β-catenin is a multifunctional protein involved both in cell adhesion and in activation of transcription. Calcium-dependent intercellular adhesion transmembrane glycoprotein E-cadherin interacts by its cytoplasmic domain with reciprocally bound α, β and γ catenin. β-catenin links this complex through α-actinin to the cytoskeleton. Functional cadherin-catenin system is important for invasiveness of tumor cells. β-catenin level in cytoplasm is controlled by glycogen synthase kinase-3 β. When activity of this kinase is blocked (e.g. by excessive stimulation of Wnt signaling pathway), hypophosphorylated stable form of β-catenin accumulates in the cytoplasm, translocates to the nucleus and activates transcription of genes including those that are involved in cell cycle control. As a result, cell division and neoplastic transformation are promoted.