Alkylation of DNA by the new anticancer agent 3,6-diaziridinyl-2,5-bis(carboethoxyamino)-1,4-benzoquinone (AZQ).

The bifunctional cross-linking activity of 3,6-diaziridinyl-2,5-bis(carboethoxyamino)-1,4-benzoquinone (AZQ, NSC 182986) on isolated calf thymus DNA was studied, using ethidium bromide fluorescence assay. Between 1 and 350 microM AZQ produced a dose-dependent cross-linking effect in the presence of a 10-fold excess of sodium borohydride. No cross-linking was observed in the absence of the reducing agent. AZQ can also be activated by NADH and NADPH at pH 4. The AZQ cross-linking activity exhibited a strong pH dependency, highest at acidic pH, lower at alkaline pH and not seen under neutral conditions. It was also significantly inhibited under anaerobic conditions. At pH 5 the binding ratio was 1 molecule of AZQ per 191 bases at an AZQ dose of 300 microM. Our results suggest that reduced AZQ behaved like a bifunctional alkylating agent.