Analysis of a database containing gene expression of 2509 breast cancer patients using cBioportal (Cerami et al., 2012; Gao et al., 2013; Pereira et al., 2016) showed that in breast tumor samples, decreased gene expressions of CTNNB1 (a pivotal effector of the canonical Wnt signaling pathway) and YAP1 (YAP) were accompanied by reduced gene expressions of CD44 and ALDH1A1 that are associated with mesenchymal and epithelial CSC phenotypes (Fig. 6F). This evidence concerns the gene YAP1 and breast cancer.