ESR1 and breast cancer: Concomitantly, FASN inhibition augmented the E2-mediated downregulation of ERα protein (Supplementary Figure 2), strongly suggesting that FASN signaling regulates ERα signaling by functionally synergizing (MAPK/ERK) or antagonizing (PI3K/AKT) key molecular components of non-genomic ERα cross-talk to negatively regulate E2-stimulated breast cancer cell growth and survival while promoting the reduction of ERα protein (Figure 7).