The fundamental roles of GPXs and glutathione in regulating intracellular ROS level and maintaining homeostasis of intracellular microenvironment have been well demonstrated, and altered expression of GPX family members including GPX1 has been reported in various diseases including cancers [26, 28, 29] (upregulation: lung cancer [8], breast cancer [9]; downregulation: colorectal cancer [10], thyroid cancer [11], gastric cancer [12]). The gene discussed is GPX1; the disease is lung cancer.