?-catenin activation down-regulates cell-cell junction-related genes and induces epithelial-to-mesenchymal transition in colorectal cancers.
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ABSTRACT: WNT signaling activation in colorectal cancers (CRCs) occurs through APC inactivation or ?-catenin mutations. Both processes promote ?-catenin nuclear accumulation, which up-regulates epithelial-to-mesenchymal transition (EMT). We investigated ?-catenin localization, transcriptome, and phenotypic differences of HCT116 cells containing a wild-type (HCT116-WT) or mutant ?-catenin allele (HCT116-MT), or parental cells with both WT and mutant alleles (HCT116-P). We then analyzed ?-catenin expression and associated phenotypes in CRC tissues. Wild-type ?-catenin showed membranous localization, whereas mutant showed nuclear localization; both nuclear and non-nuclear localization were observed in HCT116-P. Microarray analysis revealed down-regulation of Claudin-7 and E-cadherin in HCT116-MT vs. HCT116-WT. Claudin-7 was also down-regulated in HCT116-P vs. HCT116-WT without E-cadherin dysregulation. We found that ZEB1 is a critical EMT factor for mutant ?-catenin-mediated loss of E-cadherin and Claudin-7 in HCT116-P and HCT116-MT cells. We also demonstrated that E-cadherin binds to both WT and mutant ?-catenin, and loss of E-cadherin releases ?-catenin from the cell membrane and leads to its degradation. Alteration of Claudin-7, as well as both Claudin-7 and E-cadherin respectively caused tight junction (TJ) impairment in HCT116-P, and dual loss of TJs and adherens junctions (AJs) in HCT116-MT. TJ loss increased cell motility, and subsequent AJ loss further up-regulated that. Immunohistochemistry analysis of 101 CRCs revealed high (14.9%), low (52.5%), and undetectable (32.6%) ?-catenin nuclear expression, and high ?-catenin nuclear expression was significantly correlated with overall survival of CRC patients (P?=?0.009). Our findings suggest that ?-catenin activation induces EMT progression by modifying cell-cell junctions, and thereby contributes to CRC aggressiveness.
SUBMITTER: Kim WK
PROVIDER: S-EPMC6895046 | biostudies-literature | 2019 Dec
REPOSITORIES: biostudies-literature
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