MKI67 and cancer: In particular, two hormone-receptors (estrogen-receptor (ER) and progesterone-receptor (PR)), HER2 (the Human Epidermal growth factor Receptor 2 (HER2) is a growth-promoting protein and plays an important role in several signaling pathways) and Ki-67 (Ki-67 is a nuclear antigen expressed by all proliferating cells during late G1 through the M phases of the cell cycle, peaking in the G2-M and with a rapid decline after mitosis and is thus an indicator of cancer cells growth).