NADPH oxidase 4 (NOX4) is the most widely distributed NOX catalytic subunit.3,4 NOX4 is abundantly present in hepatocytes and HSCs and can directly or indirectly regulate the cell signaling network through reactive oxygen species (ROS).3 NOX4 is the key factor that promotes liver fibrosis via apoptosis and HSCs activation. The gene discussed is NOX4; the disease is Hepatic fibrosis.