylketone (z-IETD-fmk), or overexpression of viral FLICE/caspase-8-inhibitory protein (FLIP) from equine herpesvirus type 2 E8 also had an inhibitory effect, supporting a major involvement of a caspase 8-dependent mitochondrial pathway. Interestingly, FADD was phosphorylated, and etoposide-induced JNK/caspase activation and apoptosis were enhanced in the cells arrested at G2/M transition, but not in those overexpressing mutant FADD, in which 194 serine was replaced by alanine. Our results demonstrate that phosphorylated FADD-dependent activation of the JNK/caspase pathway plays a pivotal role in sensitization to etoposide-induced apoptosis in prostate cancer cells.
authors.affiliation: Second Department of Pathology, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8521, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Shimada
authors.forename: Mitsutoshi
authors.initials: M
authors.lastname: Nakamura
authors.forename: Eiwa
authors.initials: E
authors.lastname: Ishida
authors.forename: Munehiro
authors.initials: M
authors.lastname: Kishi
authors.forename: Shin
authors.initials: S
authors.lastname: Yonehara
authors.forename: Noboru
authors.initials: N
authors.lastname: Konishi
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis / Q000187:drug effects*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000378:metabolism* / Q000502:physiology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle; D004789:Enzyme Activation / Q000187:drug effects; D005047:Etoposide / Q000494:pharmacology*; D053200:Fas-Associated Death Domain Protein; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D048031:JNK Mitogen-Activated Protein Kinases; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000473:pathology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology; D012694:Serine / Q000378:metabolism; D014407:Tumor Cells, Cultured; D051020:bcl-X Protein
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C494811:BCL2L1 protein, human; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; D002352:Carrier Proteins; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D047908:Intracellular Signaling Peptides and Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D012694:Serine; D005047:Etoposide; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases