title: Adenine-containing DNA-DNA cross-links of antitumor nitrogen mustards.
abstract: Nitrogen mustards (NMs) are useful chemotherapeutic agents in the treatment of lymphoma, leukemia, multiple myeloma, and ovarian carcinoma. The antitumor activity of NMs has been attributed to their ability to cross-link the twin strands of DNA. The resulting bifunctional lesions, if not repaired, can inhibit DNA replication and transcription, eventually leading to cell cycle arrest, apoptosis, and the inhibition of tumor growth. The predominant bifunctional DNA lesions of NM have been reported to involve the distal guanine bases in the opposite strands of 5'-GNC sequences. In the present work, the formation of guanine-adenine and adenine-adenine adducts of N,N-bis(2-chloroethyl)methylamine (mechlorethamine) in double-stranded DNA is demonstrated. Guanine-adenine cross-links of mechlorethamine were identified as 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. All three adducts were produced interstrand, while N3A-N7G-EMA was the dominant intrastrand G-A cross-link. The prevalent adenine-adenine mechlorethamine lesions have the structure of N,N-bis(2-[N3-adenyl]ethyl)methylamine (bis-N3A-EMA). DNA-derived lesions have the same HPLC retention times, UV spectra, and MS/MS fragmentation patterns as the authentic standards prepared independently. bis-N3A-EMA lesions were produced in a concentration-dependent manner in calf thymus DNA treated with increasing amounts of mechlorethamine. Furthermore, HPLC-ESI-MS/MS analysis was used to demonstrate the formation of analogous N3-N3 adenine lesions in DNA treated with aromatic nitrogen mustards, N,N-bis(2-chloroethyl)-p-aminophenylbutyric acid and L-phenylalanine mustard. The presence of cross-linked adenine-adenine lesions may explain the enhanced cytotoxicity and mutagenicity of NMs in cells deficient in N3-alkyladenine glycosylase.
authors.affiliation: Department of Medicinal Chemistry, University of Minnesota Cancer Center, Room 760E, Box 806 Mayo, 420 Delaware Street Southeast, Minneapolis, Minnesota 55455, USA.
authors.forename: Shawn
authors.initials: S
authors.lastname: Balcome
authors.forename: Soobong
authors.initials: S
authors.lastname: Park
authors.forename: Danaè R
authors.initials: DR
authors.lastname: Quirk Dorr
authors.forename: Lucy
authors.initials: L
authors.lastname: Hafner
authors.forename: Laura
authors.initials: L
authors.lastname: Phillips
authors.forename: Natalia
authors.initials: N
authors.lastname: Tretyakova
mesh_terms: D000225:Adenine / Q000737:chemistry*; D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000737:chemistry* / Q000494:pharmacology; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D003432:Cross-Linking Reagents / Q000737:chemistry* / Q000494:pharmacology; D004247:DNA / Q000187:drug effects; D004249:DNA Damage; D008466:Mechlorethamine / Q000737:chemistry; D008558:Melphalan / Q000737:chemistry* / Q000494:pharmacology; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D018906:Antineoplastic Agents, Alkylating; D003432:Cross-Linking Reagents; D008466:Mechlorethamine; D004247:DNA; D000225:Adenine; D008558:Melphalan