ESR1 and breast cancer: Using KM plotter [20, 21], we found that high expression of GREM1 correlated with RFS in all breast cancer cases (HR = 1.32 (1.18–1.47), p-value = 6.9e− 07) and ER-negative subtype (HR = 1.51 (1.2–1.9), p-value = 0.00037), whereas in the ER-positive subtype there was a significant correlation with RFS, but the HR was just below cut-off (HR = 1.19 (1.01–1.4), p-value = 0.035) (Fig. 1b).