ESR1 and breast cancer: Interestingly, our results revealed a significant increase of CAPER expression in all major breast cancer subtypes when compared to normal healthy breast specimens (Figure 1B; ER+; 2.5-fold, p < 0.001, n = 192; HER2+; 1.7-fold, p < 0.05, n = 48; TNBC; 2-fold, p < 0.001, n = 116).