Amine-containing Anthracyclines Covalently bind AP sites in DNA Created by Nitrogen Mustards, Resulting in Reduced Cell Viability and Leading to Rapid Strand Scission via Beta- and Delta-elimination

Abstract

The cancer treatment regimen known as AC chemotherapy is one of the oldest and most commonly used regimens. Consisting of a combination of Adriamycin (Doxorubicin) and Cyclophosphamide, it has long been understood that the two compounds effect cytotoxicity through independent mechanisms of action with Adriamycin being a topoisomerase II inhibiting anthracycline and Cyclophosphamide being a DNA alkylating nitrogen mustard. A fortuitous discovery in the early 1990s showed that anthracycline compounds have the potential to covalently bind DNA through an electrophile-mediated interaction, in this case formaldehyde. Herein we report that amine-containing anthracyclines efficiently exhibit this reactivity with AP sites that are generated in elevated levels due to reactions of DNA with nitrogen mustards via covalent trapping through reductive amination and likely already contribute a previously unidentified mechanism of cytotoxicity. We also show that unreduced reactions of this type lead to rapid and efficient scission of the affected DNA strands via the known processes of β- and δ-elimination at AP sites.