Expression of ezrin correlates with malignant phenotype of lung cancer, and in vitro knockdown of ezrin reverses the aggressive biological behavior of lung cancer cells

Abstract

Ezrin, one of the ezrin-radixin-moesin proteins, is involved in the formation of cell membrane processes such as lamellipodia and filopodia and acts as a membrane-cytoskeleton linker. Its aberrant expression correlates with development and progression of several human cancers. However, the expression of ezrin and its role in lung cancer are currently unknown. In this study, we performed ezrin small interfering RNA transfection in two lung cancer cell lines and examined the effects on malignant phenotypes in cancer cells by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, wound healing, and chamber transwell assays. Ezrin knockdown significantly reduced the proliferation, migration, and invasion of lung cancer cells in vitro. To address the possible mechanisms, we evaluated the expression of adhesion molecules E-cadherin and β-catenin by Western blot and reverse transcriptase-polymerase chain reaction analyses. The results demonstrated that downregulation of ezrin reduced β-catenin and increased E-cadherin at the protein level but had no effects on their mRNA levels, suggesting posttranscriptional regulation of these two adhesion molecules. Immunofluorescence assays revealed that ezrin knockdown restored membranous expression of E-cadherin and decreased cytoplasmic β-catenin in lung cancer cells. In addition, ezrin expression was immunohistochemically evaluated on 135 normal and 183 lung cancer tissues. The expression of ezrin was significantly higher in cancer samples than paired autologous normal lung tissues. In normal bronchial epithelium, ezrin was mainly localized on the apical membrane, while in lung cancers and metastatic foci, ezrin was primarily distributed in cytoplasm. Among lung cancer tissues, expression of ezrin was higher in the invasive front of primary lesions and the highest in lymphatic metastasis. Statistical analysis demonstrated that ezrin expression correlated significantly with lymphatic metastasis and advanced TNM stage. Our data suggest that ezrin may play a crucial role in governing the biological behavior of lung cancer.