ESR1 and breast carcinoma: To understand the estrogenic activity of enterolignans, we first examined the effect of enterolignans, enterodiol (ED) and enterolactone (EL), and their precursors, sesamin (SE), matairesinol (MR) and pinoresinol (PR) (Fig 1A), on the proliferation of ER-positive human breast cancer MCF-7 cells (Fig 1B, left panel).