Integrin-induced protein kinase regulates fibronectin matrix assembly, E-cadherin expression, and tumorigenicity

Fibronectin (Fn) matrix plays important roles in many biological processes including morphogenesis and tumorigenesis. Recent studies have demonstrated a critical role of integrin cytoplasmic domains in regulating Fn matrix assembly, implying that intracellular integrin-binding proteins may be involved in controlling extracellular Fn matrix assembly, We report here that overexpression of integrin linked kinase (ILK), a newly identified serine/threonine kinase that binds to the integrin beta(1) cytoplasmic domain, dramatically stimulated Fn matrix assembly in epithelial cells. The integrin-linked kinase activity is involved in transducing signals leading to the up-regulation of Fn matrix assembly, as overexpression of a kinase-inactive ILK mutant failed to enhance the matrix assembly, Moreover, the increase in Fn matrix assembly induced by ILK overexpression was accompanied by a substantial reduction in the cellular E-cadherin. Finally, we show that ILK-overexpressing epithelial cells readily formed tumors in nude mice, despite forming an extensive Fn matrix, These results identify ILK as an important regulator of pericellular Fn matrix assembly, and suggest a novel critical role of this integrin-linked kinase in cell growth, cell survival, and tumorigenesis.