ESR1 and breast cancer: Treatment of the ER-positive, luminal-like breast cancer cell line MCF-7 with Smac mimetic LCL161 and/or TRAIL for 48 or 72 hours at most had minor effects on cell viability (Fig 1A) which contrasts the ER-positive CAMA-1 cells where the combination induces caspase-dependent cell death (Fig 1B).