NQO1, or NAD(P)H:quinone oxidoreductase 1, is an enzyme encoded by the NQO1 gene in humans. It is a protective antioxidant and a multifunctional cell protector that can modulate the oxidative stress response to DNA damage in cancer cells by binding to chromatin-binding proteins. NQO1 is a homodimeric flavoenzyme that catalyzes the two-electron reduction of quinones to hydroquinones, thereby facilitating the excretion of quinones that would otherwise form semiquinones and generate reactive oxygen species (ROS) through redox cycling. NQO1 plays a crucial role in preventing oxidative damage to DNA caused by environmental stressors and maintains the reduced forms of endogenous antioxidants such as ubiquinone and α-tocopherol quinone. It is highly expressed in many solid tumors, including non-small cell lung cancer, pancreatic cancer, breast cancer, prostate cancer, colon cancer, and head and neck cancer, while its expression is very low in normal cells/tissues, making it an ideal target for cancer therapy. NQO1 has also been implicated in the regulation of glucose and insulin metabolism, which is relevant to diabetes and metabolic syndrome, as well as in Alzheimer's disease and aging.