ESR1 and breast cancer: However, intermediate concentrations of LUT (8–16 μM) slightly promote MCF7 cells proliferation only when E2 is absent or at a concentration lower than 1 pM, whereas LUT at 8–16 μM did not promote MCF7 cells growth at concentrations (10 pM–1 nM) of E2, the level of plasma, and intra-tumoral E2 in post-menopausal women with ERα+ breast cancer (Figure S2).