PGR and breast cancer: Human BC cell lines MCF7 (ER + , PR + , HER2-), T47D (ER + , PR + , HER2-), ZR75 (ER + , PR-, HER2-), and MDA-MB-231 (ER-, PR-, HER2-) all expressed higher MFGE8 mRNA levels compared with normal mammary epithelial cells MCF10A (Fig. 3A).