ABCB1 and breast cancer: as well as human epidermal growth factor receptor 2 (Her-2), an independent prognostic factor for poor prognosis of breast cancer, and P-glycoprotein (P170) have been associated with poor prognosis [38] Our results clearly showed that strong RP215 staining was negatively correlated with the expression of PR (P = 0.013), PS-2 (P = 0.002), and nm23 (P = 0.037).