Enzyme-Activated, Hypoxia-Selective DNA Damage by 3-Amino-2-quinoxalinecarbonitrile 1,4-Di-N-oxide

Abstract

The compound 3-amino-2-quinoxalinecarbonitrile 1,4-dioxide (4) displays potent hypoxia-selective cytotoxicity in cell culture. This compound is structurally similar to the known hypoxia-selective DNA-damaging agent tirapazamine (1, TPZ), but the ability of 4 to cause DNA damage under low-oxygen conditions has not previously been characterized. The results presented here provide the first evidence that 4 causes reductively activated DNA damage under hypoxic conditions. The findings indicate that one-electron reduction of 4 by NADPH:cytochrome P450 reductase yields an oxygen-sensitive intermediate (5). This activated intermediate is rapidly destroyed by reaction with O2 under aerobic conditions, but goes forward to cause DNA damage under low-oxygen conditions. Analysis of the DNA damage indicates that reductive activation of 4 leads to production of a highly reactive, freely diffusible oxidizing radical that causes sequence-independent cleavage of the deoxyribose backbone and oxidative damage to the heterocyclic bases in duplex DNA. On the basis of the experiments reported here, the chemical nature of the DNA damage caused by redox-activated 4 is analogous to that reported previously for TPZ.

DNA strand cleaving properties and hypoxia-selective cytotoxicity of 7-chloro-2-thienylcarbonyl-3-trifluoromethylquinoxaline 1,4-dioxide

“…For example, various 1,2,4-benzotriazines, 34-40 quinoxaline 1,4-di- N -oxides (e.g. 5 ), 41-47 phenazine 5,10-di- N -oxides ( 6 ), 48-51 and imidazo[1,2-a]quinoxaline N -oxides ( 7 ) 52 exhibit hypoxia-selective cytotoxicity in preclinical tests. In some cases, the compounds also have been shown to display hypoxia-selective DNA-damaging properties analogous to tirapazamine.…”

The critical role of oxidative stress in the toxicity and metabolism of quinoxaline 1,4-di-N-oxides in vitro and in vivo

“…Furthermore, a recent study documented that during N!O reduction of QCT, ROS such as superoxide anion (O 2 À ), hydrogen peroxide (H 2 O 2 ), and hydroxyl radicals (HO ) are generated (Wang et al, 2016b). As already known, ROS generation and oxidative stress resulted from the reduction of QdNOs, which might result in wide damage such as apoptosis, and DNA, lipid and protein damage (Azqueta et al, 2007;Chowdhury et al, 2004;Wang et al, 2016a) in vivo or in vitro. During the past more than 10 years, there has been considerable focus on the potential of QdNOs to induce (Dai et al, 2015;Huang et al, 2010b;Li et al, 2015;Liu et al, 2012;Wang et al, 2015bWang et al, , 2016bWang et al, , 2015cYang et al, 2013bZhang et al, 2011Zhang et al, , 2013Zhang et al, , 2014Zhang et al, , 2015Zhao et al, 2013Zhao et al, , 2015Zou et al, 2009Zou et al, , 2011.…”

Quinoxaline 1,4-di-N-Oxide and the Potential for Treating Tuberculosis

“…In addition, quinoxalines and their mono-and di-N-oxide derivatives display a broad range of biological activities [10] and quinoxaline di-N-oxides are known to undergo bioreductions under hypoxia causing DNA damage [26][27][28] and likely other cellular damage.…”

“…Specific derivatives also show selective cytotoxicity against hypoxic cells present in solid tumors [21]. Furthermore, recent studies have demonstrated that quinoxaline 1,4-di-N-oxides are endowed with antimycobacterial, antiprotozoal [22,23], anticandida [24,25] activities and mutagenic properties [26][27][28], depending on specific chemical features.…”