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Doxorubicin generates a proapoptotic phenotype by phosphorylation of elongation factor 2

Shai J White1, Laura M Kasman, Margaret M Kelly

  • 1Department of Microbiology and Immunology, Medical University of South Carolina, 173 Ashley Ave., Charleston, SC 29425, USA.

Free Radical Biology & Medicine
|September 26, 2007
PubMed

Insights

Doxorubicin enhances prostate cancer cell sensitivity to TRAIL by reducing antiapoptotic proteins like cFLIP(S) and XIAP. This occurs via free radical-induced EF-2 phosphorylation, impacting protein synthesis and promoting apoptosis.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Cell Death Mechanisms

Background:

  • Doxorubicin sensitizes prostate cancer cells to TRAIL-induced apoptosis.
  • This sensitization correlates with decreased cellular FLICE-like inhibitor protein (cFLIP(S)) expression.
  • Previous studies ruled out transcriptional or degradation mechanisms for cFLIP(S) reduction.

Purpose of the Study:

  • Investigate the translational mechanisms behind doxorubicin-induced sensitization to TRAIL.
  • Determine the role of elongation factor 2 (EF-2) phosphorylation in this process.
  • Elucidate the involvement of free radicals and iron in doxorubicin's effects on apoptosis-related proteins.

Main Methods:

  • Treatment of prostate cancer cells with doxorubicin and hydrogen peroxide.
  • Analysis of protein expression levels (cFLIP(S), XIAP, survivin, DR5, caspases, Bax).
  • Assessment of elongation factor 2 (EF-2) phosphorylation.
  • Use of iron chelators to investigate the role of free radicals.

Main Results:

  • Doxorubicin induced sustained EF-2 phosphorylation, inhibiting protein elongation.
  • Hydrogen peroxide mimicked doxorubicin's effects, reducing cFLIP(S), XIAP, and survivin.
  • Doxorubicin-mediated decrease in cFLIP(S) and XIAP, and TRAIL-induced apoptosis, were blocked by iron chelators.
  • Expression of DR5, caspases, and Bax remained unchanged.

Conclusions:

  • Free radicals, generated by doxorubicin-iron interaction, contribute to EF-2 phosphorylation.
  • Phosphorylation of EF-2 leads to reduced expression of short-half-life antiapoptotic proteins (cFLIP(S), XIAP).
  • This reduction in protective proteins increases prostate cancer cell vulnerability to apoptosis stimuli like TRAIL.

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