ESR1 and breast cancer: Additionally, in ER+ BC patients, the activation of Wnt/β-catenin signalling was reported to play an important role in tamoxifen resistance [69], and in keeping Loh and colleagues observed that the canonical ER+ BC cell model MCF7, induced in vitro to be resistant to tamoxifen, is characterized by an enhanced EMT phenotype and activation of Wnt signalling via aberrant expression of the WNT3a ligand [70].