Involvement of hTERT in apoptosis induced by interference with Bcl-2 expression and function

Cell Death Differ. 2005 Nov;12(11):1429-38. doi: 10.1038/sj.cdd.4401670.

Abstract

Here, we investigated the role of telomerase on Bcl-2-dependent apoptosis. To this end, the 4625 Bcl-2/Bcl-xL bispecific antisense oligonucleotide and the HA14-1 Bcl-2 inhibitor were used. We found that apoptosis induced by 4625 oligonucleotide was associated with decreased Bcl-2 protein expression and telomerase activity, while HA14-1 triggered apoptosis without affecting both Bcl-2 and telomerase levels. Interestingly, HA14-1 treatment resulted in a profound change from predominantly nuclear to a predominantly cytoplasmic localization of hTERT. Downregulation of endogenous hTERT protein by RNA interference markedly increased apoptosis induced by both 4625 and HA14-1, while overexpression of wild-type hTERT blocked Bcl-2-dependent apoptosis in a p53-independent manner. Catalytically and biologically inactive hTERT mutants showed a similar behavior as the wild-type form, indicating that hTERT inhibited the 4625 and HA14-1-induced apoptosis regardless of telomerase activity and its ability to lengthening telomeres. Finally, hTERT overexpression abrogated 4625 and HA14-1-induced mitochondrial dysfunction and nuclear translocation of hTERT. In conclusion, our results demonstrate that hTERT is involved in mitochondrial apoptosis induced by targeted inhibition of Bcl-2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / genetics
  • Apoptosis / physiology*
  • Benzopyrans / pharmacology
  • Blotting, Western
  • Cell Line, Tumor
  • DNA-Binding Proteins / biosynthesis
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / physiology*
  • Genes, p53 / genetics
  • HCT116 Cells
  • Humans
  • Mitochondria / genetics
  • Mitochondria / physiology
  • Neoplasms / genetics
  • Neoplasms / metabolism
  • Neoplasms / pathology
  • Nitriles / pharmacology
  • Proto-Oncogene Proteins c-bcl-2 / antagonists & inhibitors*
  • Proto-Oncogene Proteins c-bcl-2 / biosynthesis
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Telomerase / biosynthesis
  • Telomerase / genetics
  • Telomerase / metabolism
  • Telomerase / physiology*
  • Thionucleotides / genetics
  • Thionucleotides / pharmacology
  • Transfection

Substances

  • Benzopyrans
  • DNA-Binding Proteins
  • Nitriles
  • Proto-Oncogene Proteins c-bcl-2
  • Thionucleotides
  • ethyl 2-amino-6-bromo-4-(1-cyano-2-ethoxy-2-oxoethyl)-4H-chromene-3-carboxylate
  • oblimersen
  • Telomerase