Fibulin-3 suppresses Wnt/β-catenin signaling and lung cancer invasion.

The 5 year survival rate of lung cancer is <20%, with most patients dying from distant metastasis. However, the molecular mechanisms underlying lung cancer invasion and metastasis have not been fully characterized. In this study, we found that fibulin-3, a fibulin family extracellular matrix protein, functions as a suppressor of lung cancer invasion and metastasis. Fibulin-3 was downregulated in large fractions of lung tumors and cell lines, and inhibited lung cancer cell invasion and the expression of matrix metalloproteinase-7 (MMP-7), a promoter of lung cancer invasion. The expression levels of fibulin-3 and MMP-7 were inversely correlated in lung tumors. Fibulin-3 inhibited extracellular signal-regulated kinase (ERK) to activate glycogen synthase kinase 3β and suppress Wnt/β-catenin signaling, which induces MMP-7 expression in lung cancer cells. Furthermore, fibulin-3 expression impeded the growth and metastasis of lung tumors in mice. Collectively, these results suggest that downregulation of fibulin-3 contributes to lung cancer invasion and metastasis by activating Wnt/β-catenin signaling and MMP-7 expression.