NOX4 and silicosis: Since the epithelial-mesenchymal transition (EMT) or myofibrogenesis of lung epithelial cells is a hallmark of pulmonary fibrosis, a feature of silicosis [30], the alteration of Wnt/β-catenin signaling activity and NOX4 expression of BEAS-2B lung epithelial cells in response to silica dust was examined.