Estrogen and ERα enhanced β-catenin degradation and suppressed its downstream target genes to block the metastatic function of HA22T hepatocellular carcinoma cells via modulating GSK-3β and β-TrCP expression

In our previous experiments, we found -catenin was highly expressed in the tumor area with high invasive ability and poor prognosis. In this study, we have examined the mechanism by which ER regulates -catenin expression as well as the metastasis ability of hepatocellular cancer HA22T cells. To identify whether the anticancer effect of estrogen and ER is mediated through suppression of -catenin expression, we co-transfected pCMV--catenin and ER into HA22T cells, and determined the cell motility by wound healing, invasion, and migration assays. Results showed that estrogen and/or ER inhibited -catenin gene expression and repressed HA22T cell motility demonstrated that similar data was observed in cells expressing the ER stable clone. Moreover, we examined the protein-protein interaction between ER and -catenin by immunostain, co-immunoprecipitation, and Western blotting. E2 enhanced the binding of ER with -catenin and then triggered -catenin to bind with E3 ligase (TrCP) to promote -catenin degradation. Finally by employing systematic ChIP studies, we showed ER can interact directly with the -catenin promoter region following E2 treatment. All our results reveal that estrogen and ER blocked metastatic function of HA22T cells by modulating GSK3 and TrCP expression and further enhanced -catenin degradation and suppressed its downstream target genes. (c) 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 519-529, 2017.