TY - JOUR
T1 - Erythroid differentiation sensitizes K562 leukemia cells to TRAIL-induced apoptosis by downregulation of c-FLIP
AU - Hietakangas, Ville
AU - Poukkula, Minna
AU - Heiskanen, Kaisa M
AU - Karvinen, Jarkko T
AU - Sistonen, Lea
AU - Eriksson, John E
PY - 2003/2
Y1 - 2003/2
N2 - Regulation of the apoptotic threshold is of great importance in the homeostasis of both differentiating and fully developed organ systems. Triggering differentiation has been employed as a strategy to inhibit cell proliferation and accelerate apoptosis in malignant cells, in which the apoptotic threshold is often characteristically elevated. To better understand the mechanisms underlying differentiation-mediated regulation of apoptosis, we have studied death receptor responses during erythroid differentiation of K562 erythroleukemia cells, which normally are highly resistant to tumor necrosis factor (TNF) alpha-, FasL-, and TRAIL-induced apoptosis. However, upon hemin-mediated erythroid differentiation, K562 cells specifically lost their resistance to TNF-related apoptosis-inducing ligand (TRAIL), which efficiently killed the differentiating cells independently of mitochondrial apoptotic signaling. Concomitantly with the increased sensitivity, the expression of both c-FLIP splicing variants, c-FLIP(L) and c-FLIP(S), was downregulated, resulting in an altered caspase 8 recruitment and cleavage in the death-inducing signaling complex (DISC). Stable overexpression of both c-FLIP(L) and c-FLIP(S) rescued the cells from TRAIL-mediated apoptosis with isoform-specific effects on DISC-recruited caspase 8. Our results show that c-FLIP(L) and c-FLIP(S) potently control TRAIL responses, both by distinct regulatory features, and further imply that the differentiation state of malignant cells determines their sensitivity to death receptor signals.
AB - Regulation of the apoptotic threshold is of great importance in the homeostasis of both differentiating and fully developed organ systems. Triggering differentiation has been employed as a strategy to inhibit cell proliferation and accelerate apoptosis in malignant cells, in which the apoptotic threshold is often characteristically elevated. To better understand the mechanisms underlying differentiation-mediated regulation of apoptosis, we have studied death receptor responses during erythroid differentiation of K562 erythroleukemia cells, which normally are highly resistant to tumor necrosis factor (TNF) alpha-, FasL-, and TRAIL-induced apoptosis. However, upon hemin-mediated erythroid differentiation, K562 cells specifically lost their resistance to TNF-related apoptosis-inducing ligand (TRAIL), which efficiently killed the differentiating cells independently of mitochondrial apoptotic signaling. Concomitantly with the increased sensitivity, the expression of both c-FLIP splicing variants, c-FLIP(L) and c-FLIP(S), was downregulated, resulting in an altered caspase 8 recruitment and cleavage in the death-inducing signaling complex (DISC). Stable overexpression of both c-FLIP(L) and c-FLIP(S) rescued the cells from TRAIL-mediated apoptosis with isoform-specific effects on DISC-recruited caspase 8. Our results show that c-FLIP(L) and c-FLIP(S) potently control TRAIL responses, both by distinct regulatory features, and further imply that the differentiation state of malignant cells determines their sensitivity to death receptor signals.
KW - Alternative Splicing
KW - Apoptosis/physiology
KW - Apoptosis Regulatory Proteins
KW - CASP8 and FADD-Like Apoptosis Regulating Protein
KW - Carrier Proteins/genetics
KW - Caspase 8
KW - Caspase 9
KW - Caspases/metabolism
KW - Cell Differentiation/drug effects
KW - Cytochrome c Group/metabolism
KW - Death Domain Receptor Signaling Adaptor Proteins
KW - Down-Regulation
KW - HL-60 Cells/metabolism
KW - Hemin/pharmacology
KW - Humans
KW - Intracellular Membranes
KW - Intracellular Signaling Peptides and Proteins
KW - K562 Cells/metabolism
KW - Membrane Glycoproteins/metabolism
KW - Membrane Potentials/drug effects
KW - Mitochondria/metabolism
KW - Protein Isoforms
KW - Proto-Oncogene Proteins c-bcl-2/drug effects
KW - Receptors, TNF-Related Apoptosis-Inducing Ligand
KW - Receptors, Tumor Necrosis Factor/metabolism
KW - Signal Transduction
KW - TNF-Related Apoptosis-Inducing Ligand
KW - Tumor Necrosis Factor-alpha/metabolism
KW - bcl-X Protein
U2 - 10.1128/MCB.23.4.1278-1291.2003
DO - 10.1128/MCB.23.4.1278-1291.2003
M3 - Article
C2 - 12556488
SN - 0270-7306
VL - 23
SP - 1278
EP - 1291
JO - Molecular and Cellular Biology
JF - Molecular and Cellular Biology
IS - 4
ER -