PIN1 and breast cancer: Moreover, previous data suggest that besides affecting ERα, Pin1 may promote tamoxifen resistance of breast cancer by activating growth-promoting pathways (Khanal et al., 2012), down-regulating SMRT (Stanya et al., 2008) and cyclin dependent kinase (Khanal et al., 2012), facilitating tumor angiogenesis (Kim et al., 2009b, 2012) and epithelial–mesenchymal transition (Kim et al., 2009a).