To assess ERα function, encapsulated tissue microstructures derived from ER+ BC from 9 distinct patients were stimulated with 10 nM 17-β-estradiol for 24 h and the mRNA levels of the ER target genes evaluated: protein PS2 (also known as Trefoil Factor 1 -TFF1-, pS2), progesterone receptor (PGR) and amphiregulin (AREG) [23]. Here, ESR1 is linked to breast cancer.