PGR and breast cancer: For instance, the cell proliferation antigen MKI67 (also known as Ki-67) has often been shown to be a powerful predictor of poor clinical outcome19; HOTAIR expression serve as an independent biomarker for the prediction of the risk of metastasis in breast cancer patients20; ESR1 (ER), PGR (PR) and ERBB2 (HER-2) were all powerful predictive biomarker21.