It has been demonstrated that the Wnt signalling pathway maintains the undifferentiated state of breast cancer stem cells25, 26 and has been found activated in approximately 50% of breast cancer.27 Surprisingly, treatment of the Wnt signalling pathway agonist Wnt3a in MCF7 cells led to tamoxifen resistance, while treatment of the Wnt signalling pathway inhibitor IWP‐2 restored the sensitivity of MCF7 cells to tamoxifen,28 suggesting that an increase in the number of breast cancer stem cells is associated with activation of the Wnt signalling pathway. Here, WNT3A is linked to breast cancer.