DKK1 and infection: In order to investigate the interaction between the Wnt/β-catenin signaling and NOX4 in lung epithelial cells, the signaling activity was altered in BEAS-2B cells by the infection of adenoviral vector expressing mouse Wnt3a (AdWnt3a) or DKK1 (AdDKK1), and the change of ROS production in response to SiO2 exposure was measured.