Human breast cancer cells expressing mutant PIK3CA also showed activation of the WNT/β‐catenin pathway, which was detected as an increase in activated β‐catenin (ABC) protein (Fig. 2C), the ligand WNT3A mRNA (Fig. 2D, left panel), and a decrease in mRNA expression of the negative modulator of the pathway, the secreted frizzled‐related protein 1 (sFRP‐1) (Fig. 2D, right panel). Here, SFRP1 is linked to breast cancer.