Erythroid Differentiation Sensitizes K562 Leukemia Cells to TRAIL-induced Apoptosis by Downregulation of c-FLIP

Mol Cell Biol. 2003 Feb;23(4):1278-91. doi: 10.1128/mcb.23.4.1278-1291.2003.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing
  • Apoptosis / physiology*
  • Apoptosis Regulatory Proteins
  • CASP8 and FADD-Like Apoptosis Regulating Protein
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Caspase 8
  • Caspase 9
  • Caspases / metabolism
  • Cell Differentiation / drug effects
  • Cell Differentiation / physiology*
  • Cytochrome c Group / metabolism
  • Death Domain Receptor Signaling Adaptor Proteins
  • Down-Regulation
  • HL-60 Cells / metabolism
  • HL-60 Cells / pathology
  • Hemin / pharmacology
  • Humans
  • Intracellular Membranes
  • Intracellular Signaling Peptides and Proteins*
  • K562 Cells / metabolism
  • K562 Cells / pathology*
  • Membrane Glycoproteins / metabolism*
  • Membrane Glycoproteins / pharmacology
  • Membrane Potentials / drug effects
  • Mitochondria / metabolism
  • Protein Isoforms
  • Proto-Oncogene Proteins c-bcl-2 / drug effects
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Receptors, TNF-Related Apoptosis-Inducing Ligand
  • Receptors, Tumor Necrosis Factor / metabolism
  • Signal Transduction
  • TNF-Related Apoptosis-Inducing Ligand
  • Tumor Necrosis Factor-alpha / metabolism*
  • Tumor Necrosis Factor-alpha / pharmacology
  • bcl-X Protein

Substances

  • Apoptosis Regulatory Proteins
  • BCL2L1 protein, human
  • CASP8 and FADD-Like Apoptosis Regulating Protein
  • CFLAR protein, human
  • Carrier Proteins
  • Cytochrome c Group
  • Death Domain Receptor Signaling Adaptor Proteins
  • Intracellular Signaling Peptides and Proteins
  • Membrane Glycoproteins
  • Protein Isoforms
  • Proto-Oncogene Proteins c-bcl-2
  • Receptors, TNF-Related Apoptosis-Inducing Ligand
  • Receptors, Tumor Necrosis Factor
  • TNF-Related Apoptosis-Inducing Ligand
  • TNFRSF10A protein, human
  • TNFRSF10B protein, human
  • TNFSF10 protein, human
  • Tumor Necrosis Factor-alpha
  • bcl-X Protein
  • Hemin
  • CASP8 protein, human
  • CASP9 protein, human
  • Caspase 8
  • Caspase 9
  • Caspases