Nedd9 Regulates Metastasis of Non-Small Cell Lung Cancer through Activation of Epithelial-Mesenchymal Transition and Tumor Cells Migration

Abstract

Non-small cell lung cancer (NSCLC) has a low survival rate, with metastasis contributing to the vast majority of deaths. Elevated expression of the protein Nedd9 (neural precursor cell expressed, developmentally down-regulated 9) has been reported in a large subset of lung cancers and other malignancies as a promotor of aggressive phenotypes and drug resistance. This study was performed to identify the mechanisms by which Nedd9 regulates invasion and metastasis of non-small cell lung cancer in the transgenic murine model. Aiming to address the research goals, we performed a set of in vivo and in vitro experiments with the help of such methods as magnetic resonance imaging (MRI), immunohistochemical staining of tissues and microscopy, western blotting. We found that Nedd9 constitutive null genotype enhanced tumor growth in an inducible Kras / Trp53 model, in which Kras mutation is induced specifically in the lung tissue by inhalation of adenovirus. Pathological examination of the tissues demonstrated that Nedd9 null genotype also was associated with higher invasive capacity in vivo , including direct invasion to the heart. We carried out a set of experiments to unveil the mechanism underlying the phenotype discovered. Overall, our data support the model in which Nedd9 provides critical support for early stages of the NSCLC growth, and progression beyond this early stage in the absence of Nedd9 requires extensive intracellular protein signaling reprogramming, allowing tumor cells to acquire mesenchymal properties, such as increased mobility and invasion epithelial-mesenchymal transition (EMT). These results are novel and have not been previously described in the literature. The biological mechanism by which Nedd9 regulates growth, invasion, and metastasis of NSCLC has been poorly investigated, and its study carries not only fundamental implication – discovery of novel mechanisms driving tumor development, but also significant practical importance: assessment of levels of Nedd9 activity in NSCLC patients can potentially serve as a biomarker of response to chemotherapy.