Overexpression of Nemo-like Kinase Promotes the Proliferation and Invasion of Lung Cancer Cells and Indicates Poor Prognosis

Abstract

Background: Nemo-like kinase (NLK) is an evolutionarily conserved MAP kinaserelated kinase involved in the pathogenesis of several human cancers. Objective: The aim of this study was to investigate the expression and role of NLK in lung cancers, and its underlying mechanisms. Methods: We examined the expression of NLK in lung cancer tissues through western blot analysis. We enhanced or knocked down NLK expression by gene transfection or RNA interference, respectively, in lung cancer cells, and examined expression alterations of key proteins in the Wnt signaling pathway and in epithelial-mesenchymal transition (EMT). We also examined the roles of NLK in the proliferation and invasiveness of lung cancer cells by cell proliferation, colony formation, and Matrigel invasion assays. Results: NLK expression was found to be significantly higher in lung cancer tissue samples than in corresponding healthy lung tissue samples. Overexpression of NLK correlated with poor prognosis of patients with lung cancer. Overexpression of NLK upregulated β-catenin, TCF4, and Wnt target genes such as cyclin D1, c-Myc, and MMP7. N-cadherin and TWIST, the key proteins in EMT, were upregulated, while E-cadherin expression was reduced. Additionally, proliferation, colony formation, and invasion turned out to be enhanced in NLK-overexpressing cells. After NLK knockdown in lung cancer cells, we obtained the opposite results. Conclusion: NLK is overexpressed in lung cancers and indicates poor prognosis. Overexpression of NLK activates the Wnt signaling pathway and EMT and promotes the proliferation and invasiveness of lung cancer cells.