c-FLIP mediates resistance of Hodgkin/Reed-Sternberg cells to death receptor-induced apoptosis.
Resistance to death receptor-mediated apoptosis is supposed to be important for the deregulated growth of B cell lymphoma. Hodgkin/Reed-Sternberg (HRS) cells, the malignant cells of classical Hodgkin's lymphoma (cHL), resist CD95-induced apoptosis. Therefore, we analyzed death receptor signaling, in particular the CD95 pathway, in these cells. High level CD95 expression allowed a rapid formation of the death-inducing signaling complex (DISC) containing Fas-associated death domain-containing protein (FADD), caspase-8, caspase-10, and most importantly, cellular FADD-like interleukin 1beta-converting enzyme-inhibitory protein (c-FLIP). The immunohistochemical analysis of the DISC members revealed a strong expression of CD95 and c-FLIP overexpression in 55 out of 59 cases of cHL. FADD overexpression was detectable in several cases. Triggering of the CD95 pathway in HRS cells is indicated by the presence of CD95L in cells surrounding them as well as confocal microscopy showing c-FLIP predominantly localized at the cell membrane. Elevated c-FLIP expression in HRS cells depends on nuclear factor (NF)-kappaB. Despite expression of other NF-kappaB-dependent antiapoptotic proteins, the selective down-regulation of c-FLIP by small interfering RNA oligoribonucleotides was sufficient to sensitize HRS cells to CD95 and tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis. Therefore, c-FLIP is a key regulator of death receptor resistance in HRS cells.
Mathas
Stephan
S
Max-Delbrück-Center for Molecular Medicine, FG Dörken, D-13125 Berlin, Germany. mathas@rrk-berlin.de
Lietz
Andreas
A
Anagnostopoulos
Ioannis
I
Hummel
Franziska
F
Wiesner
Burkhard
B
Janz
Martin
M
Jundt
Franziska
F
Hirsch
Burkhard
B
Jöhrens-Leder
Korinna
K
Vornlocher
Hans-Peter
HP
Bommert
Kurt
K
Stein
Harald
H
Dörken
Bernd
B
D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D001483:Base Sequence; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D053455:Caspase 10; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D003513:Cycloheximide / Q000494:pharmacology; D053200:Fas-Associated Death Domain Protein; D006689:Hodgkin Disease / Q000473:pathology* / Q000503:physiopathology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins / Q000502:physiology; D016328:NF-kappa B / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D016539:Reed-Sternberg Cells / Q000187:drug effects / Q000473:pathology* / Q000502:physiology*; D053221:TNF-Related Apoptosis-Inducing Ligand; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D019014:fas Receptor / Q000502:physiology*
D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; 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; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D034741:RNA, Small Interfering; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor; D003513:Cycloheximide; C505530:CASP8 protein, human; D053455:Caspase 10; D053181:Caspase 8; D020169:Caspases; C506438:CASP10 protein, human