title: Reversible and formaldehyde-mediated covalent binding of a bis-amino mitoxantrone analogue to DNA.
abstract: The ability of a bis-amino mitoxantrone anticancer drug (named WEHI-150) to form covalent adducts with DNA, after activation by formaldehyde, has been studied by electrospray ionisation mass spectrometry and HPLC. Mass spectrometry results showed that WEHI-150 could form covalent adducts with d(ACGCGCGT)2 that contained one, two or three covalent links to the octanucleotide, whereas the control drugs (daunorubicin and the anthracenediones mitoxantrone and pixantrone) only formed adducts with one covalent link to the octanucleotide. HPLC was used to examine the extent of covalent bond formation of WEHI-150 with d(CGCGCG)2 and d(CG(5Me)CGCG)2. Incubation of WEHI-150 with d(CG(5Me)CGCG)2 in the presence of formaldehyde resulted in the formation of significantly greater amounts of covalent adducts than was observed with d(CGCGCG)2. In order to understand the observed increase of covalent adducts with d(CG(5Me)CGCG)2, an NMR study of the reversible interaction of WEHI-150 at both CpG and (5Me)CpG sites was undertaken. Intermolecular NOEs were observed in the NOESY spectra of d(ACGGCCGT)2 with added WEHI-150 that indicated that the drug selectively intercalated at the CpG sites and from the major groove. In particular, NOEs were observed from the WEHI-150 H2,3 protons to the H1' protons of G3 and G7 and from the H6,7 protons to the H5 protons of C2 and C6. By contrast, intermolecular NOEs were observed between the WEHI-150 H2,3 protons to the H2'' proton of the (5Me)C3 in d(CG(5Me)CGCG)2, and between the drug aliphatic protons and the H1' proton of G4. This demonstrated that WEHI-150 preferentially intercalates at (5Me)CpG sites, compared to CpG sequences, and predominantly via the minor groove at the (5Me)CpG site. The results of this study demonstrate that WEHI-150 is likely to form interstrand DNA cross-links, upon activation by formaldehyde, and consequently exhibit greater cytotoxicity than other current anthracenedione drugs.
authors.affiliation: School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Australian Defence Force Academy, Northcott Drive, Campbell, ACT 2600, Australia. g.collins@adfa.edu.au.
authors.forename: Shyam K
authors.initials: SK
authors.lastname: Konda
authors.affiliation: School of Chemistry, University of Wollongong, Wollongong, NSW 2522, Australia.
authors.forename: Celine
authors.initials: C
authors.lastname: Kelso
authors.affiliation: Biochemistry Department, La Trobe University, Bundoora, VIC 3083, Australia. s.cutts@latrobe.edu.au.
authors.forename: Paul P
authors.initials: PP
authors.lastname: Pumuye
authors.affiliation: Biochemistry Department, La Trobe University, Bundoora, VIC 3083, Australia. s.cutts@latrobe.edu.au and Chemical Biology Division and Infection and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia.
authors.forename: Jelena
authors.initials: J
authors.lastname: Medan
authors.affiliation: Chemical Biology Division and Infection and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, VIC 3052, Australia and Department of Medical Biology, The University of Melbourne, Parkville, VIC 3010, Australia.
authors.forename: Brad E
authors.initials: BE
authors.lastname: Sleebs
authors.affiliation: Biochemistry Department, La Trobe University, Bundoora, VIC 3083, Australia. s.cutts@latrobe.edu.au.
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Cutts
authors.affiliation: Biochemistry Department, La Trobe University, Bundoora, VIC 3083, Australia. s.cutts@latrobe.edu.au.
authors.forename: Don R
authors.initials: DR
authors.lastname: Phillips
authors.affiliation: School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Australian Defence Force Academy, Northcott Drive, Campbell, ACT 2600, Australia. g.collins@adfa.edu.au.
authors.forename: J Grant
authors.initials: JG
authors.lastname: Collins
mesh_terms: D001483:Base Sequence; D002384:Catalysis; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D005557:Formaldehyde / Q000737:chemistry*; D008942:Mitoxantrone / Q000737:chemistry*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation
chemical_list: D005557:Formaldehyde; D004247:DNA; D008942:Mitoxantrone