An acidic extracellular pH induces Src kinase-dependent loss of β-catenin from the adherens junction

Little attention has been paid to the role of adherens junctions (AJs) in acidic extracellular pH (pHe)-induced cell invasion. Incubation of HepG2 cells in acidic medium (pH 6.6) induced cell dispersion from tight cell clusters, and this change was accompanied by downregulation of β-catenin at cell junctions and a rapid activation of c-Src. Pretreatment with PP2 prevented the acidic pH-induced downregulation of β-catenin at AJ and in the membrane fractions. The acidic pHe-induced c-Src activation increased tyrosine phosphorylation of β-catenin and decreased the amount of β-catenin-associated E-cadherin. The depletion of membrane-bound β-catenin coincided with enhanced cell migration and invasion, and this acidic pHe-increased cell migration and invasion was prevented by PP2. In conclusion, this study characterizes a novel signaling pathway responsible for acidic microenvironment-promoted migration and invasive behaviors of cancer cells. ? 2008 Elsevier Ireland Ltd. All rights reserved.