Sensitization for death receptor- or drug-induced apoptosis by re-expression of caspase-8 through demethylation or gene transfer

Oncogene. 2001 Sep 13;20(41):5865-77. doi: 10.1038/sj.onc.1204750.


Resistance of tumors to treatment with cytotoxic drugs, irradiation or immunotherapy may be due to disrupted apoptosis programs. Here, we report in a variety of different tumor cells including Ewing tumor, neuroblastoma, malignant brain tumors and melanoma that caspase-8 expression acts as a key determinant of sensitivity for apoptosis induced by death-inducing ligands or cytotoxic drugs. In tumor cell lines resistant to TRAIL, anti-CD95 or TNFalpha, caspase-8 protein and mRNA expression was decreased or absent without caspase-8 gene loss. Methylation-specific PCR revealed hypermethylation of caspase-8 regulatory sequences in cells with impaired caspase-8 expression. Treatment with the demethylation agent 5-Aza-2'-deoxycytidine (5-dAzaC) reversed hypermethylation of caspase-8 resulting in restoration of caspase-8 expression and recruitment and activation of caspase-8 at the CD95 DISC upon receptor cross-linking thereby sensitizing for death receptor-, and importantly, also for drug-induced apoptosis. Inhibition of caspase-8 activity also inhibited apoptosis sensitization by 5-dAzaC. Similar to demethylation, introduction of caspase-8 by gene transfer sensitized for apoptosis induction. Hypermethylation of caspase-8 was linked to reduced caspase-8 expression in different tumor cell lines in vitro and, most importantly, also in primary tumor samples. Thus, these findings indicate that re-expression of caspase-8, e.g. by demethylation or caspase-8 gene transfer, might be an effective strategy to restore sensitivity for chemotherapy- or death receptor-induced apoptosis in various tumors in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis
  • Apoptosis Regulatory Proteins
  • Azacitidine / analogs & derivatives
  • Azacitidine / pharmacology
  • Bone Neoplasms / drug therapy
  • Bone Neoplasms / metabolism*
  • Caspase 3
  • Caspase 8
  • Caspase 9
  • Caspases / genetics
  • Caspases / metabolism*
  • DNA Modification Methylases / pharmacology
  • Decitabine
  • Down-Regulation
  • Drug Resistance, Neoplasm / physiology*
  • Enzyme Induction / drug effects
  • Gene Transfer Techniques
  • Humans
  • Membrane Glycoproteins / pharmacology*
  • Methylation
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • RNA, Messenger / metabolism
  • Receptors, Tumor Necrosis Factor / metabolism
  • Sarcoma, Ewing / drug therapy
  • Sarcoma, Ewing / metabolism*
  • TNF-Related Apoptosis-Inducing Ligand
  • Tumor Cells, Cultured
  • Tumor Necrosis Factor-alpha / pharmacology*


  • Apoptosis Regulatory Proteins
  • Membrane Glycoproteins
  • Neoplasm Proteins
  • RNA, Messenger
  • Receptors, Tumor Necrosis Factor
  • TNF-Related Apoptosis-Inducing Ligand
  • TNFSF10 protein, human
  • Tumor Necrosis Factor-alpha
  • Decitabine
  • DNA Modification Methylases
  • CASP3 protein, human
  • CASP8 protein, human
  • CASP9 protein, human
  • Caspase 3
  • Caspase 8
  • Caspase 9
  • Caspases
  • Azacitidine