A mitochondrial block and expression of XIAP lead to resistance to TRAIL-induced apoptosis during progression to metastasis of a colon carcinoma

Oncogene. 2008 Oct 9;27(46):6012-22. doi: 10.1038/onc.2008.197. Epub 2008 Jun 16.

Abstract

A pair of isogenic colon carcinoma cells, SW480 and 620, was used to investigate the mechanisms of acquired tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)-resistance during tumour progression. Whereas primary tumour SW480 cells are sensitive to TRAIL-induced apoptosis, metastatic SW620 cells are resistant. The apoptotic signalling activated by TRAIL in SW480 cells is a type II pathway. We show that in SW620 cells, although caspase-8 is recruited and activated at the death-inducing-signalling complex and Bid is cleaved, this does not lead to caspase-9 activation. Comparison of Bcl-2, Bcl-xL and Mcl-1 levels in both cell lines showed no difference. In SW620 cells transfected with a tBid-GFP construct, tBid-GFP was correctly localized to the mitochondria. Thus, the resistance of SW620 cells is at the level of the mitochondria that can withstand large amounts of tBid. Although caspase-3 was directly cleaved by caspase-8 in SW620 cells to yield the p20 fragment, no further autocatalytic maturation into the p17 fragment was observed. We show that, in contrast to SW480 cells, the SW620 cell line expresses high amounts of X-linked inhibitor of apoptosis (XIAP). Downregulation of XIAP with bortezomib or small-interfering RNA was sufficient to restore the sensitivity of SW620 cells to TRAIL-induced apoptosis in the absence of SMAC/Diablo or cytochrome c release from the mitochondria. Thus, SW620 cells have developed a dual resistance to TRAIL-induced apoptosis: a block at the level of the mitochondria and, after a conversion to a type I pathway, an increased expression of XIAP which inhibits this pathway.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology
  • Antineoplastic Agents / therapeutic use
  • Apoptosis / drug effects*
  • Apoptosis / genetics
  • BH3 Interacting Domain Death Agonist Protein / metabolism
  • BH3 Interacting Domain Death Agonist Protein / physiology
  • Boronic Acids / pharmacology
  • Boronic Acids / therapeutic use
  • Bortezomib
  • Carcinoma / drug therapy
  • Carcinoma / genetics
  • Carcinoma / metabolism
  • Carcinoma / pathology*
  • Cell Membrane Permeability / drug effects
  • Colonic Neoplasms / drug therapy
  • Colonic Neoplasms / genetics
  • Colonic Neoplasms / metabolism
  • Colonic Neoplasms / pathology*
  • Disease Progression
  • Drug Resistance, Neoplasm / drug effects
  • Drug Resistance, Neoplasm / genetics*
  • Gene Expression Regulation, Neoplastic / drug effects
  • Genes, bcl-2 / physiology
  • Humans
  • Mitochondria / drug effects*
  • Mitochondria / metabolism
  • Mitochondria / physiology
  • Pyrazines / pharmacology
  • Pyrazines / therapeutic use
  • TNF-Related Apoptosis-Inducing Ligand / pharmacology*
  • TNF-Related Apoptosis-Inducing Ligand / therapeutic use
  • Tumor Cells, Cultured
  • X-Linked Inhibitor of Apoptosis Protein / genetics*
  • X-Linked Inhibitor of Apoptosis Protein / metabolism

Substances

  • Antineoplastic Agents
  • BH3 Interacting Domain Death Agonist Protein
  • Boronic Acids
  • Pyrazines
  • TNF-Related Apoptosis-Inducing Ligand
  • X-Linked Inhibitor of Apoptosis Protein
  • XIAP protein, human
  • Bortezomib