Abstract
Epithelial to mesenchymal transition (EMT) plays a dual role in tumor progression. It enhances metastasis of tumor cells by increasing invasive capacity and promoting survival, and it decreases tumor cell sensitivity to epithelial cell-targeting agents such as epithelial growth factor receptor kinase inhibitors. In order to study EMT in tumor cells, we have characterized 3 new models of ligand-driven EMT: the CFPAC1 pancreatic tumor model and the H358 and H1650 lung tumor models. We identified a diverse set of ligands that drives EMT in these models. Hepatocyte growth factor and oncostatin M induced EMT in all models, while transforming growth factor-β induced EMT in both lung models. We observed morphologic, marker and phenotypic changes in response to chronic ligand treatment. Interestingly, stimulation with 2 ligands resulted in more pronounced EMT compared with single-ligand treatment, demonstrating a spectrum of EMT states induced by parallel signaling, such as the JAK and PI3K pathways. The EMT changes observed in response to the ligand were reversed upon ligand withdrawal, demonstrating the 'metastable' nature of these models. To study the impact of EMT on cell morphology and invasion in a 3D setting, we cultured cells in a semisolid basement membrane extract. Upon stimulation with EMT ligands, the colonies exhibited changes to EMT markers and showed phenotypes ranging from modest differences in colony architecture (CFPAC1) to complex branching structures (H358, H1650). Collectively, these 3 models offer robust cell systems with which to study the roles that EMT plays in cancer progression.