ESR1 and breast cancer: Actually, Oxy is a potent AI in human placental microsomes (IC50 of 0.81 μM) and in ER+ breast cancer cells (MCF-7aro) (IC50 of 1.18 μM), reducing MCF-7aro cells viability in an aromatase-dependent manner, being in this last case more potent than Exe [20].