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Adenine-containing DNA-DNA cross-links of antitumor nitrogen mustards

Shawn Balcome1, Soobong Park, Danaè R Quirk Dorr

  • 1Department of Medicinal Chemistry, University of Minnesota Cancer Center, Room 760E, Box 806 Mayo, 420 Delaware Street Southeast, Minneapolis, Minnesota 55455, USA.

Chemical Research in Toxicology
|July 20, 2004
PubMed

Insights

Nitrogen mustards (NMs) form novel guanine-adenine and adenine-adenine DNA adducts, including intrastrand guanine-adenine cross-links. These DNA lesions may explain the cytotoxicity and mutagenicity of nitrogen mustards in specific cellular contexts.

Area of Science:

  • Medicinal Chemistry
  • Molecular Biology
  • DNA Damage and Repair

Background:

  • Nitrogen mustards (NMs) are chemotherapy agents used to treat various cancers by cross-linking DNA.
  • The primary mechanism involves bifunctional DNA lesions, predominantly guanine-guanine cross-links, inhibiting DNA replication and transcription.
  • Previous understanding focused on guanine-guanine cross-links within 5'-GNC sequences.

Purpose of the Study:

  • To investigate the formation of guanine-adenine (G-A) and adenine-adenine (A-A) adducts induced by mechlorethamine in double-stranded DNA.
  • To characterize the structures and formation patterns of these novel DNA lesions.
  • To explore the potential implications of these adducts in the cytotoxicity and mutagenicity of nitrogen mustards.

Main Methods:

  • Treatment of double-stranded DNA with mechlorethamine, a nitrogen mustard.
  • Identification and characterization of DNA adducts using High-Performance Liquid Chromatography (HPLC), Electrospray Ionization Mass Spectrometry/Mass Spectrometry (ESI-MS/MS), UV spectroscopy, and comparison with authentic standards.
  • Analysis of adduct formation in response to varying mechlorethamine concentrations and with aromatic nitrogen mustards.

Main Results:

  • Demonstrated the formation of three interstrand guanine-adenine cross-links: N-(2-[N3-adenyl]ethyl)-N-(2-[N7-guanyl]ethyl)methylamine (N3A-N7G-EMA), N-(2-[N1-adenyl]ethyl)-N-(2-[N7-guanyl]ethyl)methylamine, and N-(2-[N(6)-adenyl]ethyl)-N-(2-[N7-guanyl]ethyl)methylamine.
  • Identified N3A-N7G-EMA as the dominant intrastrand G-A cross-link.
  • Characterized N,N-bis(2-[N3-adenyl]ethyl)methylamine (bis-N3A-EMA) as the prevalent adenine-adenine mechlorethamine lesion, formed in a concentration-dependent manner.
  • Observed analogous adenine-adenine lesions with aromatic nitrogen mustards.

Conclusions:

  • Nitrogen mustards can induce guanine-adenine and adenine-adenine DNA adducts, expanding the known spectrum of NM-induced DNA damage.
  • The formation of adenine-adenine cross-links may contribute to the enhanced cytotoxicity and mutagenicity of NMs.
  • These findings suggest a role for N3-alkyladenine glycosylase in processing these novel lesions.

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