NQO1 and cancer: NQO1 has a wide range of substrates and enzymatic functions associated with antioxidant defense and cancer development, including the NAD(P)H-dependent two-electron reduction of quinones to form hydroquinones, thus avoiding the formation of highly reactive and cytotoxic semiquinones [3,4], the maintenance of vitamin K3 and ubiquinone in their reduced state [5,6,7,8] and scavenging of superoxide anions [9].