ESR1 and breast cancer: Interestingly, the concept of “priming” cells for apoptosis has been demonstrated in breast cancer cell lines where exposure to chemotherapy or estrogen receptor antagonist resulted in increased BCL‐2 activity and sensitized cells to ABT‐199.15, 16 To explore the impact of ENZ on BCL2 family expression, we evaluated protein and messenger RNA (mRNA) expression in response to ENZ.