However, MDA-MB-231 cell line characterized by the lack of expression of estrogen receptor (ER −), progesterone receptor (PR −), and human epidermal growth factor receptor 2 (HER2 −) is an extremely aggressive, hormone-independent and often resistant to chemotherapeutic drug, making it an ideal model for triple-negative breast cancer research (Aka & Lin, 2012; Holliday & Speirs, 2011). Here, PGR is linked to triple-negative breast carcinoma.