Nucleic Acids Research Advance Access originally published online on August 31, 2009
Nucleic Acids Research 2009 37(19):6355-6370; doi:10.1093/nar/gkp700
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Nucleic Acids Research, 2009, Vol. 37, No. 19 6355-6370
© The Author(s) 2009. Published by Oxford University Press.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.5/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Gene Regulation, Chromatin and Epigenetics |
CpG methylation potentiates pixantrone and doxorubicin-induced DNA damage and is a marker of drug sensitivity
1Department of Biochemistry, La Trobe University, Victoria 3086, 2Centre for Drug Candidate Optimisation, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia and 3Cell Therapeutics Europe, I-20091 Bresso, Italy
*To whom correspondence should be addressed. Tel: +61-03-9479-1517; Fax: +61-03-9479-2467; Email: s.cutts{at}latrobe.edu.au
Received July 2, 2009. Revised August 6, 2009. Accepted August 6, 2009.
DNA methylation is an epigenetic modification of the mammalian genome that occurs predominantly at cytosine residues of the CpG dinucleotide. Following formaldehyde activation, pixantrone alkylates DNA and particularly favours the CpG motif. Aberrations in CpG methylation patterns are a feature of most cancer types, a characteristic that may determine their susceptibility to specific drug treatments. Given their common target, DNA methylation may modulate the DNA damage induced by formaldehyde-activated pixantrone. In vitro transcription, mass spectrometry and oligonucleotide band shift assays were utilized to establish that pixantrone–DNA adduct formation was consistently enhanced 2–5-fold at discrete methylated CpG doublets. The methylation-mediated enhancement was exquisitely sensitive to the position of the methyl substituent since methylation at neighboring cytosine residues failed to confer an increase in pixantrone–DNA alkylation. Covalent modification of DNA by formaldehyde-activated doxorubicin, but not cisplatin, was augmented by neighbouring CpG methylation, indicating that modulation of binding by CpG methylation is not a general feature of all alkylators. HCT116 colon cancer cells vastly deficient in CpG methylation were 12- and 10-fold more resistant to pixantrone and doxorubicin relative to the wild-type line, suggesting that these drugs may selectively recognize the aberrant CpG methylation profiles characteristic of most tumour types.