ESR1 and breast cancer: This is further supported by our observation that miR-519a-3p was higher expressed in estrogen receptor-negative (ER−) than in estrogen receptor-positive (ER+) breast cancer (Figure 5e) as well as in ER− breast cancer cell lines.29 The ER− breast cancer is mostly associated with mutations in TP53 and associated with poor survival.37 Clinical data show that miR-519a-3p expression was elevated in breast tumors with mutated TP53 (Figure 5f) and that the latter was correlated with poor relapse-free survival (Supplementary Figure S15).