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 β-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 ERα regulates β-catenin expression as well as the metastasis ability of hepatocellular cancer HA22T cells. To identify whether the anticancer effect of estrogen and ERα is mediated through suppression of β-catenin expression, we co-transfected pCMV-β-catenin and ERα into HA22T cells, and determined the cell motility by wound healing, invasion, and migration assays. Results showed that estrogen and/or ERα inhibited β-catenin gene expression and repressed HA22T cell motility demonstrated that similar data was observed in cells expressing the ERα stable clone. Moreover, we examined the protein-protein interaction between ERα and β-catenin by immunostain, co-immunoprecipitation, and Western blotting. E2 enhanced the binding of ERα with β-catenin and then triggered β-catenin to bind with E3 ligase (βTrCP) to promote β-catenin degradation. Finally by employing systematic ChIP studies, we showed ERα can interact directly with the β-catenin promoter region following E2 treatment. All our results reveal that estrogen and ERα blocked metastatic function of HA22T cells by modulating GSK3β and βTrCP expression and further enhanced β-catenin degradation and suppressed its downstream target genes.