β-Catenin Drives the FOXC2-Mediated Epithelial-Mesenchymal Transition and Acquisition of Stem Cell Properties.

Background: Aggressive forms of breast cancer, such as triple-negative breast cancer (TNBC), are associated with an increase in cancer cells that exhibit stem cell properties. The activation of the epithelial-mesenchymal transition (EMT) program, mediated by the transcription factor FOXC2, generates these stem-like cells. FOXC2 is linked to poor prognoses across various cancer types and is notably upregulated in TNBC, where it establishes and sustains these stem-like cells within the tumor population. Methods: Here, we decode the pathways regulating FOXC2 activation using EMT-enriched cell line models. Stemness was assessed using mammosphere assays and mesenchymal markers by western blot. Expression correlations with clinical data was examined using the EMTome. Results: We demonstrate that β-catenin serves as a critical mediator of mesenchymal and stemness characteristics through FOXC2 upregulation. By disrupting β-catenin, we find that FOXC2 expression, mesenchymal properties, and stemness are reduced; however, the introduction of exogenous FOXC2 expression in β-catenin deficient cells is enough to restore the mesenchymal and stemness phenotype. These findings support the idea that FOXC2 acts as the downstream regulator of β-catenin and influences both mesenchymal and stemness properties. Moreover, there is a positive correlation between the expression of β-catenin and FOXC2 in various cancer subtypes observed in clinical patient samples. Conclusions: Our study clarifies the role of the β-catenin/FOXC2 signaling axis in maintaining stemness properties, suggesting potential targets for TNBC and other cancers driven by EMT-related mesenchymal and stemness characteristics.