Silencing the receptor EphA2 suppresses the growth and haptotaxis of malignant mesothelioma cells

BACKGROUND. The over‐expression of the ephrin‐A1 ligand receptor EphA2 is associated with the growth and metastatic potential of tumors. Although EphA2 is expressed in a variety of tumors, its expression and function in malignant mesothelioma (MM) remain unknown. The authors hypothesized that expression of the receptor EphA2 in MM cells (MMCs) plays a key role in the growth and haptotactic migration of MM. They also hypothesized that silencing EphA2 expression by using small‐interfering RNA (siRNA) inhibits the proliferation and haptotaxis of MMCs and induces apoptosis in MMCs. METHODS. The expression of EphA2 in MMCs and in normal pleural mesothelial cells (PMCs) was studied by using real‐time quantitative polymerase chain reaction analysis and Western blot analysis. The growth of MMCs was determined with the WST‐1 cell‐proliferation assay. The haptotactic migration of MMCs and PMCs was determined with a Boyden chamber assay. Expression of caspases was determined with calorimetric assays. RESULTS. The results demonstrated that silencing the receptor EphA2 by siRNA significantly reduced the proliferation and haptotactic migration of MMCs compared with controls. Over‐expression of EphA2 with plasmid pcDNA/EphA2 enhanced the proliferation and haptotaxis of MMCs significantly. Knocking down EphA2 expression initiated caspase‐9–mediated apoptosis in MMCs. CONCLUSIONS. The current results suggested that constitutive expression of EphA2 may contribute to the aggressive behavior and cellular survival of MMCs. EphA2 may be an effective therapeutic target in patients with mesothelioma. Silencing the receptor EphA2 gene is a novel approach for the containment of growth and migration of tumor in patients with malignant mesothelioma. Cancer 2006. © 2006 American Cancer Society. The authors explored the hypotheses that expression of the ephrin‐A1 ligand receptor EphA2 in malignant mesothelioma cells (MMCs) plays a key role in the growth and haptotactic migration of malignant mesothelioma and that silencing EphA2 expression by using small‐interfering RNA inhibits the proliferation and haptotaxis of MMCs and induces apoptosis in MMCs. The results suggested that constitutive expression of EphA2 may contribute to the aggressive behavior and cellularsurvival of MMCs.