An aberrant nuclear localization of E-cadherin is a potent inhibitor of Wnt/β-catenin-elicited promotion of the cancer stem cell phenotype

Several studies suggest that Wnt signaling contributes to reprogramming and maintenance of cancer stem cell (CSC) states activated by loss of membranous E-cadherin expression. However, E-cadherin's exact role in Wnt/β-catenin-mediated promotion of the CSC phenotype remains unclear. Recently, a significant positive correlation has been observed between the expression of nuclear (an aberrant nuclear localization) E-cadherin and β-catenin in gastric and colorectal carcinomas. Here we conducted a series of in-vitro and in-vivo studies to show that the β-catenin/TCF4 interaction was abolished by E-cadherin and was correlated with its nuclear localization, and consequently decreased β-catenin/TCF4 transcriptional activity. Nuclear E-cadherin was a negative regulator of Wnt/β-Catenin-elicited promotion of the CSC phenotype. Using immunohistochemistry on lung cancer tissue microarrays, we found that changes in subcellular location of E-cadherin may be described by tumor grade and stage, suggesting cellular redistribution during lung tumorigenesis. Furthermore, nuclear E-cadherin expression was more significantly inversely correlated with CD133 (a lung CSC marker) expression (P<0.005) than total E-cadherin expression (P<0.05), suggesting that lung cancer as defined by nuclear E-cadherin(Low)/nuclear β-catenin(High)/CD133(High) biomarkers has superior prognostic value over total E-cadherin(Low)/nuclear β-catenin(High)/CD133(High).