Molecular Oncology
Volume 4, Issue 1 , Pages 38-51, February 2010

Topoisomerase IIα-dependent induction of a persistent DNA damage response in response to transient etoposide exposure

  • Sébastien Soubeyrand

      Affiliations

    • The Ottawa Health Research Institute, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada
  • ,
  • Louise Pope

      Affiliations

    • The Ottawa Health Research Institute, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada
  • ,
  • Robert J.G. Haché

      Affiliations

    • The Ottawa Health Research Institute, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada
    • Department of Medicine and Biochemistry, Microbiology and Immunology, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5, Canada
    • Corresponding Author InformationCorresponding author.

Received 17 August 2009; received in revised form 29 September 2009; accepted 30 September 2009. published online 16 October 2009.

Abstract 

Cytotoxicity of the topoisomerase II (topoII) poison etoposide has been ascribed to the persistent covalent trapping of topoII in DNA cleavage complexes that become lethal as cells replicate their DNA. However, short term etoposide treatment also leads to subsequent cell death, suggesting that the lesions that lead to cytotoxicity arise rapidly and prior to the onset DNA replication. In the present study 1h treatment with 25μM etoposide was highly toxic and initiated a double-stranded DNA damage response as reflected by the recruitment of ATM, MDC1 and DNA-PKcs to γH2AX foci. While most DNA breaks were rapidly repaired upon withdrawal of the etoposide treatment, the repair machinery remained engaged in foci for at least 24h following withdrawal. TopoII siRNA ablation showed the etoposide toxicity and γH2AX response to correlate with the inability of the cell to correct topoIIα-initiated DNA damage. γH2AX induction was resistant to the inhibition of DNA replication and transcription, but was increased by pre-treatment with the histone deacetylase inhibitor trichostatin A. These results link the lethality of etoposide to the generation of persistent topoIIα-dependent DNA defects within topologically open chromatin domains.

Keywords: Topoisomerase II, Etoposide, Double-stranded DNA breaks, Non-homologous end joining

Abbreviations: DSB, double-stranded DNA breaks, TopoII, topoisomerase II, CC, cleavage complex, NHEJ, non-homologous DNA end joining, DNA-PKcs, DNA-dependent protein kinase catalytic subunit

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PII: S1574-7891(09)00112-4

doi:10.1016/j.molonc.2009.09.003

Molecular Oncology
Volume 4, Issue 1 , Pages 38-51, February 2010