The cadherin-catenin adhesion system in signaling and cancer

The adhesion of cells to their neighbors determines cellular and tissue morphogenesis and regulates major cellular processes including motility, growth, differentiation, and survival. Cell-cell adherens junctions (AJs), the most common (indeed, essentially ubiquitous) type of intercellular adhesions, are important for maintaining tissue architecture and cell polarity and can limit cell movement and proliferation. AJs assemble via homophilic interactions between the extracellular domains of calcium-dependent cadherin receptors on the surface of neighboring cells. The cytoplasmic domains of cadherins bind to the submembranal plaque proteins β-catenin or plakoglobin (γ-catenin), which are linked to the actin cytoskeleton via α-catenin (Figure ​(Figure1;1; refs. 1, 2). The transmembrane assembly of cadherin receptors with the cytoskeleton is necessary for the stabilization of cell-cell adhesions and normal cell physiology. Figure 1 The dual role of β-catenin in cell adhesion and transcriptional activation. β-Catenin (β) and plakoglobin (Pg) bind to cadherin adhesion receptors, and via α-catenin (α) they associate with the actin cytoskeleton ... Malignant transformation is often characterized by major changes in the organization of the cytoskeleton, decreased adhesion, and aberrant adhesion-mediated signaling. Disruption of normal cell-cell adhesion in transformed cells may contribute to tumor cells’ enhanced migration and proliferation, leading to invasion and metastasis. This disruption can be achieved by downregulating the expression of cadherin or catenin family members or by activation of signaling pathways that prevent the assembly of AJs. The importance of the major epithelial cell cadherin, E-cadherin (E-cad, the product of the CDH1 gene), in the maintenance of normal cell architecture and behavior is underscored by the observation that hereditary predisposition to gastric cancer results from germline mutations in CDH1. Loss of E-cad expression eliminates AJ formation and is associated with the transition from adenoma to carcinoma and acquisition of metastatic capacity (3). Re-establishment of AJs in cancer cells by restoration of cadherin expression (4) exerts tumor-suppressive effects, including decreased proliferation and motility. In this Perspective, we discuss the molecular mechanisms underlying the role of the cadherin-catenin system in the regulation of cell proliferation, invasion, and intracellular signaling during cancer progression.