RT Journal Article
SR Electronic
T1 Formaldehyde-Activated Pixantrone Is a Monofunctional DNA Alkylator That Binds Selectively to CpG and CpA Doublets
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 184
OP 194
DO 10.1124/mol.108.045625
VO 74
IS 1
A1 Benny J. Evison
A1 Francis Chiu
A1 Gabriella Pezzoni
A1 Don R. Phillips
A1 Suzanne M. Cutts
YR 2008
UL http://molpharm.aspetjournals.org/content/74/1/184.abstract
AB The topoisomerase II poison mitoxantrone is important in the clinical management of human malignancies. Pixantrone, a novel aza-anthracenedione developed to improve the therapeutic profile of mitoxantrone, can efficiently alkylate DNA after formaldehyde activation. In vitro transcriptional analysis has now established that formaldehyde-activated pixantrone generates covalent adducts selectively at discrete CpG or CpA dinucleotides, suggesting that the activated complex binds to guanine or cytosine (or both) bases. The stability of pixantrone adduct-induced transcriptional blockages varied considerably, reflecting a mixture of distinct pixantrone adduct types that may include relatively labile monoadducts and more stable interstrand cross-links. 6,9-Bis-[[2-(dimethylamino)ethyl]amino]benzo[g]isoquinoline-5,10-dione (BBR 2378), the dimethyl N-substituted analog of pixantrone, could not form adducts, suggesting that pixantrone alkylates DNA through the primary amino functions located in each side chain of the drug. Pixantrone generated DNA adducts only when guanine was present in substrates and exhibited a lack of adduct formation with inosine-containing polynucleotides, confirming that the N2 amino group of guanine is the site for covalent attachment of the drug. Mass spectrometric analysis of oligonucleotide-drug complexes confirmed that formation of covalent pixantrone-DNA adducts is mediated by a single methylene linkage provided by formaldehyde and that this occurs only with guanine-containing double stranded oligonucleotide substrates. CpG methylation, an epigenetic modification of the mammalian genome, significantly enhanced the generation of pixantrone-DNA adducts within a methylated DNA substrate, indicating that the methylated dinucleotide may be a favored target in a cellular environment. The American Society for Pharmacology and Experimental Therapeutics