PREX1 and breast cancer: Among the up-regulated luminal genes are Prex1, Abca3, and Cdk6: Prex1 is overexpressed in ER+ and HER2+ breast cancers (Marotti et al., 2017), whereas Abca3 and Cdk6 are higher in normal human luminal cells (Lucas et al., 2004; Schimanski et al., 2010); Abca3 is an ERα target gene; its loss is an adverse risk factor for breast cancer recurrence and promotes acquisition of mesenchymal-like characteristics in lung epithelial cells (Lin et al., 2004; Kaltenborn et al., 2012).