Epithelial-Mesenchymal Transition (EMT) Antibody Sampler Kit

Background

Epithelial-mesenchymal transition (EMT) is an essential process during development whereby epithelial cells aquire mesenchymal, fibroblast-like properties and display reduced intracellular adhesion and increased motility. This is a critical feature of normal embryonic development, which is also utilized by malignant epithelial tumors to spread beyond their origin (1-3). This tightly regulated process is associated with a number of cellular and molecular events. EMT depends on a reduction in expression of cell adhesion molecules. Cadherins mediate calcium-dependent cell-cell adhesion and play critical roles in normal tissue development (4). E-cadherin is considered an active suppressor of invasion and growth of many epithelial cancers (4-6). Recent studies indicate that cancer cells have up-regulated N-cadherin in addition to loss of E-cadherin. This change in cadherin expression is called the "cadherin switch" and downregulation of E-cadherin is one of the hallmarks of EMT (1). Tight junctions, or zonula occludens, form a continuous barrier to fluids across the epithelium and endothelium. They function in regulation of paracellular permeability and in the maintenance of cell polarity, blocking the movement of transmembrane proteins between the apical and the basolateral cell surfaces. Tight junctions are composed of claudin and occludin proteins, which join the junctions to the cytoskeleton (7,8). Zona occludens proteins ZO-1, 2, and 3 (also known as TJP 1, 2, and 3) are peripheral membrane adaptor proteins that link junctional transmembrane proteins such as occludin and claudin to the actin cytoskeleton (9). ZO-1 and -2 are required for tight junction formation and function (10,11); mutations in ZO-1 and Claudin induce EMT (12). Vimentin is an intermediate filament of mesenchymal origin and is present at early developmental stages. Vimentin's dynamic structural changes and spatial re-organization in response to extracellular stimuli helps to coordinate various signaling pathways (13). β-catenin is a key downstream effector in the Wnt signaling pathway (14). It is implicated in two major biological processes in vertebrates: early embryonic development (15) and tumorigenesis (16). β-catenin also activates Slug. Slug (SNAI2) is a widely expressed transcriptional repressor and member of the Snail family of zinc finger transcription factors (17). Similar to the related Snail protein, Slug binds to the E-cadherin promoter region to repress transcription during development (18). The binding of Slug to integrin promoter sequences represses integrin expression and results in reduced cell adhesion (19). Down regulation of E-cadherin expression occurs during the EMT during embryonic development (20). ZEB family proteins are zinc finger and homeobox domain containing transcription factors. One of the targets suppressed by ZEB proteins is E-cadherin (1).