PGR and breast cancer: For example, E-cad expression was significantly upregulated in luminal (estrogen receptor (ER) + , progesterone receptor (PR) ± , human epidermal growth factor 2 (HER2)-, and low levels of Ki-67 protein), and HER2 positive breast cancer (ER-, PR-, and HER2 +), and remained unchanged in triple-negative breast cancer (ER-, PR-, HER2-) (TNBC) compared to normal tissues (Fig. 4D).