TCF4 and breast cancer: Consistently, the Aldefluor-positive subpopulation showed significantly higher levels of the regulatory components of Wnt/β-catenin signaling, such as LEF1, cyclin D1, β-catenin and TCF-4, compared with those in the Aldefluor-negative subpopulation in both breast cancer cell types (Fig. 2B), suggesting that the BCSC subpopulations exhibited enhanced Wnt/β-catenin signaling activity.